Regulation of Hydrophobic Structures of Antibacterial Guanidinium-Based Amphiphilic Polymers for Subcutaneous Implant Applications.

Antimicrobial peptide mimics have been used to kill bacteria and construct antibacterial materials. Precise design and construction of chemical structure are essential for easy access to highly effective antimicrobial peptide mimics. Herein, cationic guanidinium-based polymers (PGXs) with varying hydrophobic structures were synthesized to explore the structure and antibacterial activity relationship of antimicrobial peptide mimics and to construct antibacterial implants. The effect of the hydrophobic chemical structure, including carbon chain length and configuration, on the antimicrobial activities against both Escherichia coli and Staphylococcus aureus was investigated. The antibacterial activities of PGXs improved with increasing alkyl chain length, and PGXs with a straight-chain hydrophobic structure exhibited better bactericidal activities than those with cyclic alkane and aromatic hydrocarbon. Furthermore, PGXs grafted with poly(dimethylsiloxane) (PDMS-PGXs) showed a similar bactericidal change tendency of PGXs in solution. Additionally, the PDMS-PGXs showed potent antibiofilm performance in vitro, which can inhibit bacterial infection in vivo as subcutaneous implants. This study may propose a basis for the precise design and construction of antibacterial materials and provide a promising way of designing biomedical devices and implants with bacterial infection-combating activities.

One-step synthesis of photoluminescent carbon dots with excitation-independent emission for selective bioimaging and gene delivery.

Photoluminescent carbon dots (C-dots), as new members of the quantum sized carbon analogues have attracted significant attention due to their unique size, less toxicity, good compatibility and relatively easy surface modification. In this work, we report a simple, low-cost and one-step hydrothermal carbonization approach to synthesize the positively charged C-dots using PEI and FA. From the photoluminescence (PL) measurements, the as-prepared C-dots exhibit good stability and intense PL with the high quantum yield (QY) at Ca. 42%. Significantly, The as-prepared C-dots integrate the advantages of C-dots and PEI: the presence of C-dots can effectively decrease the cytotoxicity of PEI, the C-dots can be applied in biological system for selective imaging of folate receptor (FR)-positive cancerous cells from normal cells, while the cationic PEI with positive charges can make them link to plasmid DNA and efficiently transfect the therapeutic plasmid into cells. Therefore, the as-prepared with the facile synthesis method can be a promising photoluminescent probe for cancer diagnosis and gene therapy.