Dr T S Sampath Kumar (original) (raw)

Papers by Dr T S Sampath Kumar

Corrosion Reviews, May 20, 2022

The use of magnesium and its alloys as temporary implants has gained interest in the last two dec... more The use of magnesium and its alloys as temporary implants has gained interest in the last two decades due to their good mechanical properties and bio-degradability in the in-vivo conditions. However, the issues of higher corrosion rate and stress corrosion cracking persist, which are responsible for the implants' early failure. This review paper focuses on the challenges involved in the use of magnesium-based implants and the advancements in mitigating the corrosion-related issues for in-vivo use of biodegradable magnesium alloy implants. Herein we review the degradation behavior of three groups of magnesium alloys, i.e., aluminumcontaining Mg alloy, rare earth element (REE) containing Mg alloy, and aluminum-free Mg alloy in a variety of testing media. We also review various surface modification techniques such as mechanical methods, physical methods, and chemical methods adopted to address the shortcomings of the Mg alloys. Furthermore, recent developments in Mg based bioimplants such as Mg-based open porous scaffolds, nanostructured Mg alloys and Mg based bulk metallic glasses are reviewed. In the end, recent clinical trials of the Mg-based implant were reported in detail.

Nanocomposites, Oct 2, 2018

Additive manufacturing (AM) is integrated into almost each industry, with an objective to improve... more Additive manufacturing (AM) is integrated into almost each industry, with an objective to improve product functionality and decrease costs. Ever since from its introduction four decades ago, AM technologies have used numerous kinds of materials in polymers and composite materials to create complex 3D structures which were almost impossible to manufacture through conventional techniques. However, many concerns remain for widespread applications of 3D-printed materials, which include inhomogeneous distribution of particles, unavailability of spherical particles, poor surface finish, inadequate accuracy, shrinkage in the material, and mismatch in desired mechanical properties. To meet the high standards of part quality, immediate emphasize should be given to these pertaining issues and challenges needs to addressed from the grassroots level. It is understood that, electrospraying, a powder particle production technique, may hold great potential to address these challenges and needs of AM by synthesizing fine spherical particles of any material with high scalability and reproducibility. A comprehensive review has been done to discuss the necessity of electrospraying for AM by providing an extensive summary/insight in current material advances and also attempted to bring the connection between the electrospraying and commercialized AM methods. This article also encourages the readers in obtaining an understanding the leading-edge technology electrospraying and makes them to contribute toward the future generations more effectively.

Scientific Reports

Biomimicry is becoming deep-rooted as part of bioceramics owing to its numerous functional advant... more Biomimicry is becoming deep-rooted as part of bioceramics owing to its numerous functional advantages. Naturally occurring hydroxyapatite (HA) apart from primary nano structures are also characterised by various ionic substitutions. The ease of accommodating such key elements into the HA lattice is known to enhance bone healing properties of bioceramics. In this work, hydroxyapatite synthesized via biomimetic approach was substituted with individual as well as multiple cations for potential applications in bone repair. Ion substitutions of Sr, Mg and Zn was carried out on HA for the first time by using Serratia grown in a defined biomineralization medium. The individual ions of varying concentration substituted in Serratia HA (SHA) (Sr SHA, Mg SHA and Zn SHA) were analysed for crystallinity, functional groups, morphology and crystal size. All three showed decreased crystallinity, phase purity, large agglomerated aggregates and needle-shaped morphologies. Fourier transform infrared s...

Frontiers in Materials, 2022

The combination of light weight, strength, biodegradability, and biocompatibility of magnesium (M... more The combination of light weight, strength, biodegradability, and biocompatibility of magnesium (Mg) alloys can soon break the paradigm for temporary orthopedic implants. As the fulfillment of Mg-based implants inside the physiological environment depends on the interaction at the tissue–implant interface, surface modification appears to be a more practical approach to control the rapid degradation rate. This article reviews recent progress on surface modification of Mg-based materials to tailor the degradation rate and biocompatibility for orthopedic applications. A critical analysis of the advantages and limitations of the various surface modification techniques employed are also included for easy reference of the readers.

Bioactive coatings on metallic implants facilitate joining between the prosthesis and the osseous... more Bioactive coatings on metallic implants facilitate joining between the prosthesis and the osseous tissue, and increase the long-term stability and integrity of the implant. Literature suggests that current coating techniques provide inadequate adherence of the coating to the implants. A processing schedule was developed that minimizes reactions and produces thin coatings with the substrate. Hydroxyapatite and biphasic calcium phosphate (combination of hydroxyapatite and tri-calcium phosphate) coatings were carried out on 316L stainless steel implant material by a simple dip-coating method. Prior to the coating the substrate surfaces were passivated. The dip-coated implant materials were subsequently heat treated at appropriate temperatures for improving coating adhesion to the substrate. The coated implant materials have been characterized by X-ray diffraction, scanning electron microscopy and adhesion test. The results show that the dip coated hydroxyapatite and biphasic coatings of thickness of about 5-7 micron strongly attach to the 316L stainless steel substrates.

Dental, Oral and Craniofacial Research, 2017

Development of alloplastic grafts for the treatment of periodontal osseous defects are moving tow... more Development of alloplastic grafts for the treatment of periodontal osseous defects are moving towards designing biomaterials with optimized ultrastructure and composition to trigger assured biological function upon implantation. As eggshells are composed of calcium carbonate (94%) along with traces of biologically beneficial ions such as Mg 2+ , Sr 2+ , SiO 2-4 , Fand Na + etc., calcium phosphates derived from this natural source may mimic bone composition. Calcium phosphate cements (CPC) are considered better candidates for periodontal regeneration because they act both as a graft material and barrier membrane to promote guided bone regeneration and can also progressively resorb. Earlier, we have reported eggshell derived CPC (ECPC) for first time and shown to have superior physical and biological properties than the synthetically derived CPC due to the presence of trace ions in ECPC. In the current study, we have evaluated the clinical efficacy of ECPC in treating angular periodontal osseous defects. The reduction in probing pocket depth (PD), gain in clinical attachment level (CAL) and change in gingival position were measured in a series of 6 patients and radiographs were taken at baseline and at 6 months. Results showed relative increase in PD and CAL of 44.7 + 6.3 % and 50.9 + 11.5 % respectively after 6 months. Bone regeneration was identified in the radiograph through trabecular continuity in the angular defect site at the end of 6 months along with complete resorption of ECPC. The results confirm ECPC as potential biomaterial for treating angular periodontal defects.

Nanocomposites, 2018

Advances in experimental medicine and biology, 2018

Tissue engineering aims to fabricate and functionalise constructs that mimic the native extracell... more Tissue engineering aims to fabricate and functionalise constructs that mimic the native extracellular matrix (ECM) in the closest way possible to induce cell growth and differentiation in both in vitro and in vivo conditions. Development of scaffolds that can function as tissue substitutes or augment healing of tissues is an essential aspect of tissue regeneration. Although there are many techniques for achieving this biomimicry in 2D structures and 2D cell cultures, translation of successful tissue regeneration in true 3D microenvironments is still in its infancy. Electrospinning, a well known electrohydrodynamic process, is best suited for producing and functionalising, nanofibrous structures to mimic the ECM. A systematic control of the processing parameters coupled with novel process innovations, has recently resulted in novel 3D electrospun structures. This chapter gives a brief account of the various 3D electrospun structures that are being tried as tissue engineering scaffold...

The Indonesian Journal of Dental Research, 2015

The present study is focused on the development of doxycycline loaded calcium–deficient hydroxyap... more The present study is focused on the development of doxycycline loaded calcium–deficient hydroxyapatite (CDHA) microspheres for the treatment of periodontitis. The CDHA microspheres were formed by liquid immiscibility effect using gelatin and paraffin oil with varying Ca/P ratios using calcium hydroxide and diammonium hydrogen orthophosphate as precursors. The morphology of the microspheres as characterized by SEM was optimized by varying the gelatin content. The doxycycline incorporation and its release profiles were studied by UV-Visible spectroscopy in phosphate buffer at physiological conditions. The pH of the buffer solution was initially optimized to have maximum amount of drug loading. Doxycycline loading around the physiological pH of 7 has the highest amount of drug incorporation. All the microspheres exhibit similar release profiles with an initial gradual increase reaching a maximum value and then nearly constant release. The microspheres formed using 6% gelatin shows maxi...

Frontiers in Bioengineering and Biotechnology, 2016

ABSTRACT Since ancient times, use of graft materials to promote healing of defects of bone is wel... more ABSTRACT Since ancient times, use of graft materials to promote healing of defects of bone is wellknown. Traditionally, missing bone is replaced with material from either patient or donor. Multiple sources of bone grafts have been used to graft bone defects to stimulate bone healing. Hydroxyapatite is naturally occurring mineral component of bone, which is osteoconductive. This versatile biomaterial is derived from many sources. The aim of this study is to evaluate the efficacy of eggshell derived hydroxyapatite (EHA) in the bone regeneration of human maxillary cystic bone defects secondary to cystic removal/apicoectomy and compare the material properties of EHA in vitro.

Journal of Materials Science: Materials in Medicine, 2007

Regeneration of fractured or diseased bones is the challenge faced by current technologies in tis... more Regeneration of fractured or diseased bones is the challenge faced by current technologies in tissue engineering. The major solid components of human bone consist of collagen and hydroxyapatite. Collagen (Col) and hydroxyapatite (HA) have potential in mimicking natural extracellular matrix and replacing diseased skeletal bones. More attention has been focused on HA because of its crystallographic structure similar to inorganic compound found in natural bone and extensively investigated due to its excellent biocompatibility, bioactivity and osteoconductivity properties. In the present study, electrospun nanofibrous scaffolds are fabricated with collagen (80 mg/ ml) and Col/HA (1:1). The diameter of the collagen nanofibers is around 265 ± 0.64 nm and Col/HA nanofibers are 293 ± 1.45 nm. The crystalline HA (29 ± 7.5 nm) loaded into the collagen nanofibers are embedded within nanofibrous matrix of the scaffolds. Osteoblasts cultured on both scaffolds and show insignificant level of proliferation but mineralization was significantly (p \ 0.001) increased to 56% in Col/HA nanofibrous scaffolds compared to collagen. Energy dispersive X-ray analysis (EDX) spectroscopy results proved the presence of higher level of calcium and phosphorous in Col/HA nanocomposites than collagen nanofibrous scaffolds grown osteoblasts. The results of the present study suggested that the designed electrospun nanofibrous scaffold (Col/HA) have potential biomaterial for bone tissue engineering.

Bulletin of Materials Science, 1995

Hydroxyapatite/fluoroapatite solid solutions were prepared by two different methods using Indian ... more Hydroxyapatite/fluoroapatite solid solutions were prepared by two different methods using Indian coast corals. In the 'low temperature method' a known volume (50%) of hydrofluoric acid was added to the coral and an exchange reaction with diammonium phosphate was carried out to form apatite at 250°C under hydrothermal conditions. The coralline derived hydroxyapatite by the above method was reacted with 50 mol% sodium fluoride at 900°C in the 'high temperature method'. The X-ray powder diffraction, infrared spectroscopy and thermal analysis techniques were employed to characterize the fluorination of the hydroxyapatite. In vitro solubility study in phosphate buffer solution of pH 7"2 indicate the stability of the apatites. The low temperature method of fluorination seems to be advantageous due to better in vitro stability and absence of impurity phases.

Frontiers in Bioengineering and Biotechnology, 2015

Nanotechnology has tremendous potential for the management of infectious diseases caused by multi... more Nanotechnology has tremendous potential for the management of infectious diseases caused by multi-drug resistant bacteria, through the development of newer antibacterial materials and efficient modes of antibiotic delivery. Calcium phosphate (CaP) bioceramics are commonly used as bone substitutes due to their similarity to bone mineral and are widely researched upon for the treatment of bone infections associated with bone loss. CaPs can be used as local antibiotic delivery agents for bone infections and can be substituted with antibacterial ions in their crystal structure to have a wide spectrum, sustained antibacterial activity even against drug resistant bacteria. In the present work, a dual mode antibiotic delivery system with antibacterial ion substituted calcium deficient hydroxyapatite (CDHA) nanoparticles has been developed. Antibacterial ions such as zinc, silver, and strontium have been incorporated into CDHA at concentrations of 6, 0.25-0.75, and 2.5-7.5 at. %, respectively. The samples were found to be phase pure, acicular nanoparticles of length 40-50 nm and width 5-6 nm approximately. The loading and release profile of doxycycline, a commonly used antibiotic, was studied from the nanocarriers. The drug release was studied for 5 days and the release profile was influenced by the ion concentrations. The release of antibacterial ions was studied over a period of 21 days. The ion substituted CDHA samples were tested for antibacterial efficacy on Staphylococcus aureus and Escherichia coli by MIC/MBC studies and time-kill assay. AgCDHA and ZnCDHA showed high antibacterial activity against both bacteria, while SrCDHA was weakly active against S. aureus. Present study shows that the antibiotic release can provide the initial high antibacterial activity, and the sustained ion release can provide a long-term antibacterial activity. Such dual mode antibiotic and antibacterial ion release offers an efficient and potent way to treat an incumbent drug resistant infection.

Dental Materials Journal, 2020

The objective of this study was to develop electrospun polycaprolactone (PCL) membranes blended w... more The objective of this study was to develop electrospun polycaprolactone (PCL) membranes blended with hydroxyapatite (HA) and evaluate its potential in differentiating inflamed dental pulp stem/progenitor cells (IDPSCs) into odontoblasts. Electrospun nanofibrous membrane consisting of PCL blended with 10 wt% and 15 wt% of HA were fabricated and the characterization was done by Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and contact angle analysis. Cytocompatibility, cell adhesion and odontogenic differentiation ability of the membranes were assessed by MTT, Live/ Dead, SEM/DAPI and qPCR studies. The mineral deposition ability of the membranes with IDPSCs was estimated by SEM-EDS. The SEM analysis revealed a nanofibrous texture with an average fiber diameter of 140 nm for PCL, 220 nm for PCL10%HA and 250 nm for PCL15%HA. Among the membranes tested, PCL10%HA favored positive cell attachments, upregulated expression of DSPP and ALP gene and higher Ca/P ratio compared to PCL and PCL15%HA.

Journal of Materials Science: Materials in Medicine, 2019

Brushite cements are known for excellent osteoconductive and degradation properties, however, its... more Brushite cements are known for excellent osteoconductive and degradation properties, however, its widespread use is limited due to rapid setting time and poor mechanical properties. The eggshell derived calcium phosphates exhibits improved physical and biological properties due to the presence of biologically relevant ions. In this study, eggshell derived brushite cement (EB) was fabricated using β-tricalcium phosphate synthesized from eggshells. The presence of trace elements in EB prolonged its setting time. The size of brushite crystals in EB was found to be smaller than the pure brushite cement (PB) leading to increased initial compressive strength and higher in vitro degradation rate. The L6 and MG63 cell lines exhibited good biocompatibility with the cement at the end 72 h. In vivo studies of the cements were performed in rat calvarial defect model. Micro CT analysis showed faster degradation and accelerated bone formation in EB filled defect. Histological studies revealed infiltration of inflammatory cells into the implant site for both the cements till 6th week. However, inflammation was found to be significantly reduced at the 12th week in EB compared to PB leading to complete bone bridge formation. Multi-ion substituted EB seems to be a potential bone substitute material with a reasonable setting time for ease of handling, higher mechanical strength, minimal inflammatory response and higher bone regeneration.

Journal of Materials Processing Technology, 2018

Abstract Hydroxyapatite (HA) nanoparticles were dispersed in AZ31 alloy by friction stir processi... more Abstract Hydroxyapatite (HA) nanoparticles were dispersed in AZ31 alloy by friction stir processing (FSP) to produce AZ31/HA metal matrix composites. The composite surface was acid treated using HNO 3 and coated with polycaprolactone/HA (PCL/HA) mat by electrospinning. Coating parameters were optimized to obtain PCL/HA nanocomposite fibrous mat with an adhesion strength of 4B Grade (ASTM D3359-09 tape test) on AZ31/HA composite surface. Presence of HA on the substrate and in the coating helps in enhancing biomineralization and develop thick CaP layer on the surface which also facilitates controlled degradation in simulated body fluid at normal physiological conditions of pH 7.2 and 37 °C. Rat skeletal muscle cells culture study showed better adhesion and proliferation on coated samples compared to the uncoated samples. The combination of electrospun nanofibrous PCL/HA composite coating on acid pre-treated FSPed AZ31/HA composite surface seems to have the potential for biodegradable magnesium implant applications with enhanced bioactivity for tissue regeneration.

Journal of Nanoscience and Nanotechnology, 2019

Bone cancer or osteosarcoma is an aggressive cancer affecting the long bones and is treated by a ... more Bone cancer or osteosarcoma is an aggressive cancer affecting the long bones and is treated by a combination of surgery and chemotherapy. Local drug delivery directly to the site of bone cancer and the use of plant-based drugs has been explored towards improving the efficacy and decreasing the toxicity of the anti-cancer drugs. Curcumin, derived from turmeric is highly effective against cancer cells and shows very low toxicity against normal cells. Bone repair is facilitated by use of bone substitutes such as bioceramics, amongst which the carbonated apatite (CA) nanocarriers closely mimic the natural bone mineral. In the current work, we have developed CA nanocarriers based local delivery of curcumin as an adjunct treatment for bone cancer. CA nanocarriers with 6 wt.% carbonate were prepared by wet chemical synthesis using synthetic derived (6SWCA) and eggshell derived (6EWCA) precursors along with hydroxyapatite (WHA) as a control. The X-ray diffraction (XRD) patterns showed the C...

Surface Science, 1987

Our AES study on the Ni-4.9at%Ru alloy shows Ru segregation to the surface with an enthalpy of se... more Our AES study on the Ni-4.9at%Ru alloy shows Ru segregation to the surface with an enthalpy of segregation of-4 kJ/mol. On exposing the alloy to oxygen at 300 K, XPS and UPS studies show two types of oxygen species, 0 2-(529.4 eV) and 01-(531.4 eV); formation of NiO is also clearly observed. On heating the oxidized alloy surface in vacuum at 700 K, desorption of oxygen occurs as seen from the decrease in the O(ls) and O(KLL) peaks as well as the O(2p) band which was further confirmed by a thermal desorption study. Such a behaviour is attributed to the decrease in the dissociation temperature of NiO in the presence of Ru via 0 2-~ 01-conversion.

Journal of materials science. Materials in medicine, 2017

Dental caries is an infection of the mineralized tooth structures that advances when acid secrete... more Dental caries is an infection of the mineralized tooth structures that advances when acid secreted by bacterial action on dietary carbohydrates diffuses and dissolves the tooth mineral leading to demineralization. During treatment, clinicians often remove only the superficial infected tooth structures and retain a part of affected carious dentin to prevent excessive dentin loss and pulp exposure. Calcium hydroxide is used to treat the affected dentin because it is alkaline, induces pulp-dentin remineralization and decreases bacterial infection. Presence of strontium ions has also been reported to exhibit anticariogenic activity, and promote enamel and dentin remineralization. The objective of the present study was to develop novel hydroxyapatite cement from tetracalcium phosphate which gradually releases hydroxyl and strontium ions to exhibit antibacterial activity. Its potential to remineralize the dentin sections collected from extracted human molar tooth was studied in detail. Th...

Materials Technology, 2016

Metallic materials are widely studied for load-bearing applications such as orthopaedic implants.... more Metallic materials are widely studied for load-bearing applications such as orthopaedic implants. Titanium and its alloys find applications for load-bearing medical implants due to their biocompatibility, good corrosion resistance, high specific strength and good bioadhesion. However, the bioactivity of titanium which can be defined as the ability to form a hydroxyapatite (HA) layer, which is similar to the mineral phase of the bone, on its surface when in contact with the biological environment is poor. On the other hand, magnesium and its alloys are becoming the prime choice for degradable biomaterials targeted for temporary applications in cardiac and orthopaedic fields. However, controlling the degradation rate is the essential issue in developing magnesium-based biomaterials. Synthesis of nano/ultra fine grain materials to enhance the biofunctionalisation of orthopaedic implants is of considerable interest as cells live in a nano-featured environment consisting of a complex mixture of pores and fibres of the extracellular matrix. Recently severe plastic deformation (SPD) processes which can achieve considerable grain refinement, typically to the submicrometre or nanometre level, have gained significant attention in materials research. Therefore, using SPD processes to develop grain-refined titanium and magnesiumbased materials for implant applications has become a promising strategy in developing new-generation medical materials. Particularly for titanium, nanostructuring results in improved mechanical properties and increased bioactivity. Whereas for magnesium, grain refinement results in controlled degradation due to higher biomineralisation with enhanced tissue response. The present review aims to provide a comprehensive summary of the progress achieved using SPD processes in developing nano/ultra fine grain structured titanium and magnesium for implant applications. Role of smaller grain size on enhancing bioproperties is also discussed including the challenges involved in processing to achieve the grain refinement up to nano/ultra fine grain level.