Fabrication and Evaluation of Polycaprolactone Beads-on-String Membranes for Applications in Bone Tissue Regeneration

β-Tricalcium phosphate contained beaded-fiber scaffolds characterized by high early osteoinductive activity for vascularized bone regeneration

The calcium phosphate component and surface topology of a scaffold are considered the two main factors that influence osteogenic differentiation. This research reports a one-step but effective scaffold preparation method that can regulate the morphology of nanofibers and control the distribution and release behavior of calcium phosphate nanoparticles (CaPs). Two beaded-on-string CaPs-loaded electrospun scaffolds (PT7.5 and PT4.5) with composite microstructures of microbeads and nanofibers were fabricated by adjusting the concentration of the electrospinning solution. The presence of the composite microstructure was conducive to the surface exposure and sustained release of bioactive components, which in turn could significantly promote the biomineralization and protein adsorption of the scaffold. A study of the human umbilical vein endothelial cells (HUVECs) and rat-bone marrow-derived mesenchymal stem cells (rBMSCs) revealed that cells cultured on scaffolds with composite microstructures (especially PT4.5) could enhance tube formation of the HUVECs and osteogenic differentiation of rBMSCs. The PT4.5 with significantly different microbead and nanofiber sizes presented the high potential to improve the early osteoinductive activity and angiogenesis of the CaPs-loaded electrospun scaffold and expand its advantage in bone regeneration.

Antimicrobial Polymer-Peptide Conjugates Based on Maximin H5 and PEG to Prevent Biofouling of E. coli and P. aeruginosa

Many pathogens, such as Pseudomonas aeruginosa and Escherichia coli bacteria can easily attach to surfaces and form stable biofilms. The formation of such biofilms in surfaces presents a problem in environmental, biomedical, and industrial processes, among many others. Aiming to provide a plausible solution to this issue, the anionic and hydrophobic peptide Maximin H5 C-terminally deaminated isoform (MH5C) has been modified with a cysteine in the C-terminal (MH5C-Cys) and coupled to polyethylene glycol (PEG) polymers of varying sizes (i.e., 2 kDa and 5 kDa) to serve as a surface protective coating. Briefly, the MH5C-Cys was bioconjugated to PEG and purified by size exclusion chromatography while the reaction was confirmed via SDS-PAGE and MALDI ToF. Moreover, the preventive antimicrobial activity of the MH5C-Cys-PEG conjugates was performed via the growth curves method, showing inhibition of bacterial growth after 24 h. The efficacy of these peptide-polymer conjugates was extensively characterized via scanning electron microscopy (SEM), minimum inhibition concentration (MIC), minimum biofilm inhibition concentration (MBIC), and minimum biofilm eradication concentration (MBEC) assays to evaluate their ability to eradicate and prevent the biofilms. Interestingly, this work demonstrated a critical PEG polymer weight of 5 kDa as ideal when coupled to the peptide to achieve inhibition and eradication of the biofilm formation in both bacteria strains. According to the MICs (40 μM) and MBICs (300 μM), we can conclude that this conjugate (MH5C-Cys-5 kDa) has an action that prevents/inhibits the formation of biofilms and the eradication of biofilms (MBEC 500 μM). In contrast, the MH5C-Cys peptide with PEG polymer of 2 kDa did not show inhibition or eradication of the biofilms.