Composite Bone Cements with Enhanced Drug Elution.

Antibiotic-loaded bone cement (ALBC) has become an indispensable material in orthopedic surgery in recent decades, owing to the possibility of drugs delivery to the surgical site. It is applied for both infection prophylaxis (e.g., in primary joint arthroplasty) and infection treatment (e.g., in periprosthetic infection). However, the introduction of antibiotic to the polymer matrix diminishes the mechanical strength of the latter. Moreover, the majority of the loaded antibiotic remains embedded in polymer and does not participate in drug elution. Incorporation of the various additives to ALBC can help to overcome these issues. In this paper, four different natural micro/nanoscale materials (halloysite, nanocrystalline cellulose, micro- and nanofibrillated cellulose) were tested as additives to commercial Simplex P bone cement preloaded with vancomycin. The influence of all four materials on the polymerization process was comprehensively studied, including the investigation of the maximum temperature of polymerization, setting time, and monomer leaching. The introduction of the natural additives led to a considerable enhancement of drug elution and microhardness in the composite bone cements compared to ALBC. The best combination of the polymerization rate, monomer leaching, antibiotic release, and microhardness was observed for the sample containing nanofibrillated cellulose (NFC).

Fabrication of hydrogel scaffolds via photocrosslinking of methacrylated silk fibroin.

Silk fibroin is a promising biomaterial for tissue engineering due to its valuable mechanical and biological properties. However, being a natural product and a protein, it lacks the processability and uniform quality of an advanced synthetic material. Here we propose a way to overcome this contradiction using novel fibroin photocrosslinkable derivative (FBMA). FBMA was synthesized by methacrylation of native fibroin nucleophilic side groups. It was dissolved in either formic acid (FA) or hexafluoroisopropanol (HFIP), and the obtained solutions were photocrosslinked into hydrogel scaffolds of various structural forms including films, micropatterns, pads and macroporous sponges. UV-exposition of dry FBMA films through a photomask created complex microscaled patterns of the polymer. The nature of the solvent affected the properties of resulting hydrogels. When HFIP was used as the solvent, the resulting hydrogels had a storage modulus ∼4 times higher than that of hydrogels fabricated using FA and ∼20 times higher compared to the reference hydrogel obtained from pristine fibroin. Both FBMA-based hydrogels were biocompatible and supported fibroblast adhesion and growth in vitro. Cells cultivated on FBMA scaffolds produced with HFIP exhibited more spread phenotype at 4 and 24 h of cultivation, consistent with increased stiffness of the hydrogel. Hence, FBMA is an attractive material for fabrication of micropatterned scaffolds of centimeter-scale size with minutely tunable physico-chemical properties via convenient and reproducible technological processes, applicable for rapid prototyping.

Immobilization of microalgae on the surface of new cross-linked polyethylenimine-based sorbents.

We report on the use of the polyethylenimine-based (PEI) sorbents for immobilization and harvesting of microalgae (MA) cells. Specific materials assessed were porous solid polymers from highly-branched PEI synthesized by cross-linking with epichlorohydrin (ECH) or diethylene glycol diglycidyl ether (DGDE). We estimated the effect of PEI/cross-linker ratio on the MA attachment and biocompatibility of the sorbents with the MA cells. A decrease in the cross-linker percentage resulted in the enhancement of the immobilization efficiency but impaired the cell viability as was manifested by inhibition of the photosynthetic activity of the MA cells. The rate of Chlorella vulgaris cell attachment to the sorbents with ECH was faster as compared to that of the PEI-DGDE-based polymers. The cells immobilized on the PEI-ECH sorbents showed a more profound decline in their viability (assessed via photosynthetic activity). The sorbents with 60% of DGDE were characterized by high immobilization efficiency. These sorbents supported a prolonged cultivation of the immobilized MA without impairing their viability and metabolic activity. We conclude that the sorbents with a lower percentage of DGDE (<30%) and sorbents with ECH are suitable for harvesting of the MA cells intended for immediate downstream processing, potentially without the cell desorption. To the best of our knowledge, this is the first report on successful application of PEI-based sorbents in microalgal biotechnology.

Simple and versatile method for creation of non-leaching antimicrobial surfaces based on cross-linked alkylated polyethyleneimine derivatives.

Novel quaternized polyethyleneimine and cross-linked polyethyleneimine derivatives have been synthesized using both traditional and microwave-assisted techniques to create antimicrobial coatings, with octyl, dodecyl, or hexadecyl bromides as alkylating agent and various bifunctional electrophiles as cross-linkers. Quaternization has been performed using methyl iodide or dimethyl sulfate; it has been shown that methyl iodide has no advantages over dimethyl sulfate. Antimicrobial activity of the polymers against Gram-positive (S. aureus) and Gram-negative (P. aeruginosa) bacteria has been evaluated. Antimicrobial activity declines with increase in the alkylating agent chain length. Equimolar ratio of the alkylating agent and the primary amino groups in polyethyleneimine is optimal. Although cross-linking decreases the antimicrobial activity of quaternized polyethyleneimines, it improves their "non-leaching" properties (i.e. minimizes undesirable water washout of the polymeric coatings).