Cu2-xS homojunction coatings empower titanium implants with near-infrared-triggered antibacterial and antifouling properties.

For decades, implant-associated infections (IAIs) caused by pathogenic bacteria have been associated with high failure and mortality rates in implantation surgeries, posing a serious threat to global public health. Therefore, developing a functionalized biomaterial coating with anti-fouling and anti-bacterial functions is crucial for alleviating implant infections. Herein, a near-infrared-responsive anti-bacterial and anti-adhesive coating (Ti-PEG-Cu2-xS) constructed on the surface of titanium (Ti) implants is reported. This coating is composed of nano-Cu2-xS with anti-bacterial activity and super-hydrophilic polyethylene glycol (PEG). Under near-infrared irradiation, the nano-catalyst Cu2-xS on the surface of Ti-PEG-Cu2-xS induces bacterial death by catalyzing the production of singlet oxygen (1O2). The Ti-PEG-Cu2-xS coating can effectively prevent bacterial adhesion and biofilm formation. This coating combines the antibacterial mechanisms of "active attack" and "passive defense", which can kill bacteria and inhibit biofilm formation. The results of in vitro and in vivo experiments have shown that Ti-PEG-Cu2-xS exhibits excellent anti-bacterial properties under near-infrared irradiation and can effectively prevent implant-related infections caused by Escherichia coli (E. coli) ATCC 8739 and Staphylococcus aureus (S. aureus). The antibacterial efficiency of Ti-PEG-Cu2-xS coatings against E. coli was 99.96% ± 0.058% and that of S. aureus was 99.66% ± 0.26%, respectively. In addition, the Ti-PEG-Cu2-xS coating has good blood compatibility and excellent bactericidal ability. Therefore, this multifunctional coating combines a non-adhesive surface strategy and a near-infrared phototherapy sterilization method, effectively blocking the initial attachment and proliferation of bacteria on implants via photothermal/photodynamic effects and providing a promising method for preventing bacterium-induced IAIs.

Self-healing hydrogel based on poly (vinyl alcohol)-poly (lysine)-gum arabic accelerates diabetic wound healing under photothermal sterilization.

Diabetic wounds are a significant clinical challenge. Developing effective antibacterial dressings is crucial for preventing wound ulcers caused by bacterial infections. In this study, a self-healing antibacterial hydrogel (polyvinyl alcohol (PVA)-polylysine-gum arabic, PLG hydrogels) with near-infrared photothermal response was prepared by linking PVA and a novel polysaccharide-amino acid compound (PG) through borate bonding combined with freeze-thaw cycling. Subsequently, the hydrogel was modified by incorporating inorganic nanoparticles (modified graphene oxide (GM)). The experimental results showed that the PLGM3 hydrogels (PLG@GM hydrogels, 3.0 wt%) could effectively kill bacteria and promote diabetic wound tissue healing under 808-nm near-infrared laser irradiation. Therefore, this hydrogel system provides a new idea for developing novel dressings for treating diabetic wounds.

An NIR light-driven AgBiS2@ZIF-8 hybrid photocatalyst for rapid bacteria-killing.

Bacterial infection is the most common risk factor that causes the failure of implantation surgery. Therefore, the development of biocompatible implants with excellent antibacterial properties is of utmost importance. In this study, NIR light-driven AgBiS2@ZIF-8 hybrid photocatalysts for rapid bacteria-killing were prepared. AgBiS2@ZIF-8 exhibited excellent photocatalytic activity due to the rapid transfer of photoelectrons from AgBiS2 to ZIF-8, resulting in abundant reactive oxygen species (ROS) to kill bacteria. Meanwhile, AgBiS2@ZIF-8 exhibited a noteworthy photothermal effect, which could effectively convert NIR light into heat. Subsequently, the NIR light-driven antibacterial activity of AgBiS2@ZIF-8/Ti against S. aureus and E. coli was studied. The experimental results showed that AgBiS2@ZIF-8 displayed enhanced photodynamic therapy (PDT) and photothermal therapy (PTT) performance. Under irradiation with 808 nm NIR light for 10 min, AgBiS2@ZIF-8/Ti could effectively eliminate 98.55% of S. aureus in vitro, 99.34% of E. coli in vitro and 95% S. aureus in vivo. At the same time, AgBiS2@ZIF-8/Ti had good biocompatibility. Therefore, AgBiS2@ZIF-8/Ti showed potential as an antibacterial material, which provided a strategy to fight polymicrobial infections.

AgBiS2@CQDs/Ti nanocomposite coatings for combating implant-associated infections by photodynamic /photothermal therapy.

Biofilm-mediated implant-associated infections are one of the most serious complications of implantation surgery, posing a grave threat to patient well-being. Effectively addressing bacterial infections is crucial for the success of implantation procedures. In this study, we prepared a bismuth sulfide silver@carbon quantum dot composite coating (AgBiS2@CQDs/Ti) on a medical titanium surface by surface engineering design to treat implant-associated infections. The photocatalytic/photothermal activity test results confirmed the excellent photogenerated ROS and photothermal properties of AgBiS2@CQDs/Ti under near-infrared laser irradiation. In vitro antibacterial and in vivo anti-infection experiments showed that the coating combined with photodynamic and photothermal therapies to eradicate bacteria and disrupt mature biofilms under 1064 nm laser irradiation. Consequently, AgBiS2@CQDs/Ti shows promise as an implant coating for treating implant-associated infections post-surgery, thereby enhancing the success rate of implantation procedures. This study also provides a new idea for combating implant-associated infections.

Silk fibroin-based coating with pH-dependent controlled release of Cu2+ for removal of implant bacterial infections.

The implantation of medical devices is frequently accompanied by the invasion of bacteria, which may lead to implant failure. Therefore, an intelligent and responsive coating seems particularly essential in hindering implant-associated infections. Herein, a self-defensive antimicrobial coating, accompanied by silk fibroin as a valve, was successfully prepared on the titanium (Ti-Cu@SF) for pH-controlled release of Cu2+. The results showed that the layer could set free massive Cu2+ to strive against E. coli and S. aureus for self-defense when exposed to a slightly acidic condition. By contrary, a little Cu2+ was released in the physiological situation, which could avoid damage to the normal cells and showed excellent in vitro pH-dependent antibiosis. Besides, in vivo experiment confirmed that Ti-Cu@SF could work as an antibacterial material to kill S. aureus keenly and display negligible toxicity in vivo. Consequently, the design provided support for endowing the layer with outstanding biocompatibility and addressing the issue of bacterial infection during the implantation of Ti substrates.

Fabrication of Laponite-Reinforced Dextran-Based Hydrogels for NIR-Responsive Controlled Drug Release.

Natural polymer gels with sensitivity to near-infrared (NIR) light have attracted the attention of scientists working on intelligent drug delivery systems. Compared to ultraviolet or visible light, NIR light has the advantages of strong trigger levels, deep penetration through affected tissues, and fewer side effects. Herein, we present a topical photothermal hydrogel for NIR-controlled drug delivery. The proposed DexIEM-GM-Laponite hydrogel was prepared through free radical polymerization of vinyl-functionalized dextran (DexIEM), vinyl-modified graphene oxide (GM), and Laponite; thereafter, the hydrogel was loaded with ciprofloxacin (CIP, an antibacterial drug) as a model drug. With the Laponite content increased, the density of crosslinking in the hydrogel increased, and its mechanical properties improved noticeably. Under NIR irradiation, the DexIEM-GM-Laponite hydrogel exhibited a photothermal property, where the surface temperature increased from 26.8 to 55.5 °C. The simulation of subcutaneous drug delivery experiments ex vivo showed that under the specified pork tissue thickness (2, 4, and 6 mm), the CIP release remained NIR-controllable. Additionally, the results of the antibacterial performance tests indicated the excellent antibacterial effect of the hydrogel, and the blood hemolysis ratio of the hydrogel was less than 5%, signifying good blood compatibility. This work will provide an avenue for the application of NIR light-responsive materials in antimicrobial therapy.

Bio-Based Aerogel Based on Bamboo, Waste Paper, and Reduced Graphene Oxide for Oil/Water Separation.

In recent years, the discharge of industrial waste oil has increased and offshore oil leakage has occurred frequently, and thus water pollution has become a worldwide problem that attracts much attention. In this regard, a kind of oil-absorbing material with high oil-absorbing property and good mechanical property is urgently needed. Here, we reported a new type of aerogels with three-dimensional layered voids using natural bamboo powder, waste paper (WP), and graphene oxide (GO) as raw materials. The obtained aerogel had high adsorption capacity (87-121 g/g), compressibility, and high elasticity, which can separate oil from water and selectively absorb oil. This study provides not only a new treatment in agricultural waste treatment but also a facile, green, and low-cost approach to synthesize high-performance graphene-based oil absorbers, which might give us an effective solution for oil pollution of water resources worldwide.

Preparation of silane-dispersed graphene crosslinked vinyl carboxymethyl chitosan temperature-responsive hydrogel with antibacterial properties.

We synthesized a temperature-sensitive antibacterial hydrogel, defined as NIPAM-CG/GM hydrogel. First, vinyl carboxymethyl chitosan (CG) was synthesized as a crosslinking carrier and silane dispersed graphene (GM) was synthesized as a reinforcer. Then, the N-isopropylacrylamide (NIPAM) monomer was free-radical polymerized with the vinyl groups of CG and GM to form a NIPAM-CG/GM hydrogel without any crosslinking agent. The influences of different hydrogel compositions on the microstructure, compressive properties, swelling, drug loading, and drug release properties of the hydrogels were discussed, and its temperature sensitivity was also demonstrated. The results showed that the lower critical solution temperature (LCST) and mechanical properties of the hydrogel could be adjusted by controlling the amount of CG and GM. Next, its biocompatibility was characterized, and its antibacterial performance was tested against Escherichia coli and Staphylococcus aureus. The antibacterial mechanism was explained by measuring the difference in the ion concentration outside the membrane and changes in the morphology of live/dead bacteria. NIPAM-CG/GM had a high drug loading and nearly complete drug release at a physiological temperature of 37 °C. Its moderate mechanical properties, excellent biocompatibility, and antibacterial effects give NIPAM-CG/GM great potential applications as a wound dressing.

Mechanism Insight into Rapid Photodriven Sterilization Based on Silver Bismuth Sulfide Quantum Dots.

Microbial contamination and the prevalence of resistant bacteria is considered a worldwide public health problem. Therefore, recently, great efforts have been made to develop photoresponsive platforms for the simultaneous photodynamic antibacterial (PDA) and photothermal antibacterial (PTA) therapy processes as mediated by specific light. However, owing to the absorption mismatches of the photothermal agents and photodynamic photosensitizers, it has been discovered that many synergistic photoresponsive antibacterial platforms cannot be excited by a single-wavelength light. In this study, silver bismuth sulfide quantum dots (AgBiS2 QDs) identified from the literature as a near-infrared light (NIR) that triggers bifunctional materials with simultaneous photodynamic and photothermal effects for photoresponsive bacterial killing were used. Specifically, AgBiS2 QDs were successfully synthesized via a bottom-up approach, using polyethylenimine (PEI) as an assistant molecule. With PEI wrapping, the attachment between the negatively charged membrane surfaces of the bacterial cells and AgBiS2 QDs was enhanced via the electrostatic interactions. The photodriven antibacterial activity of AgBiS2 QDs was then investigated against both S. aureus and E. coli. The results revealed a significant reduction in bacterial survival. The killing effect was found to be independent of the AgBiS2 QDs, and redox potentials controlled the photogenerated electrons that thermodynamically favored the formation of multiple reactive oxygen species (ROS). A possible phototriggered antibacterial mechanism was then proposed in which the AgBiS2 QDs are anchored first to the bacterial surface and then induce breaking on its outer membrane by high local heat and ROS under single 808 nm NIR laser illumination to finally induce bacterial death.

Preparation and Antimicrobial Activity of Antibacterial Silver-Loaded Polyphosphazene Microspheres.

Poly(cyclotriphosphazene-co-4,4'-diaminodiphenyl ether) (PPO) microspheres were prepared via a precipitation polymerization method, using hexachlorocyclotriphosphazene (HCCP) and 4,4'-diaminodiphenyl ether (ODA) as monomers. Silver-loaded PPO (PPOA) microspheres were generated by the in situ loading of silver nanoparticles onto the surface by Ag+ reduction. Our results showed that PPOA microspheres were successfully prepared with a relatively uniform distribution of silver nanoparticles on microsphere surfaces. PPOA microspheres had good thermal stability and excellent antibacterial activity towards Escherichia coli and Staphylococcus aureus. Furthermore, PPOA microspheres exhibited lower cytotoxicity when compared to citrate-modified silver nanoparticles (c-Ag), and good sustained release properties. Our data indicated that polyphosphazene-based PPOA microspheres are promising antibacterial agents in the biological materials field.

High-Performance Three-Dimensional Aerogel Based on Hydrothermal Pomelo Peel and Reduced Graphene Oxide as an Efficient Adsorbent for Water/Oil Separation.

In this study, HPP-RGO aerogels, which were based on a hydrothermal pomelo peel (HPP) and reduced graphene oxide (RGO), were fabricated by using a green and eco-friendly two-step hydrothermal method. The characterization results showed that the HPP-RGO aerogel was endowed with extremely low density, high specific area, robust thermal stability, good mechanical property, stable acid-alkali resistance, superior recyclability, and excellent hydrophobicity and lipophilicity. Remarkably, the typical 40%-HPP-RGO aerogel presented a preferable adsorption capacity (45-80 g·g-1). Moreover, continuous water/oil separation was achieved via the water ring vacuum pump. The successful preparation of the HPP-RGO aerogel endows the pomelo peel with high value-added properties and improves the comprehensive utilization of agricultural wastes. Furthermore, it would open up bright prospects for the field of oil adsorption and water/oil separation.

Fabrication of a Cu Nanoparticles/Poly(ε-caprolactone)/Gelatin Fiber Membrane with Good Antibacterial Activity and Mechanical Property via Green Electrospinning.

To improve the antibacterial effect of a poly(ε-caprolactone)/gelatin (PCL/Gt) composite, Cu nanoparticles (Cu NPs) were synthesized as an antibacterial agent, and a Cu NPs/PCL/Gt fiber membrane was thus fabricated via green electrospinning. The results showed that the Cu NPs/PCL/Gt fiber membrane with a uniform and complete structure exhibited high porosity and water absorption, favorable hydrophilicity, good mechanical and thermal properties, and satisfactory antibacterial activity. The easy preparation and good comprehensive property implied the great potential application of the Cu NPs/PCL/Gt fiber membrane in various fields (e.g., wound dressing and antibacterial clothing). In addition, the synthesis in this work would offer a promising approach for the preparation of a metal nanoparticle/polymer fiber material with good antibacterial property.

Cetylpyridinium bromide/montmorillonite-graphene oxide composite with good antibacterial activity.

In this study, a cetylpyridinium bromide (CPB)/montmorillonite-graphene oxide (GM) composite (GM-CPB) was prepared by loading CPB in a carrier of GM. The chemical structure, elemental composition, morphology, thermogravimetric analysis, antibacterial activity, sustained release property and cytotoxicity were analyzed. The loading rate of CPB in a GM carrier was higher than that of the graphene oxide (GO) carrier under the same loading condition. The antibacterial activity and sustained release performance of GM-CPB were also better than that of GO-CPB; furthermore, GM-CPB showed lower cytotoxicity than CPB.

Graphene Oxide-IPDI-Ag/ZnO@Hydroxypropyl Cellulose Nanocomposite Films for Biological Wound-Dressing Applications.

In this work, we proposed a feasible approach to prepare multifunctional composite films by introducing a nanoscaled filler into a polymer matrix. Specifically, thanks to isophorone diisocyanate (IPDI) acting as a coupling agent, the hydroxyl groups and carboxyl groups on the surface of graphene oxide (GO) and the hydroxyl groups on the surface of silver-coated zinc oxide nanoparticles (Ag/ZnO) are covalently grafted, forming GO-IPDI-Ag/ZnO (AGO). The prepared AGO was then introduced into the hydroxypropyl cellulose (HPC) matrix to form AGO@HPC nanocomposite films by solution blending. AGO@HPC nanocomposite films exhibited improved mechanical, anti-ultraviolet, and antibacterial properties. Specifically, a tensile test showed that the tensile strength of the prepared AGO@HPC nanocomposite film with the addition of as low as 0.5 wt % AGO was increased by about 16.2% compared with that of the pure HPC film. In addition, AGO@HPC nanocomposite films showed a strong ultraviolet resistance and could effectively inactivate both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria at a low loading of AGO, and rapid sterilization plays a crucial role in wound-healing. In vivo results show that the AGO@HPC release of Ag+ and Zn2+ stimulates the immune function to produce a large number of white blood cells and neutrophils, thereby producing the synergistic antibacterial effects and accelerated wound-healing. Therefore, our results suggest that these novel AGO@HPC nanocomposite films with improved mechanical, anti-ultraviolet, and antibacterial properties could be promising candidates for antibacterial packaging, biological wound-dressing, etc. The abuse of antibiotics has brought about serious drug-resistant bacteria, and our nanofilm antibacterial does not entail such problems. In addition, local administration reduces the possibility of changing the body's immune system and organ toxicity, which greatly increases the safety.

Adsorption of Cd2+ and Ni2+ from Aqueous Single-Metal Solutions on Graphene Oxide-Chitosan-Poly(vinyl alcohol) Hydrogels.

The applications of graphene-based adsorbents were limited because of their complicated manufacturing technology and hi cost, thus it is very important to prepare new inexpensive and easily manufactured graphene-based adsorbents. Herein, novel GCP hydrogels with different graphene oxide (GO), chitosan (CS), and poly(vinyl alcohol) (PVA) ratios were facilely prepared through a method of freeze-thaw physical cross-linking, which was green and low-cost, and the structural characterization and adsorptive property of the optimum GCP1:2:4 hydrogel toward Cd2+ and Ni2+ in wastewater was evaluated. It was found that the GCP1:2:4 hydrogel had good mechanical strength and a special 3D interconnection porous structure. The isotherms of adsorption used the Langmuir model, and the kinetics of adsorption following the pseudo-second-order model were confirmed. Moreover, the adsorption property with respect to Cd2+ and Ni2+ in wastewater has been largely effected by the pH and was less influenced by the ionic strength and humic acid, and the GCP1:2:4 hydrogel possessed excellent adsorptive and recyclable properties. These results demonstrated that the GCP1:2:4 hydrogel could serve as a desirable adsorbent to get rid of heavy metal ions in sewage.

Antibacterial Nanorods Made of Carbon Quantum Dots-ZnO Under Visible Light Irradiation.

Due to secondary pollution from bactericidal substances, the importance of eliminating microbial contamination has become a controversial topic. Three antibacterial nanorod materials of carbon quantum dots-zinc oxide (1/3CQDs-ZnO, CQDs-ZnO, and 2CQDs-ZnO), in which ZnO nanorods are surrounded by carbon quantum dots (CQDs), were successful prepared via in-situ sol-gel chemistry. Antibacterial nanorods of CQDs-ZnO had strong antibacterial activity under visible light irradiation, and a concentration of 0.1 mg/L was able to kill more than 96% of bacteria. The photocatalytic antibacterial mechanism was also studied. CQDs-ZnO produced more than three times the free radicals than pure ZnO under visible light irradiation. These free radicals destroyed the bacterial matrix of the cell wall and released cell proteins and nucleic acids. Moreover, CQDs-ZnO showed low cytotoxicity and can be used in medical applications.

Montmorillonite-Modified Reduced Graphene Oxide Stabilizes Copper Nanoparticles and Enhances Bacterial Adsorption and Antibacterial Activity.

To increase antibacterial activity and reduce the cytotoxicity of copper nanoparticles (CuNPs), we used reduced graphene oxide with montmorillonite to support CuNPs and fixed CuNPs on reduced graphene oxide to synthesize the hybrid montmorillonite-reduced graphene oxide copper nanoparticles (MMT-rGO-CuNPs). The synthesized MMT-rGO-CuNPs complex showed a stronger antibacterial activity against Gram-positive bacteria S. aureus than Gram-negative E. coli. This may be due to the protective effect of the outer membrane of E. coli, as well as the fact that the MMT-rGO-CuNPs complex adsorbs S. aureus more strongly than E. coli. The hybrid molecule's antibacterial efficacy is the combined result of the synergistic effects of electrostatic adsorption and copper ion sterilization ability. At the same time, the MMT-rGO-CuNPs complex exhibits a lower cytotoxicity than PVP-CuNPs and provides a biocompatible composite material with a reduced cytotoxicity.

Improved Photocatalytic Hydrogen Production Performance Over NaTaO3/Reduced Graphene Oxide Composite Photocatalyst.

NaTaO3/reduced graphene oxide (RGO) composite were prepared via a two-step hydrothermal method. The as-prepared NaTaO3/RGO composite were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-Vis diffuse reflectance spectra (DRS), photoluminescence spectra (PL) and X-ray photoelectron spectroscopy (XPS). The results indicated the reduction of graphene oxide and the chemical bonding between RGO and NaTaO3 are achieved simultaneously. As a result, NaTaO3/RGO composite possessed efficient charge separation properties. Hence, in the photocatalytic measurement toward the H2 production from an aqueous Na2S/Na2SO3 solution under UV illumination, a significant improvement in the H2 production rate was observed over NaTaO3/RGO composite, compared to the pure NaTaO3 and mechanically mixed NaTaO3-RGO composite with the same RGO content. In particular, the photocatalytic H2 production rate over NaTaO3/2%RGO with RGO content of 2 wt% was 3.82 times higher than that of pure NaTaO3. Moreover, the photocatalytic hydrogen production performance of NaTaO3/2%RGO was rather stable. A plausible electron transfer mechanism was proposed to discuss the improved photocatalytic H2 production performance.

A colon targeted drug delivery system based on alginate modificated graphene oxide for colorectal liver metastasis.

A major problem associated with colon cancer is liver metastasis. A colon-targeted drug delivery system is one way to address this problem after the resection of colorectal cancer. However, traditional drug delivery systems face many challenges, such as an inability to control the release rate, inaccurate targeting, susceptibility to the microenvironment and poor stability. Here, we report the development of a graphene oxide (GO)-based, sodium alginate (ALG) functionalized colon-targeting drug delivery system, that is loaded with 5-fluorouracil (5-FU) as the anti-cancer drug (denoted as GO-ALG/5-FU). Our results demonstrate that the as-prepared drug delivery system possesses a much lower toxicity and better colon-targeting controlled-release behaviours. We show that GO-ALG/5-FU significantly inhibited tumour growth and liver metastasis and prolonged the survival time of mice. We anticipate that our assay will help improve basic research of colon-targeted drug delivery systems and provide a new way to treat colon cancer liver metastasis.