Microstructured and Degradable Bacterial Cellulose–Gelatin Composite Membranes: Mineralization Aspects and Biomedical Relevance

Abstract

Bacterial cellulose (BC)–gelatin (GEL) membranes were processed by successive periodate oxidation and a freeze-thawing/carbodiimide crosslinking procedure, first facilitating a Schiff-base reaction among respective aldehyde and hydroxyl groups, and later GEL stabilization and microstructuring. The formation of highly microporous structures within the GEL portion, with significant differences between bottom and top, was elucidated, and pores in the 27.6 ± 3 µm–108 ± 5 µm range were generated, exceeding the threshold value of ~10 µm sufficient for cell trafficking. During a relatively short (6 h) exhaustion procedure in supersaturated simulated body fluid solution, the membranes accommodated the combination of biologically relevant minerals, i.e., flake-like octacalcium phosphate (OCP) and (amorphous) apatite, onto their surface, forming a membrane with intensive swelling (650–1650%) and up to 90% weight loss in a 4-week period. The membranes´ 6-day eluates did not evoke any cytotoxic effects toward human fibroblast, MRC-5 cells. The same type of cells retained their morphology in direct contact with the membrane, attaching to the GEL porous site, while not attaching to the GEL thin-coated BC side, most probably due to combined, ablation effect of dominant β-sheet conformation and carbodiimide crosslinking. Together with arrested proliferation through the BC side, the membranes demonstrated beneficial properties for potential guided tissue regeneration (GTR) applications.

Bacterial Cellulose: Production, Modification and Perspectives in Biomedical Applications

“…The periodate oxidation was used for region-selective oxidation of BC and further coupling with gelatin biopolymer (Figure 7). Such composite demonstrate improved physiological degradation (compared to non-degradable, native BC) as well as capacity for accommodation of flake-like apatite minerals in short-term incubation within supersaturated simulated body fluid (SBF) [92].…”

Efficiency of Differently Processed Membranes Based on Cellulose as Cationic Dye Adsorbents

“…BC is produced by the gram-negative bacterium Gluconacetobacter xylinum. Nanofibrils mainly consist of cellulose type I, and the overall crystallinity index (including crystalline and amorphous segments) is 0.83 [25]. The diameter of BC nanofibrils is in the 30-60 nm range (as obtained by high-resolution SEM images).…”

“…Here, it is worth mentioning that dye removal analysis accounted for the normalised membrane surface (20 cm 2 ), and not the dry adsorbent weight, and results revealed similar values between CNF/CMC with different ratios and BC-BCox in the case of anthraquinone dye, with the first two combinations being threefold more effective than the second type. This we assume to be a consequence of higher water binding to BC and BCox itself, which have a very high swelling degree (~1500% and~1200%, respectively [25]), which is not the case with CNF/CMC, where adsorption was more preferable due to lower initial hydration. Another important reason was the much lower surface charge of BC and BCox compared to CNF/CMC membranes, presented in the titration data.…”

“…type. This we assume to be a consequence of higher water binding to BC and BCox itself, which have a very high swelling degree (~ 1500 % and ~ 1200 %, respectively [25]), which is not the case with CNF/CMC, where adsorption was more preferable due to lower initial hydration. Another important reason was the much lower surface charge of BC and BCox compared to CNF/CMC membranes, presented in the titration data.…”

“…Indeed, the wet, acidic pH (~2) conditions during processing were found to favor the esterification process [35], which in our case was identified after 24 h exposure at 60 °C, with a subsequent 2 h at 100 °C. The periodate-mediated oxidation of BC proceeded through redox cleavage of vicinal (C2 and C3) glycols, which yielded a product with aldehyde groups in positions C2 and C3 of the glucopiranose unit, i.e., 2,3-dialdehyde BC [25], as presented in Scheme 1b. This reaction is thought to proceed via a cyclic di-ester of periodate ion with vicinal hydroxyls, which subsequently undergoes an intramolecular redox process with C-C bond cleavage of the cellulose glucose units.…”