Calcium alginate gel-entrapped liposomes

Interpenetrating gelatin/alginate mixed hydrogel: The simplest method to prepare an autoclavable scaffold

The choice of sterilization method for hydrogels used for cell culture influences the ease of preparing the gel. We prepared interpenetrating gelatin/calcium alginate hydrogels containing 1% (w/v) alginate and 1-16% (w/v) gelatin by molding with the mixture of gelatin/sodium alginate solution, followed by the addition of calcium ions by incubation in calcium chloride solution. It is the simplest method to prepare autoclavable gelatin/sodium hydrogel. We measured various properties of the hydrogels including volume, Young's modulus in the compression test, storage modulus, and loss modulus in the dynamic viscoelasticity measurement. The gelatin/alginate hydrogel can be easily fabricated into any shape by this method. After autoclave treatment, the hydrogel was shrunk to smaller than the original shape in similar figures. The shape of the gelatin/alginate hydrogel can be designed into any shape with the reduction ratio of the volume. Human osteosarcoma (HOS) cells adhered to the gelatin/alginate hydrogel and then proliferated. Gelatin/calcium alginate hydrogels with a high concentration are considered to be autoclavable culture substrates because of their low deformation and gelatin elution rate after autoclaving and the high amount of cells attached to the hydrogels.

pH-Responsive Cellulose-Based Microspheres Designed as an Effective Oral Delivery System for Insulin

Functional modified cellulose microsphere (CMs) materials exhibit great application potential in drug various fields. Here, we designed pH-responsive carboxylated cellulose microspheres (CCMs) by the citric/hydrochloric acid hydrolysis method to enhance oral bioavailability of insulin by a green route. The CMs were high purity cellulose that dissolved and regenerated from a green solvent by the green sol-gel method. The prepared microspheres were characterized by spectroscopic techniques, such as field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectrum (FT-IR), X-ray diffraction (XPS), etc. The spherical porous structure and carboxylation of cellulose were confirmed by FESEM and FT-IR, respectively. Insulin was loaded into the CCMs by electrostatic interactions, and the insulin release was controlled through ionization of carboxyl groups and proton balance. In vitro insulin release profiles demonstrated the suppression of insulin release in artificial gastric fluid (AGF), while a significant increase at artificial intestinal fluid (AIF) was observed. The insulin release profile was fitted in Korsmeyer-Peppas kinetic model, and insulin release was governed by the Fickian diffusion mechanism. The stability of the secondary structure of insulin was studied by dichroism circular. Excellent biocompatibility and no cytotoxicity of designed CCMs cast them as a potential oral insulin carrier.

Development of pH Sensitive Alginate/Gum Tragacanth Based Hydrogels for Oral Insulin Delivery

Insulin entrapped alginate-gum tragacanth (ALG-GT) hydrogels at different ALG replacement ratios (100, 75, 50, 25) were prepared through an ionotropic gelation method, followed by chitosan (CH) polyelectrolyte complexation. A mild gelation process without the use of harsh chemicals was proposed to improve insulin efficiency. Retention of almost the full amount of entrapped insulin in a simulated gastric environment and sustained insulin release in simulated intestinal buffer indicated the pH sensitivity of the gels. Insulin release from hydrogels with different formulations showed significant differences ( p < 0.05). Time domain (TD) NMR relaxometry experiments also showed the differences for different formulations, and the presence of CH revealed that ALG-GT gel formulation could be used as an oral insulin carrier at optimum concentrations. The hydrogels formulated from biodegradable, biocompatible, and nontoxic natural polymers were seen as promising devices for potential oral insulin delivery.

The influence of lipid composition and surface charge on biodistribution of intact liposomes releasing from hydrogel-embedded vesicles

Mixed drug delivery systems possess advantages over discrete systems, and can be used as a strategy to design more effective formulations. They are more valuable if the embedded particles perform well, rather than using drugs that have been affected by the surrounding vehicle. In order to address this concept, different liposomes have been incorporated into hydrogel to evaluate the potential effect on the controlled release of liposomes. Radiolabeled liposomes, with respect to different acyl chain lengths (DMPC, DPPC, or DSPC) and charges (neutral, negative [DSPG], or positive [DOTAP]) were integrated into chitosan-glycerophosphate. The results obtained from the biodistribution showed that the DSPC liposomes had the highest area under the curve (AUC) values, both in the blood (206.5%ID/gh(-1)) and peritoneum (622.3%ID/gh(-1)), when compared to the DPPC and DMPC formulations, whether in liposomal hydrogel or dispersion. Interesting results were observed in that the hydrogel could reverse the peritoneal retention of negatively charged liposomes, increasing to 8 times its AUC value, to attain the highest amount among all formulations. The interactions between the liposomes and chitosan-glycerophosphate, confirmed by the Fourier transform infrared (FTIR) spectra as shifted characteristic peaks, were observed in the combined systems. Overall, the hydrogel could control the release of intact liposomes, which could be manipulated by both the liposome type and interactions between the two vehicles.

A review on composite liposomal technologies for specialized drug delivery

The combination of liposomes with polymeric scaffolds could revolutionize the current state of drug delivery technology. Although liposomes have been extensively studied as a promising drug delivery model for bioactive compounds, there still remain major drawbacks for widespread pharmaceutical application. Two approaches for overcoming the factors related to the suboptimal efficacy of liposomes in drug delivery have been suggested. The first entails modifying the liposome surface with functional moieties, while the second involves integration of pre-encapsulated drug-loaded liposomes within depot polymeric scaffolds. This attempts to provide ingenious solutions to the limitations of conventional liposomes such as short plasma half-lives, toxicity, stability, and poor control of drug release over prolonged periods. This review delineates the key advances in composite technologies that merge the concepts of depot polymeric scaffolds with liposome technology to overcome the limitations of conventional liposomes for pharmaceutical applications.

Polyionic hydrocolloids for the intestinal delivery of protein drugs: alginate and chitosan--a review

The protein pharmaceutical market is rapidly growing, since it is gaining support from the recombinant DNA technology. To deliver these drugs via the oral route, the most preferred route, is the toughest challenge. In the design of oral delivery of peptide or protein drugs, pH sensitive hydrogels like alginate and chitosan have attracted increasing attention, since most of the synthetic polymers are immunogenic and the incorporation of proteins in to these polymers require harsh environment which may denature and inactivate the desired protein. Alginate is a water-soluble linear polysaccharide composed of alternating blocks of 1-4 linked alpha-L-guluronic and beta-D-mannuronic acid residues where as chitosan is a co polymer of D-glucosamine and N-acetyl glucosamine. The incorporation of protein into these two matrices can be done under relatively mild environment and hence the chances of protein denaturation are minimal. The limitations of these polymers, like drug leaching during preparation can be overcome by different techniques which increase their encapsulation efficiency. Alginate, being an anionic polymer with carboxyl end groups, is a good mucoadhesive agent. The pore size of alginate gel microbeads has been shown to be between 5 and 200 nm and coated beads and microspheres are found to be better oral delivery vehicles. Cross-linked alginate has more capacity to retain the entrapped drugs and mixing of alginate with other polymers such as neutral gums, pectin, chitosan, and eudragit have been found to solve the problem of drug leaching. Chitosan has only limited ability for controlling the release of encapsulated compound due to its hydrophilic nature and easy solubility in acidic medium. By simple covalent modifications of the polymer, its physicochemical properties can be changed and can be made suitable for the peroral drug delivery purpose. Ionic interactions between positively charged amino groups in chitosan and the negatively charged mucus gel layer make it mucoadhesive. The favourable properties like biocompatibility, biodegradability, pH sensitiveness, mucoadhesiveness, etc. has enabled these polymers to become the choice of the pharmacologists as oral delivery matrices for proteins.