Piyali Basak

Sustained release of antibiotic from polyurethane coated implant materials.

Implant associated infections are of increasing importance. To minimize the risks of implant-associated infections recent biomedical strategies have led to the modification of the medical device surfaces. The modifications are in the terms of increasing surface biocompatibility and decreasing bacterial adherence, which can be achieved by applying a coating of biocompatible polymer onto the said surfaces. Entrapping anti-infective agents in a polymer matrix provides an approach to kill bacteria and combat the possibility of any residual infection. We have prepared a biodegradable polyester urethane coat for implant materials, which have the property to accommodate antibiotics within itself. These polyurethane coating materials were characterized by FTIR spectroscopy, swelling property in SBF, gravimetric analysis, drug release, and biocompatibility study. Drug release rates, bacterial colonization and morphological features were also evaluated to predict and understand the antimicrobial activity of these delivery systems. Drug release characteristics were investigated and the physico-chemical mechanisms of the delivery were discussed. Results suggest that the polyester urethane can be used as an implant coating material and can be used as a matrix for the sustained delivery of anti-infective agent.

Stearic acid based oleogels: a study on the molecular, thermal and mechanical properties.

Stearic acid and its derivatives have been used as gelators in food and pharmaceutical gel formulations. However, the mechanism pertaining to the stearic acid based gelation has not been deciphered yet. Keeping that in mind, we investigated the role of stearic acid on physic-chemical properties of oleogel. For this purpose, two different oil (sesame oil and soy bean oil) formulations/oleogels were prepared. In depth analysis of gel kinetics, gel microstructure, molecular interactions, thermal and mechanical behaviors of the oleogels were done. The properties of the oleogels were dependent on the type of the vegetable oil used and the concentration of the stearic acid. Avrami analysis of DSC thermograms indicated that heterogeneous nucleation was coupled with the one-dimensional growth of gelator fibers as the key phenomenon in the formation of oleogels. Viscoelastic and pseudoplastic nature of the oleogels was analyzed in-depth by fitting the stress relaxation data in modified Pelegs model and rheological studies, respectively. Textural studies have revealed that the coexistence of hydrogen bond dissipation and formation of new bonds is possible under stress conditions in the physical oleogels.

Poly (vinyl alcohol) hydrogels for pH dependent colon targeted drug delivery

Oral drug administration is convenient with pH dependent drug delivery system since the drug has to pass through different pH environments in gastro intestinal (GI) tract. The pH dependent swelling/shrinking behavior of hydrogel drug carrier controls the drug release without affecting the function of drug. pH dependent hydrogels of poly (vinyl alcohol) (PVA) were prepared by cross linking with maleic acid (MA). The hydrogels were characterized by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, DSC, porosimetry, SEM, TEM, biocompatibility study and by measuring their swelling behavior in water, simulated gastric fluid (SGF) and intestinal fluid (SIF). Swelling of the hydrogels was found to be highest in SIF (pH: 7.5) and lowest in SGF (pH: 1.2) resembling that required in colon targeted drug delivery systems. Since the swelling behavior of the gel is pH dependent, these hydrogels were studied for colon targeted drug delivery in an in-vitro set-up resembling the condition of GI tract. The ratio of PVA and MA in the hydrogel was varied to study the effect on the drug diffusion rate. For drug delivery study, vitamin B12 and salicylic acid were used as model drugs. The hydrogel, loaded with model drugs vitamin B12 and salicylic acid also demonstrated colon specific drug release with a relatively higher drug release in SIF (pH: 7.5) than that in SGF (pH: 1.2).

Surface Cross-Linked Poly (Vinyl Alcohol) Hydrogel for Colon Targeted Drug Release

A series of surface cross-linked PVA hydrogels (previously bulk cross-linked with maleic anhydride) were prepared for different cross-linker (glutaraldehyde) concentration. FTIR-ATR study revealed the cross-linking reaction. Surface cross-linking results in contraction of pores and increase in hydrophobicity, pore tortuosity around the surface of the membrane. As a result swelling, drug release decreases with increasing glutaraldehyde concentration. After surface cross-linking swelling of the hydrogels in simulated gastric fluid (SGF) further decreased to attain half of the value as observed for only bulk cross-linked membranes. Surface cross-linking has improved the colon-targeted release characteristics of the drugs from the PVA hydrogels.

Stearate organogel-gelatin hydrogel based bigels: physicochemical, thermal, mechanical characterizations and in vitro drug delivery applications.

Over the past decade, researchers have been trying to develop alternative gel based formulations in comparison to the traditional hydrogels and emulgels. In this perspective, bigels were synthesized by mixing gelatin hydrogel and stearic acid based organogel by hot emulsification method. Two types of bigels were synthesized using sesame oil and soy bean oil based stearate organogels. Gelatin based emulgels prepared using sesame oil and soy bean oil were used as the controls. Microscopic studies revealed that the bigels contained aggregates of droplets, whereas, emulgels showed dispersed droplets within the continuum phase. The emulgels showed higher amount of leaching of oils, whereas, the leaching of the internal phase was negligible from the bigels. Presence of organogel matrix within the bigels was confirmed by XRD, FTIR and DSC methods. Bigels showed higher mucoadhesive and mechanical properties compared to emulgels. Cyclic creep-recovery and stress relaxation studies confirmed the viscoelastic nature of the formulations. Four elemental Burgers model was employed to analyze the cyclic creep-recovery data. Cyclic creep-recovery studies suggested that the deformation of the bigels were lower due to the presence of the organogels within its structure. The formulations showed almost 100% recovery after the creep stage and can be explained by the higher elastic nature of the formulations. Stress relaxation study showed that the relaxation time was higher in the emulgels as compared to the bigels. Also, the % relaxation was higher in emulgels suggesting its fluid dominant nature. The in vitro biocompatibility of the bigels was checked using human epidermal keratinocyte cell line (HaCaT). Both emulgels and bigels were biocompatible in nature. The in vitro drug (ciprofloxacin) release behavior indicated non-Fickian diffusion of the drug from the matrices. The drug release showed good antimicrobial effect against Escherichia coli. Based on the results, it was concluded that the developed bigels may have huge potential to be used as alternatives to emulgels.

Biodegradation of Polyethylene Glycol-Based Polyether Urethanes

The biodegradation of polyethylene glycol (PEG of different molecular weights) based polyether urethanes were studied under soil burial condition for 180 days under indoor normal hydrothermal conditions and by cultured bacteria (Pseudomonas aeruginosa) for 30 days at 37°C. The biodegradation was estimated from the weight loss, tensile strength, ultimate elongation and also by FTIR spectroscopy, optical, scanning electron microscopy. The weight loss and losses in tensile strength, elongation at break of the polymer is maximum in case of PUPEG4000 and minimum in case of PUPEG200 (both in case of soil burial condition and in cultured bacteria).

Synthesis and characterization of polyvinyl alcohol hydrogel

Ability of the hydrogels to absorb and retain fluids and bioactive materials made them the centre of attraction for researchers. Physiochemical properties (e.g. swelling, ionic strength etc) of a hydrogel can be changed by varying the concentration of crosslinker and by crosslinker itself. These changes are exploited for various purposes such as controlled and sustained drug delivery systems, biosensors etc. We have crosslinked polyvinyl alcohol chemically with different acid crosslinkers such as maleic acid, maleic anhydride, citric acid and tartaric acid. Effect of crosslinking ratio on swelling of hydrogels in different pH solution including water has been studied. Besides that FTIR of the hydrogels reveal the chemical changes during crosslinking. Biocompatibility of hydrogels was evaluated through MTT assay.

Synthesis of gelatin nano/submicron particles by binary nonsolvent aided coacervation (BNAC) method.

A newly developed modified coacervation method is utilized to synthesize gelatin nano/submicron particles (GN/SPs) as a drug carrier. Binary nonsolvent aided coacervation (BNAC) method is a modified single step coacervation method, which has yielded approximately a threefold lower particle size and higher average yield in terms of weight percentage of around 94% in comparison to the conventional phase separation methods. In this study 0.5% (w/v) gelatin aqueous solution with a binary nonsolvent system of acetone and ethanol was used. Nanoparticle synthesis was optimized with respect to nonsolvent system type and pH. pH7 has resulted a minimum particle size of 55.67 (±43.74) nm in anhydrous medium along with a swollen particle size of 776nm (±38.57) in aqueous medium with a zeta potential of (-16.3±3.51) mV in aqueous medium. Swelling ratio of 13.95 confirms the crosslinked hydrogel nature of the particles. Furthermore, drug loading efficiency of the gelatin particles prepared at 7pH was observed with nitrofurazone as the model drug. Results of drug release study indicate the potential use of GN/SPs as drug loading matrix for wound management such as burn wound management.

Encapsulation of Sorbitan Ester-Based Organogels in Alginate Microparticles

Leaching of the internal apolar phase from the biopolymeric microparticles during storage is a great concern as it undoes the beneficial effects of encapsulation. In this paper, a novel formulation was prepared by encapsulating the sunflower oil-based organogels in alginate microparticles. Salicylic acid and metronidazole were used as the model drugs. The microparticles were prepared by double emulsion methodology. Physico-chemical characterization of the microparticles was done by microscopy, FTIR, XRD, and DSC studies. Oil leaching studies, biocompatibility, mucoadhesivity, in vitro drug release, and the antimicrobial efficiency of the microparticles were also performed. The microparticles were found to be spherical in shape. Gelation of the sunflower oil prevented leaching of the internal phase from the microparticles. Release of drugs from the microparticles followed Fickian kinetics and non-Fickian kinetics in gastric and intestinal environments, respectively. Microparticles showed good antimicrobial activity against both Gram-positive (Bacillus subtilis) and Gram-negative (Escherichia coli) bacteria. The results suggested that the developed formulations hold promise to carry oils without leakage of the internal phase. Encapsulation of organogels within the microparticles has improved the drug entrapment efficiency and improved characteristics for controlled delivery applications.

Biodegradation of Polyester Urethane in Simulated Body Fluid

Biodegradation of the polyester urethane (PEU) has been performed in simulated body fluid (SBF) at 37°C for an extended period of time. Changes in physicochemical properties and toxic effects of polymer matrix as a result of degradation have been evaluated. Effect of soft segment to hard segment ratio on the degradation rate of PEU matrix has also been assessed. Biocompatibility testing of the degradation medium has been performed. This biodegradable coating may be used as coating on biomaterials, including implants as a matrix for entrapping antibiotics. Entrapped antibiotics would release in a control manner to prevent infection in biomaterials.