New Nano-Crystalline Hydroxyapatite-Polycarboxy/Sulfo Betaine Hybrid Materials: Synthesis and Characterization

Hybrid materials based on calcium phosphates and synthetic polymers can potentially be used for caries protection due to their similarity to hard tissues in terms of composition, structure and a number of properties. This study is focused on the biomimetic synthesis of hybrid materials consisting of hydroxiapatite and the zwitterionic polymers polysulfobetaine (PSB) and polycarboxybetaine (PCB) using controlled media conditions with a constant pH of 8.0-8.2 and Ca/P = 1.67. The results show that pH control is a dominant factor in the crystal phase formation, so nano-crystalline hydroxyapatite with a Ca/P ratio of 1.63-1.71 was observed as the mineral phase in all the materials prepared. The final polymer content measured for the synthesized hybrid materials was 48-52%. The polymer type affects the final microstructure, and the mineral particle size is thinner and smaller in the synthesis performed using PCB than using PSB. The final intermolecular interaction of the nano-crystallized hydroxyapatite was demonstrated to be stronger with PCB than with PSB as shown by our IR and Raman spectroscopy analyses. The higher remineralization potential of the PCB-containing synthesized material was demonstrated by in vitro testing using artificial saliva.

Fabrication of hydrophilic zwitterionic microspheres via inverse suspension polymerization for the enrichment of N-glycopeptides

A kind of zwitterionic microsphere was prepared via one-step inverse suspension polymerization employing 3-[N,N-dimethyl-[2-(2-methylpropyl-2-enyloxy) ethyl] ammonium] propane-1-sulfonate (MSA) and N,N-methylene bisacrylamide (BIS) as the precursors. The preparation conditions were carefully investigated and optimized by regulating the content of total monomers, ratio of MSA to BIS, ratio of water to oil, and content of stabilizer. The properties of microspheres were characterized by helium ion microscopy (HIM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), N₂ adsorption/desorption measurement, and water contact angle measurement. The particle size of resulting polydisperse microspheres ranged from 15-25 μm, exhibiting high specific surface area of 138 m² g^-1. Owing to great hydrophilicity, the resulting zwitterionic microspheres could be directly used as hydrophilic interaction chromatography (HILIC) sorbent to enrich glycopeptides from biosamples without any chemical modification. A total of 19 N-glycopeptides was enriched from 10 μg of IgG digest. Besides, up to 383 N-glycopeptides and 224 N-glycosylation sites were unambiguously identified from 2 μL of human serum digest by cLC-MS/MS after enrichment with zwitterionic microspheres, indicating their great enrichment performance to N-glycopeptides. The approach of preparing hydrophilic zwitterionic microspheres contains only one synthesis reaction and is suitable for large-scale preparation.

Development of Antimicrobial and Antifouling Universal Coating via Rapid Deposition of Polydopamine and Zwitterionization

Biomaterials-associated infections (BAIs) are related to bacterial colonization on medical devices, which lead to a serious medical burden, such as increased healthcare cost, prolonged hospital stays, and high mortality and morbidity. To reduce the risk of infections, in this work, a new approach which makes use of a bioinspired coating with dual antimicrobial and antifouling functions was developed through rapid deposition of functional polydopamine (pDA) and antimicrobial copper ions, and subsequent conjugation of zwitterionic antifouling sulfobetaine (SB) moieties by the aza-Michael addition reaction. pDA permits surface-independent versatile functionalization on a variety of substrates, such as TiO₂, SiO₂, gold, plastics, and Nitinol alloy. The characterizations for chemical elemental compositions and hydrophilicity by X-ray photoelectron spectroscopy and contact angle goniometer, respectively, indicating the successful grafting of SB moieties and the presence of copper ions in the pDA adlayers. Ellipsometric thicknesses of the thin films were followed to monitor the formation of pDA films and the changes after the post conjugation. UV-vis spectroscopy and inductively coupled plasma-mass spectrometry revealed the coordination structure of catechol-Cu, and release profile of Cu²⁺ from the constructed functional coatings. The superhydrophilic and charge-balanced SB interface allowed effective resistance of bacterial adsorption. Intriguingly, we scrutinized that the release of bactericidal copper ions enables killing the residual amount of adsorbed bacteria. Moreover, viability tests for fibroblast cells indicate the excellent biocompatibility of the developed medical coatings. For real-world implementation, the antifouling and antimicrobial coatings were applied on commercially available silicone-based urinary catheters, and the existence of bacteria was evaluated by using the plate-counting assay. The results showed an undetectable level of living bacteria. Consequently, the dual functional medical coating offers a promising approach to eliminate BAIs for practical applications.