Assessment of multicomponent hydrogel scaffolds of poly(acrylic acid-2-hydroxy ethyl methacrylate)/gelatin for tissue engineering applications

The article describes the design of the multicomponent hydrogel system of poly(acrylic acid-HEMA)/gelatin for tissue engineering application. Derivative of polycaprolactone-diol (polycaprolactone diacrylate (PCL-DAr)) was used to cross-link acrylate monomers whereas gelatin was kept free for cell proliferation. Epigallocatechin gallate (EGCG), an anti-oxidant phytochemical, was loaded by diffusion method. Its in vitro release study in PBS (pH 6.5) at 37 ± 0.2°C (75 rpm) revealed a sustained release profile upto 20 days. Fitting of drug release data in Korsmeyer-Peppas model equation revealed probable release mechanism through the value of release coefficient ( n), which was found to depend on formulations composition. Drug-polymer interaction, thermal behavior, and surface morphology were investigated by attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopic (SEM). Swelling behavior of hydrogel in PBS (pH 6.5 and 7.4, 0.2 M) and in distilled water was found to increase with increasing AAc/HEMA ratio. Compression modulus decreased from 203 ± 3.7 KPa to 11.6 ± 1.1KPa, at 30% strain, whereas displacement values significantly increased from 3.2 ± 0.2 to 4.7 ± 0.6 mm at 20 N force ( p < 0.05), with increasing AAc/HEMA ratio. Percentage cell viability was analyzed using indirect 3-[4, 5-dimethylthiazolyl-2]-2,5-diphenyltetrazo-liumbromide (MTT) assay with fibroblast L929 cells; showed ≥92.3% cell viability after 24 h incubation. Cell proliferation on the scaffold surface was found to increase with incorporation of HEMA in P(AAc)/G cross-linked hydrogel matrix upto a certain extent. These biocompatible, elastic, and swellable hydrogels can serve as a matrix for drug delivery and tissue engineering applications.

Biophysical assessment of DC iontophoresis and current density on transdermal permeation of methotrexate

INTRODUCTION

The effect of DC iontophoresis using low (0.2 mA/cm(2)) and high current density (0.5 mA/cm(2)) on transdermal permeation of methotrexate loaded into polyacrylamide hydrogel patch was investigated.

RESULTS

Flux of 20.57 ± 1.02 μg/cm(2)/h and 36.8 ± 2.21 μg/cm(2)/h was achieved with low and high current density DC iontophoresis, respectively. Attenuated total reflectance-Fourier Transform infrared (ATR-FTIR) spectra and microscopic studies of the treated skin samples supported the permeation results. A greater decrease in the peak height of asymmetric, symmetric C-H stretching vibration and ester peak was noticed with 0.5 mA/cm(2) current density as compared to 0.2 mA/cm(2) current density samples. Furthermore, an increase in the ratio of amide I and amide II bands from 2.6 to 11 with increase in current density was noticed, thus indicating that hydration levels are associated with iontophoresis and play an important role in increasing the drug permeation. Scanning electron microscopy revealed increase in pore size of the hair follicles. Light microscopy studies of the skin samples treated with low current density DC iontophoresis demonstrated epidermal thinning and focal disruptions, spongiosis and appendageal dilatations. With higher current density, disruption of epidermis in almost half of the sectioned area, loss of appendages and fractured collagen in the dermis was noticed. Moreover, the reversibility studies conducted in vivo on mice revealed that the recovery process had started within 24 h and is complete in 48 h for lower current density treated animals. However, the histological changes associated with 0.5 mA/cm(2) current density were not reversible in 48 h and edema, appendageal dilatations along with focal disruption of epidermis persisted.

CONCLUSION

Hence our study suggests that high density current is not well-tolerated by the skin.

Investigation on the synergistic effect of a combination of chemical enhancers and modulated iontophoresis for transdermal delivery of insulin

PURPOSE

The main objective of this study was to assess the flux enhancement of insulin transdermally by utilizing a complex of chemical enhancers in combination with modulated iontophoresis.

METHODS

The experiments were performed on porcine epidermis model under three different circumstances, namely, (a) 1-hour modulated iontophoresis alone; (b) pretreatment with vehicle and chemical enhancer combinations and (c) combination of (a) and (b). The mechanism of action of the enhancers was studied using infra-red spectra by derivative and curve-fitting techniques and Confocal laser scanning microscopy. The efficacy of the optimized combination was tested in vivo in streptozocin-diabetic Wistar rats.

RESULTS

A blend of 1,8 cineole, oleic acid and sodium deoxycholate in propylene glycol : ethanol (7:3) resulted in 45% enhancement, when permeation was performed in combination with iontophoresis as compared to the latter alone. In-depth analysis of infra-red spectra revealed that each of the enhancers acted differentially on lipid-protein domains of the stratum corneum thereby supporting the observed synergism. Movement of fluorescently labeled insulin depicted highlighted follicular regions and paracellular accumulation of the probe after iontophoresis and chemical enhancer treatment respectively. Presence of the fluorescent peptide in these regions 4 hour after treatment with the combination reinforced the results of the permeation studies. Finally the combination of modulated iontophoresis with chemical enhancer blend resulted in lowering of blood glucose for 8 hour in vivo.

CONCLUSIONS

The study proved the applicability of modulated iontophoresis with chemical pretreatment in delivering insulin transdermally.

Evaluation of folate conjugated pegylated thermosensitive magnetic nanocomposites for tumor imaging and therapy

Superparamagnetic iron oxide nanoparticles (SPIONs) have been receiving great attention lately in biomedical applications, such as in magnetic resonance imaging and drug delivery. However, their systemic administration still remains a challenge due to their hydrophobic nature with instances of aggregation leading to fast reticuloendothelial system (RES) uptake. In this study, magnetic nanocomposites with thermosensitive polymer have been investigated. Random polymers of N-isopropylacrylamide (NIPAAM), acrylic acid (AA) and PEGMA have been coated on SPIONs followed by conjugation with folic acid. Particles of ∼200 nm and low polydispersity 0.1-0.2 having a critical temperature (T(c)) of 44 °C were formed. Thermogravimetric and powder X-ray diffraction studies showed that the nanocomposites were composed of 90% cubic face-centered magnetite. Nearly 76.5% doxorubicin was loaded onto the nanoparticles by diffusion method. Drug release was higher at the hyperthermia temperature (72.42 ± 5.25% in 48 h) proving the thermoresponsive nature of the polymer. Folate conjugated samples showed a magnetization value of 32 emu/g as well as high r1 and r2 relaxivities in magnetic resonance imaging. R2 weighted images of nanocomposites were darker than the control with 20 μg/mL as the darkest. At this concentration the magnetic composites showed nearly 95% viability in L929 fibroblast cells. These thermoresponsive nanosystems with pegylated surfaces and size of ∼200 nm are therefore highly suitable for in vivo imaging and hyperthermia based drug delivery.

Flexible polymerosomes--an alternative vehicle for topical delivery

Self-assembled vesicles of poly(caprolactone)-poly(ethylene glycol)-poly(caprolactone) co-polymer of 122+/-20 nm were prepared by solvent evaporation method and analyzed morphologically by TEM and AFM. Transmission electron micrographs showed the presence of double-walled deformable structures with average wall thickness of 25 nm. AFM depicted somewhat flattened tops resembling a 'pancake' further confirming the flexibility of the nanocarriers. Permeation studies of fluorescently labelled vesicles in cadaver epidermis confirmed their presence across the stratum corneum within 2h of application and accumulation in the deeper layers thereafter. The flexible nature of these nanosystems makes them an efficient alternative to liposomes for targeting melanomas and basal cell carcinomas.

Evaluation of pharmacological efficacy of 'insulin-surfoplex' encapsulated polymer vesicles

The present study has been designed to study whether formation of ion-pair complex or 'surfoplex' can enhance the pharmacological efficacy of protein-loaded PCL-PEG-based polymerosomes. Insulin was selected as the model protein and was complexed with sodium deoxycholate, a naturally occurring bile salt. The surfoplexes were characterized for extent and site of complexation, stability, mass and partition coefficient. The lipophilicity of insulin was enhanced 5-fold upon complexation resulting in an increase in entrapment efficiency by 10-50% for all formulations compared to free insulin. The release of insulin from the systems was also modulated with reduction in burst release by 30%. The surfoplex was found to be therapeutically active for 8h duration (C(max) serum insulin=64.15+/-13.28 mIU/mL) in diabetic rat model. However, pharmacological efficacy of the complex-loaded nanoparticles (Nps) did not show significant enhancement with respect to insulin-loaded systems. The study therefore suggests that while ion-pair complexes may improve the in vitro kinetics of protein-loaded carriers, their therapeutic potential is dependent on the intensity of interactions between the peptide chains and polymer matrix.

Effect of DC/mDC iontophoresis and terpenes on transdermal permeation of methotrexate: In vitro study

The systemic toxicity caused by methotrexate limits its use and transdermal delivery would be a possible alternative. Transdermal permeation of methotrexate loaded into polyacrylamide-based hydrogel patch, across mice skin was studied in vitro after pretreatment with terpenes and ethanol, alone or in combination with iontophoresis (DC/mDC). Polyacrylamide patches gave the maximum flux as compared to the copolymers of acrylamide and acrylic acid. Of the terpenes used, pure menthol showed maximum enhancement (38%), whereas pure limonene elicited a minimum of 9.9% enhancement. Binary combination of menthol and ethanol increased the permeation to 54.9%, which was further enhanced to 93.69% and 117% when used in combination with DC and square wave (mDC) iontophoresis, respectively. ATR-FTIR of the stratum corneum treated with terpenes showed a split in the asymmetric C-H stretching vibrations along with decrease in peak heights and areas of asymmetric, symmetric C-H stretching, C=O stretching and amide bands. A split in amide II band was observed with iontophoresis. ATR-FTIR studies suggest conformational changes in the lipid-protein domains thereby increasing permeation. Histopathological studies on treated skin samples, gave an insight about the anatomical changes brought by the application of various enhancers. Binary mixture of menthol and ethanol in combination with square wave gave best results.

Efficacy of antibiotics-loaded interpenetrating network (IPNs) hydrogel based on poly(acrylic acid) and gelatin for treatment of experimental osteomyelitis: in vivo study

The safety and efficacy of gentamycin sulphate (GS)- or vancomycin hydrochloride (VCl)-loaded polymer devices based on poly(acrylic acid) and gelatin crosslinked selectively using 0.3 mol % N,N'-methylene bisacrylamide and 1 wt% glutaraldehyde were evaluated by varying the drug concentration onto the devices. The placebo and drug-loaded device of AxGx (acrylic acid:gelatin: 1:1 w/w) were employed for the treatment of experimental osteomyelitis in rabbit. Rabbits were categorized into four groups. Twelve rabbits in each group were treated with 12+/-1 mg of AxGx-1a (22% w/w GS), 12+/-1 mg of AxGx-1b (44% w/w GS), 16+/-1 mg of AxGx-1b (44% w/w GS) and 16+/-1 mg of AxGx-1c (44% w/w VCl). The drug concentration was measured following implantation in the adjacent tissue of femoral cavity, and serum. In femoral cavity maximum drug concentration was found on the 7th day with all the four types of devices. No drug was found after 21 days, at the local site with devices AxGx-1a and AxGx-1b (12+/-1 mg), whereas it was detected after 6 weeks with 16+/-1 mg device (44% w/w GS or VCl). Macroscopic evaluation after treatment revealed that swelling, redness, local warmth and drainage decreased depending upon the drug loading of the implants. Sequential radiographs, histology, microbiologic assay and scanning electron micrography demonstrated devices AxGx-1b and AxGx-1c (16+/-1 mg of 44% w/w drug loading) to be the most suitable device, which heals the infection after 6 weeks of treatment. No significant difference (p>0.05) in the rate of healing was observed between GS- and VCl-loaded devices. None of the implant showed toxic level of drug in serum at any given time.

Effect of composition of interpenetrating polymer network hydrogels based on poly(acrylic acid) and gelatin on tissue response: a quantitative in vivo study

The local tissue response of the biomaterial is the most important criteria for determination of its biocompatibility. In the present study, full and semi-interpenetrating polymer networks (IPN) based on polyacrylic acid (AAc) and gelatin (Ge) crosslinked with 0.5 mol % N,N'-methylene bisacrylamide (BAm) and 4% glutaraldehyde (GA), respectively, were evaluated for tissue response in rats. IPNs with varying ratios of AAc and Ge were implanted subcutaneously in rats. Gentamicin sulfate (GS)-loaded IPN samples were also studied to evaluate the possible therapeutic use of these polymers. The site of implantation was biopsied and processed for light microscopy (LM) with image analysis for assessment of tissue reaction at 2-, 6-, and 12-week intervals. The tissue reaction was evaluated as a function of composition and time. The degree of neutrophil, lymphocyte and macrophage infiltration, fibrosis, granuloma formation, integration with extracellular matrix, vascular proliferation, and damage of adjacent structures were assessed. Polymers with >66% crosslinked Ge (Gx) showed persistence of acute inflammatory reaction till 3 months, with marked tissue injury and fibrosis. On the other hand, high crosslinked AAc (Ax) content showed chronic inflammatory reaction with high macrophage infiltration. Macrophages took active part in phagocytosis, degradation, and removal of polymers without granuloma formation or significant giant cell reaction. The IPNs with acrylic acid and gelatin in the ratio of 1:1 showed least tissue reaction and thus appeared to be most biocompatible. The majority of the polymers showed integration with extracellular matrix and growth of capillaries in and around the polymer. The heamogram, liver and renal function tests, and histology of vital organs were all normal. GS loading showed no additional local or systemic reaction suggesting the potential usefulness of the hydrogels as carrier for drugs such as GS.

Studies on biodegradation and release of gentamicin sulphate from interpenetrating network hydrogels based on poly(acrylic acid) and gelatin: in vitro and in vivo

Interpenetrating network hydrogels (IPNs) based on poly(acrylic acid) and gelatin (Ge) were evaluated for in vitro and in vivo biodegradation and in vivo release of gentamicin sulphate. In vitro and in vivo degradation studies demonstrated that with the increase of acrylic acid content in the polymer, the rate of degradation decreases, and a reverse phenomenon was observed with increasing Ge content in the hydrogel. The rate of in vivo degradation was much lower than in vitro degradation. Incorporation of gentamicin sulphate in hydrogel further reduces their degradation. In vitro and in vivo drug release profile showed a burst effect, followed by controlled release. Drug concentration was measured in the local skin tissue, blood serum, kidney, liver and spleen. The local skin tissue concentration of 50% and 100% gentamicin sulphate, loaded full IPNs (i.e., Ax-1 and Ax-2), was found to be higher (20+/-2mug/g) than the minimum bactericidal concentration for Staphylococcus aureus (1.2mug/g) and Pseudomonas aeruginosa (10mug/g), respectively, for a study time of 60 days.

The effect of composition of poly(acrylic acid)-gelatin hydrogel on gentamicin sulphate release: in vitro

Hydrogels based on poly(acrylic acid) and gelatin crosslinked with N,N'-methylene bisacrylamide (0.5mol%) and glutaraldehyde (4%), respectively, forming an interpenetrating network were employed as matrices, for studying the loading and release of gentamicin sulphate. The release kinetics of gentamicin sulphate was evaluated in water (pH approximately 5.8), phosphate buffer (pH 7.4) and citrate buffer (pH 4) at 37+/-0.1 degrees C. The drug release in phosphate buffer was faster as compared to water or citrate buffer. Fitting the data of release studies in Peppas model indicated that the release of drug from full IPNs in phosphate buffer (pH 7.4), water (pH approximately 5.8) and citrate buffer (pH 4) were diffusion controlled. However, semi-IPNs showed both anomalous and Fickian diffusion mechanisms. With increasing gelatin percentage in the polymer, rate of drug release was faster and almost 85% of the loaded drug was released within 7 days in phosphate buffer (pH 7.4).

Reversibility with sodium bicarbonate of styrene maleic anhydride, an intravasal injectable contraceptive, in male rats

A copolymer of styrene and maleic anhydride (SMA) was dissolved in dimethyl sulphoxide (DMSO) and injected into the lumen of the vas deferens of rats. The polymer was retained in the lumen for a period of more than 90 days. Sodium bicarbonate (10%), pH 8.9, was used to flush the polymeric material from the vas deferens lumen. The reversibility and patency of the vas deferens was thus obtained. Sodium bicarbonate proved to be an effective alternative to dimethyl sulphoxide for reversal.

Phase II clinical trial of a vas deferens injectable contraceptive for the male

Following up on an earlier clinical trial demonstrating the safety of an intra-vas deferens injection of a contraceptive drug named Risug, comprised of styrene maleic anhydride (SMA) in a solvent vehicle of dimethylsulphoxide (DMSO), a study to assess the contraceptive effectiveness of a specific dose (60 mg) of SMA bilaterally was planned and implemented. Male subjects and their wives with normal reproductive profiles were the volunteer subjects. The wives were not using any contraceptives. The results reconfirm the safety and show that for a period of at least 1 year, the treatment leads to azoospermia in the male and gives pregnancy protection.

Phase I clinical trial of an injectable contraceptive for the male

Earlier studies on the rat and the monkey had demonstrated that an injection of styrene maleic anhydride (SMA) in a solvent vehicle of dimethyl sulphoxide (DMSO) into the lumen of the vas deferens is toxicologically safe and has contraceptive action. Phase I clinical trial was therefore undertaken on 38 male volunteers giving varying doses of SMA, ranging between 5 mg and 140 mg, into each vas deferens. A dose of 70 mg is the predicted therapeutic dose based on animal data. That the compound is within the vas deferens lumen during the period of the safety assessment is inferred from the effect on the spermatozoa count in ejaculates which reach azoospermic levels in the higher dose ranges. The treatment is well tolerated with only minimal side effects in a few cases and no long-term adverse effects.

Endoscopic fine needle aspiration cytology in the diagnosis of gastro-oesophageal and colorectal malignancies

In a prospective study we compared the diagnostic accuracy of endoscopic fine needle aspiration cytology with that of brush cytology and forceps biopsy in relation to gross tumour pattern and site in 265 confirmed consecutive cases of malignancy of the oesophagus, stomach, colon, and rectum. Aspiration cytology gave the highest diagnostic accuracy (94%), which was significantly better than that of brush cytology (84.9%) and biopsy (87.2%) (p less than 0.005). The difference was mainly related to tumour pattern. When compared to brush cytology and biopsy aspiration cytology was significantly better in submucosal tumours (92.9% v 7.1% and 14.3%, p less than 0.001); in infiltrative malignancies (95.8% v 90.1% and 78.9%, p less than 0.01), and in ulceronecrotic malignancies (90.9% v 36.4% and 45.4%, p less than 0.05). In polypoid malignancies there was a significant trend (p less than 0.05) in favour of forceps biopsy, with a diagnostic yield of 100% compared with 95% for aspiration cytology and 93.3% for brush cytology. The accuracy of the different techniques was not significantly related to the site of the tumour. The cumulative accuracy of aspiration cytology and biopsy was significantly better than that of biopsy and brush cytology (98.5% v 90.9%, p less than 0.005). Aspiration cytology was diagnostic in 21 of 24 lesions that were negative with both brush cytology and biopsy. There were no false positive cytology or histology results. We conclude that aspiration cytology is a simple, safe, and reliable technique with a high diagnostic yield and is of particular value in submucosal, infiltrative, and ulceronecrotic tumours.

Leiomyoblastoma stomach

Three patients with epithelioid leiomyomatous tumors (leiomyoblastomas) of the stomach are presented.