Polybetaines, that have moieties bearing both cationic (quaternary ammonium group) and anionic groups (carboxylate, sulfonate, phosphate/phosphinate/phosphonate groups) situated in the same structural unit represent an important class of smart polymers with unique and specific properties, belonging to the family of zwitterionic materials. According to the anionic groups, polybetaines can be divided into three major classes: poly(carboxybetaines), poly(sulfobetaines) and poly(phosphobetaines). The structural diversity of polybetaines and their special properties such as, antifouling, antimicrobial, strong hydration properties and good biocompatibility lead to their use in nanotechnology, biological and medical fields, water remediation, hydrometallurgy and the oil industry. In this review we aimed to highlight the recent developments achieved in the field of biomedical applications of polybetaines such as: antifouling, antimicrobial and implant coatings, wound healing and drug delivery systems.

Crosslinked porous microparticles have received great attention as drug delivery systems lately due to their unique set of properties: the capability to form various polymer–drug combinations, low immunogenicity, patient compliance and ability to release drugs in a delayed or controlled manner. Moreover, polymers with betaine groups have shown some unique features such as antifouling, antimicrobial activity, biocompatibility and strong hydration properties. Herein, novel porous zwitterionic microparticles were prepared in two stages. The first step involves the synthesis of porous microparticles based on glycidyl methacrylate, N-vinylimidazole and triethyleneglycol dimethacrylate using the suspension polymerization technique, the second step being the synthesis of zwitterionic porous microparticles by polymer–analogous reaction in presence of sodium monochloroacetate as betainization agent. Both types of microparticles were characterized structurally and morphologically by FT-IR spectroscopy, energy dispersive X-ray analysis, scanning electron microscopy, dynamic vapors sorption and mercury porosimetry. The tetracycline loading into crosslinked and zwitterionic microparticles was also performed, the maximum tetracycline loading capacities being 87 mg/g and 135 mg/g, respectively. The drug release mechanism, elucidated by various mathematical models, is controlled by both diffusion and swelling processes as a function of the zwitterionic and/or porous microparticle structure. Both types of microparticles presented antibacterial activity against the two reference strains used in this study: Escherichia coli and Staphylococcus aureus.

The aim of this study was to examine the use of zwitterionic microparticles as new and efficient macromolecular supports for the sorption of an antibiotic (doxycycline hydrochloride, DCH) from aqueous solution. The effect of relevant process parameters of sorption, like dosage of microparticles, pH value, contact time, the initial concentration of drug and temperature, was evaluated to obtain the optimal experimental conditions. The sorption kinetics were investigated using Lagergren, Ho, Elovich and Weber–Morris models, respectively. The sorption efficiency was characterized by applying the Langmuir, Freundlich and Dubinin–Radushkevich isotherm models. The calculated thermodynamic parameters (ΔH, ΔS and ΔG) show that the sorption of doxycycline hydrochloride onto zwitterionic microparticles is endothermic, spontaneous and favorable at higher temperatures. The maximum identified sorption capacity value is 157.860 mg/g at 308 K. The Higuchi, Korsmeyer–Peppas, Baker–Lonsdale and Kopcha models are used to describe the release studies. In vitro release studies show that the release mechanism of doxycycline hydrochloride from zwitterionic microparticles is predominantly anomalous or non-Fickian diffusion. This study could provide the opportunity to expand the use of these new zwitterionic structures in medicine and water purification.