Antibacterial Structural Color Hydrogels

The hyaluronic acid-gelatin hierarchical hydrogel for osteoporotic bone defect repairment

Osteoporotic bone defects are serious medical problems due to their sparse bone structure, difficulty in restoration and reconstruction, and high recurrence rates, which also result in heavy economic and social burdens. Herein, we developed a hierarchical hydrogel composed of alendronate sodium (AS)/Mg2+-loaded inverse opal methylpropenylated gelatin (GelMA) hydrogel microspheres (IOHM-AS-Mgs) within methylpropenylated poly(hyaluronic acid) (HAMA) for osteoporotic bone defect treatment. The IOHM-AS-Mgs displayed good cytocompatibility and cell adhesion and strongly stimulated osteogenesis at the transcriptomic and protein levels. When this treatment was applied to the osteoporotic bone defect area, HAMA was used to fix the microspheres. The results of the microcomputed tomography (micro-CT) and histological analyses indicated that the hierarchical hydrogel had the best therapeutic effect. Therefore, this hydrogel is a new candidate for osteoporotic bone defect treatment.

Silk Fibroin Microneedles Loaded with Lipopolysaccharide-Pretreated Bone Marrow Mesenchymal Stem Cell-Derived Exosomes for Oral Ulcer Treatment

Oral ulcers, superficial lesions on the surface of the oral mucosa, have a high incidence rate, and their main symptoms include local pain and erosion. Lipopolysaccharide (LPS)-preconditioned bone marrow mesenchymal stem cells and their secreted exosomes (LPS-pre-Exos) have been shown to promote recovery in various inflammatory conditions and wounds. However, studies documenting LPS-pre-Exos as a therapeutic intervention for oral mucosal-like diseases are lacking. In this study, we prepared a silk fibroin microneedle (MN) patch consisting of LPS-pre-Exos and zeolitic imidazolate framework-8 (ZIF-8) that localized at the tip and base, respectively, and used this MN patch for oral ulcer treatment. Upon insertion into the oral mucosa, continuous LPS-pre-Exos release was observed, which promoted macrophage polarization and tissue healing. Additionally, the ZIF-8 framework in the MN patch facilitated the controlled release of Zn2+, which demonstrated potent antimicrobial properties via synergistic effects. The in vitro experimental results showed that the silk fibroin MN patch can continuously release LPS-pre-Exos and Zn2+ for more than 7 days. Thus, the LPS-pre-Exos and ZIF-8-loaded silk fibroin MN patch exhibited good anti-inflammatory and antibacterial properties, promoting oral ulcer healing, and showed good histocompatibility. Hence, it may represent a potentially valuable strategy for facilitating oral ulcer healing.

Preparation of antibacterial hydrogel from poly(aspartic hydrazide) and quaternized N-[3-(dimethylamino) propyl] methylacrylamide copolymer with antioxidant and hemostatic effects for wound repairing

Hydrogels as wound dressing have attracted extensive attention in past decade because they can provide moist microenvironment to promote wound healing. Herein, this research designed a multifunctional hydrogel with antibacterial property and antioxidant activity fabricated from quaternary ammonium bearing light emitting quaternized TPE-P(DAA-co-DMAPMA) (QTPDD) and poly(aspartic hydrazide) (PAH). The protocatechuic aldehyde (PCA) grafted to the hydrogel through dynamic bond endowed the hydrogel with antioxidant activity and the tranexamic acid (TXA) was loaded to enhance the hemostatic performance. The hydrogel possesses preferable gelation time for injectable application, good antioxidant property and tissue adhesion, improved hemostatic performance fit for wound repairing. Furthermore, the hydrogel has excellent antimicrobial property to both E. coli and S. aureus based on quaternary ammonium structure. The hydrogel also showed good biocompatibility and the in vivo experiments proved this hydrogel can promote the wound repairing rate. This study suggests that TXA/hydrogel with quaternary ammonium structure and dynamic grafted PCA have great potential in wound healing applications.

Bioinspired medical indwelling catheters with hierarchically structured coatings exhibiting specific wettability and antibacterial property

The use of medical indwelling catheters in conjunction with implantable medical devices has saved countless lives in various medical procedures. However, biofilm formation on catheter surfaces remains a persistent problem that can lead to chronic infections and device failure. Current approaches to addressing this issue involve the use of biocidal agents or self-cleaning surfaces, but these methods are limited in their effectiveness. Superwettable surfaces have shown great promise in preventing biofilm formation by manipulating the adhesive properties between bacteria and catheter surfaces. In this study, we present a novel medical indwelling catheter with hierarchically structured coatings that exhibit specific wettability and antibacterial properties. By integrating the hierarchical structure and specific wettability, we have developed an indwelling catheter with high flexibility and self-cleaning ability, which is very promising in biomedical engineering applications. Our approach draws inspiration from natural examples, such as the compound eyes of mosquitoes and lotus leaves, and represents a significant step forward in the development of effective anti-infection strategies for medical indwelling catheters.

Fabrication of antibacterial polydopamine-carboxymethyl cellulose-Ag nanoparticle hydrogel coating for urinary catheters

Urinary tract infections caused by catheter insertion are prevalent in hospital clinics, which can induce serious complications such as bacteriuria and sepsis, and even lead to patient death. The disposable catheters currently used in clinical practice suffer from poor biocompatibility and high infection rate. In this paper, we developed a polydopamine (PDA)-carboxymethylcellulose (CMC)-Ag nanoparticles (AgNPs) coating with both good antibacterial and anti-adhesion properties to bacteria on the surfaces of a disposable medical latex catheter by a simple dipping method. The antibacterial efficiency of the coated catheters against Gram-negative E. coli and Gram-positive S. aureus bacteria was evaluated with both inhibition zone tests and fluorescence microscopy. Compared with the untreated catheter, the PDA-CMC-AgNPs coated catheters showed both good antibacterial and anti-adhesion properties to bacteria, which inhibited the adhesion of live bacteria and dead bacteria by 99.0% and 86.6%, respectively. This novel PDA-CMC-AgNPs composite hydrogel coating has great potential in applications in catheters and other biomedical devices to reduce infections.

Chestnut-Tannin-Crosslinked, Antibacterial, Antifreezing, Conductive Organohydrogel as a Strain Sensor for Motion Monitoring, Flexible Keyboards, and Velocity Monitoring

Flexible sensing devices (FSDs) fabricated using conductive hydrogels have attracted researchers' extensive enthusiasm in recent years due to their versatility. Considering the complexity of their application environments, the integration of various functional characteristics (e.g., excellent mechanical, antibacterial, and antifreezing properties) is an important guarantee for FSDs to stably perform their applications in different environments. Herein, we developed a multifunctional conductive polyvinyl alcohol (PVA) organohydrogel PVA-CT-Ag-Al-Gly (PCAAG) by using a green, natural, and cheap biomass, chestnut tannin (CT), as a crosslinking agent, nano-silver particles (AgNPs) as an antimicrobial agent, aluminum trichloride (AlCl₃) as a conducting medium, and the mixed water-glycerol as the solvent system. In this organohydrogel system, CT acted not only as the reducing and stabilizing agent for the preparation of antibacterial AgNPs but also as the crosslinking agent owing to its strong multiple hydrogen bonding interactions with PVA, realizing its multifunctional application. The PCAAG organohydrogel possessed outstanding physical and mechanical properties (350.54% of the maximum fracture strain and 1.55 MPa of the maximum tensile strength), considerable bacteriostatic effects against both Escherichia coli and Staphylococcus aureus, and excellent freeze resistance (it could function normally at -20 °C). The motion-monitoring sensor based on the PCAAG organohydrogel exhibited excellent specificity recognition for both large-amplitude (e.g., elbow bending, wrist bending, finger bending, running and walking, etc.) and small-amplitude (frowning and swallowing) human movements. The flexible keyboard constructed by using the PCAAG organohydrogel could easily achieve the transformation between digital signals and electrical signals, and the signal output had both specificity and stability. The velocity-monitoring sensor fabricated by using the PCAAG organohydrogel could accurately measure the speed of the object movement (less than 3% of relative error). In short, the present PCAAG organohydrogel solves the problems of the single application environment and a few application scenarios of traditional conductive hydrogels and possesses remarkable application potential as a multifunctional FSD in many fields such as artificial intelligence, sport management, soft robots, and human-computer interface.

Wide-Gamut Biomimetic Structural Colors from Interference-Assisted Two-Photon Polymerization

Two-photon polymerization (TPP) is an emerging direct laser writing technique for the fabrication of structural colors. However, its coloration ability is suppressed as the vertical resolution is up to several microns. To solve this issue, an interference-assisted TPP technique was employed. Laser interference at a highly reflective interface produced the periodic energy redistribution along the vertical direction, turning the laser voxel into multilayer structures and confirming this technology as a facile and robust method for precise control of its vertical feature size. Biomimetic structural colors (BSCs) inspired from the ridge-lamella configurations in the Morph butterflies were fabricated using this improved TPP technique. The coloration mechanisms of the multilayer interference from the lamella layers, the thin-film interference from the fusion of multilayers, and the hybrid situations were systematically studied. These BSC colors were grouped as pixel palettes with various TPP parameters corresponding to each other, and they spanned almost the entire standard red-green-blue color space. Moreover, under optimized conditions, it was possible to fabricate a 1 cm² area within 2.5 h. These features make interference-assisted TPP an ideal coloration method for practical applications, such as display, decoration, sensing, and so on.

Low-dimensional nanomaterials for antibacterial applications

The excessive use of antibiotics has led to a rise in drug-resistant bacteria. These "superbugs" are continuously emerging and becoming increasingly harder to treat. As a result, new and effective treatment protocols that have minimal risks of generating drug-resistant bacteria are urgently required. Advanced nanomaterials are particularly promising due to their drug loading/releasing capabilities combined with their potential photodynamic/photothermal therapeutic properties. In this review, 0-dimensional, 1-dimensional, 2-dimensional, and 3-dimensional nanomaterial-based systems are comprehensively discussed for bacterial-based diagnostic and treatment applications. Since the use of these platforms as antibacterials is relatively new, this review will provide appropriate insight into their construction and applications. As such, we hope this review will inspire researchers to explore antibacterial-based nanomaterials with the aim of developing systems for clinical applications.

Highly synergistic, electromechanical and mechanochromic dual-sensing ionic skin with multiple monitoring, antibacterial, self-healing, and anti-freezing functions

A novel electromechanical and mechanochromic dual-sensing ionic skin (DSI-skin) with multiple biological functions is achieved by mimicking biological skin.

Advances of hydrogel dressings in diabetic wounds

The hydrogel dressings with various functions for diabetic wound treatment.

Photonics in nature and bioinspired designs: sustainable approaches for a colourful world

Biological systems possess nanoarchitectures that have evolved for specific purposes and whose ability to modulate the flow of light creates an extraordinary diversity of natural photonic structures. In particular, the striking beauty of the structural colouration observed in nature has inspired technological innovation in many fields. Intense research has been devoted to mimicking the unique vivid colours with newly designed photonic structures presenting stimuli-responsive properties, with remarkable applications in health care, safety and security. This review highlights bioinspired photonic approaches in this context, starting by presenting many appealing examples of structural colours in nature, followed by describing the versatility of fabrication methods and designed coloured structures. A particular focus is given to optical sensing for medical diagnosis, food control and environmental monitoring, which has experienced a significant growth, especially considering the advances in obtaining inexpensive miniaturized systems, more reliability, fast responses, and the use of label-free layouts. Additionally, naturally derived biomaterials and synthetic polymers are versatile and fit many different structural designs that are underlined. Progress in bioinspired photonic polymers and their integration in novel devices is discussed since recent developments have emerged to lift the expectations of smart, flexible, wearable and portable sensors. The discussion is expanded to give emphasis on additional functionalities offered to related biomedical applications and the use of structural colours in new sustainable strategies that could meet the needs of technological development.

An antibacterial and biocompatible multilayer biomedical coating capable of healing damages

Besides the excellent biocompatibility and high antibacterial property, multifunctional biomedical coatings with a long service time is highly desirable for extended applications, which is still an ongoing challenge. The self-healing property enables new directions for effectively prolonging their service life and significantly improving their reliability. Herein, an efficient and simple method is used to facilely prepare antibacterial, biocompatibile multilayer polyelectrolyte coatings, which are capable of healing damages. The synthetic strategy involves the alternate deposition of Chitosan (CS) and sodium carboxymethyl cellulose (CMC) via the layer-by-layer (LBL) self-assembly technique. The CS/CMC multilayer polyelectrolyte coating features high antibacterial property, fast and efficient self-healing property, and excellent biocompatibility. These features allow the CS/CMC polyelectrolyte coating to have extended lifespan and to be highly promising for novel functional stent coating applications.

A CS/CMC multilayer polyelectrolyte coating was developed, which features fast and efficient self-healing property, high antibacterial property, and excellent biocompatibility.

Two-Dimensional Device with Light-Controlled Capability for Treatment of Cancer-Relevant Infection Diseases

Concurrent infection in cancer treatment is the leading cause of high cancer mortality that requires urgent action. Currently developed diagnostic methods are hindered by the difficulty of rapidly and reliably screening small amounts of pathogens in the blood and then release pathogens for downstream analysis, limiting the advance of cancer concurrent infection diseases diagnosis and targeted treatment. Herein, we present a near-infrared (NIR) light-responsive black phosphorus (BP)-based device that effectively captures and releases pathogen for downstream drug-resistance analysis. The aptamer-modified BP nanostructures exhibit enhanced topographical interactions and binding capabilities with pathogen, enabling highly efficient and selective capture of pathogen in serum. NIR light irradiation induces BP nanostructure to generate a local thermal effect, which regulates the three-dimensional structure of the aptamer and causes efficient release of pathogen from the substrate surface. The released pathogen is resistant to ampicillin as demonstrated by downstream genetic analysis. The design of the functionalized light-controlled device for monitoring pathogen behavior shows great potential for assisting in cancer therapy and promoting personalized healthcare.

Bioinspired structural color patch with anisotropic surface adhesion

Patch plays an important role in clinical medicine for its broad applications in tissue repair and regeneration. Here, inspired by the diverse adhesion, anti-adhesion, and responsive structural color phenomena in biological interfaces, we present a hybrid hydrogel film with an adhesive polydopamine (PDA) layer and an anti-adhesive poly(ethylene glycol) diacrylate (PEGDA) layer in an inverse opal scaffold. It was demonstrated that the resultant hydrogel film could serve as a functional tissue patch with an excellent adhesion property on one surface for repairing injured tissues and an anti-adhesion property on the other surface for preventing adverse adhesion. Besides, because of the responsive structural color, the patch was imparted with self-reporting mechanical capability, which could provide a real-time color-sensing feedback to monitor the heartbeat activity. Moreover, the catechol groups on PDA imparted the patch with high tissue adhesiveness and self-healing capability in vivo. These features give the bioinspired patch high potential in biomedical applications.

Self-assembled colloidal arrays for structural color

Structural color materials that are colloidally assembled as inspired by nature are attracting increased interest in a wide range of research fields. The assembly of colloidal particles provides a facile and cost-effective strategy for fabricating three-dimensional structural color materials. In this review, the generation mechanisms of structural colors from colloidally assembled photonic crystalline structures (PCSs) and photonic amorphous structures (PASs) are first presented, followed by the state-of-the-art and detailed technologies for their fabrication. The variable optical properties of PASs and PCSs are then discussed, focusing on their spatial long- and short-order structures and surface topography, followed by a detailed description of the modulation of structural color by refractive index and lattice distance. Finally, the current applications of structural color materials colloidally assembled in various fields including biomaterials, microfluidic chips, sensors, displays, and anticounterfeiting are reviewed, together with future applications and tasks to be accomplished.

Inverse opal substrate-loaded mesenchymal stem cells contribute to decreased myocardial remodeling after transplantation into acute myocardial infarction mice

Background

The two-dimensional incubation method is now the most commonly method for mesenchymal stem cell (MSC) production. however, gene expression and secretion of growth factors are relatively low; thus, the transplanted cells cannot be effectively utilized for potential clinical applications after acute myocardial infarction (AMI).

Objectives

We aimed to investigate whether our newly made substrates of inverse opal with specific surface microstructures for MSC culturing can increase the viability of the cells and can contributes to decreased myocardial remodeling after transplanted to AMI mice.

Methods

The inverse opal structure is fabricated by the convenient bottom-up approach of the self-assembly of colloidal nanoparticles. Mouse-derived MSCs were then cultured on the substrates when expanded at different times to investigate the cell growth status including morphology. Then the inverse opal substrates loaded MSCs were transplanted to AMI mice, cardiomyocyte apoptosis and LV remodeling were further compared. To explore the possible mechanisms of curation, the secretions and viability of MSCs on substrates were determined using mice ELISA kits and JC-1 mitochondrial membrane potential assay kits respectively at normal and hypoxic conditions.

Results

6 times expanded inverse opals allowed greatly the orderly growth of MSCs as compared to four (34% ± 10.6%) and two (20%±7.2%) times expanded as well as unexpanded (13%±4.1%) (P<0.001). Nearly 90% of MSCs showed orientation angle intervals of less than 30° when at the 6X expanded (89.6%±25%) compared to the percent of cells with 30°-60° (8.7%±2.6%) or ≥60° (1.7%±1.0%) orientation angle (P<0.001). After inverse opal loaded MSCs transplanted to AMI mice, greatly decreased apoptosis of cardiomyocytes (20.45%±8.64% vs.39.63%±11.71%, P<0.001) and infarction area (5.87±2.18 mm² vs 9.31±3.11 mm², P<0.001) were identified. In the end, the viability of inverse opal loaded MSCs determined by membrane potential (P<0.001) and the secretion of growth factors including VEGF-α, SDF-1 and Ang-1 (P<0.001) were both confirmed significantly higher than that of the conventional culture in petri dish.

Conclusion

The structure of inverse opal can not only adjust the arrangement of MSCs but also contribute to its orientated growth. Inverse opal loaded MSCs transplantation extremely curbed myocardial remodeling, the underlying mechanisms might be the high viability and extremely higher secretions of growth factors of MSCs as devoted by this method.

Folic Acid-Functionalized Hybrid Photonic Barcodes for Capture and Release of Circulating Tumor Cells

Recovery of circulating tumor cells (CTCs) from cancer patients by an efficient CTCs capture and release method can greatly increase their application in diagnostics and treatment of cancers. In this paper, we presented a folic acid (FA)-functionalized hybrid photonic barcode for capture and release of CTCs. The hybrid photonic barcodes were formed by two nano-ordered parts, poly(ethylene glycol) diacrylate (PEGDA) inverse opal structure for sustaining integrity and methacrylated gelatin (GelMA) gel filler for conjugating FA molecules to mediate cell capture. The nano-ordered structures of the hybrid photonic barcodes not only increased contact area, but also decreased steric hindrance among FA molecules. Thus, the topographic interaction between the barcodes and CTCs was greatly enhanced. In addition, GelMA gel was soft and extracellular matrix (ECM) alike, which was beneficial to decrease impairment to CTCs during the CTCs-barcode interaction as well as preserving their viability. Demonstrated by four CTCs types, Hela (epithelial tissue, folate receptor positive, FR+), A02 (bone marrow, FR+), Raji (lymphoid tissue, FR+), and A549 (epithelial tissue, folate receptor negative, FR-), FR+ CTCs could be captured efficiently with reliability and specificity. The captured cells could be controllably released with high viability just by quick trypsinization. The whole processes were simple and efficient. These features indicated that the FA-functionalized hybrid photonic barcodes were promising for full recovery of CTCs from cancer patients, which was important for diagnosis and treatment of cancer.

An injectable supramolecular hydrogel hybridized with silver nanoparticles for antibacterial application

Silver nanoparticles (AgNPs) show long-lasting and broad-spectrum antibacterial activity. Herein, PEGylated AgNPs were prepared in situ by complexing AgNO₃ with the random copolymer of poly(ethylene glycol) methyl ether methacrylate (PEGMA) and polyacrylic acid via electrostatic interaction followed by in situ reduction. AgNP hybrid supramolecular hydrogels were thus prepared through host-guest inclusion between PEGMA side chains and α-cyclodextrins in aqueous solution. The hydrogels were physically cross-linked by both pseudopolyrotaxane crystallization and AgNPs, which showed temperature responsiveness and self-healing properties. By hybridizing AgNPs, the hydrogels showed excellent antibacterial properties against S. aureus and E. coli bacteria as well as low cytotoxicity and have potential applications as injectable antibacterial materials.