Ncediwe Tsolekile - Academia.edu (original) (raw)

Papers by Ncediwe Tsolekile

Research paper thumbnail of Status and progress on fabricating automotive-based aluminium metal matrix composites using FSP technique

Materials Today: Proceedings, 2021

Research paper thumbnail of Determination of fumonisins in maize by HPLC with ultraviolet detection of o-phthaldialdehyde derivatives

Mycotoxin Research, 2009

Fumonisins are mycotoxins that are produced by various Fusarium species and occur naturally in ma... more Fumonisins are mycotoxins that are produced by various Fusarium species and occur naturally in maize and maize-based foods. Fumonisins are carcinogenic, causing liver cancer in rats, and are associated with oesophageal cancer and neural tube defects in humans. Analytical methods for individual fumonisin analogues in maize rely on reversed-phase high-performance liquid chromatographic (HPLC) separation after suitable extraction and clean-up. As fumonisins lack a useful chromophore or fluorophore, HPLC detection is achieved by suitable derivatization and sensitive, specific fluorescence detection. A widely used and validated method involves extract clean-up on strong anion exchange solid phase extraction cartridges and precolumn derivatization with o-phthaldialdehyde (OPA). However, many laboratories requiring infrequent fumonisin analysis are only equipped with HPLC with ultraviolet (UV) detection. A HPLC system equipped with both UV and fluorescence detectors connected in series was used to determine the extent to which UV offers an alternative to fluorescence detection in the above analytical method. Comparison of the detection systems using fumonisin standards indicated that fluorescence is about 20-times more sensitive than UV. Analysis of maize samples with differing fumonisin contamination levels indicated that, at fumonisin B 1 levels above 1,000 µg/kg, the two detection systems were comparable and gave repeatabilities equal or less than 10% on six replicate analyses. Although a sensitive fumonisin analysis requires fluorescence detection, UV may offer an alternative in certain circumstances.

Research paper thumbnail of HPLC determination of fumonisin mycotoxins in maize: A comparative study of naphthalene-2,3-dicarboxaldehyde and o-phthaldialdehyde derivatization reagents for fluorescence and diode array detection

Journal of Chromatography B, 2011

Fumonisins are mycotoxins produced by various species of Fusarium and occur naturally in contamin... more Fumonisins are mycotoxins produced by various species of Fusarium and occur naturally in contaminated maize and maize-based foods. Ingestion of fumonisins has considerable health implications for humans and animals. Since fumonisins lack a useful chromophore or fluorophore, their determination in maize is routinely achieved via HPLC with fluorescence detection (FLD) after precolumn derivatization. This study optimized naphthalene-2,3-dicarboxaldehyde (NDA) derivatization of fumonisins in naturally contaminated maize following strong anion exchange (SAX) solid phase extraction (SPE) clean-up and utilizing diode array detection (DAD) as a practical alternative simultaneously to FLD. The limit of detection (LOD) for fumonisin B(1) (FB(1)), fumonisin B(2) (FB(2)) and fumonisin B(3) (FB(3)) with FLD was 0.11 ng, 0.50 ng and 0.27 ng, respectively, and with DAD it was 13.8 ng, 12.5 ng and 6.6 ng, respectively injected on column. The coefficient of variation (CV, n = 6) for FB(1), FB(2) and FB(3) in a naturally contaminated samples obtained with FLD was 2.6%, 1.8% and 5.3%, respectively, compared to 6.0%, 3.4% and 9.5%, respectively, obtained with DAD. Subsequently the optimized NDA derivatization was compared to the widely used o-phthaldialdehyde (OPA) derivatization agent as well as alternative sample clean-up with immunoaffinity column (IAC) by analyzing naturally contaminated maize samples (n = 15) ranging in total fumonisin (TFB = FB(1)+FB(2)+FB(3)) levels from 106 to 6000 μg/kg. After immunoaffinity column clean-up of extracted samples, the recoveries of spiked maize samples for NDA-FLD of FB(1), FB(2) and FB(3) were 62%, 94% and 64%, respectively. NDA proved to be an effective derivatization reagent of fumonisin in naturally contaminated maize samples following IAC clean-up, except for DAD at TFB levels below 1000 μg/kg. In contrast NDA derivatization following SAX clean-up produced results comparable to OPA only for levels below 1000 μg/kg. Aside from the difference in detection limits, FLD and DAD produced comparable results irrespective of the clean-up method or the derivatization agent.

Research paper thumbnail of Cell Viability Study of ZnCuInS/ZnS–TPPS4 Conjugates against Different Cell Lines as a Promising Fluorescent Probe

Organics

In the present work, we report a simple synthetic strategy for fabricating ZnCuInS/ZnS–TPPS4 conj... more In the present work, we report a simple synthetic strategy for fabricating ZnCuInS/ZnS–TPPS4 conjugates and study its cytotoxicity as a promising material for imaging and phototherapy applications. The quaternary QDs were synthesized using eco-friendly materials such as glutathione and water as a solvent, while the anionic 10,15,20-(4-sulphonatophenyl) porphyrin (TPPS4) was synthesized via the acidification of a meso-tetraphenylporphyrin precursor. Interest in TPPS4 results from its high-water dispersity, stability, and ability to generate singlet oxygen. Conjugation of ZnCuInS/ZnS QDs with TPPS4 was performed by titrating porphyrin with different amounts of ZnCuInS/ZnS QDs while keeping all other experimental parameters constant. Comparative analysis of the conjugate to the bare QDs and porphyrin revealed enhanced spectral and photophysical properties. Comparative cytotoxicity assays were performed for TPPS4 and ZnCuInS/ZnS–TPPS4 conjugates in BHK21, Hela, A549, Hek 293 and B16-F10...

Research paper thumbnail of Application of Quantum Dots in Lateral Flow Immunoassays: Non-Communicable and Communicable Diseases

Quantum Dots - Recent Advances, New Perspectives and Contemporary Applications [Working Title]

Quantum Dots (QDs) are ideal fluorescent labels for lateral flow assays (LFA) due to their unique... more Quantum Dots (QDs) are ideal fluorescent labels for lateral flow assays (LFA) due to their unique optical properties and resistance to chemical and photo-degradation. Lateral flow assay, known as immunochromatography test, is a diagnostic strip test that uses paper or membrane-based devices to detect the presence/absence of an analyte with the pregnancy test, the most known LFA. Diagnostic tools for non-communicable (NCDs) and communicable diseases (CDs) are available. However, other NCDs and CDs do not have LFAs as first-line diagnosis/point-of-care. QDs are promising fluorescent labels as they improve the LFA’s colourimetric sensitivity and fluorescence stability. This chapter discusses the tailoring and application of QDs in LFA. Particular focus on the applications of QDs in LFA for detecting or screening NCDs (i.e. cancers etc.) and CDs (i.e. SARS-CoV-2, HIV/AIDs etc.).The book chapter concludes by discussing different challenges and perspectives of QDs in LFA.

Research paper thumbnail of Application of Nanomaterials in Photodynamic Therapy

Biomedical Application of Nanoparticles

Research paper thumbnail of Effect of ZnS coating on the optoelectronic properties of aqueous glutathione capped AgInS quantum dots

Journal of Alloys and Compounds, 2022

Ternary I–III–VI quantum dots (QDs) have proved to be promising alternatives to the traditional b... more Ternary I–III–VI quantum dots (QDs) have proved to be promising alternatives to the traditional binary Cd- QDs due to their inherently lower toxicities, greener synthetic methods, and tunable optoelectronic properties. Their application in the development of biosensors, electroluminescent devices, and a range of other electrochemical applications has resulted in the I–III–VI QDs receiving widespread attention in var ious fields. In this paper, water-soluble glutathione capped AgInS core QDs and AIS/ZnS core/shell QDs were synthesized using an eco-friendly hydrothermal method. Electrochemical properties of the AgInS core QDs and AgInS/ZnS core/shell QDs were evaluated using cyclic voltammetry (CV) and differential pulse tammetry (DPV). DPV of AgInS core QDs exhibited distinguished oxidation peaks centred at − 0.05 and − 0.88 V vs Ag/AgCl of Ag and In ions, respectively, while the AgInS/ZnS QDs showed three symmetrically oxidation peaks at potentials − 0.87, − 0.66 and − 0.42 V of Zn, In and Ag ions, respectively. The total number of electrons, electron transport diffusion coefficient, De (in cm2 s1), and surface concentration of soluble species were evaluated and calculated using the Randles-Sevcik equation. The number of electrons was found to be 1.08 and 0.75 for AgInS QDs and AgInS/ZnS QDs, respectively using the Ag peak and the De value of AgInS QDs was greater than AgInS/ZnS QDs. This indicates that the electron diffusion was the slowest in the AgInS/ZnS QDs. The as-synthesized AgInS core QDs and AgInS/ZnS core-shell QDs exhibited chemical and electrochemical composition-dependent properties. This suggests the material is suitable for the velopment of biosensors.

Research paper thumbnail of Polyvinylpyrrolidone as a polymer template for Cu In S quantum dots: Effect on optical properties

Materials Today: Proceedings, 2021

Research paper thumbnail of Mn-Doped ZnSe Quantum Dots as Fluorimetric Mercury Sensor

Nonmagnetic and Magnetic Quantum Dots, 2018

Quantum dots (QDs), because of their exciting optical properties, have been explored as alternati... more Quantum dots (QDs), because of their exciting optical properties, have been explored as alternative fluorescent sensors to conventional organic fluorophores which are routinely employed for the detection of various analytes via fluorometry. QD probes can detect toxic metal ions, anions, organic molecules with good selectivity and sensitivity. This chapter investigates the synthesis of Mn-doped ZnSe QDs using nucleation-doping strategy. The as-synthesized QDs were characterized by various analytical tools such as ultravioletvisible (UV-vis) absorption, photoluminescence (PL) spectroscopy, X-ray diffractometry (XRD) and transmission electron microscopy (TEM). It was found that Mn doping of QDs significantly increases the PL intensity. The PL of the resulting QDs was examined in the presence of different metal ions to check its selective response. Among the various metal ions, Hg 2+ exhibits a drastic quenching of the QD's emission intensity. A Stern-Volmer plot of [Hg 2+ ] sensing using the as-synthesized QDs showed linearity in the range of 0-30 × 10 −6 ML −1 with the regression coefficient R 2 = 0.99. The detection limit was found to be 6.63 × 10 −7 ML −1. Thus, the present Mn-doped ZnSe QDs represent a simple, non-toxic fluorescent probe for the qualitative and quantitative detection of mercury ions in aqueous samples.

Research paper thumbnail of Diagnosis of Prostate Cancer and Prostatitis Using near Infra-Red Fluorescent AgInSe/ZnS Quantum Dots

International Journal of Molecular Sciences, 2021

The link between the microbiome and cancer has led researchers to search for a potential probe fo... more The link between the microbiome and cancer has led researchers to search for a potential probe for intracellular targeting of bacteria and cancer. Herein, we developed near infrared-emitting ternary AgInSe/ZnS quantum dots (QDs) for dual bacterial and cancer imaging. Briefly, water-soluble AgInSe/ZnS QDs were synthesized in a commercial kitchen pressure cooker. The as-synthesized QDs exhibited a spherical shape with a particle diameter of 4.5 ± 0.5 nm, and they were brightly fluorescent with a photoluminescence maximum at 705 nm. The QDs showed low toxicity against mouse mammary carcinoma (FM3A-Luc), mouse colon carcinoma (C26), malignant fibrous histiocytoma-like (KM-Luc/GFP) and prostate cancer cells, a greater number of accumulations in Staphylococcus aureus, and good cellular uptake in prostate cancer cells. This work is an excellent step towards using ternary QDs for diagnostic and guided therapy for prostate cancer.

Research paper thumbnail of The Therapeutic Effect of Second Near-Infrared Absorbing Gold Nanorods on Metastatic Lymph Nodes via Lymphatic Delivery System

Pharmaceutics, 2021

Photothermal therapy has been established recently as a non-invasive treatment protocol for cance... more Photothermal therapy has been established recently as a non-invasive treatment protocol for cancer metastatic lymph nodes. Although this treatment approach shows efficient tumour ablation towards lymph node metastasis, the monitoring and reporting of treatment progress using the lymphatic delivery channel still need to be explored. Herein, we investigated the anti-tumour effect of pegylated gold nanorods with a high aspect ratio (PAuNRs) delivered via the lymphatic route in a mouse model. In this study, breast carcinoma (FM3A-Luc) cells were inoculated in the subiliac lymph node (SiLN) to induce metastasis in the proper axillary lymph node (PALN). The treatment was initiated by injecting the PAuNRs into the accessory axillary lymph node (AALN) after tumour metastasis was confirmed in the PALN followed by external NIR laser irradiation under a temperature-controlled cooling system. The anti-tumour impact of the treatment was evaluated using an in vivo bioluminescence imaging system (...

Research paper thumbnail of Facile green synthesis of ZnInS quantum dots: temporal evolution of their optical properties and cell viability against normal and cancerous cells

Journal of Materials Chemistry C, 2020

Green synthesis of Zn–In–S quantum dots and their fluorescence under an ultra violet lamp.

Research paper thumbnail of Synthesis, structural and fluorescence optimization of ternary Cu–In–S quantum dots passivated with ZnS

Journal of Luminescence, 2020

Ternary I-III-VI quantum dots (QDs) have become attractive fluorescent materials due to their low... more Ternary I-III-VI quantum dots (QDs) have become attractive fluorescent materials due to their low toxicity compared to conventional binary II-VI based QDs. However, these QDs have been majorly synthesized in an organic medium under harsh conditions which is not eco-friendly. Herein, we report aqueous synthesis of glutathione (GSH) capped Cu-In-S based QDs using reflux approach at 95 • C and investigated the effect of synthetic parameters such as Cu:In precursor ratio, pH and the amount of GSH on the core QDs.. The assynthesized material was characterized using Ultraviolet-Visible (UV-vis) absorption, Photoluminescence (PL), Fourier Transform Infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Passivation of the core QDs with ZnS increased its photoluminescence with a blue shifted absorption and emission wavelength. Structural investigation of the QDs by using TEM, XRD and EDS techniques indicated the possible formation of Cu-In-Zn-S/ZnS "alloy-core/shell" structure due to the diffusion of Zn from ZnS shell into Cu-In-S crystal lattice and its occupation at vacant sites.

Research paper thumbnail of Synthesis of meso-tetra-(4-sulfonatophenyl) porphyrin (TPPS4) – CuInS/ZnS quantum dots conjugate as an improved photosensitizer

International Journal of Nanomedicine, 2019

Background: Metal-free, water-soluble and highly stable meso-tetra-(4-sulfonatophenyl) porphyrin ... more Background: Metal-free, water-soluble and highly stable meso-tetra-(4-sulfonatophenyl) porphyrin (TPPS 4) has been studied for their singlet oxygen quantum yield. However, TPPS 4 suffers from inherent shortcomings. To address these, TPPS 4 was conjugated to ternary copper indium sulphide/ zinc sulphide (CuInS 2 /ZnS) quantum dots (QDs). Purpose: We herein report for the first time the synthesis of TPPS 4-CuInS/ZnS QDs conjugate as an improved photosensitizer. Methods: Water-soluble TPPS 4 was synthesized from tetraphenylporphyrin (TPPH 2) after silica-gel purification. The CuInS/ZnS QDs were synthesized by hydrothermal method at a Cu:In ratio of 1:4. The porphyrin-QDs conjugate was formed via the daggling sulfonyl bond of the porphyrin and amine bond of the QDs. The effect of pH on the optical properties of TPPS 4 was evaluated. The effect of Zn:Cu + In ratio on the ZnS shell passivation was examined to reduce structural defects on the as-synthesized QDs. Results: Various spectroscopic techniques were used to confirm the successful conversion of the organic TPPH 2 to water-soluble TPPS 4. The singlet oxygen generation evaluation shows an improved singlet oxygen quantum yield from 0.19 for the porphyrin (TPPS 4) alone to 0.69 after conjugation (CuInS/ZnS-TPPS 4) with an increase in the reaction rate constant (k (s-1)).

Research paper thumbnail of Diamond Nanoparticles-Porphyrin mTHPP Conjugate as Photosensitizing Platform: Cytotoxicity and Antibacterial Activity

Nanomaterials, 2021

Conjugation of photosensitizers (PS) with nanoparticles has been largely used as a strategy to st... more Conjugation of photosensitizers (PS) with nanoparticles has been largely used as a strategy to stabilize PS in the biological medium resulting in photosensitizing nanoparticles of enhanced photoactivity. Herein, (Meso-5, 10, 15, 20-tetrakis (3-hydroxyphenyl) phorphyryn (mTHPP) was conjugated with diamond nanoparticles (ND) by covalent bond. Nanoconjugate ND-mTHPP showed suitable stability in aqueous suspension with 58 nm of hydrodynamic diameter and Zeta potential of −23 mV. The antibacterial activity of ND-mTHPP was evaluated against Escherichia coli for different incubation times (0–24 h). The optimal activity was observed after 2 h of incubation and irradiation (660 nm; 51 J/cm2) performed right after the addition of ND-mTHPP (100 μg/mL) to the bacterial suspension. The inhibitory activity was 56% whereas ampicillin at the same conditions provided only 14% of bacterial growth inhibition. SEM images showed agglomerate of ND-mTHPP adsorbed on the bacterial cell wall, suggesting tha...

Research paper thumbnail of Green synthesis of amino acid functionalized CuInS/ZnS- mTHPP conjugate for biolabeling application

Dyes and Pigments, 2021

Quantum dots (QDs) have been resourceful in bio-applications such as fluorescent tagging, sensing... more Quantum dots (QDs) have been resourceful in bio-applications such as fluorescent tagging, sensing, and bioassays. Their bio-recognition and subsequent acceptance as foreign bodies by biomolecules largely depend on the surface structure of the QDs. Surface functionalization is thus a critical factor in their synthesis and design. In this work, we report on the surface modification of CuInS/ZnS QDs by an α-amino acid which plays an essential role in cell division and wound healing. The CuInS/ZnS QDs was synthesized via one-step eco-friendly method in a pressure cooker. To improve the biocompatibility and stability, the purified QDs were functionalized with Larginine using carbodiimide chemistry to produce arginine (Arg) functionalized CuInS/ZnS QDs. Interest in the use of L-arginine amino acid in this study is a result of its zwitterion state, physiological properties, and most importantly its backbone structure which enables ease of conjugation. The Arg-CuInS/ZnS QDs were then conjugated to 5, 10, 15, 20-meso (hydroxyphenyl) porphyrin (mTHPP), a second-generation photosensitizing drug to improve the absorption efficiency of the porphyrin and tagging of cancer cells. This study examined for the first time the effect of amino acid functionalization on the luminescent, absorption and morphology properties of ternary CuInS/ZnS QDs and its porphyrin conjugate using various optical analyses. Furthermore, this study investigated the bio-labeling properties of the prepared material and tested this against leukemia (THP-1) cancer cell lines. The as-synthesized water-soluble biocompatible Arg-CuInS/ZnS-mTHPP conjugate proved to be useful for surface functionalization and as a possible bio-labeling agent.

Research paper thumbnail of Cytotoxicity, fluorescence tagging and gene-expression study of CuInS/ZnS QDS - meso (hydroxyphenyl) porphyrin conjugate against human monocytic leukemia cells

Scientific Reports, 2020

The toxicity of heavy metals present in binary semiconductor nanoparticles also known as quantum ... more The toxicity of heavy metals present in binary semiconductor nanoparticles also known as quantum dots (QDs) has hindered their wide applications hence the advent of non-toxic ternary quantum dots. These new group of quantum dots have been shown to possess some therapeutic action against cancer cell lines but not significant enough to be referred to as an ideal therapeutic agent. In this report, we address this problem by conjugating red emitting CuInS/ZnS QDs to a 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin -photosensitizer for improved bioactivities. The glutathione capped CuInS/ZnS QDs were synthesized in an aqueous medium using a kitchen pressure cooker at different Cu: In ratios (1:4 and 1:8) and at varied temperatures (95 °C, 190 °C and 235 °C). Optical properties show that the as-synthesized CuInS/ZnS QDs become red-shifted compared to the core (CuInS) after passivation with emission in the red region while the cytotoxicity study revealed excellent cell viability against nor...

Research paper thumbnail of Synthesis of fluorescent CulnS2/ZnS quantum dots—porphyrin conjugates for photodynamic therapy

MRS Communications, 2018

Porphyrins are photosensitisers used in photodynamic therapy (PDT) due to their tumor localizatio... more Porphyrins are photosensitisers used in photodynamic therapy (PDT) due to their tumor localization and in situ singlet oxygen generation. However, their limited absorption, insolubility, and aggregation in an aqueous medium limited their effective application in PDT. To overcome these limitations, we herein, report a large-scale aqueous synthesis of CuInS 2 /ZnS ternary quantum dots, and its conjugation to 5, 10, 15, 20-meso(4-hydroxyphenyl) porphyrin. The singlet oxygen generation of this highly aqueous soluble novel conjugate shows its potential for PDT applications.

Research paper thumbnail of Porphyrin as Diagnostic and Therapeutic Agent

Molecules, 2019

The synthesis and application of porphyrins has seen a huge shift towards research in porphyrin b... more The synthesis and application of porphyrins has seen a huge shift towards research in porphyrin bio-molecular based systems in the past decade. The preferential localization of porphyrins in tumors, as well as their ability to generate reactive singlet oxygen and low dark toxicities has resulted in their use in therapeutic applications such as photodynamic therapy. However, their inherent lack of bio-distribution due to water insolubility has shifted research into porphyrin-nanomaterial conjugated systems to address this challenge. This has broadened their bio-applications, viz. bio-sensors, fluorescence tracking, in vivo magnetic resonance imaging (MRI), and positron emission tomography (PET)/CT imaging to photo-immuno-therapy just to highlight a few. This paper reviews the unique theranostic role of porphyrins in disease diagnosis and therapy. The review highlights porphyrin conjugated systems and their applications. The review ends by bringing current challenges and future perspe...

Research paper thumbnail of Controlled, Facile Synthesis of High Aspect Ratio Silver Indium Selenide Nanorods

Journal of Electronic Materials, 2019

We herein report a facile synthesis of AgInSe 2 nanorods with a high aspect ratio in the aqueous ... more We herein report a facile synthesis of AgInSe 2 nanorods with a high aspect ratio in the aqueous phase via a completely green method without the use of any surfactant or template. It was found that the amount of selenium precursor concentration has greater control over the morphology of the nanocrystals. The higher concentration of selenium (Ag:In:Se = 1:4:6.2) in the reaction produced long nanorods with a high aspect ratio (> 30) together with few spherical nanocrystals, whereas the lower Se concentration of selenium (Ag:In: Se = 1:4:3.75 or 3.85) produced aggregates of spherical particles with particle diameter of 5.2 ± 0.4 nm. We inferred that increase in the reaction kinetic drive coupled with slower growth rate as the selenium concentration increased enhanced more interaction between the existing spherical particles in the product solution and resulted in the formation of elongated particles. This method is simple, cost-effective and eco-friendly for the synthesis of Se based ternary semiconductor nanorods.

Research paper thumbnail of Status and progress on fabricating automotive-based aluminium metal matrix composites using FSP technique

Materials Today: Proceedings, 2021

Research paper thumbnail of Determination of fumonisins in maize by HPLC with ultraviolet detection of o-phthaldialdehyde derivatives

Mycotoxin Research, 2009

Fumonisins are mycotoxins that are produced by various Fusarium species and occur naturally in ma... more Fumonisins are mycotoxins that are produced by various Fusarium species and occur naturally in maize and maize-based foods. Fumonisins are carcinogenic, causing liver cancer in rats, and are associated with oesophageal cancer and neural tube defects in humans. Analytical methods for individual fumonisin analogues in maize rely on reversed-phase high-performance liquid chromatographic (HPLC) separation after suitable extraction and clean-up. As fumonisins lack a useful chromophore or fluorophore, HPLC detection is achieved by suitable derivatization and sensitive, specific fluorescence detection. A widely used and validated method involves extract clean-up on strong anion exchange solid phase extraction cartridges and precolumn derivatization with o-phthaldialdehyde (OPA). However, many laboratories requiring infrequent fumonisin analysis are only equipped with HPLC with ultraviolet (UV) detection. A HPLC system equipped with both UV and fluorescence detectors connected in series was used to determine the extent to which UV offers an alternative to fluorescence detection in the above analytical method. Comparison of the detection systems using fumonisin standards indicated that fluorescence is about 20-times more sensitive than UV. Analysis of maize samples with differing fumonisin contamination levels indicated that, at fumonisin B 1 levels above 1,000 µg/kg, the two detection systems were comparable and gave repeatabilities equal or less than 10% on six replicate analyses. Although a sensitive fumonisin analysis requires fluorescence detection, UV may offer an alternative in certain circumstances.

Research paper thumbnail of HPLC determination of fumonisin mycotoxins in maize: A comparative study of naphthalene-2,3-dicarboxaldehyde and o-phthaldialdehyde derivatization reagents for fluorescence and diode array detection

Journal of Chromatography B, 2011

Fumonisins are mycotoxins produced by various species of Fusarium and occur naturally in contamin... more Fumonisins are mycotoxins produced by various species of Fusarium and occur naturally in contaminated maize and maize-based foods. Ingestion of fumonisins has considerable health implications for humans and animals. Since fumonisins lack a useful chromophore or fluorophore, their determination in maize is routinely achieved via HPLC with fluorescence detection (FLD) after precolumn derivatization. This study optimized naphthalene-2,3-dicarboxaldehyde (NDA) derivatization of fumonisins in naturally contaminated maize following strong anion exchange (SAX) solid phase extraction (SPE) clean-up and utilizing diode array detection (DAD) as a practical alternative simultaneously to FLD. The limit of detection (LOD) for fumonisin B(1) (FB(1)), fumonisin B(2) (FB(2)) and fumonisin B(3) (FB(3)) with FLD was 0.11 ng, 0.50 ng and 0.27 ng, respectively, and with DAD it was 13.8 ng, 12.5 ng and 6.6 ng, respectively injected on column. The coefficient of variation (CV, n = 6) for FB(1), FB(2) and FB(3) in a naturally contaminated samples obtained with FLD was 2.6%, 1.8% and 5.3%, respectively, compared to 6.0%, 3.4% and 9.5%, respectively, obtained with DAD. Subsequently the optimized NDA derivatization was compared to the widely used o-phthaldialdehyde (OPA) derivatization agent as well as alternative sample clean-up with immunoaffinity column (IAC) by analyzing naturally contaminated maize samples (n = 15) ranging in total fumonisin (TFB = FB(1)+FB(2)+FB(3)) levels from 106 to 6000 μg/kg. After immunoaffinity column clean-up of extracted samples, the recoveries of spiked maize samples for NDA-FLD of FB(1), FB(2) and FB(3) were 62%, 94% and 64%, respectively. NDA proved to be an effective derivatization reagent of fumonisin in naturally contaminated maize samples following IAC clean-up, except for DAD at TFB levels below 1000 μg/kg. In contrast NDA derivatization following SAX clean-up produced results comparable to OPA only for levels below 1000 μg/kg. Aside from the difference in detection limits, FLD and DAD produced comparable results irrespective of the clean-up method or the derivatization agent.

Research paper thumbnail of Cell Viability Study of ZnCuInS/ZnS–TPPS4 Conjugates against Different Cell Lines as a Promising Fluorescent Probe

Organics

In the present work, we report a simple synthetic strategy for fabricating ZnCuInS/ZnS–TPPS4 conj... more In the present work, we report a simple synthetic strategy for fabricating ZnCuInS/ZnS–TPPS4 conjugates and study its cytotoxicity as a promising material for imaging and phototherapy applications. The quaternary QDs were synthesized using eco-friendly materials such as glutathione and water as a solvent, while the anionic 10,15,20-(4-sulphonatophenyl) porphyrin (TPPS4) was synthesized via the acidification of a meso-tetraphenylporphyrin precursor. Interest in TPPS4 results from its high-water dispersity, stability, and ability to generate singlet oxygen. Conjugation of ZnCuInS/ZnS QDs with TPPS4 was performed by titrating porphyrin with different amounts of ZnCuInS/ZnS QDs while keeping all other experimental parameters constant. Comparative analysis of the conjugate to the bare QDs and porphyrin revealed enhanced spectral and photophysical properties. Comparative cytotoxicity assays were performed for TPPS4 and ZnCuInS/ZnS–TPPS4 conjugates in BHK21, Hela, A549, Hek 293 and B16-F10...

Research paper thumbnail of Application of Quantum Dots in Lateral Flow Immunoassays: Non-Communicable and Communicable Diseases

Quantum Dots - Recent Advances, New Perspectives and Contemporary Applications [Working Title]

Quantum Dots (QDs) are ideal fluorescent labels for lateral flow assays (LFA) due to their unique... more Quantum Dots (QDs) are ideal fluorescent labels for lateral flow assays (LFA) due to their unique optical properties and resistance to chemical and photo-degradation. Lateral flow assay, known as immunochromatography test, is a diagnostic strip test that uses paper or membrane-based devices to detect the presence/absence of an analyte with the pregnancy test, the most known LFA. Diagnostic tools for non-communicable (NCDs) and communicable diseases (CDs) are available. However, other NCDs and CDs do not have LFAs as first-line diagnosis/point-of-care. QDs are promising fluorescent labels as they improve the LFA’s colourimetric sensitivity and fluorescence stability. This chapter discusses the tailoring and application of QDs in LFA. Particular focus on the applications of QDs in LFA for detecting or screening NCDs (i.e. cancers etc.) and CDs (i.e. SARS-CoV-2, HIV/AIDs etc.).The book chapter concludes by discussing different challenges and perspectives of QDs in LFA.

Research paper thumbnail of Application of Nanomaterials in Photodynamic Therapy

Biomedical Application of Nanoparticles

Research paper thumbnail of Effect of ZnS coating on the optoelectronic properties of aqueous glutathione capped AgInS quantum dots

Journal of Alloys and Compounds, 2022

Ternary I–III–VI quantum dots (QDs) have proved to be promising alternatives to the traditional b... more Ternary I–III–VI quantum dots (QDs) have proved to be promising alternatives to the traditional binary Cd- QDs due to their inherently lower toxicities, greener synthetic methods, and tunable optoelectronic properties. Their application in the development of biosensors, electroluminescent devices, and a range of other electrochemical applications has resulted in the I–III–VI QDs receiving widespread attention in var ious fields. In this paper, water-soluble glutathione capped AgInS core QDs and AIS/ZnS core/shell QDs were synthesized using an eco-friendly hydrothermal method. Electrochemical properties of the AgInS core QDs and AgInS/ZnS core/shell QDs were evaluated using cyclic voltammetry (CV) and differential pulse tammetry (DPV). DPV of AgInS core QDs exhibited distinguished oxidation peaks centred at − 0.05 and − 0.88 V vs Ag/AgCl of Ag and In ions, respectively, while the AgInS/ZnS QDs showed three symmetrically oxidation peaks at potentials − 0.87, − 0.66 and − 0.42 V of Zn, In and Ag ions, respectively. The total number of electrons, electron transport diffusion coefficient, De (in cm2 s1), and surface concentration of soluble species were evaluated and calculated using the Randles-Sevcik equation. The number of electrons was found to be 1.08 and 0.75 for AgInS QDs and AgInS/ZnS QDs, respectively using the Ag peak and the De value of AgInS QDs was greater than AgInS/ZnS QDs. This indicates that the electron diffusion was the slowest in the AgInS/ZnS QDs. The as-synthesized AgInS core QDs and AgInS/ZnS core-shell QDs exhibited chemical and electrochemical composition-dependent properties. This suggests the material is suitable for the velopment of biosensors.

Research paper thumbnail of Polyvinylpyrrolidone as a polymer template for Cu In S quantum dots: Effect on optical properties

Materials Today: Proceedings, 2021

Research paper thumbnail of Mn-Doped ZnSe Quantum Dots as Fluorimetric Mercury Sensor

Nonmagnetic and Magnetic Quantum Dots, 2018

Quantum dots (QDs), because of their exciting optical properties, have been explored as alternati... more Quantum dots (QDs), because of their exciting optical properties, have been explored as alternative fluorescent sensors to conventional organic fluorophores which are routinely employed for the detection of various analytes via fluorometry. QD probes can detect toxic metal ions, anions, organic molecules with good selectivity and sensitivity. This chapter investigates the synthesis of Mn-doped ZnSe QDs using nucleation-doping strategy. The as-synthesized QDs were characterized by various analytical tools such as ultravioletvisible (UV-vis) absorption, photoluminescence (PL) spectroscopy, X-ray diffractometry (XRD) and transmission electron microscopy (TEM). It was found that Mn doping of QDs significantly increases the PL intensity. The PL of the resulting QDs was examined in the presence of different metal ions to check its selective response. Among the various metal ions, Hg 2+ exhibits a drastic quenching of the QD's emission intensity. A Stern-Volmer plot of [Hg 2+ ] sensing using the as-synthesized QDs showed linearity in the range of 0-30 × 10 −6 ML −1 with the regression coefficient R 2 = 0.99. The detection limit was found to be 6.63 × 10 −7 ML −1. Thus, the present Mn-doped ZnSe QDs represent a simple, non-toxic fluorescent probe for the qualitative and quantitative detection of mercury ions in aqueous samples.

Research paper thumbnail of Diagnosis of Prostate Cancer and Prostatitis Using near Infra-Red Fluorescent AgInSe/ZnS Quantum Dots

International Journal of Molecular Sciences, 2021

The link between the microbiome and cancer has led researchers to search for a potential probe fo... more The link between the microbiome and cancer has led researchers to search for a potential probe for intracellular targeting of bacteria and cancer. Herein, we developed near infrared-emitting ternary AgInSe/ZnS quantum dots (QDs) for dual bacterial and cancer imaging. Briefly, water-soluble AgInSe/ZnS QDs were synthesized in a commercial kitchen pressure cooker. The as-synthesized QDs exhibited a spherical shape with a particle diameter of 4.5 ± 0.5 nm, and they were brightly fluorescent with a photoluminescence maximum at 705 nm. The QDs showed low toxicity against mouse mammary carcinoma (FM3A-Luc), mouse colon carcinoma (C26), malignant fibrous histiocytoma-like (KM-Luc/GFP) and prostate cancer cells, a greater number of accumulations in Staphylococcus aureus, and good cellular uptake in prostate cancer cells. This work is an excellent step towards using ternary QDs for diagnostic and guided therapy for prostate cancer.

Research paper thumbnail of The Therapeutic Effect of Second Near-Infrared Absorbing Gold Nanorods on Metastatic Lymph Nodes via Lymphatic Delivery System

Pharmaceutics, 2021

Photothermal therapy has been established recently as a non-invasive treatment protocol for cance... more Photothermal therapy has been established recently as a non-invasive treatment protocol for cancer metastatic lymph nodes. Although this treatment approach shows efficient tumour ablation towards lymph node metastasis, the monitoring and reporting of treatment progress using the lymphatic delivery channel still need to be explored. Herein, we investigated the anti-tumour effect of pegylated gold nanorods with a high aspect ratio (PAuNRs) delivered via the lymphatic route in a mouse model. In this study, breast carcinoma (FM3A-Luc) cells were inoculated in the subiliac lymph node (SiLN) to induce metastasis in the proper axillary lymph node (PALN). The treatment was initiated by injecting the PAuNRs into the accessory axillary lymph node (AALN) after tumour metastasis was confirmed in the PALN followed by external NIR laser irradiation under a temperature-controlled cooling system. The anti-tumour impact of the treatment was evaluated using an in vivo bioluminescence imaging system (...

Research paper thumbnail of Facile green synthesis of ZnInS quantum dots: temporal evolution of their optical properties and cell viability against normal and cancerous cells

Journal of Materials Chemistry C, 2020

Green synthesis of Zn–In–S quantum dots and their fluorescence under an ultra violet lamp.

Research paper thumbnail of Synthesis, structural and fluorescence optimization of ternary Cu–In–S quantum dots passivated with ZnS

Journal of Luminescence, 2020

Ternary I-III-VI quantum dots (QDs) have become attractive fluorescent materials due to their low... more Ternary I-III-VI quantum dots (QDs) have become attractive fluorescent materials due to their low toxicity compared to conventional binary II-VI based QDs. However, these QDs have been majorly synthesized in an organic medium under harsh conditions which is not eco-friendly. Herein, we report aqueous synthesis of glutathione (GSH) capped Cu-In-S based QDs using reflux approach at 95 • C and investigated the effect of synthetic parameters such as Cu:In precursor ratio, pH and the amount of GSH on the core QDs.. The assynthesized material was characterized using Ultraviolet-Visible (UV-vis) absorption, Photoluminescence (PL), Fourier Transform Infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Passivation of the core QDs with ZnS increased its photoluminescence with a blue shifted absorption and emission wavelength. Structural investigation of the QDs by using TEM, XRD and EDS techniques indicated the possible formation of Cu-In-Zn-S/ZnS "alloy-core/shell" structure due to the diffusion of Zn from ZnS shell into Cu-In-S crystal lattice and its occupation at vacant sites.

Research paper thumbnail of Synthesis of meso-tetra-(4-sulfonatophenyl) porphyrin (TPPS4) – CuInS/ZnS quantum dots conjugate as an improved photosensitizer

International Journal of Nanomedicine, 2019

Background: Metal-free, water-soluble and highly stable meso-tetra-(4-sulfonatophenyl) porphyrin ... more Background: Metal-free, water-soluble and highly stable meso-tetra-(4-sulfonatophenyl) porphyrin (TPPS 4) has been studied for their singlet oxygen quantum yield. However, TPPS 4 suffers from inherent shortcomings. To address these, TPPS 4 was conjugated to ternary copper indium sulphide/ zinc sulphide (CuInS 2 /ZnS) quantum dots (QDs). Purpose: We herein report for the first time the synthesis of TPPS 4-CuInS/ZnS QDs conjugate as an improved photosensitizer. Methods: Water-soluble TPPS 4 was synthesized from tetraphenylporphyrin (TPPH 2) after silica-gel purification. The CuInS/ZnS QDs were synthesized by hydrothermal method at a Cu:In ratio of 1:4. The porphyrin-QDs conjugate was formed via the daggling sulfonyl bond of the porphyrin and amine bond of the QDs. The effect of pH on the optical properties of TPPS 4 was evaluated. The effect of Zn:Cu + In ratio on the ZnS shell passivation was examined to reduce structural defects on the as-synthesized QDs. Results: Various spectroscopic techniques were used to confirm the successful conversion of the organic TPPH 2 to water-soluble TPPS 4. The singlet oxygen generation evaluation shows an improved singlet oxygen quantum yield from 0.19 for the porphyrin (TPPS 4) alone to 0.69 after conjugation (CuInS/ZnS-TPPS 4) with an increase in the reaction rate constant (k (s-1)).

Research paper thumbnail of Diamond Nanoparticles-Porphyrin mTHPP Conjugate as Photosensitizing Platform: Cytotoxicity and Antibacterial Activity

Nanomaterials, 2021

Conjugation of photosensitizers (PS) with nanoparticles has been largely used as a strategy to st... more Conjugation of photosensitizers (PS) with nanoparticles has been largely used as a strategy to stabilize PS in the biological medium resulting in photosensitizing nanoparticles of enhanced photoactivity. Herein, (Meso-5, 10, 15, 20-tetrakis (3-hydroxyphenyl) phorphyryn (mTHPP) was conjugated with diamond nanoparticles (ND) by covalent bond. Nanoconjugate ND-mTHPP showed suitable stability in aqueous suspension with 58 nm of hydrodynamic diameter and Zeta potential of −23 mV. The antibacterial activity of ND-mTHPP was evaluated against Escherichia coli for different incubation times (0–24 h). The optimal activity was observed after 2 h of incubation and irradiation (660 nm; 51 J/cm2) performed right after the addition of ND-mTHPP (100 μg/mL) to the bacterial suspension. The inhibitory activity was 56% whereas ampicillin at the same conditions provided only 14% of bacterial growth inhibition. SEM images showed agglomerate of ND-mTHPP adsorbed on the bacterial cell wall, suggesting tha...

Research paper thumbnail of Green synthesis of amino acid functionalized CuInS/ZnS- mTHPP conjugate for biolabeling application

Dyes and Pigments, 2021

Quantum dots (QDs) have been resourceful in bio-applications such as fluorescent tagging, sensing... more Quantum dots (QDs) have been resourceful in bio-applications such as fluorescent tagging, sensing, and bioassays. Their bio-recognition and subsequent acceptance as foreign bodies by biomolecules largely depend on the surface structure of the QDs. Surface functionalization is thus a critical factor in their synthesis and design. In this work, we report on the surface modification of CuInS/ZnS QDs by an α-amino acid which plays an essential role in cell division and wound healing. The CuInS/ZnS QDs was synthesized via one-step eco-friendly method in a pressure cooker. To improve the biocompatibility and stability, the purified QDs were functionalized with Larginine using carbodiimide chemistry to produce arginine (Arg) functionalized CuInS/ZnS QDs. Interest in the use of L-arginine amino acid in this study is a result of its zwitterion state, physiological properties, and most importantly its backbone structure which enables ease of conjugation. The Arg-CuInS/ZnS QDs were then conjugated to 5, 10, 15, 20-meso (hydroxyphenyl) porphyrin (mTHPP), a second-generation photosensitizing drug to improve the absorption efficiency of the porphyrin and tagging of cancer cells. This study examined for the first time the effect of amino acid functionalization on the luminescent, absorption and morphology properties of ternary CuInS/ZnS QDs and its porphyrin conjugate using various optical analyses. Furthermore, this study investigated the bio-labeling properties of the prepared material and tested this against leukemia (THP-1) cancer cell lines. The as-synthesized water-soluble biocompatible Arg-CuInS/ZnS-mTHPP conjugate proved to be useful for surface functionalization and as a possible bio-labeling agent.

Research paper thumbnail of Cytotoxicity, fluorescence tagging and gene-expression study of CuInS/ZnS QDS - meso (hydroxyphenyl) porphyrin conjugate against human monocytic leukemia cells

Scientific Reports, 2020

The toxicity of heavy metals present in binary semiconductor nanoparticles also known as quantum ... more The toxicity of heavy metals present in binary semiconductor nanoparticles also known as quantum dots (QDs) has hindered their wide applications hence the advent of non-toxic ternary quantum dots. These new group of quantum dots have been shown to possess some therapeutic action against cancer cell lines but not significant enough to be referred to as an ideal therapeutic agent. In this report, we address this problem by conjugating red emitting CuInS/ZnS QDs to a 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin -photosensitizer for improved bioactivities. The glutathione capped CuInS/ZnS QDs were synthesized in an aqueous medium using a kitchen pressure cooker at different Cu: In ratios (1:4 and 1:8) and at varied temperatures (95 °C, 190 °C and 235 °C). Optical properties show that the as-synthesized CuInS/ZnS QDs become red-shifted compared to the core (CuInS) after passivation with emission in the red region while the cytotoxicity study revealed excellent cell viability against nor...

Research paper thumbnail of Synthesis of fluorescent CulnS2/ZnS quantum dots—porphyrin conjugates for photodynamic therapy

MRS Communications, 2018

Porphyrins are photosensitisers used in photodynamic therapy (PDT) due to their tumor localizatio... more Porphyrins are photosensitisers used in photodynamic therapy (PDT) due to their tumor localization and in situ singlet oxygen generation. However, their limited absorption, insolubility, and aggregation in an aqueous medium limited their effective application in PDT. To overcome these limitations, we herein, report a large-scale aqueous synthesis of CuInS 2 /ZnS ternary quantum dots, and its conjugation to 5, 10, 15, 20-meso(4-hydroxyphenyl) porphyrin. The singlet oxygen generation of this highly aqueous soluble novel conjugate shows its potential for PDT applications.

Research paper thumbnail of Porphyrin as Diagnostic and Therapeutic Agent

Molecules, 2019

The synthesis and application of porphyrins has seen a huge shift towards research in porphyrin b... more The synthesis and application of porphyrins has seen a huge shift towards research in porphyrin bio-molecular based systems in the past decade. The preferential localization of porphyrins in tumors, as well as their ability to generate reactive singlet oxygen and low dark toxicities has resulted in their use in therapeutic applications such as photodynamic therapy. However, their inherent lack of bio-distribution due to water insolubility has shifted research into porphyrin-nanomaterial conjugated systems to address this challenge. This has broadened their bio-applications, viz. bio-sensors, fluorescence tracking, in vivo magnetic resonance imaging (MRI), and positron emission tomography (PET)/CT imaging to photo-immuno-therapy just to highlight a few. This paper reviews the unique theranostic role of porphyrins in disease diagnosis and therapy. The review highlights porphyrin conjugated systems and their applications. The review ends by bringing current challenges and future perspe...

Research paper thumbnail of Controlled, Facile Synthesis of High Aspect Ratio Silver Indium Selenide Nanorods

Journal of Electronic Materials, 2019

We herein report a facile synthesis of AgInSe 2 nanorods with a high aspect ratio in the aqueous ... more We herein report a facile synthesis of AgInSe 2 nanorods with a high aspect ratio in the aqueous phase via a completely green method without the use of any surfactant or template. It was found that the amount of selenium precursor concentration has greater control over the morphology of the nanocrystals. The higher concentration of selenium (Ag:In:Se = 1:4:6.2) in the reaction produced long nanorods with a high aspect ratio (> 30) together with few spherical nanocrystals, whereas the lower Se concentration of selenium (Ag:In: Se = 1:4:3.75 or 3.85) produced aggregates of spherical particles with particle diameter of 5.2 ± 0.4 nm. We inferred that increase in the reaction kinetic drive coupled with slower growth rate as the selenium concentration increased enhanced more interaction between the existing spherical particles in the product solution and resulted in the formation of elongated particles. This method is simple, cost-effective and eco-friendly for the synthesis of Se based ternary semiconductor nanorods.