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Biomedical subjects

C P Sharma

Publications and source records attributed to C P Sharma.

At least 19 recordsLinked to original sources
PubMed1992

Protein interaction with tantalum: changes with oxide layer and hydroxyapatite at the interface.

For metallic implants the surface nature is extremely important because blood and tissue interactions with metal depend upon it. Protein adsorption is the initial reaction that takes place when an implant comes in contact with blood or tissue. We attempted to coat different thicknesses of oxide layers and hydroxyapatite on tantalum and examined the changes in water contact angle and adsorption of albumin and fibrinogen. Protein adsorption studies were performed with 125I-labeled proteins. A decrease in water contact angle was observed as the oxide layer thickness of tantalum increased. Fibrinogen adsorption increased on oxide layer coated and hydroxyapatite coated surfaces, compared to bare tantalum.

Adsorption↗
PubMed1992

On the regulation of beta 2 integrins.

The complex functions played by beta 2 integrins in mediating a large variety of adhesive interactions of leukocytes are highly regulated. This regulation results in transient adaptations/associations, permitting physical and functional recycling of these receptors during chemotaxis, phagocytosis and target-cell killing. The structural definition of these adaptations will lead not only to a better understanding of how these receptors are regulated in leukocytes but also shed valuable light on how these integrins integrate diverse extracellular signals into spatially and temporaly coordinated cellular responses.

Amino Acid Sequence↗
PubMed1992

Chitosan beads and granules for oral sustained delivery of nifedipine: in vitro studies.

Nifedipine was embedded in a chitosan matrix to develop a prolonged-release form. The in vitro release profiles of nifedipine from chitosan beads and microgranules were monitored by UV spectrophotometer. The studies were performed in a rotating shaker (100 rev min-1) in 0.1 M HCl buffer (pH 2.0) or 0.1 M phosphate buffer (pH 7.4). Comparison was made between drug-loaded microbeads and microgranules. The amount and percentage of drug release were much higher in HCl than in phosphate buffer, probably due to the salt formation of the matrix (chitosan hydrochloride) at acid pH. The release rate of nifedipine from chitosan matrix was slower for beads than granules. These findings suggest the possibility of modifying the formulations to obtain the desired controlled release of the drug in an oral sustained-delivery system.

Administration, Oral↗
PubMed1992

Polylysine-immobilized chitosan beads as adsorbents for bilirubin.

Hyperbilirubinemia generally relates to an elevated bilirubin level in the blood and is usually an indication of a disease of the blood, liver, or biliary tract. Hemoperfusion using synthetic resins as sorbents has been one of the ways to reduce bilirubin. In this study, chitosan, a natural polysaccharide having structural characteristics similar to glycosaminoglycans and which is nontoxic and biocompatible, has been used for bilirubin binding. Several layers of poly-L-lysine have been coated covalently onto chitosan beads, using N2 plasma and carbodiimide treatments. Such surface-modified chitosan beads exhibited high binding affinities for bilirubin (1.13 +/- 0.18 mg/g beads) in aqueous phosphate buffer solutions at 4 degrees C in relation to activated charcoal (0.74 +/- 0.2 mg/g). The polylysine-coated resins have been reported to have an improved binding affinity for bilirubin over cholestyramine. It seems that the surface-immobilized polylysine has an increased bilirubin binding affinity and is highly stable. The binding capacity is proportional to the amount of polylysine bonded to the chitosan beads. The hemolytic potential of all modified beads is compatible with polystyrene control tubes. Studies were also performed against albumin as proof of specificity toward bilirubin binding. The albumin-coated beads have shown the highest blood compatibility and selectivity over the other modified beads. However, it appears that polylysine-modified chitosan may be an excellent sorbent system for hemoperfusion due to its high binding affinity, capacity, and blood compatibility. Further studies are needed to determine its behavior under clinical conditions.

Adsorption↗
PubMed1992

Effect of fabrication, sterilization and mediators--blood compatibility of polyurethanes.

The possible changes in the surface and physical properties of polyether urethane urea (PEUU) implants, including their interaction with blood, due to the different preparation methods, sterilization techniques and long term storage in different environmental conditions have been investigated by conducting the studies of mechanical properties, contact angle, platelet adhesion and protein adsorption. Considerable variations in the mechanical properties have been observed for the PEUU grafts stored in different conditions. Changes in platelet adhesion and albumin adsorption have also been observed in the case of samples that underwent different sterilization methods. The effect of mediators like bromelain, an enzyme present in pineapple juice, on albumin adsorption and platelet adhesion on PEUU surfaces have been investigated. It seems the presence of pineapple juice increases the adsorption of albumin and reduces the adhesion of platelets on PEUU surfaces.

Biocompatible Materials↗
PubMed1991

Effect of plasma glow, glutaraldehyde and carbodiimide treatments on the enzymic degradation of poly (L-lactic acid) and poly (gamma-benzyl-L-glutamate) films.

The hydrolytic and enzymic degradation of poly(L-lactic acid) (PLA) and poly(gamma-benzyl L-glutamate) (PBGA) films, together with a series of surface treatments, were studied, as a function of exposure time. The degradation of these polymers was monitored by weight loss, contact angle, pH changes and tensile strength studies. Glutaraldehyde treatment retained the maximum strength of PLA in buffer, followed by carbodiimide, compared with control films. On the other hand, plasma glow reversed the effect. The ability of alpha-chymotrypsin, carboxypeptidase, ficin, esterase, bromelain and leucine aminopeptidase to modulate the degradation of PLA and PBGA was also investigated. Addition of these enzymes to the polymer-buffer system reduced the tensile strength of these polymers variably. Among the six enzymes studied, leucine aminopeptidase showed the highest enzymic effect on the degradation of the glutaraldehyde-treated and bare PLA or bare PBGA films. However, glutaraldehyde-cross-linked PLA demonstrated maximum stability in buffers or in all other enzyme systems studied compared with bare PLA. It is conceivable that surface treatments on these polymers might have altered their physical and chemical configuration and the subsequent degradation properties. Surface modifications may provide new ways of controlling the biodegradation of polymers for a variety of biomedical applications.

Biocompatible Materials↗
PubMed1991

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.

Animals↗
PubMed1991

Titanium-protein interaction: changes with oxide layer thickness.

Since titanium is being used for various biomedical applications requiring enhanced blood compatibility, which may be partly due to its extremely stable oxide layer, an attempt is made here to understand the effect of oxide layer thickness on protein adsorption. Different thickness of oxide layers have been coated on titanium foil using anodizing method and thickness of oxide layers deposited have been measured by an ellipsometer. Studies of competitive adsorption of proteins, using I125 labelled protein from a mixture of 25 mg% albumin, 15 mg% gamma-globulin and 7.5 mg% fibrinogen indicate an increased adsorption of proteins onto the oxide layer coated surfaces compared to the bare surface.

Adsorption↗
PubMed1991

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.

Adsorption↗
PubMed1991

Surface modification of corneal contact lens with phosphoryl choline by glow discharge.

Polymers like poly(methylmethacrylate) (PMMA) and poly(2-hydroxyethylmethacrylate) (PHEMA) are widely used in the development of hard and soft contact lenses. Cell adhesion and deposition of chemicals such as calcium, lipoproteins and mucin on the lens surface cause visual acuity which is the main problem in extended uses of contact ocular lenses. In order to minimise the cell adhesion and other type of depositions, a method of surface modification of lens involving the use of phosphoryl choline, a phospholipid and the glow discharge technique has been described. The power variation of the lenses after modification has been checked using Topcon lensometer. The possible power changes of the modified samples due to the exposure to the normal light in the laboratory, darkness, ultraviolet (U.V.) light or saline have been investigated by taking the visible and ultra violet spectra using Beckman spectrophotometer. Surface energy variations after modifications of the samples have been checked by sessile drop water contact angle measurements. Glow discharge treatment increases the hydrophilicity of the samples. It seems, the modifications do not affect the power of hard contact lens significantly. It is also observed that the exposure of samples to the normal light in the laboratory, darkness, U.V. light or saline make no significant change in the visible and ultraviolet spectra of the samples before and after modification.

Air↗
PubMed1991

Polyether urethane urea membrane for an improved hemodialysis.

This paper reviews our current activities of developing polyether urethane urea membranes for hemodialysis application. It is observed that the processing parameters such as precipitation medium, precipitation temperature etc. can influence the porosity of the membrane and subsequently the permeability property. Polyurethane/poly(methyl methacrylate) blended membranes have also shown high permeability. All the membranes are subjected to different sterilization processes and the pore sizes before and after sterilization are determined. The changes in the pore size due to sterilization seems to effect the permeability.

Biocompatible Materials↗
PubMed1991

Biodegradable chitosan matrix for the controlled release of steroids.

Chitosan, a polysaccharide, having structural characteristics similar to glycosaminoglycans, seems to be nontoxic and bioabsorbable. This study highlights the use of chitosan matrix for controlled drug delivery systems. The steroid drugs, namely testosterone, progesterone and beta-oestradiol were mixed with chitosan and the films were prepared by evaporation technique. The in vitro release profile of these steroids from the film matrix was monitored, as a function of time, in phosphate buffered saline (PBS, pH 7.4) at 37 degree C using a U-V-spectrophotometer. The degradation, of these chitosan and drug loaded chitosan films, was also investigated by weight loss and tensile strength studies. The steroid release from chitosan films was compared with the release of these drugs from their microbeads. It appears, the films and the microbeads stayed intact during the dissolution study of 90 days and the possibility of using these systems in contraceptive applications and novel drug delivery systems are discussed.

Biocompatible Materials↗
PubMed1991

The effect of anesthetics and analgesics on protein adsorption, platelet adhesion, and plasma recalcification time at blood-polymer interface.

Protein adsorption and subsequent cellular reactions are important biological events at the blood-polymer interface. Mediators like drugs, vitamins, and steroid hormones play a significant role in protein adsorption. An attempt is made to understand the effect of several i.v. agents on protein-platelet interaction with an artificial surface, polycarbonate. Pentothal, an anesthetic; lignocaine, a local anesthetic; pethidine, a narcotic anesthetic; Calmpose, a tranquilizer; and Novalgin, an analgesic, were drugs used for this study. Competitive adsorption of proteins is evaluated using a trace-labeled technique from a mixture of proteins (25 mg/dl of albumin, 15 mg/dl of tau-globulin, and 7.5 mg/dl of fibrinogen). Platelet and lymphocyte adhesion and plasma recalcification time are studied from calf blood. It is observed that these agents modulate the protein and cellular interaction and also the blood coagulation time. Therefore, proper selection of such including agents should not be overlooked for an implant surgery or while ministering to a patient with an implant.

Adsorption↗
PubMed1991

Influence of antihypertensive drugs and steroid hormones on protein adsorption/desorption on polycarbonate.

To develop artificial materials for prolonged use in the vascular system, the complicated process of surface-induced thrombosis needs to be better understood. It is documented that certain antihypertensive drugs can inhibit platelet adhesion to an artificial surface; on the other hand, steroid drugs increase platelet surface attachment to variable degrees. This study demonstrates the changes in protein-surface binding with certain antihypertensive and antianginal drugs--namely, digoxin, sorbitrate, thyroxine, sembrina and hydralazine--and five steroid hormones--estrone, progesterone, beta-estradiol, 7(OH) progesterone, and testosterone--using trace labelling methods. It seems that the addition of these antihypertensive drugs to the polymer-protein system has increased the level of surface-bound albumin and reduced the fibrinogen surface concentration to variable degrees. A reversed pattern of protein-surface attachment has been evident with steroid hormones. Thus, it appears that the changes in platelet attachment due to various drugs may be dependent on the availability of fibrinogen receptors at the polymer interface, along with other possible biological factors. Prolonged use of antihypertensive drugs may not have any significant side effect for patients having an implant. However, the use of steroids or steroid-containing oral contraceptive agents may not be advisable for patients having an artificial implant in contact with blood. A better understanding of the mechanism of these drugs under in vivo conditions is needed to correlate these findings.

Antihypertensive Agents↗
PubMed1990

Albumin adsorption on to aluminium oxide and polyurethane surfaces.

The changes in protein adsorption onto aluminium surfaces coated with different thicknesses of oxide layers were examined. The oxide layers on aluminium substrates were derived by the anodizing technique. Protein adsorption studies were conducted using 125I-labelled albumin and the amount of albumin adsorbed was estimated with the help of a gamma counter. An increase in albumin adsorption was observed on oxide layer coated aluminium surfaces. The effect of anti-Hageman factor on albumin and fibrinogen adsorption on to bare aluminium, oxide layer coated aluminium and bare polyether urethane urea surfaces was also investigated. It was observed that the presence of anti-Hageman factor increased the adsorption of albumin and fibrinogen on to all these substrates.

Adsorption↗