By P. M. Pasca and Simona Cavalu

https://chalcogen.ro/929_PascaPM.pdf

Knowing the biological and pharmacological properties of propolis, the first goal of our study was to prepare and characterize a propolis nano-formulation (NPs) in order to be used for wound healing applications. The ability of propolis NPs to stimulate the migration of dermal fibroblasts in vitro was assessed by scratch test assay. The concentration of 200 μg/mL propolis NPs was found to have similar effect as the positive control. The second goal was to prepare a propolis-collagen membrane and to investigate the morphological and nanoindentation properties by AFM. The ultrastructure network of collagen fibrils was not affected by incorporation of propolis NPs, showing a nano-porous structure, favorable for soft tissue regeneration applications. Enzymatic degradation assay indicated a reduced degradation rate upon incorporation of propolis NPs in collagen matrix.

Ionotropic gelation method was applied for the preparation of propolis NPS. The nanoparticles were formed spontaneously due to ionic interaction between the protonated amine groups in chitosan and the negatively charged counter-ion TPP, being stabilized by Tween 80.

The tridimensional network of collagen fibrils is visible in both specimens (with or without propolis NPs incorporated) emphasizing the details of repetitive structure of the D-bands pattern of a single collagen fibril, with periodic gaps and grooves, in concordance with some previous published work [32, 33]. The periodicity of D-bands is less visible after propolis NPs incorporation. Moreover, after propolis NPs incorporation and freeze drying procedure, an obvious porous ultrastructure formation was noticed, as a result of fibers self-assembly.

A collagen-based membrane was prepared and investigated by AFM in terms of morphological features and nanoindentation. The network of collagen fibrils was not affected by propolis NPs, showing a nano-porous structure, favorable for soft tissue regeneration applications. Enzymatic degradation assay indicated a reduced degradation rate upon incorporation of propolis NPs in collagen matrix. Corroborating the above mentioned results, we consider that modified-collagen membrane by adding propolis NPs in a controlled concentration, might represent a promising natural alternative to synthetic bandages for wound healing applications. Of course, further in vitro and in vivo tests are necessary to evaluate the biological performances of collagen-modified membranes, in terms of tissue adaptation and integration. (Simona Cavalu, PM Pasca, Digest Journal of Nanomaterials and Biostructures, Volume 16, Issue 3, Pages 929 – 938July-September 2021).