In vitro evaluation of the biocompatibility and bioactivity of a SLM-fabricated NiTi alloy with superior tensile property.

Because nickel-titanium (NiTi) alloys have unique functions, such as superelasticity, shape memory, and hysteresis similar to bone in the loading-unloading cycles of their recoverable deformations. They likely offer good bone integration, a low loosening rate, individual customization, and ease of insertion. Due to the poor processability of NITI, traditional methods cannot manufacture NiTi products with complex shapes. Orthopedic NiTi implants need to show an adequate fracture elongation of at least 8%. Additive manufacturing can be used to prepare NiTi implants with complex structures and tunable porosity. However, as previously reported, additively manufactured NiTi alloys could only exhibit a maximum tensile fracture strain of 7%. In new reports, a selective laser melting (SLM)-NiTi alloy has shown greater tensile strain (15.6%). Nevertheless, due to the unique microstructure of additive manufacturing NiTi that differs from traditional NITI, the biocompatibility of SLM-NITI manufactured by this new process requires further evaluation In this study, the effects of the improved NiTi alloy on bone marrow mesenchymal stem cell (BMSC) proliferation, adhesion, and cell viability were investigated via in vitro studies. A commercial Ti-6Al-4V alloy was studied side-by-side for comparison. Like the Ti-6Al-4V alloy, the SLM-NiTi alloy exhibited low cytotoxicity toward BMSCs and similar effect on cell adhesion or cell viability. This study demonstrates that the new SLM-NiTi alloy, which has exhibited improved mechanical properties, also displays excellent biocompatibility. Therefore, this alloy may be a superior implant material in biomedical implantation.

Effect of Strontium-Substituted Calcium Phosphate Coatings Prepared by One-Step Electrodeposition at Different Temperatures on Corrosion Resistance and Biocompatibility of AZ31 Magnesium Alloys.

As potential degradable biomaterials, magnesium (Mg) alloys have development prospects in the field of orthopedic load-bearing, whereas the clinical application has encountered a bottleneck due to a series of problems caused by its rapid corrosion. In this study, strontium-substituted calcium phosphate (CaP) coatings with different structures were prepared on the surface of the Mg matrix by a simple one-step electrodeposition method at different temperatures, which enhanced the poor corrosion resistance of the Mg matrix. The coated sample prepared at 65 °C reduced the corrosion current density by 3 orders of magnitude and increased the impedance by nearly 2 orders of magnitude compared with bare Mg alloy, thanks to its dense fibrous structure similar to that of natural bones. Although the coating composition varies with different preparation temperatures, CaP, as an inorganic component similar to natural bone, has good cytocompatibility. Doping the right amount of strontium, which is a trace element in human bones, is beneficial to stimulate osteoblast differentiation, inhibit the activity of osteoclasts, and induce the formation of bone tissues. This provides a new option for modifying the Mg alloy with CaP coatings as a base.

Study of the influence of macro-structure and micro-structure on the mechanical properties of stag beetle upper jaw.

Macrostructural control of stress distribution and microstructural influence on crack propagation is one of the strategies for obtaining high mechanical properties in stag beetle upper jaws. The maximum bending fracture force of the stag beetle upper jaw is approximately 154, 000 times the weight of the upper jaw. Here, we explore the macro and micro-structural characteristics of two stag beetle upper jaws and reveal the resulting differences in mechanical properties and enhancement mechanisms. At the macroscopic level, the elliptic and triangular cross-sections of the upper jaw of the two species of stag beetles have significant effects on the formation of cracks. The crack generated by the upper jaws with a triangular section grows slowly and deflects easily. At the microscopic level, the upper jaw of the two species is a chitin cross-layered structure, but the difference between the two adjacent fiber layers at 45° and 50° leads to different deflection paths of the cracks on the exoskeleton. The mechanical properties of the upper jaw of the two species of stag beetle were significantly different due to the interaction of macro-structure and micro-structure. In addition, a series of bionic samples with different cross-section geometries and different fiber cross angles were designed, and mechanical tests were carried out according to the macro-structure and micro-structure characteristics of the stag beetle upper jaw. The effects of cross-section geometry and fiber cross angle on the mechanical properties of bionic samples are compared and analyzed. This study provides new ideas for designing and optimizing highly loaded components in engineering. STATEMENT OF SIGNIFICANCE: The upper jaw of the stag beetle is composed of a complex arrangement of chitin and protein fibers, providing both rigidity and flexibility. This structure is designed to withstand various mechanical stresses, including impacts and bending forces, encountered during its burrowing activities and interactions with its environment. The study of the upper jaw of the stag beetle can provide an efficient structural design for engineering components that are subjected to high loads. Understanding the relationship between structure and mechanical properties in the stag beetle upper jaw holds significant implications for biomimetic design and engineering.

Novel-Ink-Based Direct Ink Writing of Ti6Al4V Scaffolds with Sub-300 µm Structural Pores for Superior Cell Proliferation and Differentiation.

Ti6Al4V scaffolds with pore sizes between 300 and 600 µm are deemed suitable for bone tissue engineering. However, a significant proportion of human bone pores are smaller than 300 µm, playing a crucial role in cell proliferation, differentiation, and bone regeneration. Ti6Al4V scaffolds with these small-sized pores are not successfully fabricated, and their cytocompatibility remains unknown. The study presents a novel ink formula specifically tailored for fabricating Ti6Al4V scaffolds featuring precise and unobstructed sub-300 µm structural pores, achieved by investigating the rheological properties and printability of five inks containing 60-77.5 vol% Ti6Al4V powders and bisolvent binders. Ti6Al4V scaffolds with 50-600 µm pores are fabricated via direct ink writing and subjected to in vitro assays with MC3T3-E1 and bone marrow mesenchymal stem cells. The 100 µm pore-sized scaffolds exhibit the highest cell adhesion and proliferation capacity based on live/dead assay, FITC-phalloidin/4',6-diamidino-2-phenylindole staining, and cell count kit 8 assay. The alizarin red staining, real-time quantitative PCR assay, and immunocytochemical staining demonstrate the superior osteogenic differentiation potential of 100 and 200 µm pore-sized scaffolds. The importance of sub-300 µm structrual pores is highlighted, redefining the optimal pore size for Ti6Al4V scaffolds and advancing bone tissue engineering and clinical medicine development.

Bio-inspired copper ion-chelated chitosan coating modified UHMWPE fibers for enhanced interfacial properties of composites.

Ultra-high molecular weight polyethylene (UHMWPE) fibers are broadly applied in lightweight and high-strength composite fiber materials. However, the development of UHMWPE fibers is limited by their smooth and chemically inert surfaces. To address the issues, a modified UHMWPE fibers material has been fabricated through the chelation reaction between Cu2+ and chitosan coatings within the surface of fibers after plasma treatment, which is inspired by the hardening mechanism, a crosslinked network between metal ions and proteins/polysaccharides of the tips and edges in arthropod-specific cuticular tools. The coatings improve the surface wettability and interfacial bonding ability, which are beneficial in extending the application range of UHMWPE fibers. More importantly, compared to the unmodified UHMWPE fiber cloths, the tensile property of the modified fiber cloths is increased by 18.89% without damaging the strength, which is infrequent in modified UHMWPE fibers. Furthermore, the interlaminar shear strength and fracture toughness of the modified fibers laminate are increased by 37.72% and 135.90%, respectively. These improvements can be attributed to the synergistic effects between the surface activity and the tiny bumps of the modified UHMWPE fibers. Hence, this work provides a more straightforward and less damaging idea of fiber modification for manufacturing desirable protective and medical materials.

Adhesion Behavior in Fish: From Structures to Applications.

In nature, some fish can adhere tightly to the surface of stones, aquatic plants, and even other fish bodies. This adhesion behavior allows these fish to fix, eat, hide, and migrate in complex and variable aquatic environments. The adhesion function is realized by the special mouth and sucker tissue of fish. Inspired by adhesion fish, extensive research has recently been carried out. Therefore, this paper presents a brief overview to better explore underwater adhesion mechanisms and provide bionic applications. Firstly, the adhesion organs and structures of biological prototypes (e.g., clingfish, remora, Garra, suckermouth catfish, hill stream loach, and goby) are presented separately, and the underwater adhesion mechanisms are analyzed. Then, based on bionics, it is explained that the adhesion structures and components are designed and created for applications (e.g., flexible gripping adhesive discs and adhesive motion devices). Furthermore, we offer our perspectives on the limitations and future directions.

Stearic Acid Treatment Enhancing Corrosion Resistance of Biomimetic-Deposited Calcium Phosphate Dihydrate Coating on Medical Degradable Magnesium Alloy.

Magnesium (Mg) alloys, a degradable material, have been studied for medical applications due to their excellent mechanical and chemical properties. However, their applications are limited by rapid corrosion. In this work, stearic acid and sodium stearate were used to treat the silane-induced calcium phosphate dihydrate coating to improve its protection for the Mg alloy further without changing the bone-like structure of calcium phosphate. The different effects of stearic acid treatment and sodium stearate treatment were compared. Electrochemical test and immersion test results confirmed that the corrosion resistance of the stearic acid-treated composite coating was greatly enhanced with a reduced corrosion current density by 3 orders of magnitude and hydrogen evolution reduced to 1/25 after 14 days. The stearic acid-treated coating also exhibited improved in vitro biocompatibility corroborated by promoted cell viability and better cell morphology.

A photothermal therapy enhanced mechano-bactericidal hybrid nanostructured surface.

Polymeric materials that have been extensively applied in medical devices, wearable electronics, and food packaging are readily contaminated by bothersome pathogenic bacteria. Bioinspired mechano-bactericidal surfaces can deliver lethal rupture for contacted bacterial cells through mechanical stress. However, the mechano-bactericidal activity based only on polymeric nanostructures is not satisfactory, especially for the Gram-positive strain which is generally more resistant to mechanical lysis. Here, we show that the mechanical bactericidal performance of polymeric nanopillars can be significantly enhanced by the combination of photothermal therapy. We fabricated the nanopillars through the combination of low-cost anodized aluminum oxide (AAO) template-assisted method with an environment-friendly Layer-by-Layer (LbL) assembly technique of tannic acid (TA) and iron ion (Fe3+). The fabricated hybrid nanopillar exhibited remarkable bactericidal performances (more than 99%) toward both Gram-negative Pseudomonas aeruginosa (P. aeruginosa) and stubborn Gram-positive Staphylococcus aureus (S. aureus) bacteria. Notably, this hybrid nanostructured surface displayed excellent biocompatibility for murine L929 fibroblast cells, indicating a selective biocidal activity between bacterial cells and mammalian cells. Thus, the concept and antibacterial system described here present a low-cost, scalable, and highly repeatable strategy for the construction of physical bactericidal nanopillars on polymeric films with high performance and biosafety, but without any risks of causing antibacterial resistance.

Biocompatible mechano-bactericidal nanopatterned surfaces with salt-responsive bacterial release.

Bio-inspired nanostructures have demonstrated highly efficient mechano-bactericidal performances with no risk of bacterial resistance; however, they are prone to become contaminated with the killed bacterial debris. Herein, a biocompatible mechano-bactericidal nanopatterned surface with salt-responsive bacterial releasing behavior is developed by grafting salt-responsive polyzwitterionic (polyDVBAPS) brushes on a bio-inspired nanopattern surface. Benefiting from the salt-triggered configuration change of the grafted polymer brushes, this dual-functional surface shows high mechano-bactericidal efficiency in water (low ionic strength condition), while the dead bacterial residuals can be easily lifted by the extended polymer chains and removed from the surface in 1 M NaCl solution (high ionic strength conditions). Notably, this functionalized nanopatterned surface shows selective biocidal activity between bacterial cells sand eukaryotic cells. The biocompatibility with red blood cells (RBCs) and mammalian cells was tested in vitro. The histocompatibility and prevention of perioperative contamination activity were verified by in vivo evaluation in a rat subcutaneous implant model. This nanopatterned surface with bacterial killing and releasing activities may open new avenues for designing bio-inspired mechano-bactericidal platforms with long-term efficacy, thus presenting a facile alternative in combating perioperative-related bacterial infection. STATEMENT OF SIGNIFICANCE: Bioinspired nanostructured surfaces with noticeable mechano-bactericidal activity showed great potential in moderating drug-resistance. However, the nanopatterned surfaces are prone to be contaminated by the killed bacterial debris and compromised the bactericidal performance. In this study, we provide a dual-functional antibacterial conception with both mechano-bactericidal and bacterial releasing performances not requiring external chemical bactericidal agents. Additionally, this functionalized antibacterial surface also shows selective biocidal activity between bacteria and eukaryotic cells, and the excellent biocompatibility was tested in vitro and in vivo. The new concept for the functionalized mechano-bactericidal surface here illustrated presents a facile antibiotic-free alternative in combating perioperative related bacterial infection in practical application.

Bio-Inspired Self-Adaptive Nanocomposite Array: From Non-antibiotic Antibacterial Actions to Cell Proliferation.

Pathogenic bacterial infection and poor native tissue integration are two major issues encountered by biomaterial implants and devices, which are extremely hard to overcome within a single surface, especially for those without involvement of antibiotics. Herein, a self-adaptive surface that can transform from non-antibiotic antibacterial actions to promotion of cell proliferation is developed by in situ assembly of bacteriostatic 3,3'-diaminodipropylamine (DADP)-doped zeolitic imidazolate framework-8 (ZIF-8) on bio-inspired nanopillars. Initially, the nanocomposite surface shows impressive antibacterial effects, even under severe bacterial infection, due to the combination of mechano-bactericidal activity from a nanopillar structure and bacteriostatic activity contributed by pH-responsive release of DADP. After the complete degradation of the ZIF-8 layer, the refurbished nanopillars not only can still physically rupture bacterial membrane but also facilitate mammalian cell proliferation, due to the obvious difference in cell size. More strikingly, the nanocomposite surface totally avoids the usage of antibiotics, eradicating the potential risk of antimicrobial resistance, and the surface exhibited excellent histocompatibility and lower inflammatory response properties as revealed by in vivo tests. This type of self-adaptive surface may provide a promising alternative for addressing the intractable implant-associated requirements, where antibiotic-free antibacterial activity and native tissue integration are both highly needed.

Protocol to construct biomimetic carbon fiber composites with improved interfacial strength.

Weak interfacial strength restricts the mechanical properties of carbon fiber-reinforced composites. Here, inspired by natural hook-groove microstructure system (HGMS) of black kite (Milvus migrans), we detail the steps to construct a biomimetic HGMS based on dopamine-functionalized carbon fibers (CFs) and zinc oxide nanorods (ZnO NRs) using a two-step modification approach. We describe the fabrication of biomimetic carbon fiber composites using vacuum-assisted contact molding (VACM) and subsequent characterization using standard comprehensive mechanical tests techniques. For complete details on the use and execution of this protocol, please refer to Wang et al. (2022).

Biomechanical comparison between bioabsorbable and medical titanium screws in distal chevron osteotomy of first metatarsal in hallux valgus treatment.

Polylactic acid (PLA) composite materials have been used for manufacturing surgical internal fixations owing to their satisfactory mechanical strength and absorbability. This, in turn, reduces the pain and risks associated with the secondary operation on patients. Although the mechanical properties of bioabsorbable materials have been considerably enhanced via modifications and optimization, the strength and stiffness of these materials are considerably inferior to those of metals. Therefore, whether PLA fixation can satisfy the required mechanical properties has been a consistent subject of interest in clinical practice. In this study, the mechanical properties of PLA bioabsorbable (Changchun SinoBiomaterials Co., Ltd., China) and titanium hollow screws (Shanghai Carefix Medical Instrument Co., Ltd., China) were compared in hallux valgus surgery with chevron osteotomy. Three-dimensionally printed osteotomy guides were used for cutting the artificial first metatarsal model (SKU3422, Sawbones) to reduce the errors due to the variations in individual bone densities and osteotomy angles; the cut parts were subsequently fixed with the PLA and titanium alloy screws. A digital image correlation system was used to obtain the full-field strain of the specimen to evaluate the mechanical behaviors under static and fatigue loads. The experimental results demonstrated that, by designing a reasonable osteotomy angle, the compressive strength of the specimen with PLA screws under chevron osteotomy can be as high as that of the specimen with titanium screws. Moreover, their stiffness can reach up to 60%-90% that of titanium screws. After 240,000 cycles of compression, the PLA screws maintained their strength and stiffness. These bioabsorbable fixtures can effectively prevent stress shielding under a suitable osteotomy. Hence, as an optimal substitute for metal fixtures, an increase in clinical applications to surgery is anticipated, along with progressive in-depth research on the biomechanical properties of bioabsorbable materials.

Degradable Bioinspired Hypersensitive Strain Sensor with High Mechanical Strength Using a Basalt Fiber as a Reinforced Layer.

Flexible strain sensors have received extensive attention due to their broad application prospects. However, a majority of present flexible strain sensors may fail to maintain normal sensing performances upon external loads because of their low strength and thus their performances are affected drastically with increasing loads, which severely restricts large-area popularization and application. Scorpions with hypersensitive vibration slit sensilla are coincident with a similar predicament. Herein, it is revealed that scorpions intelligently use risky slits to detect subtle vibrations, and meanwhile, the distinct layered composites of the main body of this organ prevent catastrophic failure of the sensory structure. Furthermore, the extensive use of flexible sensors will generate a mass of electronic waste just as obsoleting silicon-based devices. Considering mechanical properties and environmental issues, a flexible strain sensor based on an elastomer (Ecoflex)-wrapped fabric with the woven structure was designed and fabricated. Note that introducing a "green" basalt fiber (BF) into a degradable elastomer can effectively avoid environmental issues and significantly enhance the mechanical properties of the sensor. As a result, it shows excellent sensitivity (gauge factor (GF) ∼138.10) and high durability (∼40,000 cycles). Moreover, the reduced graphene oxide (RGO)/BF/Ecoflex flexible strain sensor possesses superior mechanical properties (tensile strength ∼20 MPa) and good flexibility. More significantly, the sensor can maintain normal performances under large external tensions, impact loads, and even underwater environments, providing novel design principles for environmentally friendly flexible sensors under extremely harsh environments.

Bioinspired nanopillar surface for switchable mechano-bactericidal and releasing actions.

Constructing safe and effective antibacterial surfaces has continuously received great attention, especially in healthcare-related fields. Bioinspired mechano-bactericidal nanostructure surfaces could serve as a promising strategy to reduce surface bacterial contamination while avoiding the development of antibiotic resistance. Although effective, these nanostructure surfaces are prone to be contaminated by the accumulation of dead bacteria, inevitably compromising their long-term antibacterial activity. Herein, a bioinspired nanopillar surface with both mechano-bactericidal and releasing actions is developed, via grafting zwitterionic polymer (poly(sulfobetaine methacrylate) (PSBMA)) on ZnO nanopillars. Under dry conditions, this nanopillar surface displays remarkable mechano-bactericidal activity, because the collapsed zwitterionic polymer layer makes no essential influence on nanopillar structure. Once being incubated with aqueous solution, the surface could readily detach the killed bacteria and debris, owing to the swelling of the zwitterionic layer. Consequentially, the surface antibacterial performances can be rapidly and controllably switched between mechano-bactericidal action and bacteria-releasing activity, guaranteeing a long-lasting antibacterial performance. Notably, these collaborative antibacterial behaviors are solely based on physical actions, avoiding the risk of triggering bacteria resistance. The resultant nanopillar surface also enjoys the advantages of substrate-independency and good biocompatibility, offering potential antibacterial applications for biomedical devices and hospital surfaces.

Corrosion Resistance and Biocompatibility of Calcium Phosphate Coatings with a Micro-Nanofibrous Porous Structure on Biodegradable Magnesium Alloys.

Magnesium (Mg) and its alloys have exhibited great potential for orthopedic applications; however, their poor corrosion resistance and potential cytotoxicity have hindered their further clinical applications. In this study, we prepared a calcium phosphate (Ca-P) coating with a micro-nanofibrous porous structure on the Mg alloy surface by a chemical conversion method. The morphology, composition, and corrosion performance of the coatings were investigated by scanning electron microscope (SEM), energy-dispersive spectrometer (EDS), X-ray diffraction (XRD), immersion tests, and electrochemical measurements. The effects of the preparation temperature of the Ca-P coatings were analyzed, and the results confirmed that the coating obtained at 60 °C had the densest structure and the best corrosion resistance. In addition, a systematic investigation into cell viability, ALP activity, and cell morphology confirmed that the Ca-P coating had excellent biocompatibility, which could effectively promote the proliferation, differentiation, and adhesion of osteoblasts. Hence, the Ca-P coating demonstrates great potential in the field of biodegradable Mg-based orthopedic implant materials.

The effect of microstructure on mechanical properties of corn cob.

As a natural biomass resource, corn cob has excellent mechanical properties and a special layered structure. To investigate the relationship between the mechanical properties and microstructure of corn cob, the ultra-deep field 3D microscope was used to characterize the macro geometric parameters, and the scanning electron microscopy (SEM) was observe the microstructure of the corn cob. The Fourier transform infrared spectrometer was used to analyze the fiber composition, revealing the contribution of fiber composition to the mechanical properties. Axial compression, radial compression, and three-point bending tests were performed on corn cob using a universal testing machine. Moreover, an impact testing machine was used for impact tests. The results show that a corn cob is structurally divided into the pith, woody ring, and glume, mainly composed of cellulose, hemicellulose, and lignin in fiber composition, respectively. The pith is a porous sponge-like tissue that has a greater bearing capacity while maintaining a low density. It is also a progressively hardening material with good buffering properties under impact loads. The woody ring is the primary source of mechanical strength, whose microstructure is a hollow tubular structure composed of cellulose and bonded by lignin. The internal microstructure of the glume is also porous and spongy, but the mechanical properties are mainly manifested in its macrostructure. The results of this study may provide a reference for the subsequent processing and industrial application of corn cob, and the unique structure of corn cob is also an excellent bionic prototype for lightweight design.

Investigation of microstructure and dissimilar materials connection patterns of mantis shrimp saddle.

The microstructure and dissimilar materials connection patterns of mantis shrimp saddle were investigated. The outer layer with layered helical structure and inner layer with slablike laminae structure constructed the microstructure characteristics of saddle. The merus and membrane were characterized by layered structure. The lamina of saddle connected the corresponding lamina in merus and membrane, building the continuous and smooth coupling connection patterns. The entitative "hard-hard" and "hard-soft" transitions of dissimilar materials at micro level enhanced the steady transmit of driven force. The saddle exhibited high mechanical strength. With the increase of in-situ tensile displacement, the number of fractured fragments on saddle outer layer surface increased, which subjected to tensile load and defused the damage in the form of mineralized surface fragmentation. In the inner part of saddle, the fracture of mineralized laminae and crack deflection mechanisms bore the tensile load influence. The combination of microstructure with high mechanical strength and continues micro lamina connection endowed the concise dissimilar materials connection and efficient elastic energy storage property of saddle, which can be treated as the bionic models for design and preparation of fiber reinforced resin composite, hyperelastic material and so on.

The microstructure, mechanical properties, corrosion performance and biocompatibility of hydroxyapatite reinforced ZK61 magnesium-matrix biological composite.

Magnesium (Mg)-based composites, as biomaterials, have attracted widespread attention due to their adjustable mechanical properties like elastic modulus, ductility, ultimate tensile strength, and corrosion resistance. In this study, hydroxyapatite (HA) reinforced ZK61 Mg-matrix composites were prepared by powder metallurgy and hot extrusion methods. The influence of the content of HA (10 wt%, 20 wt%, and 30 wt%) on the microstructure, density, mechanical properties, corrosion property and biocompatibility were investigated. The results showed that the density and yield strength of the composites match those of natural bone. Moreover, the composite with 10 % HA (ZK61-10HA) exhibited the best corrosion resistance, as determined by the electrochemical measurement and immersion test in simulated body fluid (SBF) at 37 °C. In addition, the ZK61-10HA composite significantly enhanced the cell viability (≥78 %) compared with ZK61 alloy in vitro testing. It is demonstrated that the mechanical properties, corrosion resistance and biocompatibility of Mg alloy can be effectively controlled by adjusting the content of HA, which suggested that the ZK61-HA composites were promising candidates for degradable implant materials.

Thermoresponsive Nanostructures: From Mechano-Bactericidal Action to Bacteria Release.

Overuse of antibiotics can increase the risk of notorious antibiotic resistance in bacteria, which has become a growing public health concern worldwide. Featured with the merit of mechanical rupture of bacterial cells, the bioinspired nanopillars are promising alternatives to antibiotics for combating bacterial infections while avoiding antibacterial resistance. However, the resident dead bacterial cells on nanopillars may greatly impair their bactericidal capability and ultimately impede their translational potential toward long-term applications. Here, we show that the functions of bactericidal nanopillars can be significantly broadened by developing a hybrid thermoresponsive polymer@nanopillar-structured surface, which retains all of the attributes of pristine nanopillars and adds one more: releasing dead bacteria. We fabricate this surface through coaxially decorating mechano-bactericidal ZnO nanopillars with thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) brushes. Combining the benefits of ZnO nanopillars and PNIPAAm chains, the antibacterial performances can be controllably regulated between ultrarobust mechano-bactericidal action (∼99%) and remarkable bacteria-releasing efficiency (∼98%). Notably, both the mechanical sterilization against the live bacteria and the controllable release for the pinned dead bacteria solely stem from physical actions, stimulating the exploration of intelligent structure-based bactericidal surfaces with persistent antibacterial properties without the risk of triggering drug resistance.

Self-enriched mesoporous silica nanoparticle composite membrane with remarkable photodynamic antimicrobial performances.

Mesoporous silica nanoparticle (MSN) demonstrates great potentials as a loading platform for bactericidal agents, but may be limited by its application form of bulk or powder. Herein, we developed MSN surface-enriched composite membranes with remarkable photodynamic antimicrobial activities via a facile electrospinning method. The mixture of zein and polycaprolactone (PCL) was served as the polymeric matrix, while the methylene blue (MB) loaded MSN was modified by trichloro (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane (THFS) and acted as reactive oxygen species (ROS) generator to exert their antimicrobial performances. Owing to its low surface energy, the fluorinated MSN tended to be enriched on the surface of the nanofiber, hence significantly enhancing the ROS generation. Moreover, benefiting from the surface enrichment of the fluorinated nanoparticles, the composite membrane displayed obvious surface hydrophobicity and exhibited discernible bacterial repellency. Subsequently, upon visible light (660 nm) irradiation, the composite membrane demonstrated remarkable photodynamic antibacterial activities against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) but without essential detrimental impacts on the mammalian cells. We envision that this self-enriched MSN composite membrane may find broad applications in bacterial infection-resistant areas.