Photoinduced reversible addition–fragmentation chain transfer (RAFT) polymerization generally adopts high-energy ultraviolet (UV) or blue light. In combination with photoredox catalyst, the excitation light wavelength was extended to the visible and even near-infrared (NIR) region for photoinduced electron transfer RAFT polymerization. In this report, we introduce for the first time a surface NIR-light-initiated RAFT polymerization on upconversion nanoparticles (UCNPs) without adding any photocatalyst and construct a functional inorganic core/polymer shell nanohybrid for application in cancer theranostics. The multilayer core–shell UCNPs (NaYF4:Yb/Tm@NaYbF4:Gd@NaNdF4:Yb@NaYF4), with surface anchorings of chain transfer agents, can serve as efficient NIR-to-UV light transducers for initiating the RAFT polymerization. A hierarchical double block copolymer brush, consisting of poly(acrylic acid) (PAA) and poly(oligo(ethylene oxide)methacrylate-co-2-(2-methoxy-ethoxy)ethyl methacrylate) (PEG for short), was grafted from the surface in sequence. The targeting arginine–glycine–aspartic (RGD) peptide was modified at the end of the copolymer through the trithiolcarbonate end group. After loading of doxorubicin, the UCNPs@PAA-b-PEG-RGD exhibited an enhanced U87MG cancer cell uptake efficiency and cytotoxicity. Besides, the unique upconversion luminescence of the nanohybrids was used for the autofluoresence-free cell imaging and labeling. Therefore, our strategy verified that UCNPs could efficiently activate RAFT polymerization by NIR photoirradiation and construct the complex nanohybrids, exhibiting prospective biomedical applications due to the low phototoxicity and deep penetration of NIR light.Keywords: cancer therapy; drug-delivery system; NIR light initiation; surface RAFT polymerization; upconversion nanoparticles;

Marine economy is seriously affected by marine biofouling, which has plagued people for thousands of years. Although various strategies have been developed to protect artificial surfaces against marine biofouling, cost-effective biofouling-resistant coating is still a goal in pursue. Herein, a cost-effective liquid-infused porous slippery surface (LIPSS) was facilely prepared by using poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) elastomer to form microsphere surfaces, followed by infusing fluorocarbon lubricants into the porous structure. The as-prepared slippery surfaces were characterized by static water contact angle, sliding velocity and sliding angle analysis. We also investigated the adhesion behavior of Escherichia coli (E. coli) and limnetic algae on different surfaces. It is confirmed that the slippery surfaces have better anti-biofouling properties than the porous SEBS reference. This cost-effective approach is feasible and easily produced, and may potentially be used as fouling-resistant surfaces.

•Hierarchical antibacterial surface was constructed via living SI-PIMP.•Antifouling and bactericidal functions were integrated in a hierarchical surface.•The pQAC layer was facilely adjusted to optimize the final performance.•Optimized hierarchical surface showed long-lasting antibacterial performance.Bacterial infections are problematic in many healthcare-associated devices. Antibacterial surfaces integrating the strength of bacteria repellent and bactericidal functions exhibit an encouraging efficacy in tackling this problem. Herein, a hierarchical dual-function antibacterial polymer brush coating that integrates an antifouling bottom layer with a bactericidal top layer is facilely constructed via living photograft polymerization. Excellent resistance to bacterial attachment is correlated with the antifouling components, and good bactericidal activity is afforded by the bactericidal components, and therefore the hierarchical coating shows an excellent long-term antibacterial capability. In addition, due to the presence of the hydrophilic background layer, the hierarchical surface has the greatly improved biocompatibility, as shown by the suppression of platelet adhesion and activation, the inhibition of erythrocyte adhesion and damage, and low toxicity against mammalian cells. The hierarchical polymer brush system provides the basis for the development of long-term antibacterial and biocompatible surfaces.

Styrenic thermoplastic elastomers (STPEs), particularly for poly(styrene-b-isobutylene-b-styrene) (SIBS), have aroused great interest in the indwelling and implant applications. However, the biomaterial-associated infection is a great challenge for these hydrophobic elastomers. Here, benzyl chloride (BnCl) groups are initially introduced into the SIBS backbone via Friedel–Crafts chemistry, followed by reaction with methyl 3-(dimethylamino) propionate (MAP) to obtain a cationic carboxybetaine ester-modified elastomer. The as-prepared elastomer is able to kill bacteria efficiently, while upon the hydrolysis of carboxybetaine esters into zwitterionic groups, the resultant surface has antifouling performances against proteins, platelets, erythrocytes, and bacteria. This STPE that switches from bactericidal efficacy during storage to the antifouling property in service has great potential in biomedical applications, and is generally applicable to the other styrene-based polymers.

Bacteria-responsive surfaces popularly exert their smart antibacterial activities by bacteria-triggered delivery of antibacterial agents; however, the antibacterial agents should be additionally reloaded for the renewal of these surfaces. Herein, a reversible, nonleaching bacteria-responsive antibacterial surface is prepared by taking advantage of a hierarchical polymer brush architecture. In this hierarchical surface, a pH-responsive poly(methacrylic acid) (PMAA) outer layer serves as an actuator modulating the surface behavior on demand, while antimicrobial peptides (AMP) are covalently immobilized on the inner layer. The PMAA hydration layer renders the hierarchical surface resistant to initial bacterial attachment and biocompatible under physiological conditions. When bacteria colonize the surface, the bacteria-triggered acidification allows the outermost PMAA chains to collapse, therefore exposing the underlying bactericidal AMP to on-demand kill bacteria. In addition, the dead bacteria can be released once the PMAA chains resume their hydrophilicity because of the environmental pH increase. The functionality of the nonleaching surface is reversible without additional reloading of the antibacterial agents. This approach provides a new methodology for the development of smart surfaces in a variety of practical biomedical applications.Keywords: bacteria-responsive; cationic antimicrobial peptides; hierarchical architecture; pH-responsive polymer; smart surfaces

Infection and thrombosis associated with medical implants cause significant morbidity and mortality worldwide. As we know, current technologies to prevent infection and thrombosis may cause severe side effects. To overcome these complications without using antimicrobial and anticoagulant drugs, we attempt to prepare a liquid-infused poly(styrene-b-isobutylene-b-styrene) (SIBS) microfiber coating, which can be directly coated onto medical devices. Notably, the SIBS microfiber was fabricated through solution blow spinning. Compared to electrospinning, the solution blow spinning method is faster and less expensive, and it is easy to spray fibers onto different targets. The lubricating liquids then wick into and strongly adhere the microfiber coating. These slippery coatings can effectively suppress blood cell adhesion, reduce hemolysis, and inhibit blood coagulation in vitro. In addition, Pseudomonas aeruginosa (P. aeruginosa) on the lubricant infused coatings slides readily, and no visible residue is left after tilting. We furthermore confirm that the lubricants have no effects on bacterial growth. The slippery coatings are also not cytotoxic to L929 cells. This liquid-infused SIBS microfiber coating could reduce the infection and thrombosis of medical devices, thus benefiting human health.Keywords: antibacterial; hemocompatibility; microfiber; slippery coating; solution blow spinning; thermoplastic elastomer

A facile, low-cost and time-saving method was proposed to prepare antibacterial polyurethane-g-polyethylene glycol (TPU-g-PEG) nanofiber composite by anchoring silver nanoparticles (AgNP) onto nanofibers via ultrasonication assistance. Firstly, antifouling PEG as bacteria-repelling component was chemically grafted onto TPU nanofibers through UV photo-graft polymerization to obtain TPU-g-PEG nanofibers; then AgNP as bactericidal component were immobilized onto the TPU-g-PEG nanofibers under the assistance of ultrasonication. Even if the nanofibers were immersed into PBS solution and incubated for 7 days, the released content of AgNP characterized by ICP-MS was 2.688 μg which was much lower than that of reference reported method. The TPU-g-PEG/Ag nanofiber composites exhibited excellent hemocompatibility, including suppression of platelet and red blood cell adhesion, the lower hemolysis ratios, and the higher blood clotting index. Importantly, the as-prepared nanofiber composites performed better antibacterial properties in vitro assays employing gram negative and positive strains, because of the bacterial resistance of the grafted PEG and the bactericidal effect of silver. Our approach has significant potential for the development of infection-resistant wound dressing.

The discovery of antibacterial functions for carbon nanotubes (CNT) has triggered great interest because of the excellent antibacterial properties of CNT. However, there are two obstacles, i.e., cell toxicity and CNT aggregation in a polymer matrix, which greatly limit the antibacterial application of CNT in medical devices. In this study, a facile, cost-effective, time-saving and environmentally friendly approach was proposed to impart the antibacterial property to thermoplastic polyurethane (TPU) electrospun nanofibers with CNT. The ultrasonication technique was explored to in situ anchor the CNT onto the TPU electrospun nanofibers to achieve the bactericidal property. This effectively circumvented the aggregation of CNT when the TPU/CNT electrospun nanofibers were prepared. In addition, the anchor preparation was efficient taking only 10 min to complete and it was also non-toxic because the green solvent ethanol was used as the dispersion solvent. PEG was chemically grafted onto the TPU (TPU-g-PEG) electrospun nanofibers through UV photo-graft polymerization. Although CNT exhibit a good bactericidal property, they could be toxic to human cells. Incorporation of PEG could not only effectively reduce the toxicity of CNT to the human cells but also decrease bacterial attachment. The TPU-g-PEG/CNT nanofibers exhibited excellent hemocompatibility, including suppression of red blood cell adhesion, and lower hemolysis ratios. Importantly, the as-prepared nanofibers had better antibacterial properties due to the bacterial resistance of the grafted PEG and the bactericidal effect of CNT. Our facile approach has significant potential for the infection-resistant wound dressing.

Although polycationic surfaces have high antimicrobial efficacies, they suffer from high toxicity to mammalian cells and severe surface accumulation of dead bacteria. For the first time, we propose a surface-initiated photoiniferter-mediated polymerization (SI-PIMP) strategy of constructing a “cleaning” zwitterionic outer layer on a polycationic bactericidal background layer to physically hinder the availability of polycationic moieties for mammalian cells in aqueous service. In dry conditions, the polycationic layer exerts the contact-active bactericidal property toward the adherent bacteria, as the zwitterionic layer collapses. In aqueous environment, the zwitterionic layer forms a hydration layer to significantly inhibit the attachment of planktonic bacteria and the accumulation of dead bacteria, while the polycationic layer kills bacteria occasionally deposited on the surface, thus preserving the antibacterial capability for a long period. More importantly, the zwitterionic hydrated layer protects the mammalian cells from toxicity induced by the bactericidal background layer, and therefore hierarchical antibacterial surfaces present much better biocompatibility than that of the naked cationic references. The dominant antibacterial mechanism of the hierarchical surfaces can switch from the bactericidal efficacy in dry storage to the bacteria repellent capability in aqueous service, showing great advantages in the infection-resistant applications.

High-efficiency immunoassay platforms with controlled surface roughness (single- and dual-scale structured surface) were prepared by combining a facile layer-by-layer particle deposition approach with oriented immobilization of antibodies through boronic acid moieties. The as-prepared surfaces showed significantly enhanced antibody loading capacity and antigen recognition, as proved by fluorescence images.

Despite the advanced modern biotechniques, thrombosis and bacterial infection of biomedical devices remain common complications that are associated with morbidity and mortality. Most antifouling surfaces are in solid form and cannot simultaneously fulfill the requirements for antithrombosis and antibacterial efficacy. In this work, we present a facile strategy to fabricate a slippery surface. This surface is created by combining photografting polymerization with osmotically driven wrinkling that can generate a coarse morphology, and followed by infusing with fluorocarbon liquid. The lubricant-infused wrinkling slippery surface can greatly prevent protein attachment, reduce platelet adhesion, and suppress thrombus formation in vitro. Furthermore, E. coli and S. aureus attachment on the slippery surfaces is reduced by ∼98.8% and ∼96.9% after 24 h incubation, relative to poly(styrene-b-isobutylene-b-styrene) (SIBS) references. This slippery surface is biocompatible and has no toxicity to L929 cells. This surface-coating strategy that effectively reduces thrombosis and the incidence of infection will greatly decrease healthcare costs.Keywords: antibacterial; antifouling; photografting polymerization; poly(styrene-b-isobutylene-b-styrene) (SIBS); slippery surface

We propose a facile UV strategy to construct a hierarchically three-dimensional (3D) substrate that comprises a polystyrene (PS) microsphere layer on the cycloolefin polymer (COP) substrate and densely packed hydrophilic polymer brushes grafting from this 3D backbone. This hierarchical substrate gives a high antibody loading capacity and 3D manner of analyte capture, therefore enhancing detection signal while reducing background noise.

•Chitosan was modified with carboxybetaine ester brush via a ‘click’-type azlactone reaction.•The as-prepared CS switched from bactericidal during storage to antifouling before service.•The as-modified wound dressing has great potential in biomedical applications.A facile approach to functionalize chitosan (CS) non-woven surface with the bactericidal and antifouling switchable moieties is presented. Azlactone-cationic carboxybetaine ester copolymer was firstly prepared, then chemically attached onto CS non-woven surface through the fast and efficient ‘click’-type interfacial reaction between CS primary amines and azlactone moieties. The CS non-woven surface functionalized with cationic carboxybetaine esters is able to kill bacteria effectively. Upon the hydrolysis of carboxybetaine esters into zwitterionic groups, the resulting zwitterionic surface can further prevent the attachment of proteins, platelets, erythrocytes and bacteria. This CS non-woven that switches from bactericidal performance during storage to antifouling property before its service has great potential in wound dressing applications.

The development of technologies for a biomedical detection platform is critical to meet the global challenges of various disease diagnoses. In this study, an inert cycloolefin polymer (COP) support was modified with two-layer polymer brushes possessing dual functions, i.e., a low fouling poly[poly(ethylene glycol) methacrylate] [p(PEGMA)] bottom layer and a poly(acrylic acid) (PAA) upper layer for antibody loading, via a surface-initiated photoiniferter-mediated polymerization strategy for fluorescence-based immunoassay. It was demonstrated through a confocal laser scanner that, for the as-prepared COP-g-PEG-b-PAA-IgG supports, nonspecific protein adsorption was suppressed, and the resistance to nonspecific protein interference on antigen recognition was significantly improved, relative to the COP-g-PAA-IgG references. This strategy for surface modification of a polymeric platform is also applicable to the fabrication of other biosensors.Keywords: antibody immobilization; cycloolefin polymer (COP); hierarchical architecture; immunoassay; surface-initiated photoiniferter-mediated polymerization (SI-PIMP);

Hydrophobic thermoplastic elastomers, e.g., poly(styrene-b-isobutylene-b-styrene) (SIBS), have found various in vivo biomedical applications. It has long been recognized that biomaterials can be adversely affected by bacterial contamination and clinical infection. However, inhibiting bacterial colonization while simultaneously preserving or enhancing tissue-cell/material interactions is a great challenge. Herein, SIBS substrates were functionalized with nucleases under mild conditions, through polycarboxylate grafts as intermediate. It was demonstrated that the nuclease-modified SIBS could effectively prevent bacterial adhesion and biofilm formation. Cell adhesion assays confirmed that nuclease coatings generally had no negative effects on L929 cell adhesion, compared with the virgin SIBS reference. Therefore, the as-reported nuclease coating may present a promising approach to inhibit bacterial infection, while preserving tissue-cell integration on polymeric biomaterials.Keywords: antibacterial; cell adhesion; deoxyribonuclease (DNase); poly(styrene-b-isobutylene-b-styrene) (SIBS); ribonuclease (RNase)

The biostable poly(styrene-b-isobutylene-b-styrene) (SIBS) elastomers are well-known for their large-scale in vivo application as drug-eluting coatings in coronary stents. In this study, the SIBS elastomers were modified with a poly(dopamine) (PDA) adherent layer, followed by integrating both chitosan (CS) and hyaluronic acid (HA) onto their surfaces. The as-prepared samples (SIBS-CS-g-HA) presented excellent cytocompatibility because CS facilitates cell attachment and HA enhances cell proliferation. The initial adhesion test of E. coli on SIBS-CS-g-HA showed effective antiadhesive properties. The in vitro antibacterial test confirmed that SIBS-CS-g-HA has good antibacterial activity.

Inert cycloolefin polymers (COPs), which possess excellent optical properties, are a series of ideal materials for fabricating cheap disposable biosensor platforms. However, their antibioadhesion properties are expected to be improved prior to their application as biosensor supports. In this study, for the first time the COP supports were modified with well-controlled neutral, anionic and cationic polymer brushes via surface-initiated photoiniferter-mediated polymerization. This graft polymerization was confirmed by infrared spectroscopy, and X-ray photoelectron spectroscopy. The antibioadhesion properties of the modified supports were evaluated through a series of biological experiments. It was found that among these modified samples, the anionic poly(2-carboxyethyl acrylate)-modified COP supports presented the best antibioadhesion performances, i.e., suppressing protein adsorption, platelet adhesion and red blood cell attachment.

Development of technologies for biomedical detection platform is critical to meet the global challenges of various disease diagnoses, especially for point-of-use applications. Because of its natural simplicity, effectiveness, and easy repeatability, random covalent-binding technique is widely adopted in antibody immobilization. However, its antigen-binding capacity is relatively low when compared to site-specific immobilization of antibody. Herein, we report that a detection platform modified with boronic acid (BA)-containing sulfobetaine-based polymer brush. Mainly because of the advantage of oriented immobilization of antibody endowed with BA-containing three-dimensional polymer brush architecture, the platform had a high antigen-binding capacity. Notably, nonspecific protein adsorption was also suppressed by the zwitterionic pendants, thus greatly enhanced signal-to-noise (S/N) values for antigen recognition. Furthermore, antibodies captured by BA pendants could be released in dissociation media. This new platform is promising for potential applications in immunoassays.Keywords: antibody immobilization; atom transfer radical polymerization (ATRP); boronic acid (BA); immunoassay; zwitterionic-based materilals;

Styrenic thermoplastic elastomers (STPEs), particularly for poly(styrene-b-isobutylene-b-styrene) (SIBS), have aroused great interest in the indwelling and implant applications. However, the biomaterial-associated infection is a great challenge for these hydrophobic elastomers. Here, benzyl chloride (BnCl) groups are initially introduced into the SIBS backbone via Friedel–Crafts chemistry, followed by reaction with methyl 3-(dimethylamino) propionate (MAP) to obtain a cationic carboxybetaine ester-modified elastomer. The as-prepared elastomer is able to kill bacteria efficiently, while upon the hydrolysis of carboxybetaine esters into zwitterionic groups, the resultant surface has antifouling performances against proteins, platelets, erythrocytes, and bacteria. This STPE that switches from bactericidal efficacy during storage to the antifouling property in service has great potential in biomedical applications, and is generally applicable to the other styrene-based polymers.

We propose a facile UV strategy to construct a hierarchically three-dimensional (3D) substrate that comprises a polystyrene (PS) microsphere layer on the cycloolefin polymer (COP) substrate and densely packed hydrophilic polymer brushes grafting from this 3D backbone. This hierarchical substrate gives a high antibody loading capacity and 3D manner of analyte capture, therefore enhancing detection signal while reducing background noise.

High-efficiency immunoassay platforms with controlled surface roughness (single- and dual-scale structured surface) were prepared by combining a facile layer-by-layer particle deposition approach with oriented immobilization of antibodies through boronic acid moieties. The as-prepared surfaces showed significantly enhanced antibody loading capacity and antigen recognition, as proved by fluorescence images.