The adherence of bacteria and the formation of biofilm on implants is a serious problem that often leads to implant failure. A series of antimicrobial coatings have been constructed to resist bacterial adherence or to kill bacteria through contact with or release of antibacterial agents. The accumulation of dead bacteria facilitates further bacterial contamination and biofilm development. Herein, we have designed and constructed a novel, reversibly switchable bactericidal and antifouling surface through surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization to combine thermally responsive N-isopropylacrylamide (NIPAAm) and bactericidal quaternary ammonium salts (2-(dimethylamino)-ethyl methacrylate (DMAEMA)). Measurements of spectroscopic ellipsometry and water contact angle and X-ray photoelectron spectroscopy were used to examine the process of the surface functionalization. The temperature-responsive P(DMAEMA-co-NIPAAm) copolymer coating can switch by phase transition between a hydrophobic capturing surface at high temperatures and a relatively hydrophilic antifouling surface at lower temperatures. The quaternary ammonium salts of PDMAEMA displayed bactericidal efficiency against both Escherichia coli and Staphylococcus aureus. The functionalized surface could efficiently prevent bovine serum albumin adsorption and had good biocompatibility against human lens epithelial cells.

Graphene quantum dots (GQDs) are nano-sized graphene slices. With their small size, lamellar and aromatic-ring structure, GQDs tend to enter into the cell nucleus and interfere with DNA activity. Thus, GQD alone is expected to be an anticancer reagent. Herein, we developed GQDs that suppress the growth of tumor by selectively damaging the DNA of cancer cells. The amine-functionalized GQDs were modified with nucleus targeting TAT peptides (TAT-NGs) and further grafted with cancer-cell-targeting folic acid (FA) modified PEG via disulfide linkage (FAPEG-TNGs). The resulting FAPEG-TNGs exhibited good biocompatibility, nucleus uptake, and cancer cell targeting. They adsorb on DNA via the π–π and electrostatic interactions, which induce the DNA damage, the upregulation of the cell apoptosis related proteins, and the suppression of cancer cell growth, ultimately. This work presents a rational design of GQDs that induce the DNA damage to realize high therapeutic performance, leading to a distinct chemotherapy strategy for targeted tumor therapy.

Photodynamic therapy (PDT) is attractive for treatment of various cancers, with a high selectivity, minimal long-term effect, and excellent cosmetic appeal. Well water-dispersive photosensitizers with strong optical absorption within the tissue transparency window (700−1000 nm) are needed for efficient PDT. However, clinically used PDT agents based on oligomeric porphyrin units (e.g., protoporphyrin IX) are effective at 532 nm irradiation only. Herein, we synthesized a two-dimensional covalent organic polymer (COP) containing fully conjugated multiple porphyrin macrocycles with sulfonic acid side groups. The resultant COP-P-SO 3 H is well water-dispersive, showing strong optical absorption within the desired therapeutic window and a high quantum yield of reactive oxygen species, especially singlet oxygen ( 1 O 2 ), for efficiently killing tumor cells upon near-infrared light irradiation. Our first-principles calculations revealed that the observed high yield 1 O 2 resulted from the unique side-on parallel diatomic adsorption (Yeager mode) of triplet oxygen molecules on the highly conjugated porphyrin rings in the photoexcited COP-P-SO 3 H.

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