Stabilization of liposomes with collagen

Evaluation of the antifungal properties of nanoliposomes containing rhinacanthin-C isolated from the leaves of Rhinacanthus nasutus

Fungal infections represent a challenging threat to the human health. Microsporum gypseum and Trichophyton rubrum are pathogenic fungi causing various topical mycoses in humans. The globally emerging issue of resistance to fungi demands the development of novel therapeutic strategies. In this context, the application of nanoliposomes as vehicles for carrying active therapeutic agents can be a suitable alternative. In this study, rhinacanthin-C was isolated from Rhinacanthus naustus and encapsulated in nano-liposomal formulations, which were prepared by the modified ethanol injection method. The two best formulations composed of soybean phosphatidylcholine (SPC), cholesterol (CHL), and tween 80 (T80) in a molar ratio of 1:1:0 (F1) and 1:1:0.5 (F2) were proceeded for experimentation. The physical characteristics and antifungal activities were performed and compared with solutions of rhinacanthin-C. The rhinacanthin-C encapsulating efficiencies in F1 and F2 were 94.69 ± 1.20% and 84.94 ± 1.32%, respectively. The particle sizes were found to be about 221.4 ± 13.76 nm (F1) and 115.8 ± 23.33 nm (F2), and zeta potential values of -38.16 mV (F1) and -40.98 mV (F2). Similarly, the stability studies of rhinacanthin-C in liposomes demonstrated that rhinacanthin-C in both formulations was more stable in mediums with pH of 4.0 and 6.6 than pure rhinacanthin-C when stored at the same conditions. Rhinacanthin-C in F1 was slightly more stable than F2 when stored in mediums with a pH of 10.0 after three months of storage. However, rhinacanthin-C in both formulations was less stable than pure rhinacanthin-C in a basic medium of pH 10.0. The antifungal potential was evaluated against M. gypsum and T. rubrum. The findings revealed a comparatively higher zone of inhibition for F1. In the MIC study, SPC: CHL: T80 showed higher inhibition against M. gypseum and a slightly higher inhibition against T. rubrum compared to free rhinacanthin-C solution. Moreover, rhinacanthin-C showed significant interaction against 14α-demethylase in in silico study. Overall, this study demonstrates that nanoliposomes containing rhinacanthin-C can improve the stability and antifungal potential of rhinacanthin-C with sustained and prolonged duration of action and could be a promising vehicle for delivery of active ingredients for targeting various fungal infections.

Biophysical studies on collagen-lipid interaction

The potential use of liposomes as a delivery system is still limited by the poor understanding of the interaction mechanisms of liposomes underlying with biological media. Interaction between liposomes and protein is important for the structure and function of cells. In the present work, the interaction between collagen and dipalmitoyl phosphatidylcholine (DPPC) liposomes was studied by solubilization using a nonionic detergent, octylglucoside (OG), as well as a monolayer technique. The solubilization of the liposomal membrane was found to proceed in three stages of transition from the vesicular form to the mixed micellar form. Moreover, the amount of detergent needed to completely solubilize the liposomal membrane was increased after the incubation of liposomes with collagen, indicating an increased membrane resistance to the detergent and hence, a change in the natural membrane permeation properties. The addition of collagen in the subphase of different monolayer films induced a considerable shift towards a larger area/molecule in the compression-isotherm curves. This is either due to the insertion of collagen into the monolayer via its hydrophobic residues or to adsorption causing a protein layer to be located parallel to the lipid monolayer. It was concluded that collagen significantly altered the physical state of the liposome membrane, which may be attributed to collagen interaction with the liposomal surface and/or to its incorporation within the bilayer membrane.

Kinetics of in vitro release of a model nucleoside deoxyuridine from crosslinked insoluble collagen and collagen-gelatin microspheres

The objective of this research is to investigate the effect of highly crosslinked insoluble collagen and collagen-gelatin hybrid matrices as platforms for controlled release of a highly water soluble model nucleoside, deoxyuridine as well as a high molecular weight model compound fluoroscienisothoicyanate (FITC)-dextran. Collagen and gelatin can be considered as biodegradable proteinous materials. Microspheres of deoxyuridine and FITC-dextran were prepared by emulsification solvent evaporation technique using collagen alone and collagen-gelatin combination. The microencapsulation efficiency, particle size and in vitro release profiles were compared. Microencapsulation efficiency of approximately 10% was obtained with collagen while 20% encapsulation efficiency was obtained when collagen was used in combination with gelatin. Particle size range became wider when only collagen was used as compared to collagen-gelatin combination. A slower release profile was observed for crosslinked as compared to noncrosslinked microspheres. This study demonstrated diffusion controlled release of both compounds from the two polymers used. A good correlation was obtained between theoretically predicted and experimentally obtained in vitro release rates for both deoxyuridine and FITC-dextran using Higuchi's square root model.

Interaction of type-I collagen with phospholipid monolayer

The effects of type-I collagen on dipalmitoyl phosphatidylcholine (DPPC) and dimyristoyl phosphatidylcholine (DMPC) monolayer films with different compositions were studied using monolayer technique. The addition of collagen in the subphase of different monolayer films induced a considerable shift towards larger area/molecule in the compression-isotherm curves. This is either referred to the insertion of collagen into the monolayer by its hydrophobic residues or to an adsorption process causing a protein layer to be located parallel to the lipid monolayer [1]. The variation of collagen interaction with different lipid compositions was also verified through the penetration-kinetics experiment. Comparing our results to the results of Pajean et al. [2] and Pajean and Herbage [3] on the effect of collagen on the stability of lipid vesicles implies that the collagen induced stability could be explained on the basis of collagen-lipid monolayer interaction.

Coating liposomes with collagen (Mr 50,000) increases uptake into liver

Collagen-coated small unilamellar liposomes were prepared by incubation of two hydrophobic derivatives of collagen (average Mr 50 000) with preformed vesicles. The introduction of hexyl and lauryl residues to the collagen molecule improved by 10-fold the ability of collagen to coat liposomes. In vitro stability of the different coated vesicles prepared, was studied by their ability to retain entrapped carboxyfluorescein as a function of the time. Coated vesicles were clearly more stable in vitro than control liposomes, except for those containing the lauryl derivative in a protein/phospholipid weight ratio higher than 10(-3). Vesicle clearance from circulation as well as tissue distribution were also determined. Pharmacokinetics (determined by both fluorescence and radioactive techniques) were highly dependent on the injected dose, phospholipids used and the content of collagen. Half-lives were maximum for liposomes composed of saturated phospholipids injected at a dose of 2 micromol phospholipid. Besides, blood elimination of collagen-containing vesicles was about 2-fold faster and liver uptake 1.5 to 2-fold higher than control liposomes.

Recent developments of collagen-based materials for medical applications and drug delivery systems

In this review, an attempt was made to summarize some of the recent developments in the application of collagen as a biomaterial and in drug delivery systems. The main applications covered include: collagen for burn/wound cover dressings; osteogenic and bone filling materials; antithrombogenic surfaces; and immobilization of therapeutic enzymes. Recently, collagen used as a carrier for drug delivery has attracted many researchers throughout the world. The use of collagen for various drug delivery systems has also been reviewed in this article. Collagen-based drug delivery systems include: injectable microspheres based on gelatin (degraded form of collagen); implantable collagen-synthetic polymer hydrogels; interpenetrating networks of collagen; and synthetic polymers collagen membranes for ophthalmic delivery. Recent efforts to use collagen-liposomal composites for controlled drug delivery, as well as collagen as controlling membranes for transdermal delivery, were also reviewed. In this review, the main emphasis was on the work done in our laboratory.

Collagen microparticles: preparation and properties

Collagen microparticles (CMPs) of diameters ranging from about 3 to 40 microns were prepared by the method of emulsifying and cross-linking native collagen. The particle size was mainly controlled by the molecular weight of the collagen used: an increase in denaturation of the collagen resulted in smaller particle sizes. Consequently, controlled denaturation is the best method to control the size of CMPs. Total denaturation results in the degradation product gelatin and subsequently yields very small nanoparticles with a minimum diameter of about 0.1 micron. Collagen microparticles can be used as carriers for lipophilic drugs e.g. retinol, tretinoin, or tetracaine and lidocaine in free base form. Another feature of the biodegradable CMPs is their thermal stability, thus their sterilization can be readily achieved.