Selective laser melting (SLM) is emerging as a promising 3D printing method for orthopedic and dental applications. However, SLM-based Ti6Al4V components frequently exhibit high roughness values and partial surface defects. Laser polishing (LP) is a newly developed technology to improve the surface quality of metals. In this research, LP is applied to improve the surface finish of components. The results show that the laser beam can neatly ablate the aggregates of metallic globules and repair cracks and pores on the surface, resulting in a smooth surface with nanocomposites. Overall, the results indicate that using LP optimizes surface morphology to favor fatigue behavior and osteoblastic differentiation. These findings provide foundational data to improve the surface roughness of a laser-polished implant and pave the way for optimized mechanical behavior and biocompatibility via the laser process.

Bone substitutes with strong antibacterial properties and bone regeneration effects have an inherent potential in the treatment of severe bone tissue infections, such as osteomyelitis. In this study, vancomycin (Van) was loaded into zeolitic imidazolate framework-8 (ZIF-8) to prepare composite particles, which is abbreviated as V@Z. As a pH-responsive particle, ZIF-8 can be cleaved in the weak acid environment caused by bacterial infection to realize the effective release of drugs. Then, V@Z was loaded into polyvinyl alcohol (PVA) fiber by electrospinning to prepare PVA/V@Z composite bone filler. The drug-loading rate of V@Z was about 6.735%. The membranes exhibited super hydrophilicity, water absorption and pH-controlled Van release behavior. The properties of anti E. coli and S. aureus were studied under the pH conditions of normal physiological tissues and infected tissues (pH 7.4 and pH 6.5, respectively). It was found that the material had good surface antibacterial adhesion and antibacterial property. The PVA/V@Z membrane had the more prominent bacteria-killing effect compared with the same amount of single antibacterial agent containing membrane such as ZIF-8 or Van loaded PVA, and the antibacterial rate was up to 99%. The electrospun membrane had good biocompatibility and can promote MC3T3-E1 cell spreading on it.

It is critical to construct stimuli-responsive multifunctional nanoparticles for the drug delivery system for cancer treatment. Zeolitic imidazolate framework-8 (ZIF-8) has a large specific surface area and decomposes quickly under acidic conditions, which presents an excellent potential in pH-sensitive drug carriers. However, the mere chemotherapeutic drug loaded into ZIF-8 is a monotherapy and may restrict the therapeutic efficacy of malignancies. In this work, an effective nanoparticle-based delivery platform is established to simultaneously encapsulate doxorubicin (DOX) and MXene quantum dot (MQD) in ZIF-8 nanoparticles (MQD@ZIF-8/DOX). Under near-infrared (NIR) laser (808 nm) and UV light (365 nm) irradiation, MQD@ZIF-8 demonstrates a high photothermal conversion efficiency and reactive oxygen species (ROS) production, which shows excellent photothermal therapy and photodynamic therapy effects. Furthermore, the release of DOX-loaded into MQD@ZIF-8 nanoparticles is significantly increased under NIR laser irradiation and at pH 5.6, indicating that acidic conditions and NIR laser irradiation can be effectively combined to stimulate the drug release. The cellular experiments show that MQD@ZIF-8/DOX has an obvious killing effect on HeLa cells and achieves the combined anti-tumor effect of chemotherapy and phototherapy.

Naturally inspired nanostructured surfaces, by mechanically inhibiting bacterial adhesion or killing bacteria, effectively prevent the emergence of antibiotic resistance, making them a promising strategy against healthcare-associated infections. However, the current mechanical antibacterial mechanism of nanostructures is not clear, thus limiting their potential application in medical devices. This work mainly investigates the mechanical influence mechanism of biomimetic nanostructure parameters on bacterial adhesion and growth status. The results of 12 h bacterial culture showed that compared to flat surfaces, nanostructures reduced the adhesion of both E. coli and S. aureus bacteria by 49%~82%. The bactericidal efficiency against E. coli increased by 5.5%~31%, depending on the shape of the nanostructures. Nanostructures with smaller tip diameters exhibited the best anti-bacterial adhesion effects. Nanostructures with sharp tips and larger interspaces showed greater bactericidal effects against E. coli. Surfaces with larger tip diameters had the poorest antibacterial effects. Subsequently, a finite element model was established to quantitatively analyze the mechanical interactions between bacteria and nanostructures. It was found that different nanostructures affect bacterial adhesion and growth by altering the contact area with bacteria and inducing stress and deformation on the cell wall. Nanostructures with smaller tip diameters reduced the attachment area to bacteria, thereby reducing bacterial adhesion strength. Nanostructures with larger interspaces induced greater stress and deformation on the cell wall, thereby enhancing bactericidal efficiency. Finally, experimental verification with L929 cells confirmed that nanostructures do not cause mechanical damage to the cells. These studies deepen our understanding of the antibacterial mechanism of biomimetic nanostructures and provide new insights for the design of optimal nanostructures.

The construction of micro-nano composite structures is an effective method to improve the biological inertness of medical stainless steel surfaces. However, micro-nano structures often result in superhydrophobic surfaces, which hinder cell-surface contact. Additionally, the influence of surface structures on wettability has impeded research into the effects of wettability on the biological properties of medical stainless steel surfaces. In this study, femtosecond laser technology was used to fabricate micro-nano composite structures on 316L stainless steel surfaces. Reversible wettability transitions (between superhydrophobicity and superhydrophilicity) were achieved without altering the surface microstructure via UV irradiation and dark storage. The effects of superhydrophobicity and superhydrophilicity on the biological activity of stainless steel surfaces were investigated through in vitro mineralization experiments, BSA adsorption assays, and in vitro cell adhesion/proliferation tests. These findings provide new insights for the surface design of medical stainless steel and the mechanistic study of how wettability influences biological performance.