In situ polydopamine functionalized poly-L-lactic acid nanofibers with near-infrared-triggered antibacterial and reactive oxygen species scavenging capability

Polydopamine-curcumin coating of titanium for remarkable antibacterial activity via synergistic photodynamic and photothermal properties

Combined photothermal therapy (PTT) and photodynamic therapy (PDT) has emerged as a novel and effective antibacterial strategy. In order to endow titanium (Ti) with antibacterial properties, the Ti-PDA-Cur composite was prepared using the excellent adhesion properties of polydopamine (PDA) to load curcumin (Cur) on the surface of Ti. The Ti-PDA-Cur coating can produce singlet oxygen (1O2) and heat under 405 + 808 nm light irradiation, which can effectively kill Staphylococcus aureus and Escherichia coli. Moreover, the cytotoxicity and hemolysis rate of Ti-PDA-Cur were low, indicating its good biocompatibility. Therefore, this study provided a new strategy for the development of new Ti implants.

Fabrication of antibacterial poly (L-lactic acid)/tea polyphenol blend films via reactive blending using SG copolymer

Poly (L-lactic acid) (PLLA) composite materials with both excellent antibacterial properties and mechanical properties are highly desirable for both food packaging and biomedical applications. However, a facile method to prepare transparent PLLA composite films with both excellent antibacterial and mechanical properties is still lacking. In this work, blend films based on PLLA, tea polyphenols (TP) and poly (styrene-co-glycidyl methacrylate) (SG) copolymers (PLLA/TP/SG) were prepared by melt blending using twin screw extruder. The blend films showed high transparency with a brownish color originated from tea polyphenols. Both SEM and DSC analyses confirmed that the blends are thermodynamically compatible. GPC and mechanical assessments demonstrated that the PLLA/TP binary blends exhibit reduced molecular weight and compromised mechanical properties, compared to neat PLLA. However, incorporating SG copolymer resulted in increased molecular weight and improved mechanical properties for the PLLA/TP/SG blends. The FT-IR spectra exhibited a shift to lower wavenumber for the absorption peak associated with the benzene ring on TPs after blending with PLLA and SG, indicating the occurrence of transesterification between PLLA and TP. Plate coating studies revealed that the PLLA/TP/SG blends with TP incorporation at 5 wt% exhibited a bacteriostatic rate of 99.99 % against Staphylococcus aureus and Escherichia coli. Overall, our study reveals that the PLLA/TP/SG blend films exhibit excellent antibacterial properties coupled with good mechanical properties, rendering them a promising candidate for antibacterial packaging materials.

Effects of aligned PLGA/SrCSH composite scaffolds on in vitro growth and osteogenic differentiation of human mesenchymal stem cells

Strontium (Sr) has important functions in bone remodeling. Incorporating strontium-doped α-calcium sulfate hemihydrate (SrCSH) into poly(lactic-co-glycolic acid) (PLGA) fibrous scaffolds were expected to increase its bio-activity and provide a potential material for bone tissue engineering. In the present study, Sr-containing aligned PLGA/SrCSH fibrous scaffolds similar to the architecture of natural bone were prepared via wet spinning. CCK-8 assay revealed that Sr-containing scaffolds possessed better bioactivity and supported favorable cell growth effectively. The aligned PLGA/SrCSH fibers exerted a contact effect on cell attachment, inducing regular cell alignment and influencing a series of cell behaviors. Releasing of high concentration Sr from a-PLGA/SrCSH scaffolds could induce high expression levels of BMP-2, increase ALP activity and upregulate RUNX-2 expression, and further promote the expressions of COL-I and OCN and the maximum mineralization. This study demonstrated that Sr and ordered structure in a-PLGA/SrCSH fibrous scaffolds could synergistically enhance the osteogenic differentiation of umbilical cord mesenchymal stem cells (UCMSCs) by regulating cell arrangement and expressions of osteogenic genes.

Multifunctional hemostatic polysaccharide-based sponge enhanced by tunicate cellulose: A promising approach for photothermal antibacterial activity and accelerated wound healing

Fast and effective hemostasis and protection against wound infection play a crucial role in trauma care. In this study, a sponge scaffold with a self-expanding interpenetrating macropore structure was designed via two-step cross-linking method for hemostasis and photothermal antimicrobial activity. Oxidized Konjac glucomannan (OKGM) and chitosan (CS) were crosslinked once to form a dynamic covalent bonding network, and a basic three-dimensional fiber porous network framework was constructed by uniformly dispersing Tunicate nanocellulose (TCNCs). Secondary crosslinking introduced Polydopamine (PDA NPs) into the sponge, while dynamic hydrogen bonds were interleaved to stabilize the frame. PDA NPs enhanced the sponge's antibacterial and antioxidant properties due to its good photothermal conversion efficiency and oxygen radical scavenging ability. Compared to cotton gauze and gelatin sponges, the composite sponges showed superior blood cell adhesion and platelet activation. In tests on rat liver trauma models, composite sponges showed shorter hemostasis time (12 ± 2.17 s) and less blood loss (0.1 ± 0.052 g). Sponges can protect wound tissue through their adhesion properties. In the full-thickness wound model infected with S. aureus, the composite sponge accelerated wound healing. Overall, this composite sponge has great potential for clinical use as a wound dressing.

Phase Change Material-Embedded Multifunctional Janus Nanofiber Dressing with Directional Moisture Transport, Controlled Release of Anti-Inflammatory Drugs, and Synergistic Antibacterial Properties

Wound healing is a systematic and complex process that involves various intrinsic and extrinsic factors affecting different stages of wound repair. Therefore, multifunctional wound dressings that can modulate these factors to promote wound healing are in high demand. In this work, a multifunctional Janus electrospinning nanofiber dressing with antibacterial and anti-inflammatory properties, controlled release of drugs, and unidirectional water transport was prepared by depositing coaxial nanofibers on a hydrophilic poly(ε-caprolactone)@polydopamine-ε-polyl-lysine (PCL@PDA-ε-PL) nanofiber membrane. The coaxial nanofiber was loaded with the phase change material lauric acid (LA) in the shell layer and anti-inflammatory ibuprofen (IBU) in the core layer. Among them, LA with a melting point of 43 °C served as a phase change material to control the release of IBU. The phase transition of LA was induced by near-infrared (NIR) irradiation that triggered the photothermal properties of PDA. Moreover, the Janus nanofiber dressing exhibited synergistic antimicrobial properties for Escherichia coli and Staphylococcus aureus due to the photothermal properties of PDA and antibacterial ε-PL. The prepared Janus nanofiber dressing also exhibited anti-inflammatory activity and biocompatibility. In addition, the Janus nanofiber dressing had asymmetric wettability that enabled directional water transport, thereby draining excessive wound exudate. The water vapor transmission test indicated that the Janus nanofiber dressing had good air permeability. Finally, skin wound healing evaluation in rats confirmed its efficacy in promoting wound healing. Therefore, this strategy of designing and manufacturing a multifunctional Janus nanofiber dressing had great potential in wound healing applications.

Advances in photothermal regulation strategies: from efficient solar heating to daytime passive cooling

Photothermal regulation concerning solar harvesting and repelling has recently attracted significant interest due to the fast-growing research focus in the areas of solar heating for evaporation, photocatalysis, motion, and electricity generation, as well as passive cooling for cooling textiles and smart buildings. The parallel development of photothermal regulation strategies through both material and system designs has further improved the overall solar utilization efficiency for heating/cooling. In this review, we will review the latest progress in photothermal regulation, including solar heating and passive cooling, and their manipulating strategies. The underlying mechanisms and criteria of highly efficient photothermal regulation in terms of optical absorption/reflection, thermal conversion, transfer, and emission properties corresponding to the extensive catalog of nanostructured materials are discussed. The rational material and structural designs with spectral selectivity for improving the photothermal regulation performance are then highlighted. We finally present the recent significant developments of applications of photothermal regulation in clean energy and environmental areas and give a brief perspective on the current challenges and future development of controlled solar energy utilization.

Aligned Electroactive Electrospun Fibrous Scaffolds for Peripheral Nerve Regeneration

Effective repair and functional recovery of large peripheral nerve deficits are urgent clinical needs. A biofunctional electroactive scaffold typically acts as a "bridge" for the repair of large nerve defects. In this study, we constructed a biomimetic piezoelectric and conductive aligned polypyrrole (PPy)/polydopamine (PDA)/poly-l-lactic acid (PLLA) electrospun fibrous scaffold to improve the hydrophilicity and cellular compatibility of PLLA and restore the weakened piezoelectric effect of PDA, which is beneficial in promoting Schwann cell differentiation and dorsal root ganglion neuronal extension and alignment. The aligned PPy/PDA/PLLA fibrous scaffold bridged the sciatic nerve of Sprague-Dawley rats with a 10 mm deficit, prevented autotomy, and promoted nerve regeneration and functional recovery, thereby activating the calcium and AMP-activated protein kinase signaling pathways. Therefore, electroactive fibrous scaffolds exhibit great potential for neural tissue regeneration.

A bioinspired antibacterial and photothermal membrane for stable and durable clean water remediation

Solar-driven steam generation has been considered as a prevalent and sustainable approach to obtain clean fresh water. However, the presence of microorganisms in seawater may cause the biofouling and degradation of polymeric photothermal materials and clog the channels for water transportation, leading to a decrease in solar evaporation efficiency during long-term usage. Herein, we have reported a facile strategy to construct a robust cellulose membrane device coated by tobramycin-doped polydopamine nanoparticles (PDA/TOB@CA). The PDA/TOB@CA membrane not only exhibited synergistic antibacterial behaviors with long-term and sustained antibiotic release profiles, but also achieved a high water evaporation rate of 1.61 kg m^-2 h^-1 as well as an evaporation efficiency of >90%. More importantly, the high antibacterial activity endowed the PDA/TOB@CA membrane with superb durability for stable reuse over 20 cycles, even in microbe-rich environments. Therefore, we envision that this study could pave a new pathway towards the design and fabrication of robust antibacterial and photothermal materials for long-term and stable clean water production.

A critical review on polydopamine surface-modified scaffolds in musculoskeletal regeneration

Increasing concern about age-related diseases, particularly musculoskeletal injuries and orthopedic conditions, highlights the need for strategies such as tissue engineering to address them. Surface modification has been developed to create pro-healing interfaces, personalize scaffolds and provide novel medicines. Polydopamine, a mussel-inspired adhesive polymer with highly reactive functional groups that adhere to nearly all substrates, has gained attention in surface modification strategies for biomaterials. Polydopamine was primarily developed to modify surfaces, but its effectiveness has opened up promising approaches for further applications in bioengineering as carriers and nanoparticles. This review focuses on the recent discoveries of the role of polydopamine as a surface coating material, with focus on the properties that make it suitable for tackling musculoskeletal disorders. We report the evolution of using it in research, and discuss papers involving the progress of this field. The current research on the role of polydopamine in bone, cartilage, muscle, nerve, and tendon regeneration is discussed, thus giving comprehensive overview about the function of polydopamine both in-vitro and in-vivo. Finally, the report concludes presenting the critical challenges that must be addressed for the clinical translation of this biomaterial while exploring future perspectives and research opportunities in this area.

Multi-functional nanofilms capable of angiogenesis, near-infrared-triggered anti-bacterial activity and inflammatory regulation for infected wound healing

Chronic infected wound healing is a critical challenge in clinical practice owing to the involvement of multiple physiological processes, including bacteria-related, inflammatory regulation and angiogenesis. Therefore, a multi-functional strategy with synergistic anti-bacterial, anti-inflammatory and pro-angiogenic effects should be developed. Owing to their biomimetic structural features and controlled delivery of active agents, electrospun nanofilms are promising biomaterials for the treatment of skin defects. In this study, we fabricated multi-functional nanofilms with pro-angiogenic, anti-bacterial and anti-inflammatory capacities. First, strontium (Sr) ions were incorporated into poly(L-lactic-co-caprolactone) (PLCL) nanofilms. Subsequently, polydopamine (PDA) and zinc oxide (ZnO) were decorated onto the surface of Sr-loaded PLCL nanofilms to prepare ZnO/PDA@PLCL@Sr nanofilms. In vitro results showed that ZnO/PDA@PLCL@Sr nanofilms were biocompatible, exhibited angiogenic activity and significantly inhibited the growth of Staphylococcus aureus and Escherichia coli upon near-infrared -light irradiation. Furthermore, ZnO/PDA@PLCL@Sr nanofilms were found to drive the transformation of macrophages into the M2 phenotype. In vivo results further validated that ZnO/PDA@PLCL@Sr nanofilms exhibited pro-angiogenic and anti-bacterial activities and regulated inflammation to accelerate wound -healing in a rat model of bacteria-infected skin defects. In conclusion, we successfully developed a multi-functional biomaterial with pro-angiogenic, anti-bacterial and anti-inflammatory capacities to treat chronic infected wounds.

Electrospun hydroxyapatite loaded L-polylactic acid aligned nanofibrous membrane patch for rotator cuff repair

Rotator cuff repair remains a challenge clinically due to the high retear rate after surgical intervention. There is a significant need to develop functional biomaterials facilitating tendon-to-bone integration. In this study, hydroxyapatite (HA) incorporated polylactic acid (PLLA) aligned nanofibrous membranes were fabricated by electrospinning as a low-cost sustainable rotator cuff patch. The morphology, physical, mechanical and in vitro cell assays of the nanofibrous membranes were characterized. The results showed that the nanofibrous membrane maintained a rough surface and weakened hydrophobicity. It has excellent cytocompatibility, and the cells were oriented along the direction of fiber arrangement. What's more, the PLLA-HA nanofibrous membrane could increase the alkaline phosphatase (ALP) expression in rat bone marrow mesenchymal stem cells (BMSCs), indicating that the electrospinning PLLA-HA nanofibrous membrane can better induce the bone formation of rat BMSCs cells. When the mass ratio of PLLA to HA exceeds 3: 1, with the increase of the HA content, the patch showed rising induction ability. The results suggested that electrospinning PLLA-HA nanofibrous membranes are an ideal patch for promoting tendon-bone healing and reducing the secondary tear rate. Furthermore, the use of biodegradable polymers and low-cost preparation methods presented the possibility for commercial production of these nanofibrous membranes.

Antibacterial Activity of Antibiotic-Releasing Polydopamine-Coated Nephrite Composites for Application in Drug-Eluting Contact Lens

The aim of this study is to prepare ciprofloxacin (CIP) or levofloxacin (LEVO)-incorporated and polydopamine (PDA)-coated nephrite composites for application in drug-eluting contact lenses. PDA was coated onto the surface of nephrite to improve antibacterial activity and to payload antibiotics. CIP or LEVO was incorporated into the PDA layer on the surface of nephrite. Furthermore, CIP-incorporated/PDA-coated nephrite composites were embedded into the contact lenses. PDA-coated nephrite composites showed dull and smooth surfaces according to the dopamine concentration while nephrite itself has sharp surface morphology. CIP- or LEVO-loaded/PDA-coated nephrite composites also have dull and smooth surface properties. Nano and/or sub-micron clusters were observed in field emission-scanning electron microscopy (FE-SEM) observation, indicating that PDA nanoparticles were accumulated and coated onto the surface of nephrite. Furthermore, CIP- or LEVO-incorporated/PDA-coated nephrite composites showed the sustained release of CIP or LEVO in vitro and these properties contributed to the enhanced antibacterial activity of composites compared to nephrite or PDA-coated nephrite composites. CIP-incorporated/PDA-coated nephrite composites were embedded in the contact lenses and then, in an antibacterial study, they showed higher bactericidal effect against Staphylococcus aureus (S. aureus) compared to nephrite itself or PDA-coated nephrite composites. We suggest that CIP- or LEVO-loaded/PDA-coated nephrite composite-embedded contact lenses are a promising candidate for therapeutic application.

Nanotechnologies for control of pathogenic microbial biofilms

Biofilms are formed at interfaces by microorganisms, which congregate in microstructured communities embedded in a self-produced extracellular polymeric substance (EPS). Biofilm-related infections are problematic due to the high resistance towards most clinically used antimicrobials, which is associated with high mortality and morbidity, combined with increased hospital stays and overall treatment costs. Several new nanotechnology-based approaches have recently been proposed for targeting resistant bacteria and microbial biofilms. Here we discuss the impacts of biofilms on healthcare, food processing and packaging, and water filtration and distribution systems, and summarize the emerging nanotechnological strategies that are being developed for biofilm prevention, control and eradication. Combination of novel nanomaterials with conventional antimicrobial therapies has shown great potential in producing more effective platforms for controlling biofilms. Recent developments include antimicrobial nanocarriers with enzyme surface functionality that allow passive infection site targeting, degradation of the EPS and delivery of high concentrations of antimicrobials to the residing cells. Several stimuli-responsive antimicrobial formulation strategies have taken advantage of the biofilm microenvironment to enhance interaction and passive delivery into the biofilm sites. Nanoparticles of ultralow size have also been recently employed in formulations to improve the EPS penetration, enhance the carrier efficiency, and improve the cell wall permeability to antimicrobials. We also discuss antimicrobial metal and metal oxide nanoparticle formulations which provide additional mechanical factors through externally induced actuation and generate reactive oxygen species (ROS) within the biofilms. The review helps to bridge microbiology with materials science and nanotechnology, enabling a more comprehensive interdisciplinary approach towards the development of novel antimicrobial treatments and biofilm control strategies.