Samuel Mabbott | The University of Manchester (original) (raw)

Papers by Samuel Mabbott

Research paper thumbnail of 2p or not 2p: tuppence-based SERS for the detection of illicit materials

The Analyst, 2013

Deposition of silver onto British 2p coins has been demonstrated as an efficient and cost effecti... more Deposition of silver onto British 2p coins has been demonstrated as an efficient and cost effective approach to producing substrates capable of promoting surface enhanced Raman scattering (SERS). Silver application to the copper coins is undemanding taking just 20 s, and results in the formation of multiple hierarchial dendritic structures. To demonstrate that the silver deposition sites were capable of SERS the highly fluorescent Rhodamine 6G (R6G) probe was used. Analyses indicated that Raman enhancement only occurs at the silver deposition sites and not from the roughened copper surface. The robustness of the substrate in the identification and discrimination of illegal and legal drugs of abuse was then explored. Application of the drugs to the substrates was carried out using spotting and soaking methodologies. Whilst little or no SERS spectra of the drugs were generated upon spotting, soaking of the substrate in a methanolic solution of the drugs yielded a vast amount of spectral information. Excellent reproducibility of the SERS method and classification of three of the drugs, 4-methylmethcathinone (mephedrone), 5,6methylenedioxy-2-aminoindane (MDAI) and 3,4-methylenedioxy-N-methylamphetamine (MDMA) were demonstrated using principal components analysis and partial least squares.

Research paper thumbnail of Towards point-of-care detection of microRNAs using paper-based microfluidics

Optical Diagnostics and Sensing XXI: Toward Point-of-Care Diagnostics

Human immunodeficiency virus (HIV) weakens a person’s immune system by destroying cells which are... more Human immunodeficiency virus (HIV) weakens a person’s immune system by destroying cells which are important to fighting the disease and infection. HIV is a major global public health issue with an estimated 38 million people living with HIV at the end of 2019. There is no cure for HIV. However, increased access to effective prevention, diagnosis and treatment has enabled people living with HIV to lead healthy lives. Rapid diagnosis forms an important part of the WHO’s strategy for ensuring those who are HIV positive have immediate access to care. Perhaps more critical however is that effective diagnostic testing informs individuals of their HIV status, reducing the risk of transmission. HIV prevalence within the US is disproportionately high amongst Black/African American and Hispanic/Latino American populations who often have limited access to advanced medical clinics. In this paper, we present a lateral flow device designed to detect miR-150-5p; an emerging biomarker of HIV. Based on our preliminary results shown here, we are capable of detecting the miRNA sequence at sub-ng uL-1 using colorimetric analysis, without prior amplification of the target material. We have also detailed our initial results obtained from surface-enhanced Raman scattering measurements made at the device capture line, whilst the standard deviations are large, the technique shows lots of promise for lowering the detection limit in the future.

Research paper thumbnail of Article pubs.acs.org/ac Optimization of Parameters for the Quantitative Surface-Enhanced Raman Scattering Detection of Mephedrone Using a Fractional Factorial Design and a Portable Raman Spectrometer

ABSTRACT: A new optimization strategy for the SERS detection of mephedrone using a portable Raman... more ABSTRACT: A new optimization strategy for the SERS detection of mephedrone using a portable Raman system has been developed. A fractional factorial design was employed, and the number of statistically significant experiments (288) was greatly reduced from the actual total number of experiments (1722), which minimized the workload while maintaining the statistical integrity of the results. A number of conditions were explored in relation to mephedrone SERS signal optimization including the type of nanoparticle, pH, and aggregating agents (salts). Through exercising this design, it was possible to derive the significance of each of the individual variables, and we discovered four optimized SERS protocols for which the reproducibility of the SERS signal and the limit of detection (LOD) of mephedrone were established. Using traditional nanoparticles with a combination of salts and pHs, it was shown that the relative standard deviations of mephedronespecific Raman peaks were as low as 0....

Research paper thumbnail of Synthesis and SERS Activity of Core-Satellite Nanoparticles using Heterobifunctional PEG linkers

Nanoscale Advances

Surface-enhanced Raman spectroscopy (SERS) is a sensitive analytical technique, capable of magnif... more Surface-enhanced Raman spectroscopy (SERS) is a sensitive analytical technique, capable of magnifying the vibrational intensity of a molecule absorbed onto the surface of metallic nanostructures. Various solution-based SERS-active metallic nanostructures...

Research paper thumbnail of Raman spectroscopic analysis of skin as a diagnostic tool for Human African Trypanosomiasis

PLOS Pathogens

Human African Trypanosomiasis (HAT) has been responsible for several deadly epidemics throughout ... more Human African Trypanosomiasis (HAT) has been responsible for several deadly epidemics throughout the 20th century, but a renewed commitment to disease control has significantly reduced new cases and motivated a target for the elimination of Trypanosoma brucei gambiense-HAT by 2030. However, the recent identification of latent human infections, and the detection of trypanosomes in extravascular tissues hidden from current diagnostic tools, such as the skin, has added new complexity to identifying infected individuals. New and improved diagnostic tests to detect Trypanosoma brucei infection by interrogating the skin are therefore needed. Recent advances have improved the cost, sensitivity and portability of Raman spectroscopy technology for non-invasive medical diagnostics, making it an attractive tool for gambiense-HAT detection. The aim of this work was to assess and develop a new non-invasive diagnostic method for T. brucei through Raman spectroscopy of the skin. Infections were pe...

Research paper thumbnail of Advances in Biofunctional SERS-Active Nanoparticles for Future Clinical Diagnostics and Therapeutics

Research paper thumbnail of Paper Microfluidic Device with a Horizontal Motion Valve and a Localized Delay for Automatic Control of a Multistep Assay

Research paper thumbnail of Detection of cardiovascular disease associated miR-29a using paper-based microfluidics and surface enhanced Raman scattering

The Analyst

Detection of miR-29a-3p, a microRNA associated with myocardial infarction, was achieved at a leve... more Detection of miR-29a-3p, a microRNA associated with myocardial infarction, was achieved at a level of pg/L through the combination of three-dimensional paper-based microfluidics, colorimetric detection, and surface enhanced Raman scattering...

Research paper thumbnail of A SERS approach for rapid detection of microRNA-17 in the picomolar range

The Analyst

A SERS sensor was designed as a biomarker based diagnostic tool for preeclampsia with an effectiv... more A SERS sensor was designed as a biomarker based diagnostic tool for preeclampsia with an effective sensing performance.

Research paper thumbnail of Multiplex imaging of live breast cancer tumour models through tissue using handheld surface enhanced spatially offset resonance Raman spectroscopy (SESORRS)

Chemical Communications

Multiplexed imaging of three nanotags within live breast cancer tumour models through depths of 1... more Multiplexed imaging of three nanotags within live breast cancer tumour models through depths of 10 mm using handheld SESORRS.

Research paper thumbnail of Surface enhanced resonance Raman spectroscopy (SERRS) for probing through plastic and tissue barriers using a handheld spectrometer

The Analyst

Through tissue imaging of a live breast cancer tumour model using handheld surface enhanced reson... more Through tissue imaging of a live breast cancer tumour model using handheld surface enhanced resonance Raman spectroscopy (SERRS).

Research paper thumbnail of Through barrier detection of ethanol using handheld Raman spectroscopy-Conventional Raman versus spatially offset Raman spectroscopy (SORS)

Journal of Raman Spectroscopy

Spatially offset Raman spectroscopy (SORS) provides chemical analysis at depth even when obscurin... more Spatially offset Raman spectroscopy (SORS) provides chemical analysis at depth even when obscuring barriers such as plastic or tissue are present. As the collection probe is moved further away from the point of laser excitation, scattered photons from deeper layers begin to dominate the acquired spectra, thus giving rise to through barrier detection. Here we demonstrate the potential of conventional Raman (CR) and SORS for through barrier detection using handheld spectrometers. We report the collection of Raman signals from an ethanol solution through plastic at thicknesses of up to 21 mm using SORS in combination with multivariate analysis. SORS is compared to conventional Raman, where we also demonstrate impressive through barrier detection of ethanol at depths up to 9 mm. We also highlight the advantage of applying multivariate analysis for through barrier detection using CR or SORS, particularly when peaks with similar spectral features are present in both the barrier and analyte spectra. In addition, to the best of our knowledge, this is the first report of the assessment of the maximum level of through barrier detection using handheld CR and SORS instruments with a back-scattering geometry.

Research paper thumbnail of Towards establishing a minimal nanoparticle concentration for applications involving surface enhanced spatially offset resonance Raman spectroscopy (SESORRS) in vivo

The Analyst

Detection of SERRS nanotags at picomolar concentrations through 5 mm of tissue using SESORS.

Research paper thumbnail of Through tissue imaging of a live breast cancer tumour model using handheld surface enhanced spatially offset resonance Raman spectroscopy (SESORRS)

Chemical Science

Detection of a live 3D tumour model through 15 mm of tissue using SESORRS.

Research paper thumbnail of Objective assessment of SERS thin films: comparison of silver on copper via galvanic displacement with commercially available fabricated substrates

Anal. Methods

Reproducibility of SERS signal acquired from thin films developed in-house and commercially has b... more Reproducibility of SERS signal acquired from thin films developed in-house and commercially has been assessed using seven data analysis methods.

Research paper thumbnail of Correction to Thermoresponsive Polymer Micropatterns Fabricated by Dip-Pen Nanolithography for a Highly Controllable Substrate with Potential Cellular Applications

ACS Applied Materials & Interfaces, 2017

Research paper thumbnail of Ferric plasmonic nanoparticles, aptamers, and magnetofluidic chips: toward the development of diagnostic surface-enhanced Raman spectroscopy assays

Journal of biomedical optics, Dec 1, 2016

Conjugation of aptamers and their corresponding analytes onto plasmonic nanoparticles mediates th... more Conjugation of aptamers and their corresponding analytes onto plasmonic nanoparticles mediates the formation of nanoparticle assemblies: molecularly bound nanoclusters that cause a measurable change in the colloid’s optical properties. The optimization of a surface-enhanced Raman spectroscopy (SERS) competitive binding assay utilizing plasmonic “target” and magnetic “probe” nanoparticles for the detection of the toxin bisphenol-A (BPA) is presented. These assay nanoclusters were housed inside three types of optofluidic chips patterned with magnetically activated nickel pads, in either a straight or array pattern. Both Fe 2 O 3 and Fe 2 CoO 4 were compared as potential magnetic cores for the silver-coated probe nanoparticles. We found that the Ag @ Fe 2 O 3 particles were, on average, more uniform in size and more stable than Ag @ Fe 2 CoO 4 , whereas the addition of cobalt significantly improved the collection time of particles. Using Raman mapping of the assay housed within the mag...

Research paper thumbnail of Thermoresponsive Polymer Micropatterns Fabricated by Dip-Pen Nanolithography for a Highly Controllable Substrate with Potential Cellular Applications

ACS Applied Materials & Interfaces, 2016

We report a novel approach for patterning thermoresponsive hydrogels based on N,Ndiethylacrylamid... more We report a novel approach for patterning thermoresponsive hydrogels based on N,Ndiethylacrylamide (DEAAm) and bifunctional Jeffamine ED-600 by dip-pen nanolithography (DPN). The direct writing of micron-sized thermoresponsive polymer spots was achieved with efficient control over feature size. A Jeffamine-based ink prepared through the combination of organic polymers, such as DEAAm, in an inorganic silica network was used to print thermosensitive arrays on a thiol-silanised silicon oxide substrate. The use of a Jeffamine hydrogel, acting as a carrier matrix, allowed a reduction in the evaporation of ink molecules with high volatility, such as DEAAm, and facilitated the transfer of ink from tip to substrate. The thermoresponsive behaviour of polymer arrays which swell/de-swell in aqueous solution in response to a change in temperature was successfully characterised by atomic force microscopy (AFM) and Raman spectroscopy: a thermally-induced change in height and hydration state was observed, respectively. Finally, we demonstrate that cells can adhere to and interact with these dynamic features and exhibit a change in behaviour when cultured on the substrates above and below the transition temperature of the Jeffamine/DEAAm thermoresponsive hydrogels. This 3 demonstrates the potential of these micropatterned hydrogels to act as a controllable surface for cell growth.

Research paper thumbnail of Detection of potentially toxic metals by SERS using salen complexes

The Analyst, 2016

Four metal ions have been clearly discriminated using SERS by coordinating each species to salen.... more Four metal ions have been clearly discriminated using SERS by coordinating each species to salen. The spectra acquired demonstrated characteristic differences, allowing identification of each metal ion.

Research paper thumbnail of Comparison of Fe2O3and Fe2CoO4core-shell plasmonic nanoparticles for aptamer mediated SERS assays

Colloidal Nanoparticles for Biomedical Applications XI, 2016

Conjugation of oligonucleotides or aptamers and their corresponding analytes onto plasmonic nanop... more Conjugation of oligonucleotides or aptamers and their corresponding analytes onto plasmonic nanoparticles mediates the formation of nanoparticle assemblies: molecularly bound bundles of nanoparticles which cause a measurable change in the colloid's optical properties. Here, we present further optimization of a "SERS off" competitive binding assay utilizing plasmonic and magnetic nanoparticles for the detection of the toxin bisphenol A (BPA). The assay involves 1) a 'target' silver nanoparticle functionalized with a Raman reporter dye and PEGylated BPA-binding DNA aptamers, and 2) a version of the toxin BPA, bisphenol A diglycidyl ether (BADGE), PEGylated and immobilized onto a silver coated magnetic 'probe' nanoparticle. When mixed, these target and probe nanoparticles cluster into magnetic dimers and trimers and an enhancement in their SERS spectra is observed. Upon introduction of free BPA in its native form, target AgNPs are competitively freed; reversing the nanoparticle assembly and causing the SERS signal to "turn-off" and decrease in response to the competitive binding event. The assay particles were housed inside two types of optofluidic chips containing magnetically active nickel pads, in either a straight or spotted pattern, and both Fe2O3 and Fe2CoO4 were compared as magnetic cores for the silver coated probe nanoparticle. We found that the Ag@ Fe2O3 particles were, on average, more uniform in size and more stable than Ag@ Fe2CoO4, while the addition of cobalt significantly improved the collection time of particles within the magnetic chips. Using 3D Raman mapping, we found that the straight channel design with the Ag@ Fe2O3 particles provided the most uniform nanoparticle organization, while the spotted channel design with Ag@ Fe2CoO4 demonstrated a larger SERS enhancement, and thus a lower limit of detection.

Research paper thumbnail of 2p or not 2p: tuppence-based SERS for the detection of illicit materials

The Analyst, 2013

Deposition of silver onto British 2p coins has been demonstrated as an efficient and cost effecti... more Deposition of silver onto British 2p coins has been demonstrated as an efficient and cost effective approach to producing substrates capable of promoting surface enhanced Raman scattering (SERS). Silver application to the copper coins is undemanding taking just 20 s, and results in the formation of multiple hierarchial dendritic structures. To demonstrate that the silver deposition sites were capable of SERS the highly fluorescent Rhodamine 6G (R6G) probe was used. Analyses indicated that Raman enhancement only occurs at the silver deposition sites and not from the roughened copper surface. The robustness of the substrate in the identification and discrimination of illegal and legal drugs of abuse was then explored. Application of the drugs to the substrates was carried out using spotting and soaking methodologies. Whilst little or no SERS spectra of the drugs were generated upon spotting, soaking of the substrate in a methanolic solution of the drugs yielded a vast amount of spectral information. Excellent reproducibility of the SERS method and classification of three of the drugs, 4-methylmethcathinone (mephedrone), 5,6methylenedioxy-2-aminoindane (MDAI) and 3,4-methylenedioxy-N-methylamphetamine (MDMA) were demonstrated using principal components analysis and partial least squares.

Research paper thumbnail of Towards point-of-care detection of microRNAs using paper-based microfluidics

Optical Diagnostics and Sensing XXI: Toward Point-of-Care Diagnostics

Human immunodeficiency virus (HIV) weakens a person’s immune system by destroying cells which are... more Human immunodeficiency virus (HIV) weakens a person’s immune system by destroying cells which are important to fighting the disease and infection. HIV is a major global public health issue with an estimated 38 million people living with HIV at the end of 2019. There is no cure for HIV. However, increased access to effective prevention, diagnosis and treatment has enabled people living with HIV to lead healthy lives. Rapid diagnosis forms an important part of the WHO’s strategy for ensuring those who are HIV positive have immediate access to care. Perhaps more critical however is that effective diagnostic testing informs individuals of their HIV status, reducing the risk of transmission. HIV prevalence within the US is disproportionately high amongst Black/African American and Hispanic/Latino American populations who often have limited access to advanced medical clinics. In this paper, we present a lateral flow device designed to detect miR-150-5p; an emerging biomarker of HIV. Based on our preliminary results shown here, we are capable of detecting the miRNA sequence at sub-ng uL-1 using colorimetric analysis, without prior amplification of the target material. We have also detailed our initial results obtained from surface-enhanced Raman scattering measurements made at the device capture line, whilst the standard deviations are large, the technique shows lots of promise for lowering the detection limit in the future.

Research paper thumbnail of Article pubs.acs.org/ac Optimization of Parameters for the Quantitative Surface-Enhanced Raman Scattering Detection of Mephedrone Using a Fractional Factorial Design and a Portable Raman Spectrometer

ABSTRACT: A new optimization strategy for the SERS detection of mephedrone using a portable Raman... more ABSTRACT: A new optimization strategy for the SERS detection of mephedrone using a portable Raman system has been developed. A fractional factorial design was employed, and the number of statistically significant experiments (288) was greatly reduced from the actual total number of experiments (1722), which minimized the workload while maintaining the statistical integrity of the results. A number of conditions were explored in relation to mephedrone SERS signal optimization including the type of nanoparticle, pH, and aggregating agents (salts). Through exercising this design, it was possible to derive the significance of each of the individual variables, and we discovered four optimized SERS protocols for which the reproducibility of the SERS signal and the limit of detection (LOD) of mephedrone were established. Using traditional nanoparticles with a combination of salts and pHs, it was shown that the relative standard deviations of mephedronespecific Raman peaks were as low as 0....

Research paper thumbnail of Synthesis and SERS Activity of Core-Satellite Nanoparticles using Heterobifunctional PEG linkers

Nanoscale Advances

Surface-enhanced Raman spectroscopy (SERS) is a sensitive analytical technique, capable of magnif... more Surface-enhanced Raman spectroscopy (SERS) is a sensitive analytical technique, capable of magnifying the vibrational intensity of a molecule absorbed onto the surface of metallic nanostructures. Various solution-based SERS-active metallic nanostructures...

Research paper thumbnail of Raman spectroscopic analysis of skin as a diagnostic tool for Human African Trypanosomiasis

PLOS Pathogens

Human African Trypanosomiasis (HAT) has been responsible for several deadly epidemics throughout ... more Human African Trypanosomiasis (HAT) has been responsible for several deadly epidemics throughout the 20th century, but a renewed commitment to disease control has significantly reduced new cases and motivated a target for the elimination of Trypanosoma brucei gambiense-HAT by 2030. However, the recent identification of latent human infections, and the detection of trypanosomes in extravascular tissues hidden from current diagnostic tools, such as the skin, has added new complexity to identifying infected individuals. New and improved diagnostic tests to detect Trypanosoma brucei infection by interrogating the skin are therefore needed. Recent advances have improved the cost, sensitivity and portability of Raman spectroscopy technology for non-invasive medical diagnostics, making it an attractive tool for gambiense-HAT detection. The aim of this work was to assess and develop a new non-invasive diagnostic method for T. brucei through Raman spectroscopy of the skin. Infections were pe...

Research paper thumbnail of Advances in Biofunctional SERS-Active Nanoparticles for Future Clinical Diagnostics and Therapeutics

Research paper thumbnail of Paper Microfluidic Device with a Horizontal Motion Valve and a Localized Delay for Automatic Control of a Multistep Assay

Research paper thumbnail of Detection of cardiovascular disease associated miR-29a using paper-based microfluidics and surface enhanced Raman scattering

The Analyst

Detection of miR-29a-3p, a microRNA associated with myocardial infarction, was achieved at a leve... more Detection of miR-29a-3p, a microRNA associated with myocardial infarction, was achieved at a level of pg/L through the combination of three-dimensional paper-based microfluidics, colorimetric detection, and surface enhanced Raman scattering...

Research paper thumbnail of A SERS approach for rapid detection of microRNA-17 in the picomolar range

The Analyst

A SERS sensor was designed as a biomarker based diagnostic tool for preeclampsia with an effectiv... more A SERS sensor was designed as a biomarker based diagnostic tool for preeclampsia with an effective sensing performance.

Research paper thumbnail of Multiplex imaging of live breast cancer tumour models through tissue using handheld surface enhanced spatially offset resonance Raman spectroscopy (SESORRS)

Chemical Communications

Multiplexed imaging of three nanotags within live breast cancer tumour models through depths of 1... more Multiplexed imaging of three nanotags within live breast cancer tumour models through depths of 10 mm using handheld SESORRS.

Research paper thumbnail of Surface enhanced resonance Raman spectroscopy (SERRS) for probing through plastic and tissue barriers using a handheld spectrometer

The Analyst

Through tissue imaging of a live breast cancer tumour model using handheld surface enhanced reson... more Through tissue imaging of a live breast cancer tumour model using handheld surface enhanced resonance Raman spectroscopy (SERRS).

Research paper thumbnail of Through barrier detection of ethanol using handheld Raman spectroscopy-Conventional Raman versus spatially offset Raman spectroscopy (SORS)

Journal of Raman Spectroscopy

Spatially offset Raman spectroscopy (SORS) provides chemical analysis at depth even when obscurin... more Spatially offset Raman spectroscopy (SORS) provides chemical analysis at depth even when obscuring barriers such as plastic or tissue are present. As the collection probe is moved further away from the point of laser excitation, scattered photons from deeper layers begin to dominate the acquired spectra, thus giving rise to through barrier detection. Here we demonstrate the potential of conventional Raman (CR) and SORS for through barrier detection using handheld spectrometers. We report the collection of Raman signals from an ethanol solution through plastic at thicknesses of up to 21 mm using SORS in combination with multivariate analysis. SORS is compared to conventional Raman, where we also demonstrate impressive through barrier detection of ethanol at depths up to 9 mm. We also highlight the advantage of applying multivariate analysis for through barrier detection using CR or SORS, particularly when peaks with similar spectral features are present in both the barrier and analyte spectra. In addition, to the best of our knowledge, this is the first report of the assessment of the maximum level of through barrier detection using handheld CR and SORS instruments with a back-scattering geometry.

Research paper thumbnail of Towards establishing a minimal nanoparticle concentration for applications involving surface enhanced spatially offset resonance Raman spectroscopy (SESORRS) in vivo

The Analyst

Detection of SERRS nanotags at picomolar concentrations through 5 mm of tissue using SESORS.

Research paper thumbnail of Through tissue imaging of a live breast cancer tumour model using handheld surface enhanced spatially offset resonance Raman spectroscopy (SESORRS)

Chemical Science

Detection of a live 3D tumour model through 15 mm of tissue using SESORRS.

Research paper thumbnail of Objective assessment of SERS thin films: comparison of silver on copper via galvanic displacement with commercially available fabricated substrates

Anal. Methods

Reproducibility of SERS signal acquired from thin films developed in-house and commercially has b... more Reproducibility of SERS signal acquired from thin films developed in-house and commercially has been assessed using seven data analysis methods.

Research paper thumbnail of Correction to Thermoresponsive Polymer Micropatterns Fabricated by Dip-Pen Nanolithography for a Highly Controllable Substrate with Potential Cellular Applications

ACS Applied Materials & Interfaces, 2017

Research paper thumbnail of Ferric plasmonic nanoparticles, aptamers, and magnetofluidic chips: toward the development of diagnostic surface-enhanced Raman spectroscopy assays

Journal of biomedical optics, Dec 1, 2016

Conjugation of aptamers and their corresponding analytes onto plasmonic nanoparticles mediates th... more Conjugation of aptamers and their corresponding analytes onto plasmonic nanoparticles mediates the formation of nanoparticle assemblies: molecularly bound nanoclusters that cause a measurable change in the colloid’s optical properties. The optimization of a surface-enhanced Raman spectroscopy (SERS) competitive binding assay utilizing plasmonic “target” and magnetic “probe” nanoparticles for the detection of the toxin bisphenol-A (BPA) is presented. These assay nanoclusters were housed inside three types of optofluidic chips patterned with magnetically activated nickel pads, in either a straight or array pattern. Both Fe 2 O 3 and Fe 2 CoO 4 were compared as potential magnetic cores for the silver-coated probe nanoparticles. We found that the Ag @ Fe 2 O 3 particles were, on average, more uniform in size and more stable than Ag @ Fe 2 CoO 4 , whereas the addition of cobalt significantly improved the collection time of particles. Using Raman mapping of the assay housed within the mag...

Research paper thumbnail of Thermoresponsive Polymer Micropatterns Fabricated by Dip-Pen Nanolithography for a Highly Controllable Substrate with Potential Cellular Applications

ACS Applied Materials & Interfaces, 2016

We report a novel approach for patterning thermoresponsive hydrogels based on N,Ndiethylacrylamid... more We report a novel approach for patterning thermoresponsive hydrogels based on N,Ndiethylacrylamide (DEAAm) and bifunctional Jeffamine ED-600 by dip-pen nanolithography (DPN). The direct writing of micron-sized thermoresponsive polymer spots was achieved with efficient control over feature size. A Jeffamine-based ink prepared through the combination of organic polymers, such as DEAAm, in an inorganic silica network was used to print thermosensitive arrays on a thiol-silanised silicon oxide substrate. The use of a Jeffamine hydrogel, acting as a carrier matrix, allowed a reduction in the evaporation of ink molecules with high volatility, such as DEAAm, and facilitated the transfer of ink from tip to substrate. The thermoresponsive behaviour of polymer arrays which swell/de-swell in aqueous solution in response to a change in temperature was successfully characterised by atomic force microscopy (AFM) and Raman spectroscopy: a thermally-induced change in height and hydration state was observed, respectively. Finally, we demonstrate that cells can adhere to and interact with these dynamic features and exhibit a change in behaviour when cultured on the substrates above and below the transition temperature of the Jeffamine/DEAAm thermoresponsive hydrogels. This 3 demonstrates the potential of these micropatterned hydrogels to act as a controllable surface for cell growth.

Research paper thumbnail of Detection of potentially toxic metals by SERS using salen complexes

The Analyst, 2016

Four metal ions have been clearly discriminated using SERS by coordinating each species to salen.... more Four metal ions have been clearly discriminated using SERS by coordinating each species to salen. The spectra acquired demonstrated characteristic differences, allowing identification of each metal ion.

Research paper thumbnail of Comparison of Fe2O3and Fe2CoO4core-shell plasmonic nanoparticles for aptamer mediated SERS assays

Colloidal Nanoparticles for Biomedical Applications XI, 2016

Conjugation of oligonucleotides or aptamers and their corresponding analytes onto plasmonic nanop... more Conjugation of oligonucleotides or aptamers and their corresponding analytes onto plasmonic nanoparticles mediates the formation of nanoparticle assemblies: molecularly bound bundles of nanoparticles which cause a measurable change in the colloid's optical properties. Here, we present further optimization of a "SERS off" competitive binding assay utilizing plasmonic and magnetic nanoparticles for the detection of the toxin bisphenol A (BPA). The assay involves 1) a 'target' silver nanoparticle functionalized with a Raman reporter dye and PEGylated BPA-binding DNA aptamers, and 2) a version of the toxin BPA, bisphenol A diglycidyl ether (BADGE), PEGylated and immobilized onto a silver coated magnetic 'probe' nanoparticle. When mixed, these target and probe nanoparticles cluster into magnetic dimers and trimers and an enhancement in their SERS spectra is observed. Upon introduction of free BPA in its native form, target AgNPs are competitively freed; reversing the nanoparticle assembly and causing the SERS signal to "turn-off" and decrease in response to the competitive binding event. The assay particles were housed inside two types of optofluidic chips containing magnetically active nickel pads, in either a straight or spotted pattern, and both Fe2O3 and Fe2CoO4 were compared as magnetic cores for the silver coated probe nanoparticle. We found that the Ag@ Fe2O3 particles were, on average, more uniform in size and more stable than Ag@ Fe2CoO4, while the addition of cobalt significantly improved the collection time of particles within the magnetic chips. Using 3D Raman mapping, we found that the straight channel design with the Ag@ Fe2O3 particles provided the most uniform nanoparticle organization, while the spotted channel design with Ag@ Fe2CoO4 demonstrated a larger SERS enhancement, and thus a lower limit of detection.