Vinay K. Singh

Guar gum and sesame oil based novel bigels for controlled drug delivery

Bigels are novel semi-solid formulations which have been drawing attention of many research scientists due to their numerous advantages over the conventional gels. The objective of this study was to develop and characterize novel bigels by mixing guar gum hydrogel and sorbitan monostearate-sesame oil based organogel for controlled drug delivery applications. The confocal microscopy suggested the existence of both aqueous and oil phases together as bigel. Micro-scale deformation (viscometric) analysis in conjugation with macro-scale deformation studies suggested shear-thinning and viscoelastic nature of the bigels. Thermal study suggested an increase in thermal stability with the increase in organogel proportion in the bigels. The developed bigels were biocompatible in nature. The in vitro drug release study showed that the release of ciprofloxacin (lipophilic drug) increased with a decrease in the organogel content. Further analysis showed that the drug release from all the bigels followed zero order diffusion kinetics which is desirable for a controlled release system. The drug loaded gels showed good antimicrobial efficiency against Bacillus subtilis. In conclusion, the developed bigels may be tried as matrices for topical drug delivery.

Preparation and characterization of novel carbopol based bigels for topical delivery of metronidazole for the treatment of bacterial vaginosis

The current study reports the development of bigels using sorbitan monostearate-sesame oil organogel and carbopol 934 hydrogel. The microstructures and physicochemical properties were investigated by microscopy, viscosity measurement, mechanical analysis and differential scanning calorimetry analysis. Fluorescence microscopy confirmed the formation of oil-in-water type of emulsion gel. There was an increase in the strength of the bigels as the proportion of the organogel was increased in the bigels. The developed bigels showed shear-thinning flow behavior. The stress relaxation study suggested viscoelastic nature of the bigels. The developed bigels were biocompatible. Metronidazole, drug of choice for the treatment of bacterial vaginosis, loaded bigels showed diffusion-mediated drug release. The drug loaded gels showed good antimicrobial efficiency against Escherichia coli. In gist, the developed bigels may be used as delivery vehicles for the vaginal delivery of the drugs.

Olive oil based novel thermo-reversible emulsion hydrogels for controlled delivery applications

Gels have been considered as a popular mode of delivering medicament for the treatment of sexually transmitted diseases (STDs) (e.g. human immunodeficiency virus, bacterial vaginosis, epididymitis, human papillomavirus infection and condylomata acuminata etc.). The present study discusses the development of novel olive oil based emulsion hydrogels (EHs) using sorbitan monopalmitate as the structuring agent. The developed EHs may be tried as drug delivery vehicle for the treatment of STDs. The formation of EHs was confirmed by fluorescence and confocal microscopy. FTIR studies suggested intermolecular hydrogen bonding amongst the components of the EHs. X-ray diffraction study suggested the amorphous nature of the EHs. The developed EHs have shown non-Newtonian flow behavior. The EHs were found to be biocompatible. The formulations were able to effectively deliver two model antimicrobial drugs (e.g. ciprofloxacin and metronidazole), commonly used in the treatment of the STDs.

Hydrogel-Based Controlled Release Formulations: Designing Considerations, Characterization Techniques and Applications

Hydrogels have evolved over the last decade as materials of choice in varied biomedical applications. This is associated with the inherent biocompatible nature of the hydrogels. The modulation of the properties of the hydrogels is easily possible due to the availability of polymers of varied chemistry and physical properties. This review discusses the pharmaceutical aspects of the controlled release of bioactive agents from hydrogel-based formulations.

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.

Development and Characterization of Sorbitan Monostearate and Sesame Oil-Based Organogels for Topical Delivery of Antimicrobials

The current study explains the development of sorbitan monostearate and sesame oil-based organogels for topical drug delivery. The organogels were prepared by dissolving sorbitan monostearate in sesame oil (70°C). Metronidazole was used as a model antimicrobial. The formulations were characterized using phase contrast microscopy, infrared spectroscopy, viscosity, mechanical test, and differential scanning calorimetry. Phase contrast microscopy showed the presence of needle-shaped crystals in the organogel matrix. The length of the crystals increased with the increase in the sorbitan monostearate concentration. XRD studies confirmed the amorphous nature of the organogels. Viscosity study demonstrated shear thinning behavior of the organogels. The viscosity and the mechanical properties of the organogels increased linearly with the increase in the sorbitan monostearate concentration. Stress relaxation study confirmed the viscoelastic nature of the organogels. The organogels were biocompatible. Metronidazole-loaded organogels were examined for their controlled release applications. The release of the drug followed zero-order release kinetics. The drug-loaded organogels showed almost similar antimicrobial activity against Escherichia coli when compared to the commercially available Metrogyl® gel. In gist, it can be proposed that the developed organogels had sufficient properties to be used for controlled delivery of drugs.

Gelatin–PEG based metronidazole-loaded vaginal delivery systems: preparation, characterization and in vitro antimicrobial efficiency

AbstractnBacterial vaginosis (BV) is a condition often associated with the overgrowth of pathogenic microbes with a subsequent decrease in lactic acid producing bacteria in vagina. BV is predominant in reproductive women. It has been reported not only to cause pre-term labor but is also one of the major causes of fetal morbidity and mortality. There is an increase in the vaginal discharge in BV. Due to this reason, the locally applied drug formulations are quickly washed off. It is expected that the mucoadhesive delivery vehicles will improve the bioavailability of the drug for prolonged periods. Keeping this in mind, gelatin/PEG based composite hydrogels were developed and characterized as vaginal delivery systems for the treatment of BV. The hydrogels were prepared by varying the concentration of gelatin and PEG. The hydrogels were thoroughly characterized using SEM, FTIR, DSC, and impedance spectroscopy techniques and swelling, mucoadhesive, and texture analysis studies. The in vitro release behavior of metronidazole from the hydrogels was analyzed in-depth. The antimicrobial efficiency of the MZ-loaded hydrogels was tested against E. coli, occurrence of which is predominant in BV. The properties of the hydrogels were found to be dependent on the composition of the hydrogels. The hydrogels were found to be mucoadhesive and the MZ-loaded hydrogels have shown effective antimicrobial activity against E. coli. Based on the preliminary studies, the composite hydrogels were found to be suitable for controlled drug delivery for vaginal applications.n

Development of soy lecithin based novel self-assembled emulsion hydrogels.

The current study reports the development and characterization of soy lecithin based novel self-assembled emulsion hydrogels. Sesame oil was used as the representative oil phase. Emulsion gels were formed when the concentration of soy lecithin was >40% w/w. Metronidazole was used as the model drug for the drug release and the antimicrobial tests. Microscopic study showed the apolar dispersed phase in an aqueous continuum phase, suggesting the formation of emulsion hydrogels. FTIR study indicated the formation of intermolecular hydrogen bonding, whereas, the XRD study indicated predominantly amorphous nature of the emulsion gels. Composition dependent mechanical and drug release properties of the emulsion gels were observed. In-depth analyses of the mechanical studies were done using Ostwald-de Waele power-law, Kohlrausch and Weichert models, whereas, the drug release profiles were modeled using Korsmeyer-Peppas and Peppas-Sahlin models. The mechanical analyses indicated viscoelastic nature of the emulsion gels. The release of the drug from the emulsion gels was diffusion mediated. The drug loaded emulsion gels showed good antimicrobial activity. The biocompatibility test using HaCaT cells (human keratinocytes) suggested biocompatibility of the emulsion gels.

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.

Effect of Processed Starches on the Properties of Gelatin-based Physical Hydrogels: Characterization, in vitro Drug Release and Antimicrobial Studies

Sols of starches have been reported to form phase-separated systems when mixed with the gelatin solution. This has been attributed to the thermodynamic incompatibility of the starch-gelatin systems. The current work has been designed to study the effect of processed starches on the properties of the gelatin-starch based phase-separated physical hydrogels. The hydrogels were prepared using corn starch, soluble starch and boiled starch. The hydrogels were characterized by FTIR spectroscopy, thermal studies, textural studies and impedance spectroscopy. Metronidazole was incorporated within the hydrogels. The drug-loaded gels have shown good antimicrobial activity against Escherichia coli and Bacillus subtilis.