P.R. Hari

Chitosan/calcium–alginate beads for oral delivery of insulin

A mild chitosan/calcium alginate microencapsulation process, as applied to encapsulation of biological macromolecules such as albumin and insulin, was investigated. The microcapsules were derived by adding dropwise a protein-containing sodium alginate mixture into a chitosan–CaCl2 system. The beads containing a high concentration of entrapped bovine serum albumin (BSA) as more than 70% of the initial concentration were achieved via varying chitosan coat. It was observed that approximately 70% of the content is being released into Tris-HCl buffer, pH 7.4 within 24 h and no significant release of BSA was observed during treatment with 0.1M HCl pH 1.2 for 4 h. But the acid-treated beads had released almost all the entrapped protein into Tris-HCl pH 7.4 media within 24 h. Instead of BSA, the insulin preload was found to be very low in the chitosan/calcium alginate system; the release characteristics were similar to that of BSA. From scanning electron microscopic studies, it appears that the chitosan modifies the alginate microspheres and subsequently the protein loading. The results indicate the possibility of modifying the formulation in order to obtain the desired controlled release of bioactive peptides (insulin), for a convenient gastrointestinal tract delivery system.

Adsorption of human IgG on Cu2+-immobilized cellulose affinity membrane: Preliminary study

Immobilized metal ion affinity chromatography (IMAC) is widely used. Transition metal ions have a high affinity to some peptide sequences. We have studied the selective adsorption of human IgG from a mixture of albumin, gamma-globulin, fibrinogen, and IgG onto Cu(2+) ion-immobilized cellulose membrane. Although Cu(2+) ligand is selective to IgG, in general gamma-globulins also are adsorbed. The simplicity and lower cost of Cu(2+) ion-immobilized cellulose membranes may be useful for removing IgG from blood.

Hydrogel Grafted Polymer Surfaces: Interaction and Morphology of Platelets

Besides the quantification of platelet adhesion, the morphology of adherent platelets on a polymer surface seems to be important as far as thrombogenicity is concerned. It is suggested that such events usually take place on a layer of adsorbed proteins on the surface of the blood. In the present study, we observed the morphological variation of adherent calf platelets (in vitro under static conditions) on bare and hydrogel-grafted Angioflex sheets. Electron micrographs indicate the extent of deformation of the Angioflex sheets varying with modified substrates as compared to the bare sheets.

Hydrogel grafted surfaces : protein interaction and platelet adhesion

The blood compatibility of an artificial polymeric implant largely depends on the physicochemical nature of the polymer substrate. In the present study our aim is to develop an understanding of polymer surfaces having similar surface free energy, but different chemical characteristics. We attempted to graft hydrogels onto a silastic polyurethane (Angioflex) material and optimised the surface free energy to about 35.0 ergs/cm2. We compared the protein adsorption and platelet and lymphocyte adhesion on these surfaces. It is observed that there is a relative change in behavior because of the difference in chemical nature.

Adhesion and Stability of Blood Cells onto Polymer Substrates: Effect of Glow Discharge

The adhesion of platelets, red blood cells, and lymphocytes onto various polymer substrates, hydrophobic to hydrophilic in nature, has been studied. Cell adhesion is found to be higher on hydrophilic substrates. The stability of these adhered cells has also been studied under a flow rate of 20 ml/min. Further the effect of glow discharge treatment onto various substrates is investigated. It seems the stability is more on glow discharge treated substrates due to increased surface free energy.

Modified Polyacrylamide Microspheres as Immunosorbent: Trivandrum-695012. India.

Extracorporeal immunoadsorption system has been used for the specific removal of immunologically active substances from the blood. In this study, an attempt is made to utilise polyacrylamide microspheres as a matrix for immunoadsorption. Phenyl alanine is coupled onto the polymer beads using glutaraldehyde. These modified beads exhibit a high binding affinity for gamma-globulin compared to bare beads. The surface modified ones showed selective adsorption of immunoglobulins of IgG class. The C3 adsorption pattern is not altered significantly upon modification. Modified beads are found to be less hemolytic after modification. However, more studies are to be conducted for the development of a hemoperfusion column based on this modified matrix.

Development of Silastic Polyurethane (Angioflex) Materials with Antibacterial Agent

Bioimplants incorporated with antimicrobial agents are needed to control Foreign Body Associated Infection (FBAI) in clinical settings. Attempts are made here to develop five different types of polyurethane (Angioflex), viz., (1) bare polymer, (2) bare polymer glow discharged, (3) bare polymer coated with chlorhexidine, (4) chlorhexidine coated polymer glow discharged, and (5) material (4) recoated with another layer of chlorhexidine digluconate. These materials are tested for their in vitro antibacterial effects using disc diffusion technique against five different standard clinical staphylococcus strains, viz., Wood 46 (Staph. aureus), A 182 (Staph. epidermidis), A 313 (Staph. epidermidis), A 61 (Staph. epidermidis), and A 72 (Staph. epidermidis). Maximum antibacterial effects (zone of inhibition) are observed with polyurethanes incorporated with chlorhexidine digluconate (3) and chlorhexidine incorporated and glow discharged (4). Findings of this study indicate that glow discharge does not seem to produce either additive or synergistic antibacterial effects with chlorhexidine digluconate coated Angioflex material.

Protein Adsorption - Effect of External Lubricants at the Interface

Upon exposure to blood, rapid adsorption of proteins is the initial event at the contacting surface, followed by the adhesion of platelets and other blood components. Surfaces absorbing albumin appear to possess antithrombotic character in discouraging adhesion of platelets. Therefore, for the development of a blood contacting device, the interfacial events are extremely important and need serious investigation. We have attempted to observe the variations in competitive adsorption of fibrinogen and albumin onto the polyetherurethane urea (PEUU) surface in the presence of external lubricant, such as calcium stearate and silicone fluid coating. It seems, in the presence of such mediators, that fibrinogen adsorption is increased relatively with reduction in albumin at the surface.