Dharmesh R. Chejara

A composite chitosan-gelatin bi-layered, biomimetic macroporous scaffold for blood vessel tissue engineering

A composite chitosan-gelatin macroporous hydrogel-based scaffold with bi-layered tubular architecture was engineered by solvent casting-co-particulate leaching. The scaffold constituted an inner macroporous layer concealed by a non-porous outer layer mimicking the 3D matrix of blood vessels with cellular adhesion and proliferation. The scaffold was evaluated for its morphological, physicochemical, physicomechanical and biodurability properties employing SEM, FTIR, DSC, XRD, porositometry, rheology and texture analysis. The fluid uptake and biodegradation in the presence of lysozymes was also investigated. Cellular attachment and proliferation was analysed using human dermal fibroblasts (HDF-a) seeded onto the scaffold and evaluated by MTT assay, SEM, and confocal microscopy. Results demonstrated that the scaffold had a desirable tensile strength=95.81±11kPa, elongation at break 112.5±13%, porosity 82% and pores between 100 and 230μm, 50% in vitro biodegradation at day 16 and proliferated fibroblasts over 20 days. These results demonstrate that scaffold may be an excellent tubular archetype for blood vessel tissue engineering.

Design of a novel crosslinked HEC-PAA porous hydrogel composite for dissolution rate and solubility enhancement of efavirenz.

The purpose of this research was to synthesize, characterize and evaluate a Crosslinked Hydrogel Composite (CHC) as a new carrier for improving the solubility of the anti-HIV drug, efavirenz. The CHC was prepared by physical blending of hydroxyethylcellulose (HEC) with poly(acrylic acid) (PAA) (1:1) in the presence of poly(vinyl alcohol) (PVA) (as a crosslinker) (1:5) under lyophilization. Efavirenz was loaded in situ into the CHC in varying proportions (200-600 mg). The CHC demonstrated impressive rheological properties (dynamic viscosity=6053 mPa; 500 s(-1)) and tensile strength (2.5 mPa) compared with the native polymers (HEC and PAA). The physicochemical and thermal behavior also confirmed that the CHC was compatible with efavirenz. The incorporation of efavirenz in the CHC increased the surface area (4.4489-8.4948 m(2)/g) and pore volume (469.547-776.916Å) of the hydrogel system which was confirmed by SEM imagery and BET surface area measurements. The solubility of efavirenz was significantly enhanced (150 times) in a sustained release manner over 24h as affirmed by the in vitro drug release studies. The hydration medium provided by the CHC network played a pivotal role in improving the efavirenz solubility via increasing hydrogen bonding as proved by the zeta potential measurements (-18.0 to +0.10). The CHC may be a promising alternative as an oral formulation for the delivery of efavirenz with enhanced solubility.

Microwave-assisted facile synthesis of a new tri-block chitosan conjugate with improved mucoadhesion

A new chitosan-based tri-block conjugate, O-PEG-chitosan-N-cysteine was synthesized using microwave irradiation. For synthesis of this derivative, chitosan was modified to a PEG-chitosan conjugate followed by PEG-chitosan-cysteine using 6-O PEGylation and 2-N-thiolation, respectively. The synthesized derivative was characterized using various analytical techniques such as FT-IR and (1)H NMR spectroscopy. The conjugate was also analyzed for its biochemical, biodegradation and mucoadhesive properties. The modified chitosan conjugate exhibited improved mucoadhesion behavior (14.0 h) with greater biodegradation compared to the parent polymer (6.3h). The in silico modeling corroborated with the in vitro study demonstrating a stable complex between mucin and O-PEG-chitosan-N-cysteine conjugate (ΔE=-60.100 kcal/mol) compared to mucin and chitosan conjugate. The synthesis proposed herein, involves the use of microwave irradiation which causes a substantial reduction in the reaction time (approximately 2.30 h) compared to conventional method (35 h).

A bio-injectable algin-aminocaproic acid thixogel with tri-stimuli responsiveness.

In this article a novel bio-injectable algin-aminocaproic acid (Alg-ACA) tri-stimuli responsive thixogel system is reported. The designed soft thixotrophic hydrogel (thixogel) was characterized using various analytical techniques such as FT-IR, NMR, SEM, AFM and DSC. The soft thixogel system was further investigated for stress responsiveness using different rheological studies which confirmed the thixotropic nature of the gel [Thixotropic area (Ar) of Alg-ACA (1:0.5), Alg-ACA (1:1) and Alg-ACA (1:2), were 23.5%, 43.1%, and 27.59%, respectively, which were higher than that of Na-Alg (2.08%)]. The thixogel also demonstrated temperature and ultrasonication responsiveness. This tri-stimuli responsive soft thixogel system was rendered flowable (fluid) on applying the described physical stimuli and recovered its rigid gel structure upon removal of the applied stimuli. This approach of synthesizing a thixogels may be applicable to a broad variety of other natural polymers and has the potential for use in biomedical applications.

Intestinal Targeting of Ganciclovir Release Employing a Novel HEC-PAA Blended Lyomatrix

A hydroxyethylcellulose-poly(acrylic acid) (HEC-PAA) lyomatrix was developed for ganciclovir (GCV) intestine targeting to overcome its undesirable degradation in the stomach. GCV was encapsulated within the HEC-PAA lyomatrix prepared by lyophilization. Conventional tablets were also prepared with identical GCV concentrations in order to compare the GCV release behavior from the lyomatrix and tablets. GCV incorporation (75.12%) was confirmed using FTIR, DSC, and TGA. The effect of GCV loading on the microstructure properties of the lyomatrix was evaluated by SEM, AFM, and BET surface area measurements. The in vitro drug release study showed steady and rapid release profiles from the GCV-loaded lyomatrix compared with the tablet formulation at identical pH values. Minimum GCV release was observed at acidic pH (≤40%) and maximum release occurred at intestinal pH values (≥90%) proving the intestinal targeting ability of the lyomatrix. Kinetic modeling revealed that the GCV-loaded lyomatrix exhibited zero-order release kinetics (nu2009=u20091), while the tablets were best described via the Peppas model. Textural analysis highlighted enhanced matrix resilience and rigidity gradient (12.5%, 20xa0Pa) for the GCV-loaded lyomatrix compared to the pure (7%, 9.5xa0Pa) HEC-PAA lyomatrix. Bench-top MRI imaging was used to confirm the mechanism of GCV release behavior by monitoring the swelling and erosion rates. The swelling and erosion rate of the tablets was not sufficient to achieve rapid zero-order GCV release as with the lyomatrix. These combined results suggest that the HEC-PAA lyomatrix may be suitable for GCV intestinal targeting after oral administration.

Rethinking Drug Discovery and Targeting After the Genomic Revolution

The study of the entire genome provides for a complete and better understanding of functional relationship of different genes, genes coding for protein and other regulating sequences, as phenotypic expression is a complex interplay of these and much more. The genomic revolution, in its practically applicable form, is yet to arrive. This genomic sequence information for various organisms, including humans, is now influencing drug discovery which provides opportunity for researchers to develop new drugs/medicines. Major challenges in new drug discovery are to identify targets that are essential for the organism to survive. Several latest technologies have allowed us to understand the mechanisms of disease with respect to biological system concepts, and therefore therapeutic intervention has been developed using informative database and technologies. Therefore, with developing therapeutic interventions, it is imperative for pharmaceutical researchers to rethink about new drug discovery and targeting employing information obtained from the genomic revolution. The chapter is summarized with an outline on the brief introduction on genomic revolution followed by changing scenario in drug discovery and targeting and paradigm shift in the treatment of certain major conditions such as cancer, cardiovascular diseases and tuberculosis in postgenomic era.

Neurodegenerative Disease Conditions and Genomic Treatment for Better Health

Neurodegenerative diseases are genetic and/or sporadic disease conditions characterized by progressive nervous system dysfunction involving the atrophy of central or peripheral nervous. The neurodegenerative diseases (NDs) like Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD), and amyotrophic lateral sclerosis (ALS) are responsible for more than 1% deaths and more than 2% disabilities of total world population. These NDs also impart huge socioeconomical burden on families of patients. NDs involve complex etiology with different genetic and environmental factors. The understanding of the etiology may help therapists to develop new effective symptomatic and preventive (genetic) treatments for NDs. The development in Human Genome Project helping to detect the genetic mutations causing HDs and advancement in gene and genome therapy are being implemented to correct these mutations. In this chapter, Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD), and amyotrophic lateral sclerosis (ALS) are discussed in detail for their pathophysiology, etiology, and latest symptomatic and preventive treatment. In preventive treatment, the latest achievements of the gene and genomic therapies are discussed.

Synthesis and biocompatibility of dual-responsive thermosonic injectable organogels based on crosslinked N -(isopropyl acrylamide) for tumour microenvironment targeting

A series of three dual-responsive thermosonic (thermo- and ultrasound-responsive) injectable organogels (TIOs) based on crosslinked N-(isopropyl acrylamide) (NIPAM) bearing biocompatible polymeric constituents were investigated for strong gelation in response to tumour temperature, and sol-like fluid gel formation upon the application of an ultrasonic stimulus. A time-efficient free radical polymerisation reaction of ˂15u202fmin resulted in TIO formation. Moreover, the formulation of the TIOs integrated green chemistry principles to ensure enhanced biocompatibility. Fourier Transform Infrared (FTIR) spectral analysis revealed the presence of new molecular vibrations at 847 and 771u202fcm-1 (CH deformation), which were indicative of the functionalisation of the NIPAM backbone with hydrophobic and ultrasound-responsive aromatic moieties. Thermo- and ultrasound-response analysis and rheological analysis demonstrated that the TIOs displayed a temperature-induced transition to a strong highly-structured gel, and an ultrasound-triggered increase in gel flowability dependant on the composition of the formulation. Cell proliferation studies were undertaken for the TIOs, which verified that the designed TIOs were all non-cytotoxic and promoted cell proliferation over 1, 3, and 5u202fday intervals. The rational design and formulation of a biocompatible injectable in-situ depot drug delivery system for ultimate application in tumour targeting was successfully achieved and warrant further investigation.

Customized Peptide Biomaterial Synthesis via an Environment-Reliant Auto-Programmer Stigmergic Approach

Stigmergy, a form of self-organization, was employed here to engineer a self-organizing peptide capable of forming a nano- or micro-structure and that can potentially be used in various drug delivery and biomedical applications. These self-assembling peptides exhibit several desirable qualities for drug delivery, tissue engineering, cosmetics, antibiotics, food science, and biomedical surface engineering. In this study, peptide biomaterial synthesis was carried out using an environment-reliant auto-programmer stigmergic approach. A model protein, α-gliadin (31, 36, and 38 kD), was forced to attain a primary structure with free –SH groups and broken down enzymatically into smaller fragments using chymotrypsin. This breakdown was carried out at different environment conditions (37 and 50 °C), and the fragments were allowed to self-organize at these temperatures. The new peptides so formed diverged according to the environmental conditions. Interestingly, two peptides (with molecular weights of 13.8 and 11.8 kD) were isolated when the reaction temperature was maintained at 50 °C, while four peptides with molecular weights of 54, 51, 13.8, and 12.8 kD were obtained when the reaction was conducted at 37 °C. Thus, at a higher temperature (50 °C), the peptides formed, compared to the original protein, had lower molecular weights, whereas, at a lower temperature (37 °C), two peptides had higher molecular weights and two had lower molecular weights.

Synthesis and Evaluation of a Sodium Alginate-4-Aminosalicylic Acid Based Microporous Hydrogel for Potential Viscosupplementation for Joint Injuries and Arthritis-Induced Conditions

A microporous hydrogel was developed using sodium alginate (alg) and 4-aminosalicylic acid (4-ASA). The synthesized hydrogel was characterized using various analytical techniques such as Fourier transform infrared spectroscopy (FTIR), Carbon-13 nuclear magnetic resonance (13C-NMR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). Additonal carboxyl and hydroxyl functional groups of 4-ASA provided significant lubrication and stress-triggered sol-gel transition to the conjugated hydrogel. In addition, cytotoxicity analysis was undertaken on the conjugated hydrogel using human dermal fibroblast-adult (HDFa) cells, displaying non-toxic characteristics. Drug release profiles displaying 49.6% in the first 8 h and 97.5% within 72 h, similar to the native polymer (42.8% in first 8 h and 90.1% within 72 h). Under applied external stimuli, the modified hydrogel displayed significant gelling properties and structure deformation/recovery behaviour, confirmed using rheological evaluation (viscosity and thixotropic area of 8095.3 mPas and 26.23%, respectively). The modified hydrogel, thus, offers great possibility for designing smart synovial fluids as a biomimetic aqueous lubricant for joint-related injuries and arthritis-induced conditions. In addtion, the combination of thixotropy, non-toxicity, and drug release capabilities enables potential viscosupplementation for clinical application.