Hydrogels exhibit excellent moldability, biodegradability, biocompatibility, and extracellular matrix-like properties, which make them widely used in biomedical fields. Because of their unique three-dimensional crosslinked hydrophilic networks, hydrogels can encapsulate various materials, such as small molecules, polymers, and particles; this has become a hot research topic in the antibacterial field. The surface modification of biomaterials by using antibacterial hydrogels as coatings contributes to the biomaterial activity and offers wide prospects for development. A variety of surface chemical strategies have been developed to bind hydrogels to the substrate surface stably. We first introduce the preparation method for antibacterial coatings in this review, which includes surface-initiated graft crosslinking polymerization, anchoring the hydrogel coating to the substrate surface, and the LbL self-assembly technique to coat crosslinked hydrogels. Then, we summarize the applications of hydrogel coating in the biomedical antibacterial field. Hydrogel itself has certain antibacterial properties, but the antibacterial effect is not sufficient. In recent research, in order to optimize its antibacterial performance, the following three antibacterial strategies are mainly adopted: bacterial repellent and inhibition, contact surface killing of bacteria, and release of antibacterial agents. We systematically introduce the antibacterial mechanism of each strategy. The review aims to provide reference for the further development and application of hydrogel coatings.

To reduce the risk of infection, improving the anti-infection ability of Ti-based implantation has become a very meaningful task. In this work, by employing polydopamine (PDA) as a carrier and curcumin (CUR) as an anti-biotic/inflammatory, a series of Ti-PDA@CURx (x = 0.5, 1.0, 1.5, 2.0, 2.5) was successfully fabricated and characterized by scanning electron microscopy, Fourier transform infrared spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, and the water contact angle, where Ti plates were firmly coated by PDA@CUR. The test result of CUR content shows that the maximum loading of CUR in PDA can reach 0.6506%, where the CUR concentration is 1.5 mg/mL. The antibacterial test results demonstrate that Ti-PDA@CUR-x (x = 0.5, 1.0, 1.5, 2.0, 2.5) exhibit significant antibacterial activities against Escherichia coli and S. aureu, where Ti-PDA@CUR1.5 has the highest antibacterial rate of 62.7% against Escherichia coli and 52.6% against S. aureus. The cytotoxicity test shows that Ti-PDA, Ti-PDA@CUR-x (x = 0.5, 1.0, 1.5, 2.0, 2.5) has almost no toxicity.

Dopamine (DA), which not only contains catechols, but also includes amino substances. Because DOPA derivative is dopamine, it's essentially the same as DOPA. According to the study of related experts, such as Lee, DA will self-react in the alkaline aerobic humid environment, and PDA nanofilms containing catechol units will be generated on the surface of the substance. The preliminary work showed that polydopamine (PDA) showed excellent advantages in adsorption and bio-compatibility in vivo. In addition, because of its excellent chemical properties, PDA can be used as a "platform" for "secondary modification", grafting a variety of functional small molecules onto the matrix, so as to improve the matrix's osteogenic, antibacterial properties. This paper briefly introduces the research progress of PDA in medical materials and other aspects in order to lay a foundation for PDA to be used more in medical materials research and development.

Titanium and its alloys have excellent mechanical and biocompatibility features, which are commonly utilized in the production of surgical instruments, such as scalpels, surgical tweezers, needle holders, etc. However, lacking antibacterial ability, titanium materials are susceptible to bacterial infection, which hinders the success of surgical operations. Medical titanium substrates were modified using polydopamine (PDA) coatings in this study, followed by cadmium (Cd) and copper (Cu) ions loaded into the PDA coating to endow titanium surgical instruments with antibacterial properties. The surface topography, chemical state, ion release, and other features of the specimen were analyzed. Additionally, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Cd and Cu ions against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) were quantitatively determined through serial dilution methodology. The antibacterial features of embellished substrates were investigated against both S. aureus and E. coli. The results demonstrated that the dual-ions (Cd/Cu) modified coating exhibits a reduction in ion release compared to the single ion loaded coatings, with Cd ions demonstrating a 95.13% reduction. Furthermore, the antimicrobial ability of the dual-ions (Cd/Cu) modified coating against S. aureus and E. coli was superior to the PDA coating, with antibacterial rates of 99.89% and 92.04%, respectively. The Cd/Cu co-modified coating demonstrates a balance between low ion release and excellent antimicrobial activity, having great potential for application in antimicrobial surgical instruments.

Bacterial infections, particularly those involving multidrug-resistant pathogens and biofilm-associated infections in wound and implant-related settings, remain difficult to treat with conventional antibiotics alone. Photothermal therapy (PTT) has emerged as a non-antibiotic antibacterial strategy owing to its localized heat generation, broad-spectrum antibacterial activity, spatial controllability, and low risk of inducing conventional drug resistance. The antibacterial efficacy of PTT is largely governed by photothermal agents (PTAs), whose light absorption capacity, photothermal conversion efficiency, structural stability, biosafety, and bacterial interfacial interactions determine therapeutic performance. This review summarizes recent advances in antibacterial PTT from the perspectives of PTA design, excitation windows, and therapeutic integration. Representative first near-infrared window (NIR-I) PTAs, including noble metal nanomaterials, carbon-based nanomaterials, metal sulfides/oxides, metal-organic frameworks, and organic PTAs, are discussed with emphasis on their structural characteristics, photothermal mechanisms, surface regulation strategies, and antibacterial performance. Recent progress in second near-infrared window (NIR-II) PTAs is then highlighted, particularly their advantages in deeper tissue penetration, biofilm treatment, imaging-guided therapy, and precise intervention in complex infections. PTT-based combination strategies involving photodynamic therapy, chemodynamic therapy, and immunotherapy are also reviewed to illustrate how localized heat can synergize with oxidative damage, catalytic radical generation, immune modulation, and infection microenvironment regulation to enhance antibacterial efficacy. Finally, challenges and future directions of antibacterial PTT are discussed, including improving PTA stability and biocompatibility, minimizing thermal damage to normal tissues, enhancing infection-site responsiveness, and promoting clinical translation. Overall, this review provides a materials and biointerface perspective on how PTA design, NIR excitation, and therapeutic integration can guide the development of effective antibacterial photothermal platforms and their clinical translation.