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  1. Free, publicly-accessible full text available December 9, 2023
  2. Thermosensitive chitosan hydrogels—renewable, biocompatible materials—have many applications as injectable biomaterials for localized drug delivery in the treatment of a variety of diseases. To combat infections such as Staphylococcus aureus osteomyelitis, localized antibiotic delivery would allow for higher doses at the site of infection without the risks associated with traditional antibiotic regimens. Fosfomycin, a small antibiotic in its own class, was loaded into a chitosan hydrogel system with varied beta-glycerol phosphate (β-GP) and fosfomycin (FOS) concentrations. The purpose of this study was to elucidate the interactions between FOS and chitosan hydrogel. The Kirby Bauer assay revealed an unexpected concentration-dependent inhibition of S. aureus, with reduced efficacy at the high FOS concentration but only at the low β-GP concentration. No effect of FOS concentration was observed for the planktonic assay. Rheological testing revealed that increasing β-GP concentration increased the storage modulus while decreasing gelation temperature. NMR showed that FOS was removed from the liquid portion of the hydrogel by reaction over 12 h. SEM and FTIR confirmed gels degraded and released organophosphates over 5 days. This work provides insight into the physicochemical interactions between fosfomycin and chitosan hydrogel systems and informs selection of biomaterial components for improving infection treatment.
  3. Abstract

    Ionic liquids (ILs) have been shown to be effective transdermal penetrants of pharmaceutically active ingredients, including small molecules and proteins. The presence of water within ionic liquids has been demonstrated to play a critical role in  their structural organization on the molecular level. However, the impact of water on IL transdermal transport efficacy has yet to be investigated. Herein, a water concentration gradient (0%–100% v/v) is tested to evaluate  choline trans‐2‐octenoic (CA2OE)‐mediated transport of a hydrophilic model drug dextran (10000 Da) in an ex vivo porcine skin model.Compared to 2:1, 1:1, 1:4, and 1:5 ionic ratio formulations, 50% v/v CA2OE 1:2‐water evidences the greatest success at transporting dextran to the acceptor fluid. Physicochemical characterization (dynamic light scattering (DLS), scanning electron microscopy (SEM), optical density (O.D.), Fourier transform infrared spectroscopy (FTIR), fluorescent microscopy, and rheology) is conducted to test both bulk and nanoscale‐level CA2OE 1:2–water interactions. It is hypothesized that the presence of microemulsions in the CA2OE 1:2 75% v/v formulation accounted for the severely decreased transport compared to the 50%. It is thus critical to comprehensively consider interactions between IL components, co‐solvents, anddrug molecules when formulating ILs for transdermal transport applications.

    Free, publicly-accessible full text available November 3, 2023

    Mechanical properties including the failure behavior of physically assembled gels or physical gels are governed by their network structure. To investigate such behavior, we consider a physical gel system consisting of poly(styrene)‐poly(isoprene)‐poly(styrene)[PS‐PI‐PS] in mineral oil. In these gels, the endblock (PS) molecular weights are not significantly different, whereas, the midblock (PI) molecular weight has been varied such that we can access gels with and without midblock entanglement. Small angle X‐ray scattering data reveals that the gels are composed of collapsed PS aggregates connected by PI chains. The gelation temperature has been found to be a function of the endblock concentration. Tensile tests display stretch‐rate dependent modulus at high strain for the gels with midblock entanglement. Creep failure behavior has also been found to be influenced by the entanglement. Fracture experiments with predefined cracks show that the energy release rate scales linearly with the crack‐tip velocity for all gels considered here. In addition, increase of midblock chain length resulted in higher viscous dissipation leading to a higher energy release rate. The results provide an insight into how midblock entanglement can possibly affect the mechanical properties of physically assembled triblock copolymer gels in a midblock selective solvent. © 2019 Wiley Periodicals,more »Inc. J. Polym. Sci., Part B: Polym. Phys.2019,57, 1014–1026

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