Mussel-Inspired Polymer Carpets: Direct Photografting of Polymer Brushes on Polydopamine Nanosheets for Controlled Cell Adhesion

Polydopamine Applications in Biomedicine and Environmental Science

This manuscript explores the multifaceted applications of polydopamine (PDA) across various scientific and industrial domains. It covers the chemical aspects of PDA and its potential in bone tissue engineering, implant enhancements, cancer treatment, and nanotechnology. The manuscript investigates PDA's roles in tissue engineering, cell culture technologies, surface modifications, drug delivery systems, and sensing techniques. Additionally, it highlights PDA's contributions to microfabrication, nanoengineering, and environmental applications. Through detailed testing and assessment, the study identifies limitations in PDA-related research, such as synthesis complexity, incomplete mechanistic understanding, and biocompatibility variability. It also proposes future research directions aimed at improving synthesis techniques, expanding biomedical applications, and enhancing sensing technologies to optimize PDA's efficacy and scalability.

Bioinspired Hybrid Nanostructured PEEK Implant with Enhanced Antibacterial and Anti-inflammatory Synergy

Implant-associated infections and excessive immune responses are two major postsurgical issues for successful implantation. However, conventional strategies including antibiotic treatment and inflammatory regulation are always compromised due to the comodification of various biochemical agents and instances of functional interference. It is imperative to provide implant surfaces with satisfactory antibacterial and anti-inflammatory properties. Here, a dual-effect nanostructured polyetheretherketone (PEEK) surface (NP@PDA/Zn) with bionic mechano-bactericidal nanopillars and immobilized immunomodulatory Zn2+ is designed. The constructed hybrid nanopillars display remarkable antibacterial performance against Gram-negative and Gram-positive strains through the synergy of physical and chemical bactericidal effects imposed by nanopillars and Zn2+. Meanwhile, the immunoregulatory property is evaluated through the investigation of macrophage polarization both in vitro and in vivo, and the results reveal that NP@PDA/Zn could downregulate the expression of M1-related cytokines and decrease the M1 macrophage recruitment to lower the inflammatory response. Notably, the surface exhibited exceptional biocompatibility with discerning biocidal activity between bacterial and mammalian cells and antioxidant performance that effectively scavenges ROS, minimizing potential cytotoxicity. Taken together, NP@PDA/Zn presents a convenient and promising strategy of combining synergistic bactericidal activity and inflammatory regulation without any mutual interference, which can support the development of multifunctional implant-associated materials.

Supercritical CO2 extrusion foaming of highly open-cell poly(lactic acid) foam with superior oil adsorption performance

Addressing marine oil spills and industrial water pollution necessitates the development of eco-efficient oil-absorbing materials. With increasing concern for the environment, there is a consensus to decrease the use of petroleum-based polymers. Herein, lightweight poly(lactic acid) (PLA) blend foams with varying thermoplastic polyurethane (TPU) content were fabricated via a solvent-free, eco-friendly supercritical carbon dioxide (scCO2) extrusion foaming technology. The incorporation of TPU significantly enhanced the crystallization rate of PLA, with the semi-crystallization time of PT30 and PT50 blends at 105 °C exhibiting a reduction of 77.2 % and 47.9 %, respectively, compared to neat PLA. The resulting foams exhibited an open-cell structure with excellent selective oil adsorption capabilities. Notably, the PT30 foam achieved a remarkable maximum expansion ratio of 36.0, while the PT50 foam attained the highest open-cell content of 96.2 %. The PT50 foam demonstrated an outstanding adsorption capacity, spanning from 4.7 to 18.8 g/g for diverse oils and solvents, with rapid adsorption kinetics, reaching 94.9 % of the equilibrium adsorption capacity for CCl4 within just 1 min. Furthermore, the PT50 foam retained 95.2 % of its adsorption capacity for CCl4 over 10 adsorption-desorption cycles. This study presents a scalable and sustainable approach for large-scale production of high-performance, bio-based foams, facilitating efficient oil-water separation.

High-density zwitterionic polymer brushes exhibit robust lubrication properties and high antithrombotic efficacy in blood-contacting medical devices

High-performance catheters are essential for interventional surgeries, requiring reliable anti-adhesive and lubricated surfaces. This article develops a strategy for constructing high-density sulfobetaine zwitterionic polymer brushes on the surface of catheters, utilizing dopamine and sodium alginate as the primary intermediate layers, where dopamine provides mussel-protein-like adhesion to anchor the polymer brushes to the catheter surface. Hydroxyl-rich sodium alginate increases the number of grafting sites and improves the grafting mass by more than 4 times. The developed high-density zwitterionic polymer brushes achieve long-lasting and effective lubricity (μ<0.0078) and are implanted in rabbits for four hours without bio-adhesion and thrombosis in the absence of anticoagulants such as heparin. Experiments and molecular dynamics simulations demonstrate that graft mass plays a decisive role in the lubricity and anti-adhesion of polymer brushes, and it is proposed to predict the anti-adhesion of polymer brushes by their lubricity to avoid costly and time-consuming bioassays during the development of amphoteric polymer brushes. A quantitative influence of hydration in the anti-adhesion properties of amphiphilic polymer brushes is also revealed. Thus, this study provides a new approach to safe, long-lasting lubrication and anticoagulant surface modification for medical devices in contact with blood. STATEMENT OF SIGNIFICANCE: High friction and bioadhesion on medical device surfaces can pose a significant risk to patients. In response, we have developed a safer, simpler, and more application-specific surface modification strategy that addresses both the lubrication and anti-bioadhesion needs of medical device surfaces. We used dopamine and sodium alginate as intermediate layers to drastically increase the grafting density of the zwitterionic brushes and enabled the modified surfaces to have an extremely low coefficient of friction (μ = 0.0078) and to remain non-bioadhesive for 4 hours in vivo. Furthermore, we used molecular dynamics simulations to gain insight into the mechanisms behind the superior anti-adhesion properties of the high-density polymer brushes. Our work contributes to the development and application of surface-modified coatings.

Surface Modification Progress for PLGA-Based Cell Scaffolds

Poly(lactic-glycolic acid) (PLGA) is a biocompatible bio-scaffold material, but its own hydrophobic and electrically neutral surface limits its application as a cell scaffold. Polymer materials, mimics ECM materials, and organic material have often been used as coating materials for PLGA cell scaffolds to improve the poor cell adhesion of PLGA and enhance tissue adaptation. These coating materials can be modified on the PLGA surface via simple physical or chemical methods, and coating multiple materials can simultaneously confer different functions to the PLGA scaffold; not only does this ensure stronger cell adhesion but it also modulates cell behavior and function. This approach to coating could facilitate the production of more PLGA-based cell scaffolds. This review focuses on the PLGA surface-modified materials, methods, and applications, and will provide guidance for PLGA surface modification.

GM-CSF augmented the photothermal immunotherapeutic outcome of self-driving gold nanoparticles against a mouse CT-26 colon tumor model

BACKGROUND

Hypoxia is a frequent characteristic observed in solid tumors and is strongly associated with tumor metastasis, angiogenesis, and drug resistance. While the vasculature of hypoxic tumor tissues poses obstacles to the efficient administration of conventional drugs, it may prove advantageous in sustaining hyperthermia. Photothermal therapy (PTT) offers a promising treatment strategy that utilizes the activation of photosensitizers to produce heat, thus facilitating the selective ablation of tumor tissues.

METHOD

To enhance the accumulation of photothermal agents in tumor tissue and improve the effectiveness of PTT, we developed a self-propelled hybrid called Bif@PAu-NPs. This hybrid consists of polydopamine (PDA)-coated gold nanoparticles (Au-NPs) loaded onto the anaerobic Bifidobacterium infantis (Bif).

RESULTS

The Bif@PAu-NPs actively aggregated at the tumor site because the ability of Bif can target hypoxic regions, and PAu-NPs achieved precise PTT due to their high photothermal conversion efficiency (η = 67.8%). The tumor tissues were ablated by PTT, resulting in the release of antigens through immunogenic cell death (ICD), which stimulates an immune response. The inclusion of GM-CSF enhanced the immune response by recruiting dendritic cells and initiating long-term anti-tumor immunity.

CONCLUSION

The Bif@PAu-NPs hybrid effectively suppressed the growth of both primary tumors and re-challenged tumors. The utilization Bif@PAu-NPs in conjunction with GM-SCF exhibits great potential as a photothermal-immunotherapeutic strategy for precisely treating solid tumors. In this study, the bacterial Bif@PAu-NPs biohybrid is exploited the self-driving ability of anaerobic Bifidobacterium infantis to deliver polydopamine-modified gold nanoparticles to hypoxic region of tumor. Under irradiation with 808 nm NIR laser, the hybrid exerts precise photothermal therapy to stimulate the immune response, which is further enhanced by GM-CSF, leading to recruitment of dendritic cells and initiation of a long-term anti-tumor immunity remember to prevent tumor recurrence.

Scalable Air-Tolerant μL-Volume Synthesis of Thick Poly(SPMA) Brushes Using SI-ARGET-ATRP

We present a facile procedure for preparing thick (up to 300 nm) poly(3-sulfopropyl methacrylate) brushes using SI-ARGET-ATRP by conducting the reaction in a fluid film between the substrate and a coverslip. This method is advantageous in a number of ways: it does not require deoxygenation of the reaction solution, and the monomer conversion is much higher than usual since only a minimal amount of solution (microliters) is used, resulting in a tremendous reduction (∼50×) of wasted reagents. Moreover, this method is particularly suitable for grafting brushes to large substrates.

Oxygen-Tolerant Photografting for Surface Structuring from Microliter Volumes

Here, we report an oxygen-tolerant photografting technique to grow polymer brushes employing microliter volumes of monomer solution under ambient conditions. With the key advantages that include spatial control, initiator/catalyst-free nature, and high oxygen tolerance, a series of homo-, multiblock, and arbitrary patterned polymer brushes were successfully obtained by photografting. Moreover, a dual-functional surface with hydrophilic and hydrophobic properties could easily be realized by one-pot photografting. These results illustrated the practicality and versatility of this strategy, which will allow nonexperts access to polymer brush architectures and broaden the potential applications of polymer brushes.

Homogeneous silver nanoparticle loaded polydopamine/polyethyleneimine-coated bacterial cellulose nanofibers for wound dressing

Utilizing mussel-inspired chemistry is an advanced strategy for surface modification, because dopamine (DA) can form a material-independent adhesive coating and further functionalization can be achieved, including the production of silver nanoparticles (AgNPs). Nevertheless, DA easily aggregates in the nanofiber network structure of bacterial cellulose (BC), which not only blocks the pores in the BC structure but also leads to the formation of large silver particles and the burst release of highly cytotoxic silver ions. Herein, a homogeneous AgNP-loaded polydopamine (PDA)/polyethyleneimine (PEI) coated BC was constructed via a Michael reaction between PDA and PEI. Under the action of PEI, the PDA/PEI coating was uniformly attached to the BC fiber surface with a thickness of approximately 4 nm, and homogeneous AgNPs were produced on the uniform PDA/PEI/BC (PPBC) fiber surface. The sustained release of silver ions was better from AgNPs@PPBC than from AgNPs@PDA/BC. The obtained AgNPs@PPBC exhibited excellent antibacterial activities and cytocompatibility. The results of the in vivo assay indicated that the AgNPs@PPBC dressing could inhibit S. aureus infection and inflammation, promote hair follicle growth, enhance collagen deposition, and accelerate wound healing within 12 days compared with BC. These results illustrate that the homogeneous AgNPs@PPBC dressing has great potential for treating infected wounds.

Bioinspired Polymers: Transformative Applications in Biomedicine and Regenerative Medicine

Bioinspired polymers have emerged as a promising field in biomaterials research, offering innovative solutions for various applications in biomedical engineering. This manuscript provides an overview of the advancements and potential of bioinspired polymers in tissue engineering, regenerative medicine, and biomedicine. The manuscript discusses their role in enhancing mechanical properties, mimicking the extracellular matrix, incorporating hydrophobic particles for self-healing abilities, and improving stability. Additionally, it explores their applications in antibacterial properties, optical and sensing applications, cancer therapy, and wound healing. The manuscript emphasizes the significance of bioinspired polymers in expanding biomedical applications, addressing healthcare challenges, and improving outcomes. By highlighting these achievements, this manuscript highlights the transformative impact of bioinspired polymers in biomedical engineering and sets the stage for further research and development in the field.

Development of a universal, oriented antibody immobilization method to functionalize vascular prostheses for enhanced endothelialization for potential clinical application

BACKGROUND

Thrombosis is a common cause of vascular prosthesis failure. Antibody coating of prostheses to capture circulating endothelial progenitor cells to aid endothelialization on the device surface appears a promising solution to prevent thrombus formation. Compared with random antibody immobilization, oriented antibody coating (OAC) increases antibody-antigen binding capacity and reduces antibody immunogenicity in vivo. Currently, few OAC methods have been documented, with none possessing clinical application potential.

RESULTS

Dopamine and the linker amino-PEG8-hydrazide-t-boc were successfully deposited on the surface of cobalt chromium (CC) discs, CC stents and expanded polytetrafluoroethylene (ePTFE) grafts under a slightly basic condition. CD34 antibodies were immobilized through the reaction between aldehydes in the Fc region created by oxidation and hydrazides in the linker after t-boc removal. CD34 antibody-coated surfaces were integral and smooth as shown by scanning electron microscopy (SEM), had significantly reduced or no substrate-specific signals as revealed by X-ray photoelectron spectroscopy, were hospitable for HUVEC growth as demonstrated by cell proliferation assay, and specifically bound CD34 + cells as shown by cell binding testing. CD34 antibody coating turned hydrophobic property of ePTFE grafts to hydrophilic. In a porcine carotid artery interposition model, a confluent monolayer of cobblestone-shaped CD31 + endothelial cells on the luminal surface of the CD34 antibody coated ePTFE graft were observed. In contrast, thrombi and fibrin fibers on the bare graft, and sporadic cells on the graft coated by chemicals without antibodies were seen.

CONCLUSION

A universal, OAC method was developed. Our in vitro and in vivo data suggest that the method can be potentially translated into clinical application, e.g., modifying ePTFE grafts to mitigate their thrombotic propensity and possibly provide for improved long-term patency for small-diameter grafts.

Surface polydopamine modification of bone defect repair materials: Characteristics and applications

Bone defects are a common challenge for clinical orthopedic surgeons. The existing bone defect repair materials are difficult to achieve satisfactory osseointegration between the material and the bone. Therefore, it is increasingly important to find effective methods to improve the integration of the materials with the bone and thus facilitate bone defect repair. Researchers have found that polydopamine (PDA) has a structure and properties similar to the adhesive proteins secreted by mussels in nature, with good biocompatibility, bioactivity, hydrophilicity, bio-adhesion and thermal stability. PDA is therefore expected to be used as a surface modification material for bone repair materials to improve the bonding of bone repair materials to the bone surface. This paper reviews research related to PDA-modified bone repair materials and looks at their future applications.

Polydopamine Biomaterials for Skin Regeneration

Designing biomaterials capable of biomimicking wound healing and skin regeneration has been receiving increasing attention recently. Some biopolymers behave similarly to the extracellular matrix (ECM), supporting biointerfacial adhesion and intrinsic cellular interactions. Polydopamine (PDA) is a natural bioadhesive and bioactive polymer that endows high chemical versatility, making it an exciting candidate for a wide range of biomedical applications. Moreover, biomaterials based on PDA and its derivatives have near-infrared (NIR) absorption, excellent biocompatibility, intrinsic antioxidative activity, antibacterial activity, and cell affinity. PDA can regulate cell behavior by controlling signal transduction pathways. It governs the focal adhesion behavior of cells at the biomaterials interface. These features make melanin-like PDA a fascinating biomaterial for wound healing and skin regeneration. This paper overviews PDA-based biomaterials' synthesis, properties, and interactions with biological entities. Furthermore, the utilization of PDA nano- and microstructures as a constituent of wound-dressing formulations is highlighted.

Synthetic strategies to enhance the long-term stability of polymer brush coatings

High-density, end-anchored macromolecules that form so-called polymer brushes are popular components of bio-inspired surface coatings. In a bio-memetic approach, they have been utilized to reduce friction, repel contamination and control...

Emerging 2D Nanomaterials for Biomedical Applications

Two-dimensional (2D) nanomaterials are an emerging class of biomaterials with remarkable potential for biomedical applications. The planar topography of these nanomaterials confers unique physical, chemical, electronic and optical properties, making them attractive candidates for therapeutic delivery, biosensing, bioimaging, regenerative medicine, and additive manufacturing strategies. The high surface-to-volume ratio of 2D nanomaterials promotes enhanced interactions with biomolecules and cells. A range of 2D nanomaterials, including transition metal dichalcogenides (TMDs), layered double hydroxides (LDHs), layered silicates (nanoclays), 2D metal carbides and nitrides (MXenes), metal-organic framework (MOFs), covalent organic frameworks (COFs) and polymer nanosheets have been investigated for their potential in biomedical applications. Here, we will critically evaluate recent advances of 2D nanomaterial strategies in biomedical engineering and discuss emerging approaches and current limitations associated with these nanomaterials. Due to their unique physical, chemical, and biological properties, this new class of nanomaterials has the potential to become a platform technology in regenerative medicine and other biomedical applications.

Brush-like polymers: design, synthesis and applications

With the development of controlled polymerisation, almost all polymerisation strategies have been successfully transplanted to surface-initiated polymerisation. The resulting polymer brushes have emerged as an effective tool for surface functionalization and modulation of the surface properties of materials. To meet various demands it is possible to tailor a material surface with polymer brushes that have diverse dimensionalities, morphologies and compositions. The crowded environment within polymer brushes as well as the stretched conformation of polymer chains sometimes provide unique physicochemical properties, which lead to the delicate creation of inorganic-organic hybridised nanostructures, anti-fouling coatings, biomedical carriers, and materials for use in lubrication, photonics and energy storage. So far, challenges remain in the high-precision synthesis and topological control needed to realize extended applications of polymer brushes. In this Feature Article, we highlight the topology, potential application prospects and various synthetic protocols, particularly for recently established methods, for the efficient synthesis of polymer brushes, as well as their benefits and limitations.

Thrombin immobilized polydopamine-diatom biosilica for effective hemorrhage control

In this study, an efficient composite hemostatic material (DA-diatom-T) was prepared, using a polydopamine layer as a linker to immobilize thrombin on the surface of diatom biosilica. DA-diatom-T retained the porous structure of the diatom with high water absorption capacity, which can absorb 31 times its own weight of water. The thrombin activity of DA-diatom-T was as high as 5.81 U mg-1 that could be maintained at 67% after 30 days at room temperature. DA-diatom-T exhibited non-toxicity to mouse fibroblast cell lines, favorable hemocompatibility and fast procoagulant ability. DA-diatom-T could promote the initiation of the coagulation process and increase platelet activity and blood clot strength to form a physical barrier at the wound. In an in vivo study, DA-diatom-T could significantly reduce the clotting time and reduce the bleeding volume. The above results showed that DA-diatom-T had potential as a new hemostatic material.

Surface Grafting "Band-Aid" for "Everyone": Filter Paper-Assisted Surface-Initiated Polymerization in the Presence of Air

We report herein a facile and generalized approach to the modification of solid surfaces with polymer brushes under ambient conditions: filter paper-assisted surface-initiated Cu0 -mediated controlled radical polymerization (PSI-CuCRP). The polymerization solution wetted filter paper is sandwiched between a copper plate and an initiator-modified substrate, which allows the creation of a surface-initiated polymerization (SIP) "band-aid" so that everyone can perform the surface grafting selectively with good control over the quality of the polymer brushes employing low concentration and microliter amounts of the monomer solution. The versatility of this method is demonstrated by grafting different homo-, block-, and multicomponent polymer brushes by using the same activation system and reaction conditions, the polymerization process can be precisely controlled to yield uniform polymers and show high chain-end functionality which is exemplified by in situ tetra-copolymerization. The combination of photolithography and paper cutting enables to prepare arbitrary three-dimensional patterned polymer brushes on the surface.

Recent progress in creating complex and multiplexed surface-grafted macromolecular architectures

Surface-grafted macromolecules, including polymers, DNA, peptides, etc., are versatile modifications to tailor the interfacial functions in a wide range of fields. In this review, we aim to provide an overview of the most recent progress in engineering surface-grafted chains for the creation of complex and multiplexed surface architectures over micro- to macro-scopic areas. A brief introduction to surface grafting is given first. Then the fabrication of complex surface architectures is summarized with a focus on controlled chain conformations, grafting densities and three-dimensional structures. Furthermore, recent advances are highlighted for the generation of multiplexed arrays with designed chemical composition in both horizontal and vertical dimensions. The applications of such complicated macromolecular architectures are then briefly discussed. Finally, some perspective outlooks for future studies and challenges are suggested. We hope that this review will be helpful to those just entering this field and those in the field requiring quick access to useful reference information about the progress in the properties, processing, performance, and applications of functional surface-grafted architectures.

Improved Coverage of Mouse Myelomeningocele With a Mussel Inspired Reverse Thermal Gel

BACKGROUND

Myelomeningocele (MMC) is an open neural tube defect of the spinal column. Our laboratory previously introduced a reverse thermal gel (RTG) as the first in situ forming patch for in utero MMC application. To overcome the challenges of anchoring the RTG in the wet amniotic environment to improve MMC coverage, we modified the RTG to mimic the underwater adhesive properties of mussels. We have separated this study into three separate hypotheses-based components: CONCLUSIONS: The DRTG demonstrates increased elasticity, cellular scaffolding properties, and improved MMC coverage in the Grhl3 mouse model. Future studies will be translated to the preclinical ovine model to evaluate this novel gel.

Polymer Brushes on Graphitic Carbon Nitride for Patterning and as a SERS Active Sensing Layer via Incorporated Nanoparticles

Graphitic carbon nitride (gCN) has a broad range of promising applications, from energy harvesting and storage to sensing. However, most of the applications are still restricted due to gCN poor dispersibility and limited functional groups. Herein, a direct photografting of gCN using various polymer brushes with tailorable functionalities via UV photopolymerization at ambient conditions is demonstrated. The systematic study of polymer brush-functionalized gCN reveals that the polymerization did not alter the inherent structure of gCN. Compared to the pristine gCN, the gCN-polymer composites show good dispersibility in various solvents such as water, ethanol, and tetrahydrofuran (THF). Patterned polymer brushes on gCN can be realized by employing photomask and microcontact printing technology. The polymer brushes with incorporated silver nanoparticles (AgNPs) on gCN can act as a multifunctional recyclable active sensing layer for surface-enhanced Raman spectroscopy (SERS) detection and photocatalysis. This multifunctionality is shown in consecutive cycles of SERS and photocatalytic degradation processes that can be applied to in situ monitor pollutants, such as dyes or pharmaceutical waste, with high chemical sensitivity as well as to water remediation. This dual functionality provides a significant advantage to our AgNPs/polymer-gCN with regard to state-of-the-art systems reported so far that only allow SERS pollutant detection but not their decomposition. These results may provide a new methodology for the covalent functionalization of gCN and may enable new applications in the field of catalysis, biosensors, and, most interestingly, environmental remediation.

Substrate-independent Cu(0)-mediated controlled radical polymerization: grafting of block copolymer brushes from poly(dopamine) modified surfaces

A method is presented combining poly(dopamine) chemistry and surface-initiated Cu(0)-mediated controlled radical polymerization (SI-CuCRP). Polymer brushes and block copolymer brushes are grafted independent of the original surface properties.

Liquid metal exfoliation of two dimensional polydopamine nanosheets for templated assembly of noble metal nanoparticles

A liquid metal-assisted exfoliation strategy is developed for synthesizing two-dimensional polydopamine nanosheets.

Spontaneous Growth of 3D Silver Mesoflowers on Poly(4-vinylpyridine) Brushes-Grafted-Graphene Oxide Films and Facile Creation of Nanoporosities over their Surface

Fabricating three-dimensional (3D) hierarchical noble-metal particles by spontaneous redox reactions between graphene and noble-metal salts still remains a great challenge. Herein, the fact that graphene oxide (GO) itself acts as both a platform for grafting polymer brushes and a reducing agent to reduce [Ag(NH₃ )₂ ]⁺ ions is taken advantages of. 3D flower-like Ag mesoparticles (Ag mesoflowers, Ag MFs) with tunable size and shapes can spontaneous grow on poly(4-vinylpyridine) brushes-grafted-graphene oxide (P4VP-g-GO) films in Ag(NH₃ )₂ OH solution without the use of any additional reducing agent. The residual Ag(NH₃ )₂ OH on 3D Ag MFs surface can be further reduced by NaBH₄ , causing abundant nanoporosities over the entire Ag MFs. The resulting Ag nanoporous MFs (Ag NMFs) with larger surface-to-volume ratio and higher nanoscale roughness exhibit ultrasensitivity in surface-enhanced Raman spectroscopy (SERS) detection, and the detection limit for 4-aminothiophenol is as low as 10^-13  m.

Mechanical Enhancement of Bioinspired Polydopamine Nanocoatings

Inspired by the catechol and amine-rich adhesive proteins of mussels, polydopamine (pDA) has become one of the most widely employed methods for functionalizing material surfaces, powered in part by the versatility and simplicity of pDA film deposition that takes place spontaneously on objects immersed in an alkaline aqueous solution of dopamine monomer. Despite the widespread adoption of pDA as a multifunctional coating for surface modification, it exhibits poor mechanical performance. Attempts to modify the physical properties of pDA by incorporation of oxidizing agents, cross-linkers, or carbonization of the films at ultrahigh temperatures have been reported; however, improving mechanical properties with mild post-treatments without sacrificing the functionality and versatility of pDA remains a challenge. Here, we demonstrate thermal annealing at a moderate temperature (130 °C) as a facile route to enhance mechanical robustness of pDA coatings. Chemical spectroscopy, X-ray scattering, molecular force spectroscopy, and bulk mechanical analyses indicate that monomeric and oligomeric species undergo further polymerization during thermal annealing, leading to fundamental changes in molecular and bulk mechanical behavior of pDA. Considerable improvements in scratch resistance were noted in terms of both penetration depth (32% decrease) and residual depth (74% decrease) for the annealed pDA coating, indicating the enhanced ability of the annealed coating to resist mechanical deformations. Thermal annealing resulted in significant enhancement in the intermolecular and cohesive interactions between the chains in the pDA structure, attributed to cross-linking and increased entanglements, preventing desorption and detachment of the chains from the coating. Importantly, improvements in pDA mechanical performance through thermal annealing did not compromise the ability of pDA to support secondary coating reactions as evidenced by electroless deposition of a metal film adlayer on annealed pDA.

Polymer Brushes on Hexagonal Boron Nitride

Direct covalent functionalization of large-area single-layer hexagonal boron nitride (hBN) with various polymer brushes under mild conditions is presented. The photopolymerization of vinyl monomers results in the formation of thick and homogeneous (micropatterned, gradient) polymer brushes covalently bound to hBN. The brush layer mechanically and chemically stabilizes the material and allows facile handling as well as long-term use in water splitting hydrogen evolution reactions.

Novel Mussel-Inspired Universal Surface Functionalization Strategy: Protein-Based Coating with Residue-Specific Post-Translational Modification in Vivo

Surface functionalization can effectively endow materials with desirable properties, promoting the performance between the material and environment, with extensive applications. However, a universal and straightforward surface functionalization method with biocompatibility is scarce. In this study, with synthetic biology strategy, recombinant mussel plaque protein with a zwitterionic peptide inspired by molecular chaperone was engineered through post-translational modification, in which 3,4-dihydroxyphenylalanine was residue-specifically obtained efficiently from tyrosine with tyrosinase coexpressed in vivo. The rational designed chimeric protein coating in this work could successfully anchor to various substrates and exhibit excellent antifouling performance in resisting protein adsorption, cell attachment, and bacterial adhesion with eminent biocompatibility.

Polydopamine nanotube mediated fluorescent biosensor for Hg(ii) determination through exonuclease III-assisted signal amplification

We describe a highly sensitive fluorescence biosensor incorporating polydopamine nanotubes (PDNTs) based on the mechanism of exonuclease III (Exo III) assisted signal amplification for the determination of Hg2+ in aqueous solution. Fluorescent probes of FAM labeled ssDNA (FAM-ssDNA) adsorbed on the PDNTs act as an efficient quencher. In the presence of Hg2+, the FAM-ssDNA can bind to Hg2+ to form double stranded DNA (dsDNA) via the formation of T-Hg2+-T base pairs. Then, the dsDNA was removed from the surface of the PDNTs to restore the fluorescence. The release of the dsDNA was triggered by Exo III digestion. At the same time, the liberated Hg2+ mediates a new cycle of digestion. This assay is ultrasensitive for the selective recognition of Hg2+, and a detection limit as low as 10 pM was achieved. In addition, the fluorescent biosensing system also displays remarkable specificity to Hg2+ in the presence of other possible competing ions. This approach was applied to the determination of Hg2+ in real water samples with good recovery and high efficiency for practical analysis.

Nano polydopamine crosslinked thiol-functionalized hyaluronic acid hydrogel for angiogenic drug delivery

Crosslinking of polymeric network using nanoparticles by physical or chemical method to obtain hydrogel is an emerging approach. Herein, we synthesized Polydopamine (PDA) nanoparticles via oxidative self-polymerization of dopamine in water-ethanol mixture. Thiol-functionalized hyaluronic acid was developed using cysteamine and hyaluronic acid (HA-Cys) via 1-Ethyl-3-(3-Dimethylaminopropyl) Carbodiimide - N-hydroxysuccinimide (EDC-NHS) crosslinking chemistry. Developed HA-Cys conjugate was cross-linked using PDA nanoparticles via Michael-type addition reaction. Synthesized nanoparticles were monodisperse with size of 124 ± 8 nm and had spherical morphology. FTIR characterization confirmed successful synthesis of HA-Cys conjugate and subsequent crosslinking with PDA nanoparticles. Rheological characterization revealed that hydrogels were injectable in nature with good mechanical stability. Dimethyloxalylglycine (DMOG) loaded PDA nanoparticle showed sustained drug release for period of 7 days from composite hydrogel. Hydrogel microenvironment facilitated enhanced endothelial cell migration, proliferation and attachment. Furthermore, in response to release of DMOG from developed hydrogel, cells showed enhanced capillary tube formation in vitro. Overall, these results demonstrate that PDA cross-linked thiol-functionalized hydrogel was developed in a facile manner under physiological conditions. These developed hydrogels could be potentially used in tissue engineering and drug delivery.

Engineering modifiers bearing benzophenone with enhanced reactivity to construct surface microstructures

A novel strategy is proposed to construct a patterned surface with controllable thickness by designing the chain backbone of BP-capped modifiers.

Controlled-temperature photothermal and oxidative bacteria killing and acceleration of wound healing by polydopamine-assisted Au-hydroxyapatite nanorods

Since skin wounds are subject to bacterial infection and tissue regeneration may be impeded, there is demand for biomaterials that possess rapid bactericidal and tissue repair capability. Herein we report in situ promotion of wound healing by a photothermal therapy (PTT) assisted nanocatalytic antibacterial system utilizing a polydopamine (PDA) coating on hydroxyapatite (HAp) incorporated with gold nanoparticles (Au-HAp). The PDA@Au-HAp NPs produce hydroxyl radicals (OH) via catalysis of a small concentration of H₂O₂ to render bacteria more vulnerable to the temperature change. The antibacterial efficacy against Escherichia coli and Staphylococcus aureus is 96.8% and 95.2%, respectively, at a controlled photo-induced temperature of 45 °C that causes no damage to normal tissues. By combining catalysis with near-infrared (NIR) photothermal therapy, the PDA@Au-HAp NPs provide safe, rapid, and effective antibacterial activity compared to OH or PTT alone. In addition, this system stimulates the tissue repairing-related gene expression to facilitate the formation of granulation tissues and collagen synthesis and thus accelerate wound healing. After the 10-day treatment of skin wounds in vivo, PDA@Au-HAp group exhibits quicker recovery than the control group and both sterilization and healing are completed after the 10-day treatment.

STATEMENT OF SIGNIFICANCE

This study presents in situ promotion of wound healing by a low-temperature photothermal therapy (PTT) assisted nanocatalytic antibacterial system utilizing a polydopamine (PDA) coating on hydroxyapatite (HAp) incorporated with gold nanoparticles (Au-HAp). The PDA@Au-HAp NPs produce hydroxyl radicals (OH) via catalysis of a small concentration of H₂O₂ to render bacteria more vulnerable to temperature change. After irradiation by 808 nm laser, the antibacterial efficacy against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) is 96.8% and 95.2%, respectively, at a low photo-induced temperature of 45 °C which causes no damage to normal tissues. In addition, this system stimulates the tissue repairing-related gene expression to facilitate the formation of granulation tissues and collagen synthesis and accelerate wound healing.

Guided protein/cell patterning on superhydrophilic polymer brushes functionalized with mussel-inspired polydopamine coatings

A simple approach for preparing bicomponent polymer patterns was developed by coating polydopamine (PDA) on superhydrophilic poly(2-acryl-amido-2-methylpropane sulfonic acid) (PAMPS) brushes. Well-defined and versatile arrays of proteins and cells were achieved without harm to proteins and cells.

Mussel-Inspired Biomaterials for Cell and Tissue Engineering

In designing biomaterial for regenerative medicine or tissue engineering, there are a variety of issues to consider including biocompatibility, biochemical reactivity, and cellular interaction etc. Mussel-inspired biomaterials have received much attention because of its appealing features including strong adhesiveness on moist surfaces, enhancement of cell adhesion, immobilization of bioactive molecules and its amenability to post-functionalization via catechol chemistry. In this review chapter, we give a brief introduction on the basic principles of mussel-inspired polydopamine coating, catechol conjugation, and discuss how their features play a vital role in biomedical application. Special emphasis is placed on tissue engineering and regenerative applications. We aspire to give readers of this book a comprehensive insight into mussel-inspired biomaterials that can facilitate them make significant contributions in this promising field.

Probing polydopamine adhesion to protein and polymer films: microscopic and spectroscopic evaluation

Polydopamine has been found to be a biocompatible polymer capable of supporting cell growth and attachment, and to have antibacterial and antifouling properties. Together with its ease of manufacture and application, it ought to make an ideal biomaterial and function well as a coating for implants. In this paper, atomic force microscope was used to measure the adhesive forces between polymer-, protein- or polydopamine-coated surfaces and a silicon nitride or polydopamine-functionalised probes. Surfaces were further characterised by contact angle goniometry, and solutions by circular dichroism. Polydopamine was further characterised with infrared spectroscopy and Raman spectroscopy. It was found that polydopamine functionalisation of the atomic force microscope probe significantly reduced adhesion to all tested surfaces. For example, adhesion to mica fell from 0.27 ± 0.7 to 0.05 ± 0.01 nN nm-1. The results suggest that polydopamine coatings are suitable to be used for a variety of biomedical applications.