High-Performance W-Doped Bi0.5Sb1.5Te3 Flexible Thermoelectric Films and Generators.

Bi-Sb-Te-based thermoelectric materials have the best room-temperature thermoelectric properties, but their inherent brittleness and rigidity limit their application in the wearable field. In this study, W-doped p-type Bi0.5Sb1.5Te3 (W-BST) thin films were prepared using magnetron sputtering on polyimide substrates to create thermoelectric generators (TEGs). Bending tests showed that the thin film has excellent flexibility and mechanical durability, meeting the flexible requirements of wearable devices. W doping can significantly increase the carrier concentration, Seebeck coefficient, and electrical conductivity of BST thin films. At 300 K, the power factor of the W-BST film is 2.25 times higher than that of the undoped film, reaching 13.75 µW cm-1 K-2. First-principles calculations showed that W doping introduces significant impurity peaks in the bandgap, in which W d electrons remarkably hybridize with the Sb and Te p electrons, leading to an improved electrical conductivity of BST films. Furthermore, W doping significantly reduces the work function of BST films, thereby improving the carrier mobility. A TEG module fabricated from four layers of W-BST thin films achieved a maximum output power density of 6.91 mW cm-2 at a temperature difference of 60 K. Application tests showed that the flexible TEG module could power a portable clock using the temperature difference between body temperature and room temperature. At a medium temperature of 439 K, the assembled TEG module can provide a stable output voltage of 1.51 V to power a LED. This study demonstrates the feasibility of combining inorganic thermoelectric materials with flexible substrates to create high-performance flexible TEGs.

Thermoresponsive Gels with Embedded Starch Microspheres for Optimized Antibacterial and Hemostatic Properties.

Apart from single hemostasis, antibacterial and other functionalities are also desirable for hemostatic materials to meet clinical needs. Cationic materials have attracted great interest for antibacterial/hemostatic applications, and it is still desirable to explore rational structure design to address the challenges in balanced hemostatic/antibacterial/biocompatible properties. In this work, a series of cationic microspheres (QMS) were prepared by the facile surface modification of microporous starch microspheres with a cationic tannic acid derivate, the coating contents of which were adopted for the first optimization of surface structure and property. Thermoresponsive gels with embedded QMS (F-QMS) were further prepared by mixing a neutral thermosensitive polymer and QMS for second structure/function optimization through different QMS and loading contents. In vitro and in vivo results confirmed that the coating content plays a crucial role in the hemostatic/antibacterial/biocompatible properties of QMS, but varied coating contents of QMS only lead to a classical imperfect performance of cationic materials. Inspiringly, the F-QMS-4 gel with an optimal loading content of QMS4 (with the highest coating content) achieved a superior balanced in vitro hemostatic/antibacterial/biocompatible properties, the mechanism of which was revealed as the second regulation of cell-material/protein-material interactions. Moreover, the optimal F-QMS-4 gel exhibited a high hemostatic performance in a femoral artery injury model accompanied by the easy on-demand removal for wound healing endowed by the thermoresponsive transformation. The present work offers a promising approach for the rational design and facile preparation of cationic materials with balanced hemostatic/antibacterial/biocompatible properties.

The mechanism of adipose mesenchymal stem cells to stabilize the immune microenvironment of pelvic floor injury by regulating pyroptosis and promoting tissue repair.

Pelvic organ prolapse (POP) has a high incidence rate among Chinese women. Repeated mechanical stimulation is an important factor causing POP, but the injury mechanism has not yet been elucidated. The purpose of this study is to explore the related mechanisms of pelvic floor supporting tissue damage caused by mechanical force and the application of stem cell therapy. First, we obtained vaginal wall and sacral ligament tissue samples from clinical patients for examination. Pelvic floor support tissues of POP patients displayed high expression of inflammation and immune disorders. Then, we constructed a rat model of childbirth injury. In vivo and in vitro experiments investigated the key mechanism of pelvic floor support tissue injury caused by mechanical force. We discovered that after mechanical force, a large number of reactive oxygen species (ROS) and macrophages rapidly accumulated in pelvic floor tissues. ROS stimulated macrophages to produce NLRP3 inflammatory complex, induced the release of interleukin (IL-1ß) and pyroptosis and exacerbated the inflammatory state of damaged tissues, persisting chronic inflammation of fibroblasts in supporting tissues, thus causing the pelvic floor's extracellular matrix (ECM) collagen metabolic disorder. Resultingly impeding the repair process, thereby causing the onset and progression of the disease. Through their paracrine ability, we discovered that adipose mesenchymal stem cells (ADSCs) could inhibit this series of pathological processes and promote tissue repair, asserting a good therapeutic effect. Simultaneously, to overcome the low cell survival rate and poor therapeutic effect of directly injecting cells, we developed a ROS-responsive PVA@COLI hydrogel with ADSCs. The ROS-scavenging properties of the gel could reshape the site of inflammation injury, enhance cell survival, and play a role in subsequent treatment. The findings of this study could serve as a basis for early, targeted intervention therapy for POP and representing a promising approach.

Rapid Regulation of Cardiomyocytes Adhesion on Substrates with Varied Modulus via Mechanical Cues.

In-depth understanding of the mechanisms underlying the adhesion of myocardial cells holds significant importance for the development of effective therapeutic biomaterials aimed at repairing damaged or pathological myocardial tissues. Herein, we present evidence that myocardial cells (H9C2) exhibit integrin-based mechanosensing during the initial stage of adhesion (within the first 2 h), enabling them to recognize and respond to variations in substrate stiffnesses. Moreover, the bioinformatics analysis of RNA transcriptome sequencing (RNA-seq) reveals that the gene expressions associated with initial stage focal adhesion (Ctgf, Cyr61, Amotl2, Prickle1, Serpine1, Akap12, Hbegf, and Nedd9) are up-regulated on substrates with elevated Young's modulus. The fluorescent immunostaining results also suggest that increased substrate stiffness enhances the expression of Y397-phosphorylated focal adhesion kinase (FAK Y397), talin, and vinculin and the assembly of F-actin in H9C2 cells, thereby facilitating the adhesion of myocardial cells on the substrate. Next, we utilize fluidic force microscopy (FluidFM)-based single-cell force spectroscopy (SCFS) to quantitatively evaluate the impact of substrate stiffness on the cell adhesion force and adhesion work, thus providing novel insights into the biomechanical regulation of initial cell adhesion. Our findings demonstrate that the maximum adhesion forces of myocardial cells exhibit a rise from 23.6 to 248.0 nN when exposed to substrates with different moduli. It is worth noting that once the αvß3 integrins are blocked, the disparities in the adhesion forces of myocardial cells on these substrates become negligible. These results exhibit remarkable sensitivity of myocardial cells to mechanical cues of the substrate, highlighting the role of αvß3 integrin as a biomechanical sensor for the regulation of cell adhesion. Overall, this work offers a prospective approach for the regulation of cell adhesion via integrin mechanosensing with potential practical applications in the areas of tissue engineering and regenerative medicine.

Janus nanoparticles targeting extracellular polymeric substance achieve flexible elimination of drug-resistant biofilms.

Safe and efficient antibacterial materials are urgently needed to combat drug-resistant bacteria and biofilm-associated infections. The rational design of nanoparticles for flexible elimination of biofilms remains challenging. Herein, we propose the fabrication of Janus-structured nanoparticles targeting extracellular polymeric substance to achieve dispersion or near-infrared (NIR) light-activated photothermal elimination of drug-resistant biofilms, respectively. Asymmetrical Janus-structured dextran-bismuth selenide (Dex-BSe) nanoparticles are fabricated to exploit synergistic effects of both components. Interestingly, Janus Dex-BSe nanoparticles realize enhanced dispersal of biofilms over time. Alternatively, taking advantage of the preferential accumulation of nanoparticles at infection sites, the self-propelled active motion induced by the unique Janus structure enhances photothermal killing effect. The flexible application of Janus Dex-BSe nanoparticles for biofilm removal or NIR-triggered eradication in vivo is demonstrated by Staphylococcus aureus-infected mouse excisional wound model and abscess model, respectively. The developed Janus nanoplatform holds great promise for the efficient elimination of drug-resistant biofilms in diverse antibacterial scenarios.

Sub-pm linewidth, high pulse energy, high beam quality microsecond-pulse Ti:sapphire laser at 766.699†nm.

In this letter, a sub-pm linewidth, high pulse energy and high beam quality microsecond-pulse 766.699 nm Ti:sapphire laser pumped by a frequency-doubled Nd:YAG laser is demonstrated. At an incident pump energy of 824 mJ, the maximum output energy of 132.5 mJ at 766.699 nm with linewidth of 0.66 pm and a pulse width of 100 µs is achieved at a repetition rate of 5 Hz. To the best of our knowledge, this is the highest pulse energy at 766.699 nm with pulse width of hundred micro-seconds for a Ti:sapphire laser. The beam quality factor M2 is measured to be 1.21. It could be precisely tuned from 766.623 to 766.755 nm with a tuning resolution of 0.8 pm. The wavelength stability is measured to be less than ±0.7 pm over 30 min. The sub-pm linewidth, high pulse energy and high beam quality Ti:sapphire laser at 766.699 nm can be used to create a polychromatic laser guide star together with a home-made 589 nm laser in the mesospheric sodium and potassium layer for the tip-tilt correction resulting in the near-diffraction limited imagery on a large telescope.

Rough Nanovaccines Boost Antitumor Immunity Through the Enhancement of Vaccination Cascade and Immunogenic Cell Death Induction.

Nanovaccines have attracted intense interests for efficient antigen delivery and tumor-specific immunity. It is challenging to develop a more efficient and personalized nanovaccine to maximize all steps of the vaccination cascade by exploiting the intrinsic properties of nanoparticles. Here, biodegradable nanohybrids (MP) composed of manganese oxide nanoparticles and cationic polymers are synthesized to load a model antigen ovalbumin to form MPO nanovaccines. More interestingly, MPO could serve as autologous nanovaccines for personalized tumor treatment taking advantage of in situ released tumor-associated antigens induced by immunogenic cell death (ICD). The intrinsic properties of MP nanohybrids including morphology, size, surface charge, chemical, and immunoregulatory functions are fully exploited to enhance of all steps of the cascade and induce ICD. MP nanohybrids are designed to efficiently encapsulate antigens by cationic polymers, drain to lymph nodes by appropriate size, be internalized by dendritic cells (DCs) by rough morphology, induce DC maturation through cGAS-STING pathway, and enhance lysosomal escape and antigen cross-presentation through the "proton sponge effect". The MPO nanovaccines are found to efficiently accumulate in lymph nodes and elicit robust specific T-cell immune responses to inhibit the occurrence of ovalbumin-expressing B16-OVA melanoma. Furthermore, MPO demonstrate great potential to serve as personalized cancer vaccines through the generation of autologous antigen depot through ICD induction, activation of potent antitumor immunity, and reversal of immunosuppression. This work provides a facile strategy for the construction of personalized nanovaccines by exploiting the intrinsic properties of nanohybrids.

BODIPY-Functionalized Natural Polymer Coatings for Multimodal Therapy of Drug-Resistant Bacterial Infection.

The fact that multidrug resistance (MDR) could induce medical device-related infections, along with the invalidation of traditional antibiotics has become an intractable global medical issue. Therefore, there is a pressing need for innovative strategies of antibacterial functionalization of medical devices. For this purpose, a multimodal antibacterial coating that combines photothermal and photodynamic therapies (PTT/PDT) is developed here based on novel heavy atom-free photosensitizer compound, BDP-6 (a kind of boron-dipyrromethene). The photothermal conversion efficiency of BDP-6 is of 55.9%, which could improve biocompatibility during PTT/PDT process by reducing the exciting light power density. Furthermore, BDP-6, together with oxidized hyaluronic acid, is crosslinked with a natural polymer, gelatin, to fabricate a uniform coating (denoted as polyurethane (PU)-GHB) on the surface of polyurethane. PU-GHB has excellent synergistic in vitro PTT/PDT antibacterial performance against both susceptible bacteria and MDR bacteria. The antibacterial mechanisms are revealed as that hyperthermia could reduce the bacterial activity and enhance the permeability of inner membrane to reactive oxygen species by disturbing cell membrane. Meanwhile, in an infected abdominal wall hernia model, the notable anti-infection performance, good in vivo compatibility, and photoacoustic imaging property of PU-GHB are verified. A promising strategy of developing multifunctional antibacterial coatings on implanted medical devices is provided here.

Facile fabrication of two-dimensional iodine nanosheets for antibacterial therapy.

Herein, we report a facile approach for the preparation of two-dimensional iodine nanosheets (2D iodine NSs) with good stability and high biocompatibility via an aqueous solvent-assisted ultrasonic route. Due to the large specific surface area of the 2D morphology, iodine NSs effectively interact with bacterial membranes and destroy bacterial integrity, as well as further damaging intracellular DNA, showing prominent antibacterial activity against S. aureus in vitro and in vivo.

A H2 O2 -Supplied Supramolecular Material for Post-irradiated Infected Wound Treatment.

Photodynamic therapy (PDT) is a light triggered therapy by producing reactive oxygen species (ROS), but traditional PDT may suffer from the real-time illumination that reduces the compliance of treatment and cause phototoxicity. A supramolecular photoactive G-quartet based material is reported, which is self-assembled from guanosine (G) and 4-formylphenylboronic acid/1,8-diaminooctane, with incorporation of riboflavin as a photocatalyst to the G4 nanowire, for post-irradiation photodynamic antibacterial therapy. The G4-materials, which exhibit hydrogel-like properties, provide a scaffold for loading riboflavin, and the reductant guanosine for the riboflavin for phototriggered production of the therapeutic H2 O2 . The photocatalytic activity shows great tolerance against room temperature storage and heating/cooling treatments. The riboflavin-loaded G4 hydrogels, after photo-irradiation, are capable of killing gram-positive bacteria (e.g., Staphylococcus aureus), gram-negative bacteria (e.g., Escherichia coli), and multidrug resistant bacteria (methicillin-resistant Staphylococcus aureus) with sterilization ratio over 99.999%. The post-irradiated hydrogels also exhibit great antibacterial activity in the infected wound of the rats, revealing the potential of this novel concept in the light therapy.

Fluorination of Polyethylenimines for Augmentation of Antibacterial Potency via Structural Damage and Potential Dissipation of Bacterial Membranes.

The rise of drug-resistant bacteria (e.g., methicillin-resistant Staphylococcus aureus, MRSA) has continued, making the ″super-bugs″ a formidable threat to global health. Herein, we synthesize a series of fluoroalkylated polyethylenimines (PEI-F) with different grafting degrees of fluoroalkyls via a simple ring-opening reaction and demonstrate for the first time that fluoroalkylated PEIs are able to exert potent antibacterial activity to Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Among the fluoroalkylated polymers, PEI-F3.0 shows the strongest antibacterial activity, with a minimum inhibitory concentration (MIC) of 64 µg mL-1, against both E. coli and S. aureus. More importantly, we find that PEI-F3.0 is able to kill over 99.8% of S. aureus within 1 min, which is extremely desirable for the treatment of acute and severe bacterial infections that require quick disinfection. We also demonstrate that the fluoroalkylated PEIs are able to kill bacteria via structural damage of the outer membrane (OM) and cytoplasmic membrane (CM), potential dissipation of CM, and generation of intracellular reactive oxygen species (ROS). The in vivo antibacterial test suggests that commercial Vaseline blended with 6.25 wt % of PEI-F3.0 (VL/PEI-F3.0) is able to efficaciously eradicate MRSA infection on a bacterial infected wound model and promote the healing procedure of the wound site. Therefore, the fluoroalkylated PEIs provide a promising strategy to cope with the major challenges of drug-resistant infections.

Heparinized anticoagulant coatings based on polyphenol-amine inspired chemistry for blood-contacting catheters.

Blood-contacting catheters occupy a vital position in modern clinical treatment including but not limited to cardiovascular diseases, but catheter-related thrombosis associated with high morbidity and mortality remains a major health concern. Hence, there is an urgent need for functionalized catheter surfaces with superior hemocompatibility that prevent protein adsorption and thrombus formation. In this work, we developed a strategy for constructing a kind of polyphenol-amine coating on the TPU surface (TLA) with tannic acid and lysine via simple dip-coating, inspired by dopamine adhesion. Based on the long-term stability and modifiable properties of TLA coatings, heparin was introduced by an amide reaction to provide anticoagulant activity (TLH). X-ray photoelectron spectroscopy and surface zeta potential measurements fully indicated the successful immobilization of heparin. Water contact angle measurements demonstrated good hydrophilicity and stability for 15 days of TLH coatings. Furthermore, the TLH coatings exhibited significant hemocompatibility and no cytotoxicity. The good antithrombotic properties of the functionalized surfaces were confirmed by an ex vivo blood circulation model. The present work is supposed to find potential clinical applications for preventing surface-induced thrombosis of blood-contacting catheters.

Wearable, Washable, and Highly Sensitive Piezoresistive Pressure Sensor Based on a 3D Sponge Network for Real-Time Monitoring Human Body Activities.

Wearable pressure sensors are highly desirable for monitoring human health and realizing a nice human-machine interaction. Herein, a chitosan/MXene/polyurethane-sponge/polyvinyl alcohol (CS/MXene/PU sponge/PVA)-based 3D pressure sensor is developed to simultaneously achieve wearability, washability, and high sensitivity in a wide region. In the force-sensitive layer of the sensor, MXene and CS are fully attached to the PU sponge to ensure that the composite sponge has remarkable conductivity and washability. Benefiting from the highly resistive PVA-nanowire spacer, the initial current of the sensor is reduced significantly so that the sensor exhibits extremely high sensitivity (84.9 kPa-1 for the less than 5 kPa region and 140.6 kPa-1 for the 5-22 kPa region). Moreover, the sensor has an excellent fast response time of 200 ms and a short recovery time of 30 ms, as well as non-attenuating durability over 5000 cycles. With the high sensitivity in a wide range, the sensor is capable of detecting multiple human and animal activities in real time, ranging from the large pressure of joint activities to a subtle pressure of pulse. Furthermore, the sensor also demonstrates the potential application in measuring pressure distribution. Overall, such a multifunctional pressure sensor can supply a new platform for the design and development of wearable health-monitoring equipment and an efficient human-machine interface.

Controlled Synthesis and Surface Engineering of Janus Chitosan-Gold Nanoparticles for Photoacoustic Imaging-Guided Synergistic Gene/Photothermal Therapy.

The unsymmetrical morphology and unique properties of Janus nanoparticles (JNPs) provide superior performances for biomedical applications. In this work, a general and facile strategy is developed to construct a series of symmetrical and unsymmetrical chitosan/gold nanoparticles. Taking advantage of the active motion derived from Janus structure, selective surface functionalization of polysaccharide domain, and photothermal effect of gold nanorods, Janus chitosan/gold nanoparticles (J-Au-CS) are selected as a model system to construct Janus-structured chitosan/gold nanohybrids (J-ACP). Near-infrared (NIR)-responsive J-ACP composed of polycationic chitosan nanospheres and PEGylated gold nanorods hold great potential to realize photoacoustic (PA) imaging-guided complementary photothermal therapy (PTT)/gene therapy for breast cancer. The morphology effect of chitosan/gold nanostructures on enhanced PTT, cellular uptake, and gene transfection is investigated. The feasibility of PA imaging to track the accumulation of J-ACP and guide PTT is also explored. Notably, synergistic therapy is achieved based on PTT-enhanced gene therapy. In addition, the loading function of chitosan/gold nanoparticles for fluorescence imaging is demonstrated. The current work extends the application of JNPs for imaging-guided synergistic cancer therapy and provides flexible candidates with distinct structures for diverse biomedical applications.

Bulk Modification of Thermoplastic Polyurethanes for Self-Sterilization of Trachea Intubation.

Implantable medical devices are widely used, but biomaterial-associated infections (BAIs) impose a huge economic burden and increase the mortality of patients. Therefore, BAIs are a serious concern that must be urgently resolved. Materials with antibacterial properties have become hotspots of current research and development. In the present work, quaternized chitosan (QCS) is used as an antibacterial agent and blended with thermoplastic polyurethane (TPU) to create an antibacterial material for tracheal intubation tubes. The modified TPU material (QCS-TPU) exhibited good mechanical properties and excellent long-term antibacterial performance. Under in vitro hydrodynamic conditions, QCS-TPU retained its strong antibacterial properties. QCS-TPU also possessed a low hemolysis rate and cytotoxicity. The current work is expected to provide a facile and feasible strategy for the preparation of antibacterial catheters and aid in the discovery of promising clinical applications to prevent BAIs.

Biomass-Derived Multilayer-Structured Microparticles for Accelerated Hemostasis and Bone Repair.

It is very desirable to develop advanced sustainable biomedical materials with superior biosafety and bioactivity for clinical applications. Herein, biomass-derived multilayer-structured absorbable microparticles (MQ x T y ) composed of starches and plant polyphenols are readily constructed for the safe and effective treatment of bone defects with intractable bleeding by coating multiple layers of quaternized starch (Q+) and tannic acid onto microporous starch microparticles via facile layer-by-layer assembly. MQ x T y microparticles exhibit efficient degradability, low cytotoxicity, and good blood compatibility. Among various MQ x T y microparticles with distinct Q+/T- double layers, MQ2T2 with outmost polyphenol layer possess the unique properties of platelet adhesion/activation and red blood cell aggregation, resulting in the best hemostatic performance. In a mouse cancellous-bone-defect model, MQ2T2 exhibits the favorable hemostatic effect, low inflammation/immune responses, high biodegradability, and promoted bone repair. A proof-of-concept study of beagles further confirms the good performance of MQ2T2 in controlling intractable bleeding of bone defects. The present work demonstrates that such biomass-based multilayer-structured microparticles are very promising biomedical materials for clinical use.

Molecular Sizes and Antibacterial Performance Relationships of Flexible Ionic Liquid Derivatives.

Cationic agents, such as ionic liquids (ILs)-based species, have broad-spectrum antibacterial activities. However, the antibacterial mechanisms lack systematic and molecular-level research, especially for Gram-negative bacteria, which have highly organized membrane structures. Here, we designed a series of flexible fluorescent diketopyrrolopyrrole-based ionic liquid derivatives (ILDs) with various molecular sizes (1.95-4.2 nm). The structure-antibacterial activity relationships of the ILDs against Escherichia coli (E. coli) were systematically studied thorough antibacterial tests, fluorescent tracing, morphology analysis, molecular biology, and molecular dynamics (MD) simulations. ILD-6, with a relatively small molecular size, could penetrate through the bacterial membrane, leading to membrane thinning and intracellular activities. ILD-6 showed fast and efficient antimicrobial activity. With the increase of molecular sizes, the corresponding ILDs were proven to intercalate into the bacterial membrane, leading to the destabilization of the lipid bilayer and further contributing to the antimicrobial activities. Moreover, the antibacterial activity of ILD-8 was limited, where the size was not large enough to introduce significant membrane disorder. Relative antibacterial experiments using another common Gram-negative bacteria, Pseudomonas aeruginosa (PAO1), further confirmed the proposed structure-antibacterial activity relationships of ILDs. More impressively, both ILD-6 and ILD-12 displayed significant in vivo therapeutic effects on the PAO1-infected rat model, while ILD-8 performed poorly, which confirmed the antibacterial mechanism of ILDs and proved their potentials for future application. This work clarifies the interactions between molecular sizes of ionic liquid-based species and Gram-negative bacteria and will provide useful guidance for the rational design of high-performance antibacterial agents.

Well-Defined Gold Nanorod/Polymer Hybrid Coating with Inherent Antifouling and Photothermal Bactericidal Properties for Treating an Infected Hernia.

Biomedical device-associated infection (BAI) is a great challenge in modern clinical medicine. Therefore, developing efficient antibacterial materials is significantly important and meaningful for the improvement of medical treatment and people's health. In the present work, we developed a strategy of surface functionalization for multifunctional antibacterial applications. A functionalized polyurethane (PU, a widely used biomedical material for hernia repairing) surface (PU-Au-PEG) with inherent antifouling and photothermal bactericidal properties was readily prepared based on a near-infrared (NIR)-responsive organic/inorganic hybrid coating which consists of gold nanorods (Au NRs) and polyethylene glycol (PEG). The PU-Au-PEG showed a high efficiency to resist adhesion of bacteria and exhibited effective photothermal bactericidal properties under 808 nm NIR irradiation, especially against multidrug-resistant bacteria. Furthermore, the PU-Au-PEG could inhibit biofilm formation long term. The biocompatibility of PU-Au-PEG was also proved by cytotoxicity and hemolysis tests. The in vivo photothermal antibacterial properties were first verified by a subcutaneous implantation animal model. Then, the anti-infection performance in a clinical scenario was studied with an infected hernia model. The results of animal experiment studies demonstrated excellent in vivo anti-infection performances of PU-Au-PEG. The present work provides a facile and promising approach to develop multifunctional biomedical devices.

Polycaprolactone/polysaccharide functional composites for low-temperature fused deposition modelling.

Fused deposition modelling (FDM) is a commonly used 3D printing technology. The development of FDM materials was essential for the product quality of FDM. In this work, a series of polycaprolactone (PCL)-based composites for low-temperature FDM were developed. By melt blending technique, different ratios of starch were added into PCL to improve the performances of FDM, and the printability, tensile strength, rheological properties, crystallization behaviors and biological performances of the composites were studied. The PCL/starch composite had the best performance in FDM process with the starch ratio of 9 ph at 80-90 °C. The melting strength and solidification rate of PCL/starch composites were improved. The starch also increased the crystallization temperature, degree of crystallinity and crystallization rate of PCL/starch composites, while had no negative effects on the tensile strength of PCL. Due to the low printing temperature, various kinds of bioactive components were added into PCL/starch composites for preparation of antibacterial and biocompatible materials for FDM. The present work provides a new method to develop novel low-temperature FDM materials with various functions.

Self-adaptive antibacterial surfaces with bacterium-triggered antifouling-bactericidal switching properties.

Catheter-induced infection is a severe problem in clinical practice, which induces significant morbidity, mortality and treatment costs. Therefore, there is a great requirement for developing antibacterial surfaces of catheter materials. In the present study, we develop a strategy for constructing self-adaptive antibacterial surfaces with bacterium-triggered antifouling-bactericidal switching properties on polyurethane (PU) via surface-initiated atom-transfer radical polymerization (SI-ATRP). Polymer coating with one hierarchical structure was readily constructed on the PU surface (PU-PQ-PEG), which was composed of poly[2-(dimethyl decyl ammonium)ethyl methacrylate] (PQDMAEMA) brushes as the bactericidal lower layer and polyethylene glycol (PEG) as the antifouling upper layer. The two layers were incorporated with Schiff base structures, which could be broken by the metabolism of bacteria. Under normal and mild infection conditions, PU-PQ-PEG showed excellent antifouling and biocompatible properties against proteins and bacteria. When serious infection occurred and bacteria colonized on the PU-PQ-PEG surface, the bacteria could trigger the self-adaptive antifouling-bactericidal switching of the surface. Furthermore, the self-adaptive antibacterial properties of PU-PQ-PEG were also confirmed by an in vitro circulating model to simulate hydrodynamic conditions. PU-PQ-PEG showed self-adaptive antibacterial performances both under static and hydrodynamic conditions. The results of animal experiments also demonstrated the in vivo anti-infection performance. The present work will provide a promising strategy for developing antibacterial surfaces of catheter materials with hemocompatibility.