Trimethylamine N-oxide-derived zwitterionic polymers: A new class of ultralow fouling bioinspired materials

Zwitterion nanocomposite hydrogels with bioactivity and anti-adhesion properties for rapid prevention of postoperative and recurrent adhesion

Postoperative adhesions (PAs) are a common complication after intraperitoneal surgery. Hydrogels are a physical barrier that prevents peritoneal adhesions, but their efficacy is still controversial. In this study, Laponites, a layered two-dimensional nanoscale, is incorporated into zwitterionic hydrogel (pSBLA) to enhanced biocompatibility and bioactivity to develop a nanocomposite for rapid prevention of postoperative and recurrent adhesion. The anisotropic distribution of charges in laponites results in strong hydrogen bonding and electrostatic repulsion in aqueous solutions and enables hydrogen bonding between amphiphilic ions, thereby enhancing the mechanical properties of hydrogels. The pSBLA hydrogels also possess a series of characters for an ideal anti-adhesion material, including resistance to adhesion against fibrinogen, proteins as well as cells. The mechanism underlying the extraordinary hydration of pSBLA is elucidated in this study using molecular dynamic simulations. In addition, pSBLA hydrogel is shown to represent a major advancement in anti-adhesion efficacy by completely and reliably preventing postoperative and recurrent adhesions after adhesiolysis in rat models. Furthermore, mechanistic explorations revealed that pSBLA hydrogel inhibits inflammatory responses and resists fibrosis by regulating the transforming growth factor-β/Smad signal pathway. Therefore, the pSBLA hydrogel has considerable potential for preventing post-operative adhesions in clinical settings.

Engineered Probiotics Enable Targeted Gut Delivery of Dual Gasotransmitters for Inflammatory Bowel Disease Therapy

Inflammatory bowel disease (IBD) remains an incurable condition, often accompanied by high rates of anxiety and depression, further diminishing the quality of life of patients. Endogenous gasotransmitters, such as carbon monoxide (CO) and hydrogen sulfide (H₂S), exhibit potent anti-inflammatory and immunomodulatory effects. However, their therapeutic application is limited by challenges in targeted delivery to affected tissues. Here, we propose a novel strategy for targeted gut delivery of CO/H2S through engineering Escherichia coli Nissle 1917 (EcN) with CO/H2S-releasing copolymer (POSR) loading. This engineered probiotic (POSR@EcN) enhances EcN colonization in the intestine and enables controlled, localized release of CO/H2S at inflamed sites. The release of CO/H2S modulates inflammation, restores intestinal barrier integrity, and reshapes gut microbiota by promoting beneficial bacteria and increasing short-chain fatty acids production, effectively alleviating IBD symptoms. Notably, targeted CO/H2S delivery also elevates neuroprotective metabolites like indoleacetic acid and γ-aminobutyric acid, reducing neuroinflammation via the gut-brain axis and mitigating anxiety- and depression-like behaviors in IBD mice. This approach highlights the potential of EcN as a probiotic carrier for the targeted delivery of gasotransmitters, offering a promising strategy for IBD treatment.

Protein-Nonfouling and Cell-Binding Polysulfobetaine Inducing Fast Transcytosis for Tumor-Active Drug Delivery

Long blood circulation and fast cellular uptake are essential yet paradoxical requirements for efficient tumor-targeted drug delivery carriers. For instance, polyzwitterions, generally nonfouling to proteins and cells, have been extensively explored as long-circulating drug delivery carriers but suffer ultraslow cell internalization, making them inefficient in delivering drugs to cells. Protein-resistant yet cell membrane-binding polymers will simultaneously achieve long blood circulation and fast cellular internalization, but their designs are generally complicated, such as introducing cell-membrane binding groups. Here, it is shown that the N-alkyl chain length of zwitterionic poly(sulfobetaine) can be used to tune its affinity toward proteins and cell membranes. A poly(sulfobetaine) with a moderately long N-alkyl chain became cell membrane-philic while retaining protein resistance, leading to long blood circulation and fast cellular uptake, which further triggered efficient tumor cell transcytosis and intratumor penetration. Thus, its paclitaxel (PTX)-loaded micelles demonstrated potent antitumor efficacy in triple-negative breast cancer models. This study showcases a paradigm of designing polyzwitterions harmonizing long blood circulation and fast cellular uptake properties as tumor-active drug delivery carriers.

Polymer conjugation benefits proteins beyond simply extended half-life

Polymer conjugation is well known to extend the half-life of proteins in the bloodstream. The resulting protein-polymer conjugates have gained tremendous success due to this benefit, most prominently with the numerous PEGylated protein therapeutics that have been approved by the Food and Drug Administration (FDA). Prolonged half-life of protein therapeutics is usually accompanied by improved therapeutic outcome and patient compliance. However, simply extending the half-life of proteins is no longer sufficient to address the different therapeutic requirements of different diseases. Modern medicine has placed higher functional demands for protein therapeutics, such as biological barrier permeability, lower off-target effects, and higher biosafety. Indeed, the benefits of polymer conjugation for proteins have been greatly expanded beyond just extending the half-life, such as improving therapeutic index, facilitating intracellular delivery, remodeling biodistribution, penetrating the blood-brain barrier, and promoting oral absorption. Therefore, this short review will aim to systematically reveal the benefits of polymer conjugation for proteins at molecular, nanoscale, cellular, tissue, organ, and organ system level. The challenge and new direction for the development and clinical translation of protein-polymer conjugates are also covered. STATEMENT OF SIGNIFICANCE: Since the concept was pioneered by Frank Davis in the late 1960s, protein-polymer conjugates have gained tremendous success. Therapeutics based on protein-polymer conjugates have longer half-lives in the bloodstream compared to their native forms, which reduces dosing frequency and greatly enhances patient compliance. Indeed, beyond improved pharmacokinetic, protein-polymer conjugates have demonstrated multifaceted biological benefits, such as facilitating intracellular delivery, penetrating tissue barriers, remodeling biodistribution, and promoting oral absorption. This review aims to systematically reveal the benefits of polymer conjugation for proteins at the molecular, nanoscale, cellular, tissue, organ, and organ system level. Such comprehensive understanding will not only broaden the impact of protein-polymer conjugates, but also enable researchers to advance their development in the desired direction.

More than a delivery system: the evolving role of lipid-based nanoparticles

Lipid-based nanoparticles, including liposomes and lipid nanoparticles (LNPs), make up an important class of drug delivery systems. Their modularity enables encapsulation of a wide range of therapeutic cargoes, their ease of functionalization allows for incorporation of targeting motifs and anti-fouling coatings, and their scalability facilitates rapid translation to the clinic. While the discovery and early understanding of lipid-based nanoparticles is heavily rooted in biology, formulation development has largely focused on materials properties, such as how liposome and lipid nanoparticle composition can be altered to maximize drug loading, stability and circulation. To achieve targeted delivery and enable improved accumulation of therapeutics at target tissues or disease sites, emphasis is typically placed on the use of external modifications, such as peptide, protein, and polymer motifs. However, these approaches can increase the complexity of the nanocarrier and complicate scale up. In this review, we focus on how our understanding of lipid structure and function in biological contexts can be used to design intrinsically functional and targeted nanocarriers. We highlight formulation-based strategies, such as the incorporation of bioactive lipids, that have been used to modulate liposome and lipid nanoparticle properties and improve their functionality while retaining simple nanocarrier designs. We also highlight classes of naturally occurring lipids, their functions, and how they have been incorporated into lipid-based nanoparticles. We will additionally position these approaches into the historical context of both liposome and LNP development.

Nanourchin-like Uricase-Poly(L-proline) Conjugate with Retained Enzymatic Activity, Mitigated Immunogenicity, and Sustained Efficacy Upon Repeated Administrations

The poor half-life and strong immunogenicity of proteins such as uricase (UOx), a therapeutic enzyme for chronic refractory gout and hyperuricemia, are pressing clinical challenges. Although conjugation of poly(ethylene glycol) (PEGylation) of UOx can improve the pharmacokinetics, preexisting or induced anti-PEG antibodies, which lead to accelerate blood clearance (ABC) and reduced response rate, have been a major clinical hurdle. Herein, we report the facile "grafting-from" preparation of a nanourchin-like uricase-poly(L-proline) conjugate, namely UOx-PLP, with high grafting-density, enhanced thermal, lyophilization, freeze-thaw, and proteolytic stability. Through a transient preblocking strategy in the synthesis, the UOx-PLP overcomes activity loss and retains ~82 % enzyme activity. In Sprague-Dawley rats, UOx-PLP stimulates minimum complement activation and anti-UOx antibodies. Unlike PEG-UOx gave a significantly reduced half-life after repetitive administrations, UOx-PLP shows no sign of ABC effect. Moreover, the half-life of UOx-PLP remain almost unchanged when cross-administrated to rats previously received PEG-UOx and with high titers of anti-UOx antibodies. Finally, UOx-PLP shows minimum loss of efficacy after five straight administrations in a UOx knock-out hyperuricemia mice model, whereas PEG-UOx experiences sharp loss of efficacy upon the same treatment. Overall, the simple preparation and outstanding nonclinical results highlight the enormous potential of UOx-PLP for future clinical translation.

Biomimicry-inspired zwitterionic polyurethane used for vascular implants showing water-induced stiffening and preventing intimal hyperplasia in stent

Polymeric vascular implants with ideal mechanical properties and biocompatibility are essential for dilating blood vessels and reducing the risk of secondary implant diseases. However, traditional polymer materials are still limited for vascular stents by diminished radial support post-expansion and inadequate surface modification techniques. Herein, we synthesized zwitterionic polyurethanes (ZPUs) featuring hydrophilic side chains derived from betaine sulfonate and full-hard main chains. These ZPUs demonstrate a remarkable increase in modulus during shape recovery in 37 °C warm water, ensuring that the stent remains soft during implantation for easy delivery, but becomes stiff once positioned at the lesion site to provide adequate radial support. The distinctive architecture promotes the migration of hydrophilic side chains to the surface upon hydration, establishing a "core-shell structure" with a hard interior and a highly hydrophilic surface that enhances antithrombotic properties, mitigates inflammation, and curbs intimal hyperplasia. Consequently, ZPUE20 stent showed significantly better blood flow patency than traditional PLA stent in carotid artery implantation for at least 3 months, ensuring the long-term biological safety of implantation. Compared to surface modification of bare stents, ZPU stents avoid the complex and unstable surface modifications. All in all, ZPUs represent a promising material for vascular implants, markedly improving both mechanical performance and biocompatibility.

Interaction of Grafted Polymeric N-oxides with Charged Dyes

Grafted polymeric N-oxides have recently attracted interest for antifouling applications, drug delivery, wastewater purification, and electronic devices. Their function depends on the efficiency of the grafting process and the following postgrafting oxidation step. These two parameters govern the solvent-accessible charge density on the surface, an important parameter, which is notoriously hard to determine. In this study, a novel colorimetric quantitative assay for polymeric N-oxides was developed. It allows the determination of the surface charge density of grafted polymeric N-oxides. The method is based on the adsorption of acid fuchsin (AF) to grafted N-oxides through reversible electrostatic interactions between the positively charged nitrogen atoms of the N-oxide functionality and the sulfonate groups of the dye. The process depends thus on the pH-switchable properties of polymeric N-oxides. Adsorption was achieved at a pH value of 3, where N-oxides are almost fully protonated (typical pKa 4-5). AF was desorbed from the surface at pH 7 and quantified via visible adsorption spectroscopy (UV-vis) at 556 nm to determine the amount of surface-grafted functional groups. Charge densities of diverse N-oxides grafted by free radical polymerization from polyethylene (PE) were determined to be in the range 1-3 × 1015 N+-O-/cm2. Notably, N-oxides can form covalent bonds with electron-deficient triarylmethane dyes like AF. This nucleophilic reactivity of N-oxides does not compromise the proposed assay, but it may be of relevance for dye adsorption and desorption in wastewater purification.

Trimethylamine N-oxide-derived zwitterion coating for polyurethane ureteral stents prevents encrustation formation

A ureteral stent with strong resistance to proteins, bacteria, and multivalent ions is crucial for the safe treatment of urologic diseases. Generally, the proteins, bacteria, and multivalent ions present in urine tend to bind to the stent surface, leading to aggregation, nucleation, and subsequent stent encrustation. Stent encrustation can induce or exacerbate urinary tract infections and obstructions, thereby seriously harming kidney function. Although hydrophilic coatings on ureteral stents can reduce the binding of proteins, bacteria, and multivalent ions, encrustation still occurs. To date, preventing stent encrustation formation remains a significant challenge. Here, we grafted dense trimethylamine oxide (TMAO)-derived zwitterionic polymers onto the stent surface via a branched amplification strategy. These zwitterions can strongly bind water molecules, forming a stable hydration layer that repels proteins, bacteria, and multivalent ions from adhering to the surface of the polyurethane ureteral stent, thus rendering the stent anti-encrustation. The results showed that the TMAO-derived zwitterion-coated stents exhibited a significantly reduced encrustation weight (13.8% of the original polyurethane stent) and demonstrated good safety. This approach offers a promising method for enhancing stent encrustation resistance. STATEMENT OF SIGNIFICANCE: This study successfully developed a TMAO-derived zwitterionic coating on the surface of a polyurethane stent, creating a superhydrophilic surface with a minimal contact angle of 5.2o. This surface effectively shields the stent from interactions with proteins, bacteria, and multivalent ions in urine, demonstrating favorable anti-protein adsorption and antibacterial adhesion properties. The superhydrophilic surface formed by the TMAO-derived zwitterionic coating on the stents (PTMAO-s) provides strong anti-fouling resistance and enhanced anti-encrustation properties. Under identical conditions, the encrustation resistance of PTMAO-s is approximately 7.2-fold greater than that of original polyurethane stents (PU), 3.6-fold greater than Bard commercial stents, and 2.1-fold greater than betaine-coated stents (PSBG-s).

Smart Antibacterial Fabric Response to Sweat: Constructing Reversibly Switchable Surface by Zwitterionic Block Copolymers

Although various antibacterial fabrics have been extensively developed, smart antibacterial fabrics that can achieve stimulus responses have not been developed under high humidity conditions. In this study, a smart sweat-responsive antibacterial fabric has been designed by grafting zwitterionic PTMSPMA-co-PTMAO copolymer on cotton fabric (CF) to achieve "active attack" and "passive defense" against bacteria. It exhibits desirable antibacterial properties in both H2O and dry environments with the killing rates against Escherichia coli and Staphylococcus aureus reaching over 99.97%. Additionally, the fabric exhibits significant antiadhesion effects in sweat environments, with an antiadhesion rate above 99.95%. Various characterizations of PTMSPMA-co-PTMAO-CF reveal its smart responses in killing and antiadhesion of bacteria in high-humidity environments. In H2O, the oxygen-containing anions in PTMSPMA-co-PTMAO-CF interact with H2O via the hydrogen bond, exposing more -(CH3)2-N+ to kill the bacteria and enhance the "active attack." In sweat, ions (such as Na+ and Cl-) will be electrically neutralized with the quaternary ammonium cations (-(CH3)2-N+) and oxygen-containing anions in PTMSPMA-co-PTMAO-CF, thereby significantly enhancing the antiadhesion and exhibiting "passive defense" in high-humidity environments. PTMSPMA-co-PTMAO-CF can also achieve reversible conversion of killing and antiadhesion, according to variations in the external environments. This study provides new insight on smart antibacterial fabrics in the fields of health monitoring, sports equipment, and medical protection.

An orally administered gene editing nanoparticle boosts chemo-immunotherapy in colorectal cancer

Chemoresistance and immunosuppression are common obstacles to the efficacy of chemo-immunotherapy in colorectal cancer (CRC) and are regulated by mitochondrial chaperone proteins. Here we show that the disruption of the tumour necrosis factor receptor-associated protein 1 (TRAP1) gene, which encodes a mitochondrial chaperone in tumour cells, causes the translocation of cyclophilin D in tumour cells. This process results in the continuous opening of the mitochondrial permeability transition pore, which enhances chemotherapy-induced cell necrosis and promotes immune responses. On the basis of this discovery we developed an oral CRISPR-Cas9 delivery system based on zwitterionic and polysaccharide polymer-coated nanocomplexes that disrupts the TRAP1 gene in CRC. This system penetrates the intestinal mucus layer and undergoes epithelial transcytosis, accumulating in CRC tissues. It enhances chemotherapeutic efficacy by overcoming chemoresistance and activating the tumour immune microenvironment in orthotopic, chemoresistant and spontaneous CRC models, with remarkable synergistic antitumour effects. This oral CRISPR-Cas9 delivery system represents a promising therapeutic strategy for the clinical management of CRC.

Synthesis of a Novel DMSP-Typed Zwitterion and Construction on PET Surface via Surface-Initiated RAFT Method

Mimicked by the structure of dimethyl sulfoxide propionate (DMSP), a novel zwitterion monomer of N-methylacryloyl S-methyl l-cysteine methyl sulfonium salt (NMASMCMS) was synthesized and characterized for the first time through three steps using l-cysteine as a starting material. Poly(NMASMCMS) brushes were constructed on PET sheets via surface-initiated reversible addition-fragmentation chain-transfer (SI-RAFT) polymerization. The physical and chemical structures were characterized by water contact angle (WCA), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The polymer brush grafted sheets (PET-B) had good hydrophilicity and high lubricity. Moreover, PET-B sheets exhibited excellent antifouling and hemocompatible properties with low protein adsorption, bacterial adhesion, platelet adhesion, and hemolysis.

The strategy used by naïve anti-PEG antibodies to capture flexible and featureless PEG chains

Polyethylene glycol (PEG) is widely used as a standard stealth polymer, although the induction of anti-PEG antibodies and consequent effects have drawn attention in recent years. To date, several anti-PEG antibodies induced by PEG-modified proteins via the T cell-dependent (TD) pathway, in which affinity maturation occurs, have been reported. In contrast, structures of the naïve anti-PEG antibodies before affinity maturation have not been described in the literature. Here, to understand the details of the naïve anti-PEG antibodies capturing PEG, we studied a naïve anti-PEG antibody induced by a PEG-modified liposome in the absence of affinity maturation via the T cell-independent (TI) pathway. The mutation levels, structures as well as in vitro and in silico binding properties of TI and TD anti-PEG antibodies were compared. The TI anti-PEG antibody showed no mutation and a low binding affinity toward PEG, meanwhile, it allowed PEG chain sliding and weak interaction with the terminal group. Furthermore, the naïve anti-PEG antibodies may obtain high affinities by forming tunnel structures via minimal mutations. This research provides new insights into polymer-antibody interactions, which can facilitate the development of novel stealth polymers that can avoid antibody induction.

Water-Soluble Sulfur-Ylide-Functionalized Polyacrylamides for Antibacterial Surface Applications

Surface fouling induced by biomolecules and microorganisms remains a persistent challenge in materials science, particularly in healthcare applications, where biofilm formation on medical devices may lead to infections and antimicrobial resistance. Antifouling strategies typically rely on the formation of either hydration layers or cytotoxic materials for direct antimicrobial effects. Recent advances in zwitterionic polymers derived from ylides offer a promising yet unexplored toolbox for the construction of antifouling and antimicrobial coatings. While N-oxide-based ylides have been extensively studied as building blocks for antifouling materials, sulfur-ylide-based materials, and the precise underlying mechanisms remain underexplored despite their broader chemical versatility. Here, we present a fully water-soluble acrylamide-based poly(sulfur ylide) and compare its properties to those of previously reported hydrophobic polystyrene-derived analogues. Notably, water-soluble poly(sulfur ylides) retain antimicrobial efficacy on surfaces but lose cytotoxicity in solution, unlike its hydrophobic counterpart. Computational studies reveal that the dipole moment of sulfur ylides is environmentally responsive, stabilizing in hydrophobic environments. Genetic analysis confirms outer membrane destabilization for both polymers but suggests that the hydrophobicity of the polystyrene backbone promotes stronger interactions. We suggest that future work should focus on elucidating additional interactions, including supramolecular behaviors of amphiphilic sulfur ylides, to refine their structure-property relationships and optimize their antifouling and antimicrobial properties.

Tuning Surface Functions by Hydrophilic/Hydrophobic Polymer Brushes

Polymer brushes, an optimal method for surface modification, have garnered significant interest due to their potential in surface wettability and functions regulation. This review summarizes the recent advancements in functional polymer brush surfaces based on surface wettability regulation. First, the fundamental structure and fabrication methods of polymer brushes, emphasizing the two primary strategies, "grafting-to" and "grafting-from", were introduced, and special attention was accorded to the method of subsurface-initiated atom transfer radical polymerization (SSI-ATRP) for the construction of mechanically robust polymer brushes. Subsequently, we delved into the attributes of the stimuli-responsive polymer brush surface, which can effectuate reversible surface wettability transitions in response to external stimuli. Then, this review also offered an in-depth exploration of the potential applications of polymer brushes based on their surface wettability, including lubrication, drag reduction, antifouling, antifogging, anti-icing, oil-water separation, actuation, and emulsion stability. Lastly, the challenges of polymer brush surfaces encountered in practical applications, including mechanical strength, biocompatibility, recyclability, and preparation efficiency, were addressed, and significant achievements in current research were summarized and insights into future directions were offered. This review intends to provide researchers with a comprehensive understanding of the potential applications of polymer brushes based on surface wettability regulation, and with the development of the polymer brush preparation technology, it will be anticipated that they will assume increasingly pivotal roles in various fields.

Nature-inspired surface modification strategies for implantable devices

Medical and implantable devices are essential instruments in contemporary healthcare, improving patient quality of life and meeting diverse clinical requirements. However, ongoing problems such as bacterial colonization, biofilm development, foreign body responses, and insufficient device-tissue adhesion hinder the long-term effectiveness and stability of these devices. Traditional methods to alleviate these issues frequently prove inadequate, necessitating the investigation of nature-inspired alternatives. Biomimetic surfaces, inspired by the chemical and physical principles found in biological systems, present potential opportunities to address these challenges. Recent breakthroughs in manufacturing techniques, including lithography, vapor deposition, self-assembly, and three-dimensional printing, now permit precise control of surface properties at the micro- and nanoscale. Biomimetic coatings can diminish inflammation, prevent bacterial adherence, and enhance stable tissue integration by replicating the antifouling, antibacterial, and adhesive properties observed in creatures such as geckos, mussels, and biological membranes. This review emphasizes the cutting-edge advancements in biomimetic surfaces for medical and implantable devices, outlining their design methodologies, functional results, and prospective clinical applications. Biomimetic coatings, by integrating biological inspiration with advanced surface engineering, have the potential to revolutionize implantable medical devices, providing safer, more lasting, and more effective interfaces for prolonged patient benefit.

Albumin Corona-Coated Nanoscale Metal-Organic Framework for Enzyme-Mediated Cascade Metabolization of Uric Acid in Hyperuricemia

Hyperuricemia, characterized by elevated uric acid levels, is the primary cause of gout. Recombinant uricase is one of the last-resort therapies but generates unwanted pro-inflammatory H2O2 and anti-uricase antibodies. In this work, we developed an albumin corona-coated enzyme-loaded zeolitic imidazolate framework (UCZIF) to sustainably maintain low blood uric acid level without producing H2O2. The corona coating not only preserves loaded enzymes but also reduces macrophage phagocytosis by 73.4% compared to free uricase. In addition, the uptake level of UCZIF by dendritic cells is reduced by 74.1%, and the maturation of dendritic cells is inhibited by 35.4% compared to free uricase. Animal experiments demonstrate that albumin corona-coated UCZIF effectively lowers blood uric acid level in both acute and diet-induced chronic hyperuricemia models with significantly increasing the half-life of uricase. Furthermore, compared to the generation of anti-uricase antibodies during standalone uricase treatment, the levels of anti-uricase immunoglobulins are significantly reduced by 65.5% (immunoglobulin M) and 76.3% (immunoglobulin G) with repeated administration of albumin corona-coated UCZIF. Overall, this albumin corona-coated nanoscale metal-organic framework offers a promising approach to minimize the immunogenicity induced by exogenous enzymes and further safely reduce uric acid levels in the treatment of hyperuricemia.

Multiscale Modeling and Simulation of Zwitterionic Anti-fouling Materials

Zwitterionic materials with cationic and anionic moieties in the same chain, being electrically neutral, have excellent hydrophilicity, stability, biocompatibility, and outstanding anti-biofouling performance. Because of their unique properties, zwitterionic materials are widely applied to membrane separation, drug delivery, surface coating, etc. However, what is the root of their unique properties? It is necessary to study the structure-property relationships of zwitterionic compounds to guide the design and development of zwitterionic materials. Modeling and simulation methods are considered to be efficient technologies for understanding advanced materials in principle. This Review systematically summarizes the computational exploration of zwitterionic materials in recent years. First, the classes of zwitterionic materials are summarized. Second, the different scale simulation methods are introduced briefly. To reveal the structure-property relationships of zwitterionic materials, multiscale modeling and simulation studies at different spatial and temporal scales are summarized. The study results indicated that the strong electrostatic interaction between zwitterions with water molecules promotes formation of a stable hydration layer, namely, superhydrophilicity, leading to the excellent anti-fouling properties. Finally, we offer our viewpoint on the development and application of simulation techniques on zwitterionic materials exploration in the future. This work establishes a bridge from atomic and molecular scales to mesoscopic and macroscopic scales and helps to provide an in-depth understanding of the structure-property relationships of zwitterionic materials.

Antibiofouling Coatings For Marine Sensors: Progress and Perspectives on Materials, Methods, Impacts, and Field Trial Studies

The attachment of marine organisms, for example, bacteria, proteins, inorganic molecules, and more on a sea-submerged surface is a global concern for marine industries as it controls the surface for further marine growth. Applications requiring the estimation of real-time information from oceanographic sensors conveyed for long-term deployment are vulnerable to biofouling. Therefore, an effective approach to controlling the biofouling that accumulates on marine sensors is paramount. To date, many technologies have been explored to impede biofouling; however, several factors constrain many strategies, including their reliance on environmentally toxic materials, high fabrication costs, poor coatings, and nontransparency. These challenges have motivated work to develop numerous advanced and innovative strategies based on mechanical methods, irradiation, and design of polymeric/nonpolymeric coatings with fouling resistance, fouling release, and fouling degrading coatings to protect marine sensors and housing materials from biofouling. This Review presents recent progress in the developed biofouling control strategies that have been applied to commercially available sensors and sensor housing materials. Moreover, recent findings in the literature are highlighted while considering the wettability principles for air and water environments, antifouling performance, practical feasibility, environmental and economic impact of coatings, and field trial studies. Here, we emphasize how these features can play major roles synergistically to affect antifouling coatings against nano- to microlevel organisms. This review will not only allow researchers to understand the design principles but also contribute to the development of new cost-effective strategies.

N-Oxide Zwitterionic-Based Antifouling Loose Nanofiltration Membranes with Superior Water Permeance and Effective Dye/Salt Separation

Loose nanofiltration (LNF) membranes with high permeance and separation selectivity are highly desired for the effective separation of organic dyes and inorganic salts. Herein, a novel polyamide LNF membrane was fabricated using zwitterionic amine reactant trimethylamine N-oxide-based polyethylenimine (TPEI) and trimesoyl chloride (TMC) via interfacial polymerization (IP). A thin, loose, and smooth polyamide layer was formed due to the low diffusion rate and modified chemical structure of TPEI. The optimized membrane (NF-TPEI) exhibited an extremely high water permeance of 213.0 L m-2 h-1 bar-1, accompanied by outstanding dye rejections of Congo Red (99.8%), Coomassie Brilliant Blue R250 (99.5%), and Evans Blue (99.9%). Meanwhile, the membrane possessed low rejections (<7.0%) of inorganic salts (Na2SO4, MgSO4, MgCl2, and NaCl). Additionally, the NF-TPEI membrane exhibited outstanding antifouling performance, achieving a superior recovery ratio of 96.0 and 98.1% after the filtration of humic acid and sodium alginate solution, respectively. Compared to the commercial NF270 membrane, the NF-TPEI membrane exhibited significantly improved separation performance in terms of permeance and fouling resistance, which provided more possibilities for high-performance LNF membranes toward the treatment of wastewater with organic contaminants.

Antifouling Polymer Coatings for Bioactive Surfaces

Bioactive surfaces play a pivotal role in biomedical applications by enabling precise biological interactions through immobilized functional molecules. However, their performance is often hindered by nonspecific protein adsorption and cell adhesion. Antifouling polymer coatings have emerged as an effective solution, creating hydration barriers to preserve functionality and reduce biofouling. This review provides an overview of the recent advances in the development of antifouling polymer coatings for bioactive surfaces, with particular focus on nonionic polymers, such as polyethylene glycol (PEG), and zwitterionic polymers like poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC). Among them, zwitterionic polymers, with their unique charge-balanced structures, exhibit exceptional hydration, protein resistance, and stability, making them particularly promising for biomedical applications. In addition, key applications of these bioactive surfaces, including their use in anticoagulant materials, antibacterial coatings, and biosensor interfaces, are also discussed. The discussion concludes with an address of the field's challenges and future directions, highlighting the need for innovative materials that balance antifouling properties, biocompatibility, and long-term stability for both clinical and industrial use. This review aims to review the latest advancements in antifouling polymer coatings for bioactive surfaces and provide insights into optimizing multifunctional bioactive surfaces to meet the evolving and dynamic demands of the biomedical field.

Progress in Polysaccharide-Based Hydrogels for Preventing Postoperative Adhesions: A Review

Postoperative adhesions are common complications following surgery, often accompanied by pain and inflammation that significantly diminish patients' quality of life. Moreover, managing postoperative adhesions incurs substantial cost, imposing a considerable financial burden on both patients and healthcare systems. Traditional anti-adhesion materials are confronted with limitations, such as inadequate tissue adherence in a moist environment and poor degradability, underscoring the urgent need for more effective solutions. Recently, polysaccharide-based hydrogels have received considerable attention for their potential in preventing postoperative adhesions. The hydrogels not only facilitate wound healing but also effectively reduce inflammation, providing a promising approach to preventing postoperative adhesions. This review provides an extensive analysis of the progress made in the development of polysaccharide-based hydrogels for postoperative anti-adhesion therapy. It highlights their principal benefits, outlines future research trajectories, and addresses the ongoing challenges that need to be overcome.

Bioinspired Materials for Controlling Mineral Adhesion: From Innovation Design to Diverse Applications

The advancement of controllable mineral adhesion materials has significantly impacted various sectors, including industrial production, energy utilization, biomedicine, construction engineering, food safety, and environmental management. Natural biological materials exhibit distinctive and controllable adhesion properties that inspire the design of artificial systems for controlling mineral adhesion. In recent decades, researchers have sought to create bioinspired materials that effectively regulate mineral adhesion, significantly accelerating the development of functional materials across various emerging fields. Herein, we review recent advances in bioinspired materials for controlling mineral adhesion, including bioinspired mineralized materials and bioinspired antiscaling materials. First, a systematic overview of biological materials that exhibit controllable mineral adhesion in nature is provided. Then, the mechanism of mineral adhesion and the latest adhesion characterization between minerals and material surfaces are introduced. Later, the latest advances in bioinspired materials designed for controlling mineral adhesion are presented, ranging from the molecular level to micro/nanostructures, including bioinspired mineralized materials and bioinspired antiscaling materials. Additionally, recent applications of these bioinspired materials in emerging fields are discussed, such as industrial production, energy utilization, biomedicine, construction engineering, and environmental management, highlighting their roles in promoting or inhibiting aspects. Finally, we summarize the ongoing challenges and offer a perspective on the future of this charming field.

Multifunctional Zwitterionic N-Oxide Polymers to Overcome Cascade Physiological Barriers for Efficient Anticancer Drug Delivery

For efficient anticancer drug delivery, cascade physiological barriers must be overcome, which requires the drug delivery vehicles to possess different or even opposite properties at different stages. Poly(tertiary amine-oxide) (PTAO) polymers with the zwitterionic feature have distinct antifouling properties in blood circulation, which can be reduced and protonated in hypoxic tumors to promote cellular internalization. Nevertheless, the effects of various PTAO structures have not been studied systemically and optimized. In this report, the side groups of PTAO are proposed to be optimized by modulating the structures. Poly(2-(N-oxide-hexamethyleneimino)ethyl methacrylate) (POC7A) with a cyclic seven-membered ring is screened as the optimized PTAO structure for in vivo applications. Moreover, the block copolymer POC7A-block-poly(ε-caprolactone) (POC7A-PCL) is prepared for the formation of micelles in aqueous solution for delivery of doxorubicin (DOX). The zwitterionic nature of POC7A shells with efficient bioreductive activity and protonation in the tumor microenvironment endows the micelles with excellent antifouling properties for long blood circulation, efficient tumor accumulation, deep penetration, and effective cellular internalization. Thus, the DOX-loaded micelles exhibit potent antitumor efficacy after intravenous administration. Zwitterionic POC7A can be used as antifouling shells of the anticancer drug delivery nanocarriers to overcome the cascade physiological barriers efficiently.

Harnessing Oxidized Amines as Robust Sorbents for Carbon Capture

Carbon capture and sequestration (CCS) is imperative to mitigating global climate change, but current implementation falls far short of that needed to reach net-zero global emissions by 2050. Aqueous amine solutions, conceived over a century ago, are the current leading technology for CO2 separations. However, amines suffer from chemical instability under scrubbing conditions, corrosiveness, and toxicity, hindering their long-term implementation at multiton scales. Herein, we demonstrate for the first time that tertiary amine N-oxides, an oxidative degradation product of amines, can remove CO2 from dilute streams, including flue gas from a natural gas-fired power plant. Our extensive spectroscopic and computational studies support that the nontoxic, noncorrosive, and inexpensive 4-methylmorpholine N-oxide (MMNO) captures CO2 under humid conditions via the formation of a hydrogen-bond-stabilized bicarbonate (HCO3-) species, despite being significantly less basic than an amine. Accelerated aging studies show that MMNO exhibits superior oxidative and thermal stability compared to structurally similar amines, highlighting the potential of eco-friendly N-oxides in industrial carbon capture applications.

Responsive Zwitterionic Materials for Enhanced Drug Delivery

Zwitterionic materials have traditionally been recognized as exceptional antifouling agents, imparting nanocarriers with extended circulation times in vivo. Despite much studies on antifouling ability, the responsive zwitterionic materials that change physicochemical properties stimulated by mild signals are much less explored. As is known, there are multiple biological barriers in antitumor drug delivery, including the blood circulation barrier, non-specific organ distribution, elevated tumor interstitial pressure, tumor cytomembrane barrier, and lysosomal barrier. Multiple biological barriers restrict the delivery efficiency of nanocarriers to tumors, leading to a reduced therapeutic effect and increased side effects. Therefore, it is far from satisfactory to overcome the blood circulation barrier alone for classical zwitterionic antitumor materials. To address this challenge, recently developed responsive zwitterionic materials have been engineered to overcome multiple biological barriers, thereby enabling more effective antitumor drug delivery. Furthermore, responsive zwitterionic materials could respond to signals by themselves without the need of incorporating extra stimuli-responsive groups, which maintains the simplicity of the molecular structure. In this mini-review, the recent progress of antitumor zwitterionic materials responding to pH, temperature, enzyme, or reactive oxygen species is summarized. Furthermore, prospects and challenges of responsive zwitterionic materials are provided to promote better development of this field.

Zwitterionic Hydrogels: From Synthetic Design to Biomedical Applications

Zwitterionic hydrogels have emerged as a highly promising class of biomaterials, attracting considerable attention due to their unique properties and diverse biomedical applications. Zwitterionic moieties, with their balanced positive and negative charges, endow hydrogels with exceptional hydration, resistance to nonspecific protein adsorption, and low immunogenicity due to their distinctive molecular structure. These properties facilitate various biomedical applications, such as medical device coatings, tissue engineering, drug delivery, and biosensing. This review explores the structure-property relationships in zwitterionic hydrogels, highlighting recent advances in their design principles, synthesis methods, structural characteristics, and biomedical applications. To meet the evolving and growing demand for the biomedical field, this review examines current challenges and explores future research directions for optimizing the multifunctional properties of zwitterionic hydrogels. As promising candidates for advanced biomaterials, zwitterionic hydrogels are poised to address critical challenges in biomedical applications, paving the way for improved therapeutic outcomes and broader applicability in healthcare.

Self-Adaptive Zwitterionic Polysilazane Coatings with Mechanical Robustness, High Transparency, and Broad-Spectrum Antiadhesion Properties

Antiadhesive coatings have been extensively studied owing to their wide applications in biology, environment, and energy. However, developing a mechanically robust coating with broad-spectrum antiadhesion properties remains challenging. Herein, a novel strategy for preparing hard yet flexible and self-adaptive zwitterionic polysilazane coatings with broad-spectrum antiadhesion properties (anti-biofouling, anti-liquid adhesion, and anti-scaling) is proposed. The coatings are prepared by combining polysilazane with a telomer (FT) consisting of a low-surface-energy fluorine motif and hydrolysis-induced zwitterions. Before Si─OH generation in polysilazane, the fluorine motif drives the zwitterionic precursor to enrich on the surface, generating a zwitterionic layer following pre-hydrolysis. This unique design prevents the coatings from swelling in water, allowing them to adapt to diverse environments. The fluorine motif can orient toward the surface of air, providing anti-liquid adhesion capabilities, whereas the zwitterions orient underwater to endow anti-biofouling, anti-liquid adhesion, and anti-scaling capabilities. The highly cross-linked network toughened by FT contributes to the high hardness (up to 7H) and good flexibility of the coating. The chemical bonding between the coating and substrates ensures their strong adhesion (≈2.06-7.67 MPa). This study contributes to the design of mechanically robust broad-spectrum antiadhesive coatings applicable in marine industries, optical devices, pipeline transportation, and other fields.

Polyzwitterions: controlled synthesis, soft materials and applications

Polyzwitterions refer to polymers containing both positive and negative charged groups in one side chain, which have shown unique physicochemical properties and significant potential in diverse applications due to their amphiphilic and net-neutral charged properties. This review aims to highlight the recent advances in the design and synthesis of polyzwitterions including direct polymerization of zwitterionic monomers and deionization of polymers. Furthermore, the formation of polyzwitterion based soft materials such as nanoparticles by self-assembly, hydrogels, coatings and polyzwitterion brushes, as well as the influence of the microstructure on their properties and applications are discussed. The potential applications of polyzwitterions in drug delivery, antifouling, lubrication, energy storage and antibacterial are also summarized. Finally, the prospects of polyzwitterions are proposed.

Specific isolation and quantification of PD-L1 positive tumor derived exosomes for accurate breast cancer discrimination via aptamer-functionalized magnetic composites and SERS immunoassay

PD-L1 positive tumor derived exosomes (TEXsPD-L1) play a significant role in disease progression, tumor metastasis and cancer immunotherapy. However, the overlap of PD-L1 between TEXs and non-tumor derived exosomes (non-TEXs) restricts the specific isolation and quantification of TEXPD-L1 from clinical samples. Herein, a new aptamer-functionalized and hydrophilic immunomagnetic substrate was designed by decorating generation 5 polyamidoamine dendrimers (G5 PAMAM), zwitterionic trimethylamine N-oxide (TMAO) and EpCAM (Epithelial cell adhesion molecule) aptamers on magnetic cores sequentially (Fe3O4@PAMAM@TMAO@Aptamer, named as FPTA) for rapid target and efficient capture of TEXs. The FPTA substrate gathered excellent characters of strong magnetic responsiveness of Fe3O4, abundant affinity sites of PAMAM, strong hydrophilicity of TMAO and enhanced affinity properties of EpCAM aptamers. Because of these advantages, FPTA can isolate TEXs quickly within 30min with high capture efficiency of 90.5 % ± 3.0 % and low nonspecific absorption of 8.2 % ± 2.0 % for non-TEXs. Furthermore, PD-L1 (Programmed cell death-ligand 1) positive TEXs (TEXsPD-L1) from the captured TEXs were recognized and quantitatively analyzed by utilizing SERS (surface-enhanced Raman spectroscopy) reporter molecules 4-NTP (4-Nitrothiophenol) on PD-L1 aptamers-functionalized gold immunoaffinity probe. The signal of TEXsPD-L1 was converted to SERS signal of 4-NTP at 1344 cm-1 which exhibited a linear correlation to concentration of TEXsPD-L1(R2 = 0.9905). With these merits, this strategy was further applied to clinical plasma samples from breast cancer (BC) patients and healthy controls (HC), exhibited an excellent diagnosis accuracy with area under curve (AUC) of receiver operating characteristic (ROC) curve reaching 0.988. All these results demonstrate that the FPTA immunomagnetic substrate combined with SERS immunoaffinity probe may become a generic tool for specific isolation and quantitative analysis of PD-L1 positive tumor-derived exosomes in clinics.

Experimental and computational techniques to investigate the protein resistance of zwitterionic polymers

Most surfaces undergo non-specific protein adsorption upon direct contact with protein-containing environments, resulting in the formation of a protein corona, and the nature and composition of the corona affect the properties of the material. Zwitterionic polymers have oppositely charged groups in their repeating units, which facilitate the formation of a hydration layer on the surface through electrostatic interactions. The hydration layer possesses a strong water-binding ability and can prevent protein adsorption. Therefore, the hydration effect of zwitterionic polymers has become a research focus, and many researchers have investigated this mechanism using experimental and computational methods. This paper reviews the experimental techniques and simulation methods to study the hydration effect of zwitterionic polymers and the advantages and disadvantages of different techniques are discussed.

Respiratory delivered vaccines: Current status and perspectives in rational formulation design

The respiratory tract is susceptible to various infections and can be affected by many serious diseases. Vaccination is one of the most promising ways that prevent infectious diseases and treatment of some diseases such as malignancy. Direct delivery of vaccines to the respiratory tract could mimic the natural process of infection and shorten the delivery path, therefore unique mucosal immunity at the first line might be induced and the efficiency of delivery can be high. Despite considerable attempts at the development of respiratory vaccines, the rational formulation design still warrants attention, i.e., how the formulation composition, particle properties, formulation type (liquid or solid), and devices would influence the immune outcome. This article reviews the recent advances in the formulation design and development of respiratory vaccines. The focus is on the state of the art of delivering antigenic compounds through the respiratory tract, overcoming the pulmonary bio-barriers, enhancing delivery efficiencies of respiratory vaccines as well as maintaining the stability of vaccines during storage and use. The choice of devices and the influence of deposition sites on vaccine efficiencies were also reviewed.

Zwitterion-Conjugated Protein Coatings for Enhanced Antifouling in Complex Biofluids: Underlying Molecular Interaction Mechanisms

Biofouling can cause severe infections, device malfunctions, and failures in diagnostics and therapeutics. Proteins such as bovine serum albumin (BSA) have recently been used as coatings to resist biofouling because they combine surface anchoring and antifouling properties. However, their antifouling effectiveness will significantly deteriorate in complex biofluids with high salinity, limiting their practical applications. In this work, we developed a zwitterion-conjugated protein with enhanced antifouling capability by grafting zwitterionic 2-methacryloyloxyethyl phosphorylcholine (MPC) onto BSA protein via a click reaction. This conjugated protein can easily anchor on various substrates, both inorganic and organic, and exhibits efficient and broad-spectrum fouling resistance to metabolites, proteins, and complex biofluids. Even in the complex fetal bovine serum with higher salinity, the BSA@MPC coating can also maintain 99% fouling resistance robustly, over 6-fold superior to native BSA-coated surfaces in antifouling capability. Direct surface forces measurement reveals that such outstanding antifouling properties of conjugated protein BSA@MPC could be attributed to the stable hydration layer on its surface and the steric repulsion from the antipolyelectrolyte behavior of zwitterionic MPC polymer in the high-salinity environment. Our findings advance the development of protein-based functional materials and provide valuable insights for designing novel antifouling surfaces for marine, food, and bioengineering applications.

Coassembly of Charged Copolymer Amphiphiles Featuring pH-Regulated Antifouling Properties

Understanding the formation of highly ordered structures through self-assembly is crucial for developing various biologically relevant systems. A significant expansion in the development of self-assembly chemistry features stable coassembly formation using a mixture of two oppositely charged polymers. This study provides insightful findings on the coassembly of hydrophobic coumarin-integrated cationic (P1-P3) and anionic (P1'-P3') copolymers toward the formation of vesicles in aqueous medium at pH 7.4, with a hydrodynamic diameter (Dh) of 160 ± 10 nm and electrically neutral zwitterionic surfaces, confirmed by dynamic light scattering. Upon varying the solution pH, an intriguing charge switchable behavior (+ve → 0 → -ve) and a drastic morphological transition to spherical aggregates of the vesicles were noticed. At pH 7.4, these coassembled vesicles possess a neutral surface charge, empowering them to resist nonspecific protein (pepsin and lysozyme) adsorption via electrostatic repulsion, as evidenced by size evolution and protein binding measurements. Additionally, the bilayer membrane allows for the encapsulation of hydrophilic and hydrophobic guest molecules and their sustained release in the presence of 10 mM esterase; thus, this study demonstrates potential applications of coassembly to serve as a drug delivery vehicle.

The case for poly(ylides) as a class of charge-neutral, hydrophilic polymers with applications in biomaterials science

Many applications of biomaterials require hydrophilic polymers as building blocks, including hydrogels and nanomedicinal devices. Besides enabling sufficient swelling properties in aqueous environments, hydrophilic polymers provide hydration layers, which are considered a major requirement when designing non-fouling surfaces and materials. For the last few decades, polyethylene glycol has been seen as the gold standard for such applications. However, reports on its stability and immunogenicity have urged chemists to identify alternatives with comparable or superior properties. In addition to biopolymers, zwitterionic polymers have gained increasing attention by effectively offering an overall charge-neutral scaffold capable of forming strong hydration layers. Driven by an enhanced understanding of the structure-property relationship of zwitterionic materials, poly(ylides) have emerged as a new class of hydrophilic and charge-neutral polymers. By having the negative charge adjacent to the positive charge, ylides offer not only a minimal dipole moment but also maintain their overall charge-neutral nature. Despite some early reports on their synthesis during the 1980s, polymeric ylides were largely overlooked as a class of polymers, and their utility as unique hydrophilic building blocks for the design of biomaterials and nanomedicinal tools remained elusive. In recent years, several groups have reported N-oxide and carbon-centered ylide-based polymers as highly effective building blocks for the design of antifouling materials and nanomedicines. Here, by reviewing recent progress and understanding of structure-property relationships, arguments are provided explaining why polymeric ylides should be classified as a standalone class of hydrophilic polymers. Consequently, the author concludes that the term 'poly(ylide)' or 'polymeric ylides' should be routinely used to adequately describe this emerging class of polymers.

Ultrasensitive Electrochemical Biosensor Based on Efficient PDA-APDMAO Antifouling Interface and Dual-Signal Ratio Strategy for Trace Detection of Alpha-Fetoprotein in Human Serum

In electrochemical analysis, developing biosensors that can resist the nonspecific adsorption of interfering biomolecules in human serum remains a huge challenge, which depends on the design of efficient antifouling materials. Herein, 3-aminopropyldimethylamine oxide (APDMAO) biomimetic zwitterions were prepared as antifouling interfaces. Among them, the unique positive and negative charges (N+-O-) of APDMAO promoted its hydrogen bonding with water molecules, forming a firm hydration barrier that endowed it with strong and stable antifouling performance. Meanwhile, its inherent amino groups could copolymerize with the biomimetic adhesive dopamine to form a thin layer of quinone intermediates, providing conditions for the subsequent binding of aptamers and signal probes. Importantly, the biomimetic APDMAO with functional groups and one-step oxidation characteristics solved the challenges of zwitterionic synthesis and modification, as well as improved biocompatibility of the sensing interface, thereby expanding the application potential of zwitterions as antifouling materials in sensing analysis. Thiol-containing alpha-fetoprotein (AFP) aptamers modified with methylene blue (MB) were coupled under controllable potential, greatly reducing the incubation time, which promoted the productization application of biosensors. In addition, the ratio sensing strategy using MB as internal standard factors and concanavalin-silver nanoparticles (ConA-Ag NPs) as signal probes was introduced to reduce background and instrument interferences, thus improving detection accuracy. On this basis, the proposed antifouling electrochemical biosensor achieved sensitive and accurate AFP detection over a wide dynamic range (10 fg/mL-10 ng/mL), with a low detection limit of 3.41 fg/mL (3σ/m). This work provides positive insights into the development of zwitterionic antifouling materials and clinical detection of liver cancer markers in human serum.

High-Quality Three-Dimensionally Cultured Cells Using Interfaces of Diblock Copolymers Containing Different Ratios of Zwitterionic N-Oxides

To control three-dimensional (3D) cell spheroid formation, it is well-known the surface physicochemical and mechanical properties of cell culture materials are important; however, the formation and function of 3D cells are still unclear. This study demonstrated the precise control of the formation of 3D cells and 3D cell functions using diblock copolymers containing different ratios of a zwitterionic trimethylamine N-oxide group. The diblock copolymers were composed of poly(n-butyl methacrylate) (PBMA) as the hydrophobic unit for surface coating on a cell culture dish and stabilization in water, and poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) as the precursor of N-oxide. The zwitterionic N-oxide converted from 0 to 100% using PDMAEMA. The wettability and surface zeta potential varied with different ratios of N-oxide diblock copolymer-coated surfaces, and the amount of protein adsorbed in the cell culture medium decreased monotonically with increasing N-oxide ratio. 3D cell spheroid formations were observed by seeding human umbilical cord mesenchymal stem cells (hUC-MSCs) in diblock copolymer-coated flat-bottom well plates, and the N-oxide ratio was over 40%. The cells proliferated in two-dimensions (2D) and did not form spheroids when the N-oxide ratio was less than 20%. Interestingly, the expression of undifferentiated markers of hUC-MSCs was higher on surfaces that adsorbed proteins to some extent and formed 50-150 μm spheroids in the range of 40-70% of N-oxide ratio. We revealed that a moderately protein-adsorbed surface allows precise control of spheroid formation and undifferentiated 3D cells and has potential applications for high-quality spheroids in regenerative medicine and drug screening.

Impact of the Hydrophilicity of Poly(sarcosine) on Poly(ethylene glycol) (PEG) for the Suppression of Anti-PEG Antibody Binding

A method of poly(ethylene glycol) (PEG) conjugation is known as PEGylation, which has been employed to deliver therapeutic drugs, proteins, or nanoparticles by considering the intrinsic non- or very low immunogenic property of PEG. However, PEG has its weaknesses, and one major concern is the potential immunogenicity of PEGylated proteins. Because of its hydrophilicity, poly(sarcosine) (P(Sar)) may be an attractive-and superior-substitute for PEG. In the present study, we designed a double hydrophilic diblock copolymer, methoxy-PEG-b-P(Sar) m (m = 5-55) (mPEG-P(Sar) m ), and synthesized a triblock copolymer with hydrophobic poly(l-isoleucine) (P(Ile)). We validated that double hydrophilic mPEG-P(Sar) block copolymers suppressed the specific binding of three monoclonal anti-PEG antibodies (anti-PEG mAbs) to PEG. The results of our indirect ELISAs indicate that P(Sar) significantly helps to reduce the binding of anti-PEG mAbs to PEG. Importantly, the steady suppression of this binding was made possible, in part, thanks to the maximum number of sarcosine units in the triblock copolymer, as evidenced by sandwich ELISA and biolayer interferometry assay (BLI): the intrinsic hydrophilicity of P(Sar) had a clear supportive effect on PEG. Finally, because we used P(Ile) as a hydrophobic block, PEG-P(Sar) might be an attractive alternative to PEG in the search for protein shields that minimize the immunogenicity of PEGylated proteins.

New insights into pure zwitterionic hydrogels with high strength and high toughness

Zwitterionic hydrogels are electrically neutral materials with both cationic and anionic groups that impart excellent anti-fouling properties and ion channel orientations. However, pure zwitterionic hydrogels generally exhibit low strength and toughness. In this study, it has been discovered that polymerizable zwitterionic monomers in aqueous solution exhibit a unique liquid-liquid phase separation phenomenon at a high monomer concentration of ≥50 wt%, resulting in pure and commercial zwitterionic hydrogels with high compressive strength (6.5 MPa) and high toughness (2.12 kJ m-2). This phase separation and the corresponding aggregations might be caused by strong dipole-dipole interactions among residual zwitterionic monomers under the lack of free-water condition. The synergistic effect of liquid-liquid phase separation and polymer entanglement enhances the mechanical strength, toughness, self-recovery, and anti-freezing properties of pure polyzwitterionic hydrogels. Moreover, the high fracture energy of highly elongated yet tough polyzwitterionic hydrogels facilitates the development of high crack propagation resistance, which supports an expanded role in tissue engineering, soft flexible devices, and electronics applications with improved durability. A wide range of applications for the proposed polyzwitterionic hydrogels is demonstrated by the development and testing of a strain sensor and a triboelectric nanogenerator device. Our findings provide novel insights into the network structure of pure polyzwitterionic hydrogels.

Engineering poly(dehydroalanine)-based gels via droplet-based microfluidics: from bulk to microspheres

Biomedical applications such as drug delivery, tissue engineering, and functional surface coating rely on switchable adsorption and desorption of specialized guest molecules. Poly(dehydroalanine), a polyzwitterion containing pH-dependent positive and negative charges, shows promise for such reversible loading, especially when integrated into a gel network. Herein, we present the fabrication of poly(dehydroalanine)-derived gels of different size scales and evaluate them with respect to their practical use in biomedicine. Already existing protocols for bulk gelation were remodeled to derive suitable reaction conditions for droplet-based microfluidic synthesis. Depending on the layout of the microfluidic chip, microgels with a size of approximately 30 μm or 200 μm were obtained, whose crosslinking density can be increased by implementing a multi-arm crosslinker. We analyzed the effects of the crosslinker species on composition, permeability, and softness and show that the microgels exhibit advantageous properties inherent to zwitterionic polymer systems, including high hydrophilicity as well as pH- and ionic strength-sensitivity. We demonstrate pH-regulated uptake and release of fluorescent model dyes before testing the adsorption of a small antimicrobial peptide, LL-37. Quantification of the peptide accommodated within the microgels reveals the impact of size and crosslinking density of the microgels. Biocompatibility of the microgels was validated by cell tests.

Interrupting marine fouling with active buffered coatings

Biofouling on marine surfaces causes immense material and financial harm for maritime vessels and related marine industries. Previous reports have shown the effectiveness of amphiphilic coating systems based on poly(dimethylsiloxane) (PDMS) against such marine foulers. Recent studies on biofouling mechanisms have also demonstrated acidic microenvironments in biofilms and stronger adhesion at low-pH conditions. This report presents the design and utilization of amphiphilic polymer coatings with buffer functionalities as an active disruptor against four different marine foulers. Specifically, this study explores both neutral and zwitterionic buffer systems for marine coatings, offering insights into coating design. Overall, these buffer systems were found to improve foulant removal, and unexpectedly were the most effective against the diatom Navicula incerta.

Tracing Immunological Interaction in Trimethylamine N-Oxide Hydrogel-Derived Zwitterionic Microenvironment During Promoted Diabetic Wound Regeneration

The diabetic wound healing is challenging due to the sabotaged delicate balance of immune regulation via an undetermined pathophysiological mechanism, so it is crucial to decipher multicellular signatures underlying diabetic wound healing and seek therapeutic strategies. Here, this work develops a strategy using novel trimethylamine N-oxide (TMAO)-derived zwitterionic hydrogel to promote diabetic wound healing, and explore the multi-cellular ecosystem around zwitterionic hydrogel, mapping out an overview of different cells in the zwitterionic microenvironment by single-cell RNA sequencing. The diverse cellular heterogeneity is revealed, highlighting the critical role of macrophage and neutrophils in managing diabetic wound healing. It is found that polyzwitterionic hydrogel can upregulate Ccl3+ macrophages and downregulate S100a9+ neutrophils and facilitate their interactions compared with polyanionic and polycationic hydrogels, validating the underlying effect of zwitterionic microenvironment on the activation of adaptive immune system. Moreover, zwitterionic hydrogel inhibits the formation of neutrophil extracellular traps (NETs) and promotes angiogenesis, thus improving diabetic wound healing. These findings expand the horizons of the sophisticated orchestration of immune systems in zwitterion-directed diabetic wound repair and uncover new strategies of novel immunoregulatory biomaterials.

Neutrophil Extracellular Traps-Inhibiting and Fouling-Resistant Polysulfoxides Potently Prevent Postoperative Adhesion, Tumor Recurrence, and Metastasis

Peritoneal metastasis (PM) is considered one of the most dreaded forms of cancer metastases for both patients and physicians. Aggressive cytoreductive surgery (CRS) is the primary treatment for peritoneal metastasis. Unfortunately, this intensive treatment frequently causes clinical complications, such as postoperative recurrence, metastasis, and adhesion formation. Emerging evidence suggests that neutrophil extracellular traps (NETs) released by inflammatory neutrophils contribute to these complications. Effective NET-targeting strategies thus show considerable potential in counteracting these complications but remain challenging. Here, one type of sulfoxide-containing homopolymer, PMeSEA, with potent fouling-resistant and NET-inhibiting capabilities, is synthesized and screened. Hydrating sulfoxide groups endow PMeSEA with superior nonfouling ability, significantly inhibiting protein/cell adhesion. Besides, the polysulfoxides can be selectively oxidized by ClO- which is required to stabilize the NETs rather than H2O2, and ClO- scavenging effectively inhibits NETs formation without disturbing redox homeostasis in tumor cells and quiescent neutrophils. As a result, PMeSEA potently prevents postoperative adhesions, significantly suppresses peritoneal metastasis, and shows synergetic antitumor activity with chemotherapeutic 5-Fluorouracil. Moreover, coupling CRS with PMeSEA potently inhibits CRS-induced tumor metastatic relapse and postoperative adhesions. Notably, PMeSEA exhibits low in vivo acute and subacute toxicities, implying significant potential for clinical postoperative adjuvant treatment.

In vitro biocompatibility analysis of protein-resistant amphiphilic polysulfobetaines as coatings for surgical implants in contact with complex body fluids

The fouling resistance of zwitterionic coatings is conventionally explained by the strong hydrophilicity of such polymers. Here, the in vitro biocompatibility of a set of systematically varied amphiphilic, zwitterionic copolymers is investigated. Photocrosslinkable, amphiphilic copolymers containing hydrophilic sulfobetaine methacrylate (SPe) and butyl methacrylate (BMA) were systematically synthesized in different ratios (50:50, 70:30, and 90:10) with a fixed content of photo-crosslinker by free radical copolymerization. The copolymers were spin-coated onto substrates and subsequently photocured by UV irradiation. Pure pBMA and pSPe as well as the prepared amphiphilic copolymers showed BMA content-dependent wettability in the dry state, but overall hydrophilic properties a fortiori in aqueous conditions. All polysulfobetaine-containing copolymers showed high resistance against non-specific adsorption (NSA) of proteins, platelet adhesion, thrombocyte activation, and bacterial accumulation. In some cases, the amphiphilic coatings even outperformed the purely hydrophilic pSPe coatings.

Decoration of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) with N-oxides increases the T1 relaxivity of Gd-complexes

High complex stability and longitudinal relaxivity of Gd-based contrast agents are important requirements for magnetic resonance imaging (MRI) because they ensure patient safety and contribute to measurement sensitivity. Charged and zwitterionic Gd3+-complexes of the well-known chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) provide an excellent basis for the development of safe and sensitive contrast agents. In this report, we describe the synthesis of DOTA-NOx, a DOTA derivative with four N-oxide functionalities via "click" functionalization of the tetraazide DOTAZA. The resulting complexes Gd-DOTA-NOx and Eu-DOTA-NOx are stable compounds in aqueous solution. NMR-spectroscopic characterization revealed a high excess of the twisted square antiprismatic (TSAP) coordination geometry over square antiprismatic (SAP). The longitudinal relaxivity of Gd-DOTA-NOx was found to be r1=7.7 mm-1 s-1 (1.41 T, 37 °C), an unusually high value for DOTA complexes of comparable weight. We attribute this high relaxivity to the steric influence and an ordering effect on outer sphere water molecules surrounding the complex generated by the strongly hydrated N-oxide groups. Moreover, Gd-DOTA-NOx was found to be stable against transchelation with high excess of EDTA (200 eq) over a period of 36 h, and it has a similar in vitro cell toxicity as clinically used DOTA-based GBCAs.

Aqueous photo-RAFT polymerization under ambient conditions: synthesis of protein-polymer hybrids in open air

A photoinduced reversible addition-fragmentation chain-transfer (photo-RAFT) polymerization technique in the presence of sodium pyruvate (SP) and pyruvic acid derivatives was developed. Depending on the wavelength of light used, SP acted as a biocompatible photoinitiator or promoter for polymerization, allowing rapid open-to-air polymerization in aqueous media. Under UV irradiation (370 nm), SP decomposes to generate CO2 and radicals, initiating polymerization. Under blue (450 nm) or green (525 nm) irradiation, SP enhances the polymerization rate via interaction with the excited state RAFT agent. This method enabled the polymerization of a range of hydrophilic monomers in reaction volumes up to 250 mL, eliminating the need to remove radical inhibitors from the monomers. In addition, photo-RAFT polymerization using SP allowed for the facile synthesis of protein-polymer hybrids in short reaction times (<1 h), low organic content (≤16%), and without rigorous deoxygenation and the use of transition metal photocatalysts. Enzymatic studies of a model protein (chymotrypsin) showed that despite a significant loss of protein activity after conjugation with RAFT chain transfer agents, the grafting polymers from proteins resulted in a 3-4-fold recovery of protein activity.

Stealth and Biocompatible Gold Nanoparticles through Surface Coating with a Zwitterionic Derivative of Glutathione

Gold nanoparticles (AuNPs) hold promise in biomedicine, but challenges like aggregation, protein corona formation, and insufficient biocompatibility must be thoroughly addressed before advancing their clinical applications. Designing AuNPs with specific protein corona compositions is challenging, and strategies for corona elimination, such as coating with polyethylene glycol (PEG), have limitations. In this study, we introduce a commercially available zwitterionic derivative of glutathione, glutathione monoethyl ester (GSHzwt), for the surface coating of colloidal AuNPs. Particles coated with GSHzwt were investigated alongside four other AuNPs coated with various ligands, including citrate ions, tiopronin, glutathione, cysteine, and PEG. We then undertook a head-to-head comparison of these AuNPs to assess their behavior in biological fluid. GSHzwt-coated AuNPs exhibited exceptional resistance to aggregation and protein adsorption. The particles could also be readily functionalized with biotin and interact with streptavidin receptors in human plasma. Additionally, they exhibited significant blood compatibility and noncytotoxicity. In conclusion, GSHzwt provides a practical and easy method for the surface passivation of AuNPs, creating "stealth" particles for potential clinical applications.

Polymer Brushes on Nanoparticles for Controlling the Interaction with Protein-Rich Physiological Media

The interaction of nanoparticles (NPs) with biological environments triggers the formation of a protein corona (PC), which significantly influences their behavior in vivo. This review explores the evolving understanding of PC formation, focusing on the opportunity for decreasing or suppressing protein-NP interactions by macromolecular engineering of NP shells. The functionalization of NPs with a dense, hydrated polymer brush shell is a powerful strategy for imparting stealth properties in order to elude recognition by the immune system. While poly(ethylene glycol) (PEG) has been extensively used for this purpose, concerns regarding its stability and immunogenicity have prompted the exploration of alternative polymers. The stealth properties of brush shells can be enhanced by tailoring functionalities and structural parameters, including the molar mass, grafting density, and polymer topology. Determining correlations between these parameters and biopassivity has enabled us to obtain polymer-grafted NPs with high colloidal stability and prolonged circulation time in biological media.

Bioinspired Dopamine and N-Oxide-Based Zwitterionic Polymer Brushes for Fouling Resistance Surfaces

Biofouling is a great challenge for engineering material in medical-, marine-, and pharmaceutical-related applications. In this study, a novel trimethylamine N-oxide (TMAO)-analog monomer, 3-(2-methylacrylamido)-N,N-dimethylpropylamine N-oxide (MADMPAO), was synthesized and applied for the grafting of poly(MADMPAO) (pMPAO) brushes on quartz crystal microbalance (QCM) chips by the combination of bio-inspired poly-dopamine (pDA) and surface-initiated atom transfer radical polymerization technology. The result of ion adsorption exhibited that a sequential pDA and pMPAO arrangement from the chip surface had different characteristics from a simple pDA layer. Ion adsorption on pMPAO-grafted chips was greatly inhibited at low salt concentrations of 1 and 10 mmol/L due to strong surface hydration in the presence of charged N+ and O- of zwitterionic pMPAO brushes on the outer layer on the chip surface, well known as the "anti-polyelectrolyte" effect. During BSA adsorption, pMPAO grafting also led to a marked decrease in frequency shift, indicating great inhibition of protein adsorption. It was attributed to weaker BSA-pMPAO interaction. In this study, the Au@pDA-4-pMPAO chip with the highest coating concentration of DA kept stable dissipation in BSA adsorption, signifying that the chip had a good antifouling property. The research provided a novel monomer for zwitterionic polymer and demonstrated the potential of pMPAO brushes in the development and modification of antifouling materials.

Recent advances of multifunctional zwitterionic polymers for biomedical application

Zwitterionic polymers possess equal total positive and negative charges in the repeating units, making them electrically neutral overall. This unique property results in superhydrophilicity, which makes the zwitterionic polymers highly effective in resisting protein adsorption, thus endowing the drug carriers with long blood circulation time, inhibiting thrombus formation on biomedical devices in contact with blood, and ensuring the good sensitivity of sensors in biomedical application. Moreover, zwitterionic polymers have tumor-targeting ability and pH-responsiveness, rendering them ideal candidates for antitumor drug delivery. Additionally, the high ionic conductivity of zwitterionic polymers makes them an important raw material for ionic skin. Zwitterionic polymers exhibit remarkable resistance to bacterial adsorption and growth, proving their suitability in a wide range of biomedical applications such as ophthalmic applications, and wound dressings. In this paper, we provide an in-depth analysis of the different structures and characteristics of zwitterionic polymers and highlight their unique qualities and suitability for biomedical applications. Furthermore, we discuss the limitations and challenges that must be overcome to realize the full potential of zwitterionic polymers and present an optimistic perspective for zwitterionic polymers in the biomedical fields. STATEMENT OF SIGNIFICANCE: Zwitterionic polymers have a series of excellent properties such as super hydrophilicity, anti-protein adsorption, antibacterial ability and good ionic conductivity. However, biomedical applications of multifunctional zwitterionic polymers are still a major field to be explored. This review focuses on the design and application of zwitterionic polymers-based nanosystems for targeted and responsive delivery of antitumor drugs and cancer diagnostic agents. Moreover, the use of zwitterionic polymers in various biomedical applications such as biomedical devices in contact with blood, biosensors, ionic skin, ophthalmic applications and wound dressings is comprehensively described. We discuss current results and future challenges for a better understanding of multifunctional zwitterionic polymers for biomedical applications.