SUMIT KUMAR | Punjab Technical University (original) (raw)

Papers by SUMIT KUMAR

Research paper thumbnail of Clinical spectrum of Treacher Collins syndrome

Journal of oral biology and craniofacial research

Treacher Collins syndrome (TCS) is the most common of the human mandibulofacial dysostosis disord... more Treacher Collins syndrome (TCS) is the most common of the human mandibulofacial dysostosis disorders. It is an autosomal-dominant disorder of the craniofacial development occurring between the fifth and the eighth weeks of embryonic development with an incidence of 1/50,000 live births, range between 1-40,000 and 1-70,000. We present here the various clinical, radiographical and other diagnostic findings of the TCS to correlate the clinical assessment with the diagnostic imaging and review the various investigations and management options being carried out to improve their facial deformity.

Research paper thumbnail of Alveolar ridge augmentation using distraction osteogenesis: a clinical trial

Journal of oral biology and craniofacial research

Severely resorbed ridges present a great challenge to prosthodontic rehabilitation. Available rec... more Severely resorbed ridges present a great challenge to prosthodontic rehabilitation. Available reconstructive options include autologous/alloplastic augmentation with questionable results, or regeneration of new bone under gradual and controlled tension using distraction osteogenesis. This study focused on use of distraction osteogenesis for the treatment of vertically deficient alveolar ridges to assess its feasibility and outcome. Alveolar distraction osteogenesis (ADO) was studied at 10 different intra-oral, partial or complete edentulous sites. After a latency period of 5 days, distraction was carried out for 6-7 days at the rate of 0.5 mm every 12 hours (1 mm/day). Distractor was removed after a consolidation period of 12 weeks. The mean height gained at the 10 intra-oral sites was 4.8 mm with standard deviation of ± 0.056. The mean follow-up period was 2 years. Complications of therapy included hardware failure, wound gape and extra-oral scar. The overall complication rate was 10%. Distraction osteogenesis is a promising option to aid uneventful prosthodontic rehabilitation of severe vertically resorbed alveolar ridges.

Research paper thumbnail of Effect of humic acid on cesium sorption on silica colloids

Radiochimica Acta, 2006

Page 1. Radiochim. Acta 94, 369–373 (2006) / DOI 10.1524/ract.2006.94.6.369 © by Oldenbourg Wisse... more Page 1. Radiochim. Acta 94, 369–373 (2006) / DOI 10.1524/ract.2006.94.6.369 © by Oldenbourg Wissenschaftsverlag, München Effect of humic acid on cesium sorption on silica colloids By S. Kumar1, BS Tomar1,∗, S. Ramanathan2 and VK Manchanda1 ...

Research paper thumbnail of Reconstruction of ramus-condyle unit with transport distraction osteogenesis: Report of eight cases and review of literature

Journal of Oral Biology and Craniofacial Research, 2012

This report and review of literature aimed to assess the feasibility of condylar distraction in h... more This report and review of literature aimed to assess the feasibility of condylar distraction in humans and its esthetic and functional outcome. We present a case series of eight TMJ ankylosis patients, where after a gap arthroplasty, ramus condyle unit was reconstructed using transport distraction to analyze its feasibility, esthetic and functional outcome and success. All patients had satisfactory mouth opening, and minimal pain in their follow-up period. Condylar transport distraction osteogenesis holds promise for successful TMJ reconstruction and should be the method of choice as it does not involve secondary surgery or need for an alloplast.

Research paper thumbnail of Regulation of hCLCA2 by PI3K-Akt signaling and its role in anoikis

Abstract The calcium activated chloride regulator hCLCA2 (human, calcium activated chloride chann... more Abstract The calcium activated chloride regulator hCLCA2 (human, calcium activated chloride channel) is thought to be a breast tumor suppressor. Its mouse homolog mCLCA5 is upregulated during mammary involution and in vitro by withdrawal of growth factors, cell detachment, and contact inhibition. Cell to matrix adhesion is a key factor involved in cellular homeostasis and disruption of such interaction induces a special kind of apoptosis called anoikis (homelessness). The cell has to bypass anchorage dependent growth in particular ...

Research paper thumbnail of Spray-dried nano-crystalline powders and in vitro dissolution performance

ABSTRACT Quality by Design principles has been applied to understand formulation and optimization... more ABSTRACT Quality by Design principles has been applied to understand formulation and optimization of nano-crystalline spray-dried powders of poorly soluble drugs. The objectives of this research were to: 1) investigate the effect of wet media milling on nano-crystalline suspensions; 2) investigate the effect of spray-drying process and formulation parameters on nano-crystalline suspensions; 3) understand role of bulking agents during spray or freeze-drying of nano-crystalline suspensions; and 4) investigate the effect of different sized spray-dried nano-crystals on in vitro dissolution performance. Poorly soluble drugs were utilized to investigate the aggregation of nano-crystals during the spray drying process. It was determined that temperature and excipient utilized in the formulations plays an important role in nano-crystal aggregation. Low inlet temperature (preferably less than drug melting temperature) for spray drying processing and the addition of stabilizers/excipients with favorable or strong interaction (such as ionic or hydrogen bonding etc.) with the drug will provide better stability of the nano-crystals and thus no or minimal nano-crystal aggregation. The percent yield of spray-dried powders is dependent on the glass transition temperature of the formulations and/or bulking agents utilized. Small molecular weight bulking agents (or matrix formers) prevented nano-crystal aggregation due to favorable interactions with the stabilizers. Stabilizers with favorable or strong interaction with the drug are preferred for the stability of nano-crystalline suspensions but this may cause physical and chemical instability (such as solid-state transformation, drug degradation etc.) during high intensity wet milling processing. USP apparatus II was modified to hold dialysis sacs and this method was utilized to test and distinguish nano-crystalline formulations based on their size. The developed in vitro release testing method (or dissolution method) was able to distinguish nano-crystalline formulations based on size. This method can be utilized for routine quality control assays performed in the pharmaceutical industry and potentially for the development of IVIVC for these formulations. In conclusion, QbD (or specifically DoE) studies performed in this research are examples of how this approach can be utilized to understand formation and stabilization of nano-crystalline suspensions during milling and/or drying to achieve non-aggregating stable nano-crystalline powders for desired in vitro and/or in vivo performance.

Research paper thumbnail of Nanosuspensions

Research paper thumbnail of Synthesis of NNNN Tetradentate Macrocyclic Ligand and its Pd(II), Pt(II), Ru(III), and Ir(III) Complexes: Spectroscopic, Thermal, and Antimicrobial Studies

Synthesis and Reactivity in Inorganic Metal-organic and Nano-metal Chemistry, 2010

Pd (II), Pt (II), Ru (III), and Ir (III) complexes of general stoichiometry [PdL] Cl2,[PtL] Cl2,[... more Pd (II), Pt (II), Ru (III), and Ir (III) complexes of general stoichiometry [PdL] Cl2,[PtL] Cl2,[Ru (L) Cl2] Cl, and [Ir (L) Cl2] Cl, with tetradentate macrocyclic ligand, derived from 2, 6-diaminopyridine with 3-methyl 2, 4-pentanedione has been synthesized. The ligand was ...

Research paper thumbnail of Study of cesium diffusion in borosilicate glass by heavy ion Rutherford backscattering spectrometry

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2005

Diffusion of cesium in borosilicate glass has been studied by heavy ion Rutherford backscattering... more Diffusion of cesium in borosilicate glass has been studied by heavy ion Rutherford backscattering spectrometry (HIRBS) technique using 30 MeV 19 F beam. Analysis of glass samples annealed at different temperatures for 12 h duration has been used to determine the activation ...

Research paper thumbnail of Synthesis of biodegradable amphiphilic nanocarriers by chemo-enzymatic transformations for the solubilization of hydrophobic compounds

The International journal of artificial organs, 2011

Polymeric nanocarriers possess advanced physicochemical properties that improve bioavailability, ... more Polymeric nanocarriers possess advanced physicochemical properties that improve bioavailability, enhance cellular dynamics, and control target ability in drug delivery. In particular, dendritic polyglycerol is a promising new biocompatible scaffold for drug delivery. The present study explores the chemo-enzymatic modifications on dendritic hyperbranched polyglycerol (dPG) leading to amphiphilic polymeric architectures with easily hydrolysable ester linkages. Furthermore, these architectures were studied for nile red solubilization with capacity up to 5.6 mg/L at 0.1 wt % polymer conc. This corresponds to an ~10 fold increase in solubility of nile red. The release of nile red from these polymers was observed with a half life of 8 hours at pH 5.0, while no release was found at pH 7.4. The cell viability studies of our polymeric architectures showed them to be relatively nontoxic and to have the potential for future drug delivery applications.

Research paper thumbnail of Competition between hydrogen bonding and dispersion interactions in the indole···pyridine dimer and (indole)2···pyridine trimer studied in a supersonic jet

The journal of physical chemistry. A, Jan 7, 2011

Research paper thumbnail of Structure of 7-azaindole···2-fluoropyridine dimer in a supersonic jet: competition between N-H···N and N-H···F interactions

The journal of physical chemistry. A, Jan 22, 2011

Research paper thumbnail of Purification and characterization of maltooligosaccharide-forming α-amylase from moderately halophilic Marinobacter sp. EMB8

Bioresource technology, 2012

Research paper thumbnail of Mimicking trimeric interactions in the aromatic side chains of the proteins: a gas phase study of indole...(pyrrole)2 heterotrimer

The Journal of chemical physics, Jan 7, 2012

Aromatic trimeric interactions are extremely significant in the stabilization of the specific str... more Aromatic trimeric interactions are extremely significant in the stabilization of the specific structures of the proteins as well as protein-protein, and protein-ligand interactions. Here we have reported a direct evidence of the observation of a cyclic asymmetric structure of indole...(pyrrole)(2) trimer bound by three N-H...π hydrogen bonding interactions in a supersonic jet. The experiment has been performed by using resonant two-photon ionization (R2PI), IR-UV, and UV-UV double resonance spectroscopic techniques. Density functional theory (DFT) calculations nicely corroborate the experimental results showing one weakly allowed IR-active band due to symmetric stretch of the N-H bonds and two strongly allowed IR-active bands due to two types of asymmetric stretches of the N-H bonds in the trimer. The present spectroscopic investigation demonstrates that the strength of the three N-H...π bound intermolecular interactions in the cyclic asymmetric trimer is quite different unlike the corresponding interactions of similar strength in a cyclic symmetric trimer.

Research paper thumbnail of Effect of acceptor heteroatoms on π-hydrogen bonding interactions: a study of indole···thiophene heterodimer in a supersonic jet

The Journal of chemical physics, Jan 7, 2012

Resonant two photon ionization (R2PI), IR-UV, and UV-UV double resonance spectroscopic techniques... more Resonant two photon ionization (R2PI), IR-UV, and UV-UV double resonance spectroscopic techniques combined with quantum chemistry calculations have been used to determine the structure of indole···thiophene dimer observed in a supersonic jet. With the help of combined experimental and theoretical IR spectra it has been found that the observed dimer has a N-H···π hydrogen bonded slanted T-shaped structure. The present study demonstrates the effect of heteroatoms present in the acceptors on the strength of the π-hydrogen bonding interactions. It was concluded by Sherrill and co-workers from their theoretical study of benzene···pyridine dimer that aromatic rings containing heteroatoms are poorest π-hydrogen bond acceptors [E. G. Hohenstein and C. D. Sherrill, J. Phys. Chem. A 113, 878 (2009)]. But the current spectroscopic investigation exhibits that five membered aromatic heterocycles are favorable π-hydrogen bond acceptors. In this study, it has also been shown that thiophene is a better π-hydrogen bond acceptor than furan. The present work has immense biological significance as indole is the chromophore of tryptophan residue in the proteins and thiophene derivatives have potential therapeutic applications. Thus, understanding the binding motif between indole and thiophene in the heterodimer studied in this work may help in designing efficient drugs.

Research paper thumbnail of Structure of indole···imidazole heterodimer in a supersonic jet: a gas phase study on the interaction between the aromatic side chains of tryptophan and histidine residues in proteins

The journal of physical chemistry. A, Jan 29, 2012

In this study, we have investigated the binding motifs between the aromatic side chains of trypto... more In this study, we have investigated the binding motifs between the aromatic side chains of tryptophan and histidine residues in proteins by studying the indole···imidazole heterodimer in a supersonic jet. Different spectroscopic techniques including resonant two-photon ionization (R2PI), UV-UV hole-burning, and resonant ion dip infrared (RIDIR) spectroscopy merged with quantum chemistry calculations have been used for this work. UV-UV hole-burning spectroscopy has been used to confirm the presence of only one structure of the dimer in the experiment. From the comparison of the RIDIR spectrum of the observed dimer with the theoretical IR spectra of different structures of the dimer, it is found that the dimer present in the experiment has a V-shaped structure held by N-H···N hydrogen bond, C-H···π, and weakly present π···π stacking interactions. The most important finding of the present study is that the noncovalent interactions present in the observed dimer have a close resemblance with those present between tryptophan and histidine residues in a nonfluorescent flavoprotein. The present spectroscopic investigation on the indole···imidazole dimer has also immense pharmaceutical significance as this imparts molecular level understanding about the binding motifs of the imidazole drugs with the indole chromophore present in proteins.

Research paper thumbnail of Screening and isolation of halophilic bacteria producing industrially important enzymes

Brazilian journal of microbiology : [publication of the Brazilian Society for Microbiology], 2012

Research paper thumbnail of Quality by Design approach to spray drying processing of crystalline nanosuspensions

International journal of pharmaceutics, Jan 10, 2014

Quality by Design (QbD) principles were explored to understand spray drying process for the conve... more Quality by Design (QbD) principles were explored to understand spray drying process for the conversion of liquid nanosuspensions into solid nano-crystalline dry powders using indomethacin as a model drug. The effects of critical process variables: inlet temperature, flow and aspiration rates on critical quality attributes (CQAs): particle size, moisture content, percent yield and crystallinity were investigated employing a full factorial design. A central cubic design was employed to generate the response surface for particle size and percent yield. Multiple linear regression analysis and ANOVA were employed to identify and estimate the effect of critical parameters, establish their relationship with CQAs, create design space and model the spray drying process. Inlet temperature was identified as the only significant factor (p value <0.05) to affect dry powder particle size. Higher inlet temperatures caused drug surface melting and hence aggregation of the dried nano-crystalline powders. Aspiration and flow rates were identified as significant factors affecting yield (p value <0.05). Higher yields were obtained at higher aspiration and lower flow rates. All formulations had less than 3% (w/w) moisture content. Formulations dried at higher inlet temperatures had lower moisture compared to those dried at lower inlet temperatures.

Research paper thumbnail of Formulation parameters of crystalline nanosuspensions on spray drying processing: a DoE approach

International journal of pharmaceutics, Jan 10, 2014

Nanocrystalline suspensions offer a promising approach to improve dissolution of BCS class II/IV ... more Nanocrystalline suspensions offer a promising approach to improve dissolution of BCS class II/IV compounds. Spray drying was utilized as a downstream process to improve the physical and chemical stability of dried nanocrystals. The effect of nanocrystalline suspension formulation variables on spray-drying processing was investigated. Naproxen and indomethacin nanocrystalline formulations were formulated with either Dowfax 2A1 (small molecule) or HPMC E15 (high molecular weight polymer) and spray drying was performed. A DoE approach was utilized to understand the effect of critical formulation variables, i.e. type of stabilizer, type of drug, ratio of drug-to-stabilizer and drug concentration. The powders were analyzed for particle size, moisture content, powder X-ray diffraction and dissolution. A dialysis sac adapter for USP apparatus II was developed which provided good discrimination between aggregated and non-aggregated formulations. Nanocrystal aggregation was dependent on the drug-to-stabilizer ratio. The glass transition temperature and the charge effect played a dominant role on spray-dried powder yield. Those formulations with low drug-to-excipient ratios were less aggregating and showed faster dissolution compared to those formulations with high drug-to-excipient ratios. All stable (less aggregated) formulations were subjected to accelerated storage stability testing. The Flory-Huggins interaction parameter (between drug and excipients) correlated with the spray-dried nanocrystal formulations stability.

Research paper thumbnail of Microbial mineralization of struvite: a promising process to overcome phosphate sequestering crisis

Water research, 2014

Due to extensive exploitation of non-renewable phosphate minerals, their natural reserves will ex... more Due to extensive exploitation of non-renewable phosphate minerals, their natural reserves will exhaust very soon. This necessitates looking for alternatives and an efficient methodology through which indispensable phosphorus can be harvested back. The current study was undertaken to explore the potential of a metallophilic bacterium Enterobacter sp. EMB19 for the recovery of phosphorus as phosphate rich mineral. A very low phosphate concentration strategy was adopted. The process led to the mineralization of phosphorus as homogeneous struvite crystals. For each gram of Epsom salt added, the cells effectively mineralized about 20% of the salt into struvite. The effect of different inorganic sources, culture profile and plausible mechanism involved in crystal formation was also explored. The synthesized struvite crystals typically possessed a prismatic crystal habit. The characterization and identification of the crystals were done using single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), energy dispersive X-ray analysis (EDAX) and fourier transform infrared (FTIR). The thermal characteristics were studied using thermo gravimetric analysis (TGA) and differential scanning calorimetric (DSC) processes. The synthesis of struvite by this bacterium seems to be a promising and viable strategy since it serves dual purpose (i) obtaining phosphorus and nitrogen rich fertilizer and (ii) conservation of natural phosphate reserves. This study is very significant in the sense that the process may be used for harvesting and synthesizing other valuable minerals. Also, it will provide new insights into phosphate biomineralization mechanisms.

Research paper thumbnail of Clinical spectrum of Treacher Collins syndrome

Journal of oral biology and craniofacial research

Treacher Collins syndrome (TCS) is the most common of the human mandibulofacial dysostosis disord... more Treacher Collins syndrome (TCS) is the most common of the human mandibulofacial dysostosis disorders. It is an autosomal-dominant disorder of the craniofacial development occurring between the fifth and the eighth weeks of embryonic development with an incidence of 1/50,000 live births, range between 1-40,000 and 1-70,000. We present here the various clinical, radiographical and other diagnostic findings of the TCS to correlate the clinical assessment with the diagnostic imaging and review the various investigations and management options being carried out to improve their facial deformity.

Research paper thumbnail of Alveolar ridge augmentation using distraction osteogenesis: a clinical trial

Journal of oral biology and craniofacial research

Severely resorbed ridges present a great challenge to prosthodontic rehabilitation. Available rec... more Severely resorbed ridges present a great challenge to prosthodontic rehabilitation. Available reconstructive options include autologous/alloplastic augmentation with questionable results, or regeneration of new bone under gradual and controlled tension using distraction osteogenesis. This study focused on use of distraction osteogenesis for the treatment of vertically deficient alveolar ridges to assess its feasibility and outcome. Alveolar distraction osteogenesis (ADO) was studied at 10 different intra-oral, partial or complete edentulous sites. After a latency period of 5 days, distraction was carried out for 6-7 days at the rate of 0.5 mm every 12 hours (1 mm/day). Distractor was removed after a consolidation period of 12 weeks. The mean height gained at the 10 intra-oral sites was 4.8 mm with standard deviation of ± 0.056. The mean follow-up period was 2 years. Complications of therapy included hardware failure, wound gape and extra-oral scar. The overall complication rate was 10%. Distraction osteogenesis is a promising option to aid uneventful prosthodontic rehabilitation of severe vertically resorbed alveolar ridges.

Research paper thumbnail of Effect of humic acid on cesium sorption on silica colloids

Radiochimica Acta, 2006

Page 1. Radiochim. Acta 94, 369–373 (2006) / DOI 10.1524/ract.2006.94.6.369 © by Oldenbourg Wisse... more Page 1. Radiochim. Acta 94, 369–373 (2006) / DOI 10.1524/ract.2006.94.6.369 © by Oldenbourg Wissenschaftsverlag, München Effect of humic acid on cesium sorption on silica colloids By S. Kumar1, BS Tomar1,∗, S. Ramanathan2 and VK Manchanda1 ...

Research paper thumbnail of Reconstruction of ramus-condyle unit with transport distraction osteogenesis: Report of eight cases and review of literature

Journal of Oral Biology and Craniofacial Research, 2012

This report and review of literature aimed to assess the feasibility of condylar distraction in h... more This report and review of literature aimed to assess the feasibility of condylar distraction in humans and its esthetic and functional outcome. We present a case series of eight TMJ ankylosis patients, where after a gap arthroplasty, ramus condyle unit was reconstructed using transport distraction to analyze its feasibility, esthetic and functional outcome and success. All patients had satisfactory mouth opening, and minimal pain in their follow-up period. Condylar transport distraction osteogenesis holds promise for successful TMJ reconstruction and should be the method of choice as it does not involve secondary surgery or need for an alloplast.

Research paper thumbnail of Regulation of hCLCA2 by PI3K-Akt signaling and its role in anoikis

Abstract The calcium activated chloride regulator hCLCA2 (human, calcium activated chloride chann... more Abstract The calcium activated chloride regulator hCLCA2 (human, calcium activated chloride channel) is thought to be a breast tumor suppressor. Its mouse homolog mCLCA5 is upregulated during mammary involution and in vitro by withdrawal of growth factors, cell detachment, and contact inhibition. Cell to matrix adhesion is a key factor involved in cellular homeostasis and disruption of such interaction induces a special kind of apoptosis called anoikis (homelessness). The cell has to bypass anchorage dependent growth in particular ...

Research paper thumbnail of Spray-dried nano-crystalline powders and in vitro dissolution performance

ABSTRACT Quality by Design principles has been applied to understand formulation and optimization... more ABSTRACT Quality by Design principles has been applied to understand formulation and optimization of nano-crystalline spray-dried powders of poorly soluble drugs. The objectives of this research were to: 1) investigate the effect of wet media milling on nano-crystalline suspensions; 2) investigate the effect of spray-drying process and formulation parameters on nano-crystalline suspensions; 3) understand role of bulking agents during spray or freeze-drying of nano-crystalline suspensions; and 4) investigate the effect of different sized spray-dried nano-crystals on in vitro dissolution performance. Poorly soluble drugs were utilized to investigate the aggregation of nano-crystals during the spray drying process. It was determined that temperature and excipient utilized in the formulations plays an important role in nano-crystal aggregation. Low inlet temperature (preferably less than drug melting temperature) for spray drying processing and the addition of stabilizers/excipients with favorable or strong interaction (such as ionic or hydrogen bonding etc.) with the drug will provide better stability of the nano-crystals and thus no or minimal nano-crystal aggregation. The percent yield of spray-dried powders is dependent on the glass transition temperature of the formulations and/or bulking agents utilized. Small molecular weight bulking agents (or matrix formers) prevented nano-crystal aggregation due to favorable interactions with the stabilizers. Stabilizers with favorable or strong interaction with the drug are preferred for the stability of nano-crystalline suspensions but this may cause physical and chemical instability (such as solid-state transformation, drug degradation etc.) during high intensity wet milling processing. USP apparatus II was modified to hold dialysis sacs and this method was utilized to test and distinguish nano-crystalline formulations based on their size. The developed in vitro release testing method (or dissolution method) was able to distinguish nano-crystalline formulations based on size. This method can be utilized for routine quality control assays performed in the pharmaceutical industry and potentially for the development of IVIVC for these formulations. In conclusion, QbD (or specifically DoE) studies performed in this research are examples of how this approach can be utilized to understand formation and stabilization of nano-crystalline suspensions during milling and/or drying to achieve non-aggregating stable nano-crystalline powders for desired in vitro and/or in vivo performance.

Research paper thumbnail of Nanosuspensions

Research paper thumbnail of Synthesis of NNNN Tetradentate Macrocyclic Ligand and its Pd(II), Pt(II), Ru(III), and Ir(III) Complexes: Spectroscopic, Thermal, and Antimicrobial Studies

Synthesis and Reactivity in Inorganic Metal-organic and Nano-metal Chemistry, 2010

Pd (II), Pt (II), Ru (III), and Ir (III) complexes of general stoichiometry [PdL] Cl2,[PtL] Cl2,[... more Pd (II), Pt (II), Ru (III), and Ir (III) complexes of general stoichiometry [PdL] Cl2,[PtL] Cl2,[Ru (L) Cl2] Cl, and [Ir (L) Cl2] Cl, with tetradentate macrocyclic ligand, derived from 2, 6-diaminopyridine with 3-methyl 2, 4-pentanedione has been synthesized. The ligand was ...

Research paper thumbnail of Study of cesium diffusion in borosilicate glass by heavy ion Rutherford backscattering spectrometry

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2005

Diffusion of cesium in borosilicate glass has been studied by heavy ion Rutherford backscattering... more Diffusion of cesium in borosilicate glass has been studied by heavy ion Rutherford backscattering spectrometry (HIRBS) technique using 30 MeV 19 F beam. Analysis of glass samples annealed at different temperatures for 12 h duration has been used to determine the activation ...

Research paper thumbnail of Synthesis of biodegradable amphiphilic nanocarriers by chemo-enzymatic transformations for the solubilization of hydrophobic compounds

The International journal of artificial organs, 2011

Polymeric nanocarriers possess advanced physicochemical properties that improve bioavailability, ... more Polymeric nanocarriers possess advanced physicochemical properties that improve bioavailability, enhance cellular dynamics, and control target ability in drug delivery. In particular, dendritic polyglycerol is a promising new biocompatible scaffold for drug delivery. The present study explores the chemo-enzymatic modifications on dendritic hyperbranched polyglycerol (dPG) leading to amphiphilic polymeric architectures with easily hydrolysable ester linkages. Furthermore, these architectures were studied for nile red solubilization with capacity up to 5.6 mg/L at 0.1 wt % polymer conc. This corresponds to an ~10 fold increase in solubility of nile red. The release of nile red from these polymers was observed with a half life of 8 hours at pH 5.0, while no release was found at pH 7.4. The cell viability studies of our polymeric architectures showed them to be relatively nontoxic and to have the potential for future drug delivery applications.

Research paper thumbnail of Competition between hydrogen bonding and dispersion interactions in the indole···pyridine dimer and (indole)2···pyridine trimer studied in a supersonic jet

The journal of physical chemistry. A, Jan 7, 2011

Research paper thumbnail of Structure of 7-azaindole···2-fluoropyridine dimer in a supersonic jet: competition between N-H···N and N-H···F interactions

The journal of physical chemistry. A, Jan 22, 2011

Research paper thumbnail of Purification and characterization of maltooligosaccharide-forming α-amylase from moderately halophilic Marinobacter sp. EMB8

Bioresource technology, 2012

Research paper thumbnail of Mimicking trimeric interactions in the aromatic side chains of the proteins: a gas phase study of indole...(pyrrole)2 heterotrimer

The Journal of chemical physics, Jan 7, 2012

Aromatic trimeric interactions are extremely significant in the stabilization of the specific str... more Aromatic trimeric interactions are extremely significant in the stabilization of the specific structures of the proteins as well as protein-protein, and protein-ligand interactions. Here we have reported a direct evidence of the observation of a cyclic asymmetric structure of indole...(pyrrole)(2) trimer bound by three N-H...π hydrogen bonding interactions in a supersonic jet. The experiment has been performed by using resonant two-photon ionization (R2PI), IR-UV, and UV-UV double resonance spectroscopic techniques. Density functional theory (DFT) calculations nicely corroborate the experimental results showing one weakly allowed IR-active band due to symmetric stretch of the N-H bonds and two strongly allowed IR-active bands due to two types of asymmetric stretches of the N-H bonds in the trimer. The present spectroscopic investigation demonstrates that the strength of the three N-H...π bound intermolecular interactions in the cyclic asymmetric trimer is quite different unlike the corresponding interactions of similar strength in a cyclic symmetric trimer.

Research paper thumbnail of Effect of acceptor heteroatoms on π-hydrogen bonding interactions: a study of indole···thiophene heterodimer in a supersonic jet

The Journal of chemical physics, Jan 7, 2012

Resonant two photon ionization (R2PI), IR-UV, and UV-UV double resonance spectroscopic techniques... more Resonant two photon ionization (R2PI), IR-UV, and UV-UV double resonance spectroscopic techniques combined with quantum chemistry calculations have been used to determine the structure of indole···thiophene dimer observed in a supersonic jet. With the help of combined experimental and theoretical IR spectra it has been found that the observed dimer has a N-H···π hydrogen bonded slanted T-shaped structure. The present study demonstrates the effect of heteroatoms present in the acceptors on the strength of the π-hydrogen bonding interactions. It was concluded by Sherrill and co-workers from their theoretical study of benzene···pyridine dimer that aromatic rings containing heteroatoms are poorest π-hydrogen bond acceptors [E. G. Hohenstein and C. D. Sherrill, J. Phys. Chem. A 113, 878 (2009)]. But the current spectroscopic investigation exhibits that five membered aromatic heterocycles are favorable π-hydrogen bond acceptors. In this study, it has also been shown that thiophene is a better π-hydrogen bond acceptor than furan. The present work has immense biological significance as indole is the chromophore of tryptophan residue in the proteins and thiophene derivatives have potential therapeutic applications. Thus, understanding the binding motif between indole and thiophene in the heterodimer studied in this work may help in designing efficient drugs.

Research paper thumbnail of Structure of indole···imidazole heterodimer in a supersonic jet: a gas phase study on the interaction between the aromatic side chains of tryptophan and histidine residues in proteins

The journal of physical chemistry. A, Jan 29, 2012

In this study, we have investigated the binding motifs between the aromatic side chains of trypto... more In this study, we have investigated the binding motifs between the aromatic side chains of tryptophan and histidine residues in proteins by studying the indole···imidazole heterodimer in a supersonic jet. Different spectroscopic techniques including resonant two-photon ionization (R2PI), UV-UV hole-burning, and resonant ion dip infrared (RIDIR) spectroscopy merged with quantum chemistry calculations have been used for this work. UV-UV hole-burning spectroscopy has been used to confirm the presence of only one structure of the dimer in the experiment. From the comparison of the RIDIR spectrum of the observed dimer with the theoretical IR spectra of different structures of the dimer, it is found that the dimer present in the experiment has a V-shaped structure held by N-H···N hydrogen bond, C-H···π, and weakly present π···π stacking interactions. The most important finding of the present study is that the noncovalent interactions present in the observed dimer have a close resemblance with those present between tryptophan and histidine residues in a nonfluorescent flavoprotein. The present spectroscopic investigation on the indole···imidazole dimer has also immense pharmaceutical significance as this imparts molecular level understanding about the binding motifs of the imidazole drugs with the indole chromophore present in proteins.

Research paper thumbnail of Screening and isolation of halophilic bacteria producing industrially important enzymes

Brazilian journal of microbiology : [publication of the Brazilian Society for Microbiology], 2012

Research paper thumbnail of Quality by Design approach to spray drying processing of crystalline nanosuspensions

International journal of pharmaceutics, Jan 10, 2014

Quality by Design (QbD) principles were explored to understand spray drying process for the conve... more Quality by Design (QbD) principles were explored to understand spray drying process for the conversion of liquid nanosuspensions into solid nano-crystalline dry powders using indomethacin as a model drug. The effects of critical process variables: inlet temperature, flow and aspiration rates on critical quality attributes (CQAs): particle size, moisture content, percent yield and crystallinity were investigated employing a full factorial design. A central cubic design was employed to generate the response surface for particle size and percent yield. Multiple linear regression analysis and ANOVA were employed to identify and estimate the effect of critical parameters, establish their relationship with CQAs, create design space and model the spray drying process. Inlet temperature was identified as the only significant factor (p value <0.05) to affect dry powder particle size. Higher inlet temperatures caused drug surface melting and hence aggregation of the dried nano-crystalline powders. Aspiration and flow rates were identified as significant factors affecting yield (p value <0.05). Higher yields were obtained at higher aspiration and lower flow rates. All formulations had less than 3% (w/w) moisture content. Formulations dried at higher inlet temperatures had lower moisture compared to those dried at lower inlet temperatures.

Research paper thumbnail of Formulation parameters of crystalline nanosuspensions on spray drying processing: a DoE approach

International journal of pharmaceutics, Jan 10, 2014

Nanocrystalline suspensions offer a promising approach to improve dissolution of BCS class II/IV ... more Nanocrystalline suspensions offer a promising approach to improve dissolution of BCS class II/IV compounds. Spray drying was utilized as a downstream process to improve the physical and chemical stability of dried nanocrystals. The effect of nanocrystalline suspension formulation variables on spray-drying processing was investigated. Naproxen and indomethacin nanocrystalline formulations were formulated with either Dowfax 2A1 (small molecule) or HPMC E15 (high molecular weight polymer) and spray drying was performed. A DoE approach was utilized to understand the effect of critical formulation variables, i.e. type of stabilizer, type of drug, ratio of drug-to-stabilizer and drug concentration. The powders were analyzed for particle size, moisture content, powder X-ray diffraction and dissolution. A dialysis sac adapter for USP apparatus II was developed which provided good discrimination between aggregated and non-aggregated formulations. Nanocrystal aggregation was dependent on the drug-to-stabilizer ratio. The glass transition temperature and the charge effect played a dominant role on spray-dried powder yield. Those formulations with low drug-to-excipient ratios were less aggregating and showed faster dissolution compared to those formulations with high drug-to-excipient ratios. All stable (less aggregated) formulations were subjected to accelerated storage stability testing. The Flory-Huggins interaction parameter (between drug and excipients) correlated with the spray-dried nanocrystal formulations stability.

Research paper thumbnail of Microbial mineralization of struvite: a promising process to overcome phosphate sequestering crisis

Water research, 2014

Due to extensive exploitation of non-renewable phosphate minerals, their natural reserves will ex... more Due to extensive exploitation of non-renewable phosphate minerals, their natural reserves will exhaust very soon. This necessitates looking for alternatives and an efficient methodology through which indispensable phosphorus can be harvested back. The current study was undertaken to explore the potential of a metallophilic bacterium Enterobacter sp. EMB19 for the recovery of phosphorus as phosphate rich mineral. A very low phosphate concentration strategy was adopted. The process led to the mineralization of phosphorus as homogeneous struvite crystals. For each gram of Epsom salt added, the cells effectively mineralized about 20% of the salt into struvite. The effect of different inorganic sources, culture profile and plausible mechanism involved in crystal formation was also explored. The synthesized struvite crystals typically possessed a prismatic crystal habit. The characterization and identification of the crystals were done using single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), energy dispersive X-ray analysis (EDAX) and fourier transform infrared (FTIR). The thermal characteristics were studied using thermo gravimetric analysis (TGA) and differential scanning calorimetric (DSC) processes. The synthesis of struvite by this bacterium seems to be a promising and viable strategy since it serves dual purpose (i) obtaining phosphorus and nitrogen rich fertilizer and (ii) conservation of natural phosphate reserves. This study is very significant in the sense that the process may be used for harvesting and synthesizing other valuable minerals. Also, it will provide new insights into phosphate biomineralization mechanisms.