Bioinspired Zwitterionic Surface Coatings with Robust Photostability and Fouling Resistance

Enhanced Diabetic Rat Wound Healing by Platelet-Rich Plasma Adhesion Zwitterionic Hydrogel

BACKGROUND

The skin is the largest organ in the human body and serves as a barrier for protective, immune, and sensory functions. Continuous and permanent exposure to the external environment results in different levels of skin and extracellular matrix damage. During skin wound healing, the use of good dressings and addition of growth factors to the wound site can effectively modulate the rate of wound healing. A dressing containing bioactive substances can absorb wound exudates and reduce adhesion between the wound and dressing, whereas growth factors, cytokines, and signaling factors can promote cell motility and proliferation.

AIM AND OBJECTIVES

We prepared a functional wound dressing by combining platelet-rich plasma (PRP) and zwitterionic hydrogels. Functional wound dressings are rich in various naturally occurring growth factors that can effectively promote the healing process in various types of tissues and absorb wound exudates to reduce adhesion between wounds and dressings. Furthermore, PRP-incorporated zwitterionic hydrogels have been used to repair full-thickness wounds in Sprague-Dawley rats with diabetes (DM SD).

MATERIALS AND METHODS

Fibroblasts and keratinocytes were cultured with PRP, zwitterionic hydrogels, and PRP-incorporated zwitterionic hydrogels to assess cell proliferation and specific gene expression. Furthermore, PRP-incorporated zwitterionic hydrogels were used to repair full-thickness skin defects in DM SD rats.

RESULTS

The swelling ratio of hydrogel, hydrogel + PRP1000 (108 platelets/mL), and hydrogel + PRP1000 (109 platelets/mL) groups were similar (~07.71% ± 1.396%, 700.17% ± 1.901%, 687.48% ± 4.661%, respectively) at 144 hours. The tensile strength and Young modulus of the hydrogel and hydrogel + PRP10000 groups were not significantly different. High concentrations of PRP (approximately 108 and 109 platelets/mL) effectively promoted the proliferation of fibroblasts and keratinocytes. The zwitterionic hydrogels were not cytotoxic to any cell type. High PRP concentration-incorporated zwitterionic hydrogels increased the rate of cell proliferation and significantly increased the expression of characteristic genes such as collagen, fibronectin, involucrin, and keratin. Subsequently, zwitterionic hydrogels with high PRP concentrations were used to repair full-thickness skin defects in DM SD rats, and a wound healing rate of more than 90% was recorded on day 12.

CONCLUSIONS

PRP contains high concentrations of growth factors that promote cell viability, enhance specific gene expression, and have a high medical value in cell therapy. Zwitterionic hydrogels have a 3-dimensional interconnected microporous structure and can resist cell adhesion without causing cytotoxicity. Platelet-rich plasma-incorporated zwitterionic hydrogels further enhance the cellular properties and provide an effective therapeutic option for wound healing.

A spiropyran-decorated nanocoating for dynamically regulating bacteria/cell adhesion and detachment

Microorganism adhesion and the resulting contamination of the biomaterial is one of the major causes of biomedical device failure. Stimuli-responsive materials based on dynamically regulating interactions with reversible characteristics of on-off states have attracted increasing attention. Here, a facile self-assembled biomaterial nanocoating constructed using acidity- and photoregulated spiropyran-modified nanoparticles was developed for reversibly regulating bacteria or mammalian cell adhesion-and-detachment. The coating was formed by coating a solution of spiropyran-conjugated nanoparticles around the surface of a silica gel followed by curing and drying at 60 °C for 30 min. Importantly, efficient adhesion-and-detachment of bacteria or cells could be controlled even after 8 cycles owing to the excellent acidity- and light-switched ability. Collectively, this well-defined self-assembled nanocoating as a dynamical and reversible agent provides promising insight for the development of biomedical devices, especially for biomaterial medical coatings.

Pseudo-zwitterions self-assembled from polycation and anion clusters showing exceptional water-cleanable anti-crude-oil-adhesion property

It is of great importance and practical value to develop a facile and operable surface treatment method of materials with excellent antipollution and antiadhesion property, but still a huge challenge. In this work, a series of pseudo-zwitterions are prepared from electrostatic assembly of cationic polyethyleneimine and anionic phosphonic clusters. These pseudo-zwitterionic assemblies provide a strong hydration through electrostatic interaction with water and in turn create a barrier against oil foulants, leading to a nearly zero crude oil adhesion force. The pseudo-zwitterions-decorated surfaces exhibit exceptional water-cleanable oil-repellent property, even when they are completely dried and without prehydration before fouled by crude oil. While using these pseudo-zwitterions-modified polymeric membranes for separating surfactant stabilized oil-in-water emulsion, less than 10% decline of permeating flux is observed throughout a 2-h continuous separation experiment, showing excellent emulsion separation ability and antipollution performance for high viscous oil.

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The ion pairs called pseudo-zwitterions were constructed by electrostatic self-assembly

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The pseudo-zwitterions-modified surfaces can repel crude oil without prehydration

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Pseudo-zwitterionic membrane shows exceptional antioil fouling performance

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The strategy gives a new way to endow the surfaces with excellent antiadhesion property

Antifouling enhancement of polyacrylonitrile-based membrane grafted with poly(sulfobetaine methacrylate) layers

In this work, zwitterionic polyacrylonitrile (PAN)-based membranes were synthesized via surface grafting strategy for improving the antifouling properties. The copolymer membrane consisting of PAN and poly(hydroxyethyl methacrylate) segments, was cast via nonsolvent induced phase separation, and then treated with acryloyl chloride to tether with carbon-carbon double bonds. Zwitterionic poly(sulfobetaine methacrylate) (PSBMA) layers were grafted onto membrane surface via concerted reactions of radical grafting copolymerization and quaternization with 2-(dimethylamino)ethyl methacrylate) and 1, 3-propanesultone (1, 3-PS) as the monomers. The grafting degree (GD) of PSBMA layers increases with the incremental content of monomers, leading to the enhancement in membranes surface hydrophilicity. The permeation experiments show that the flux of the zwitterionic membrane increases and then decreases with the increasing GD value, because of the surface coverage of PSBMA layers. The zwitterionic membrane has excellent separation efficiency for oil-in-water emulsion, with the rejection of a higher value than 99%. The irreversible membrane fouling caused by oil adsorption has been suppressed, as proved by the cycle-filtration tests. These outcomes confirm that oil-fouling resistances of membranes are improved obviously by the surface grafting of zwitterionic PSBMA layers.

Marine antifouling coatings with surface topographies triggered by phase segregation

Marine biofouling is a ubiquitous and longstanding challenge that causes both economic and environmental problems. To address this, several antifouling strategies have been proposed, such as the release of biocidal compounds or surface chemical/physical design. Here we report a coating with surface structures (chemical heterogeneity) triggered by phase segregation, which endues the good antifouling properties, alongside robust mechanical properties, low underwater oil adhesion, and excellent optical transparency. This is achieved by arranging the hydrophobic and hydrophilic components to control the assembly and phase separation under the cross-linking and localized swelling process. The structure designs are based on the poly(ethylene glycols) (PEG), zwitterions, and hydrophobic components, which may lower the entropic and enthalpic driving forces for the adsorption of the marine organisms. Our approach could provide an effective way of manufacturing novel coating with amphiphilic micro/nanodomains structure, particularly for the marine industry. And we also showed that the coatings were stable under different temperatures and shear environments. To illustrate the applicability of such a robust coating in marine biofouling, we demonstrated significantly reduced algal adhesion and barnacle attachment in the sea (p < 0.01). We envision that this work will provide great potential for the application in antifouling marine coatings.

Surface Modification of Intraocular Lens with Hydrophilic Poly(Sulfobetaine Methacrylate) Brush for Posterior Capsular Opacification Prevention

Purpose: The intraocular lens (IOL) is a common, yet important, implantable device used in treatment of cataract in clinics. However, the unexpected adhesion of postoperative residual lens epithelial cells (LECs) often causes serious complications, such as posterior capsular opacification (PCO), which lead to vision loss again. In this investigation, a poly(sulfobetaine methacrylate) (PSBMA) brush coating was fabricated on an IOL to generate a hydrophilic surface coating on the IOL for enhanced cell adhesion resistance so as to decrease PCO incidence. Methods: The PSBMA brush coating on the IOL surface was fabricated using surface-initiated reversible addition-fragmentation chain transfer polymerization. X-ray photoelectron spectroscopy (XPS) was used to demonstrate the surface coating preparation. The water contact angle (WCA) measurement was used to test surface hydrophilicity. In vitro LEC culture was use to evaluate the cell behavior on the IOL material surfaces, with or without PSBMA coating modification. Finally, animal cataract surgeries were carried out to evaluate in vivo biocompatibilities and anti-PCO effects. Results: The XPS and WCA measurements illustrate successful surface modification and good surface hydrophilicity. The in vitro cell culture results show that the hydrophilic PSBMA polymer brush coating evidently decreases adhesion and proliferation of LECs. Results of the in vivo cataract surgery with intraocular implantation show that PSBMA modification on the IOL surface does not induce side effects in nearby tissues, whereas posterior capsular hyperplasia can be evidently reduced. Conclusion: The PSBMA brush surface-modified IOL has good in vivo biocompatibility and it can effectively reduce the incidence of postoperative PCO.

Open-to-Air RAFT Polymerization on a Surface under Ambient Conditions

Oxygen (O₂)-mediated controlled radical polymerization was performed on surfaces under ambient conditions, enabling on-surface polymer brush growth under open-to-air conditions at room temperature in the absence of metal components. Polymerization of zwitterionic monomers using this O₂-mediated surface-initiated reversible addition fragmentation chain-transfer (O₂-SI-RAFT) method yielded hydrophilic surfaces that exhibited anti-biofouling effects. O₂-SI-RAFT polymerization can be performed on large surfaces under open-to-air conditions. Various monomers including (meth)acrylates and acrylamides were employed for O₂-SI-RAFT polymerization; the method is thus versatile in terms of the polymers used for coating and functionalization. A wide range of hydrophilic and hydrophobic monomers can be employed. In addition, the end-group functionality of the polymer grown by O₂-SI-RAFT polymerization allowed chain extension to form block copolymer brushes on a surface.

Zwitterionic Stealth Dye-Loaded Polymer Nanoparticles for Intracellular Imaging

Intracellular applications of fluorescent nanoparticles (NPs) as probes and labels are currently limited by significant molecular crowding and the high level of complexity encountered inside living cells. The solution is to develop very small, bright, and noninteracting (stealth) NPs. Combining these properties requires implementing the stealth behavior through the thinnest possible hydrophilic shell. Here, we propose a one-step process for preparing ultrasmall and bright stealth NPs based on a zwitterionic (ZI) methacrylate-based copolymer. Dye-loaded polymer NPs are assembled through nanoprecipitation of the copolymer together with the salt of a rhodamine B derivative and a bulky hydrophobic counterion to achieve high particle brightness. We found that 10 mol % ZI groups in the polymer yield NPs of less than 15 nm that are stable in physiological salt conditions and practically resistant to protein adsorption, as suggested by fluorescence correlation spectroscopy. The combination of the very small size with the nonfouling nature of these particles enables spreading of ZI polymer NPs in the whole cytosol after their microinjection into living cells. In addition, single-particle tracking showed up to four times faster diffusion of ZI NPs in the cytosol compared to PEGylated NPs. The obtained dye-loaded ZI polymer NPs open the route to intracellular single-particle tracking and biosensing applications.

Complete zwitterionic double network hydrogels with great toughness and resistance against foreign body reaction and thrombus

A new methodology for developing biocompatible double network hydrogels by using a responsive amphoteric polymer as a first framework.

Intelligent Metal-Phenolic Metallogels as Dressings for Infected Wounds

In this study, we report a metallogel developed based on metal-phenolic coordination of natural low-cost polyphenolic molecule and metal ions. Gelation occurs by mixing tannic acid (TA) and group (IV) titanium ions (Ti^IV) to form TA-Ti^IV gel. The TA-Ti^IV gel exhibits good capability to incorporate diverse metal ions by in situ co-gelation. Herein, five antimicrobial metal ions, i.e. ferric (Fe^III), copper (Cu^II), zinc (Zn^II), cobalt (Co^II) and nickel (Ni^II) ions, were employed to include in TA-Ti^IV gels for developing intelligent dressings for infected wounds. The chemical and coordinative structures of TA-Ti^IV metallogels were characterized by UV-Vis and Fourier-transform infrared (FT-IR) spectroscopies. Cytotoxicity of antimicrobial metallogels was explored by MTT assay with NIH 3T3 fibroblasts. The release of metal ions was evaluated by inductively coupled plasma mass spectrometry (ICP-MS), indicating the different releasing profiles upon the coordinative interactions of metal ions with TA. The formation and disassembly of metallogels are sensitive to the presence of acid and an oxidizer, H₂O₂, which are substances spontaneously generated in infected wounds due to the metabolic activity of bacteria and the intrinsic immune response. The Cu^II releasing rates of TA-Ti^IV-Cu^II metallogels at different pH values of 5.5, 7.4 and 8.5 have been studied. In addition, addition of H₂O₂ trigger fast release of Cu^II as a result of oxidation of galloyl groups in TA. Consequently, the antimicrobial potency of TA-Ti^IV-Cu^II metallogels can be simultaneously activated while the wounds are infected and healing. The antimicrobial property of metallogels against Gram-negative Escherichia coli, and Gram-positive Methicillin-Resistant Staphylococcus aureus (USA300) and Staphylococcus epidermidis has been investigated by agar diffusion test. In an animal model, the TA-Ti^IV-Cu^II metallogels were applied as dressings for infected wounds, indicating faster recovery in the wound area and extremely lower amount of bacteria around the wounds, compared to TA-Ti^IV gels and gauze. Accordingly, the intelligent nature derived metallogels is a promising and potential materials for medical applications.

Low-Fouling Characteristics of Ultrathin Zwitterionic Cysteine SAMs

Surface fouling remains an exigent issue for many biological implants. Unwanted solutes adsorb to reduce device efficiency and hasten degradation while increasing the risks of microbial colonization and adverse inflammatory response. To address unwanted fouling in modern implants in vivo, surface modification with antifouling polymers has become indispensable. Recently, zwitterionic self-assembled monolayers, which contain two or more charged functional groups but are electrostatically neutral and form highly hydrated surfaces, have been the focus of many antifouling coatings. Reports using various compositions of zwitterionic polymer brushes have demonstrated ultralow fouling in the ng/cm² range. These coatings, however, are thick and can hinder the target application of biological devices. Here, we report an ultrathin (8.52 Å) antifouling self-assembled monolayer composed of cysteine that is amenable to facile fabrication. The antifouling characteristics of the zwitterionic surfaces were evaluated against bovine serum albumin, fibrinogen, and human blood in real time using quartz crystal microbalance and surface plasmon resonance imaging. Compared to untreated gold surfaces, the ultrathin cysteine coating reduced the adsorption of bovine serum albumin by 95% (43 ng/cm² adsorbed) after 3 h and 90% reduction after 24 h. Similarly, the cysteine self-assembled monolayer reduced the adsorption of fibrinogen as well as human blood by >90%. The surfaces were further characterized using scanning electron microscopy: protein-enhanced adsorption and cellular adsorption in human blood was found on untreated surfaces but not on the cysteine SAM-protected surfaces. These findings suggest that surfaces can be functionalized with an ultrathin layer of cysteine to resist the adsorption of key proteins, with performance comparable to zwitterionic polymer brushes. As such, cysteine surface coatings are a promising methodology to improve the long-term utility of biological devices.

Controlled Silanization Using Functional Silatrane for Thin and Homogeneous Antifouling Coatings

Organosilicons for surface modification are gaining prominence because of their easy and rapid preparation, high availability, and effective modification for varying interfacial properties. However, their implementation has been humbled by poor control of the packing density, thickness, and molecular structures due to the uncontrollable hydrolysis and condensation. This study reports for the first time new functional silatrane chemistry for the precision deposition of a thin and homogeneous zwitterionic coating. Sulfobetaine silatrane (SBSiT) has a tricyclic caged structure and a transannular N → Si dative bond, which shows excellent chemical stability in the presence of water and an acid-modulated hydrolysis characteristic. Results from X-ray photoelectron spectroscopy indicate the progressive deposition of SBSiT on a silicon surface. Characterization using atomic force microscopy and ellipsometry shows the uniform and thin SBSiT films on silicon surfaces. The superior antifouling properties of SBSiT coatings were demonstrated by resisting bacterial and protein adsorption. More importantly, the stable and complete formation of the SBSiT coatings allows an accurate interpretation of the interfacial phenomena for sensing and nanomaterial applications.

Synergistic Effects of Ions and Surface Potentials on Antifouling Poly(3,4-ethylenedioxythiophene): Comparison of Oligo(Ethylene Glycol) and Phosphorylcholine

For electrified surfaces, ions and applied potentials play major roles in controlling the surface properties. Antifouling materials such as poly(ethylene glycol) and zwitterionic polymers that resist nonspecific protein binding and cell adhesion play a key role in various biomedical applications. In this study, we investigated and compared the antifouling properties of conducting polymers grafted with oligo(ethylene glycol) groups and phosphorylcholine (PC) groups in the presence of different anions and applied potentials. Considerable effort has been made to illustrate the different effects of manipulating the antifouling properties of these two surfaces. We prepared polymer films by applying electropolymerization to two functionalized (3,4-ethylenedioxythiophene) polymers containing triethylene glycol and PC groups, respectively. A quartz crystal microbalance with dissipation (QCM-D) was employed to characterize the negatively charged bovine serum albumin and positively charged lysozyme adsorption as a function of ionic concentration in the presence of various Hofmeister anions. The frequency changes corresponded to the protein or ion adsorption/desorption behavior on the surface. The anions adsorbed on polymer films to effectively enhance the hydration layer of the polymer surface and reduce nonspecific protein binding. We further integrated a potentiostat with the QCM-D to control the protein adsorption/desorption behaviors by applying potentials, and we conducted an electrochemical QCM-D study. Most importantly, with the synergistic effect of ions and surface potential, a nearly fresh polymer surface was regenerated. This study describes principles to maintain and regenerate the antifouling properties of electrified surfaces, which are critical for implanted bioelectronics applications.

Fabrication and Release Behavior of Microcapsules with Double-Layered Shell Containing Clove Oil for Antibacterial Applications

In this study, double-layer polyurethane/poly(urea-formaldehyde) (PU/PUF) shell microcapsules containing clove oil with antibacterial properties were successfully synthesized via in situ and interfacial polymerization reactions in an oil-in-water emulsion. The morphology, core-shell structure, and composition of the microcapsules were investigated systematically. Additionally, the release behaviors of microcapsules synthesized under different reaction parameters were studied. It was found that the release rate of clove oil can be controlled by tuning the amount of PU reactants and the length of PUF deposition time. The release profile fitted well against the Baker-Lonsdale model, which indicates diffusion as the primary release mechanism. Experimental results based on the ASTM E2315 time kill test revealed that the fabricated microcapsules have great antibacterial activities against the marine bacteria Vibrio coralliilyticus, Escherichia coli, Exiguobacterium aestuarii, and marine biofilm-forming bacteria isolated from the on-site contaminated samples, showing their great potential as an eco-friendly solution to replace existing toxic antifouling agent.

Development of a SERS strategy to overcome the nanoparticle stabilisation effect in serum-containing samples: Application to the quantification of dopamine in the culture medium of PC-12 cells

The analysis of serum samples by surface-enhanced Raman spectroscopy (SERS) has gained ground over the last few years. However, the stabilisation of colloids by the proteins contained in these samples has restricted their use in common practice, unless antibodies or aptamers are used. Therefore, this work was dedicated to the development of a SERS methodology allowing the analysis of serum samples in a simple and easy-to-implement way. This approach was based on the pre-aggregation of the colloid with a salt solution. Gold nanoparticles (AuNPs) were used as the SERS substrate and, owing to its physiopathological importance, dopamine was chosen as a model to implement the SERS approach. The presence of this neurotransmitter could be determined in the concentration range 0.5-50 ppm (2.64-264 µM) in the culture medium of PC-12 cells, with a R² of 0.9874, and at even lower concentrations (0.25 ppm, 1.32 µM) in another matrix containing fewer proteins. Moreover, the effect of calcium and potassium on the dopamine exocytosis from PC-12 cells was studied. Calcium was shown to have a predominant and dose-dependant effect. Finally, PC-12 cells were exposed to dexamethasone in order to increase their biosynthesis and release of dopamine. This increase was monitored with the developed SERS approach.

Zwitterionic peptide-capped gold nanoparticles for colorimetric detection of Ni2+

Zwitterionic nanoparticles are typically utilized as nanoprobes and delivery vehicles in nanomedicine and therapeutics due to their resistance to interferences. Their high stability also shows great potential to be applied in sensing applications. Here, we report a selective, sensitive and rapid colorimetric sensing of nickel ions (Ni²⁺) using zwitterionic polypeptide, EKEKEKPPPPC (EK)₃, capped gold nanoparticles (AuNP-(EK)₃). By taking advantage of the alternate carboxylic (-COOH)/amine (-NH₂) groups, the zwitterionic peptide can function dually by being able to sense metal ions and maintain colloidal stability. Ni²⁺ can trigger the aggregation of the AuNP-(EK)₃ nanoprobe, which results in a red-to-purple color change of the AuNP-(EK)₃ solution. Our 40 nm AuNP-(EK)₃ nanoprobe can detect Ni²⁺ as low as 34 nM within 15 min with a linear range of 60-160 nM, and is stable in soil, urine and water samples. We demonstrate that the aggregation mechanism of the nanoprobe is due to the interactions between the -NH₂ group of glutamic acid at the N-terminus of the peptide and Ni²⁺, and the aggregation process is reversible. Furthermore, the slight modification of two amino acid sequences at the N-terminus allows the nanoprobe to retain its stability, even in a high ionic strength medium. We believe that by adjusting or extending the peptide sequences, new metal ion selective peptides could be created.

Covalent Surface Modification of Silicon Oxides with Alcohols in Polar Aprotic Solvents

Alcohol-based monolayers were successfully formed on the surfaces of silicon oxides through reactions performed in polar aprotic solvents. Monolayers prepared from alcohol-based reagents have been previously introduced as an alternative approach to covalently modify the surfaces of silicon oxides. These reagents are readily available, widely distributed, and are minimally susceptible to side reactions with ambient moisture. A limitation of using alcohol-based compounds is that previous reactions required relatively high temperatures in neat solutions, which can degrade some alcohol compounds or could lead to other unwanted side reactions during the formation of the monolayers. To overcome these challenges, we investigate the condensation reaction of alcohols on silicon oxides carried out in polar aprotic solvents. In particular, propylene carbonate has been identified as a polar aprotic solvent that is relatively nontoxic, readily accessible, and can facilitate the formation of alcohol-based monolayers. We have successfully demonstrated this approach for tuning the surface chemistry of silicon oxide surfaces with a variety of alcohol containing compounds. The strategy introduced in this research can be utilized to create silicon oxide surfaces with hydrophobic, oleophobic, or charged functionalities.

Mesoscopic Structures of Poly(carboxybetaine) Block Copolymer and Poly(ethylene glycol) Block Copolymer in Solutions

The antifouling property of exogenous materials is vital for their in vivo applications. In this work, dissipative particle dynamics simulations are performed to study the self-assembled morphologies of two copolymer systems containing poly(ethylene glycol) (PEG) and poly(carboxybetaine) (PCB) in aqueous solutions. Effects of polymer composition and polymer concentration on the self-assembled structures of the two copolymers (PLA-PEG and PLA-PCB) are investigated, respectively [PLA represents poly(lactic acid)]. Results show that whatever the copolymer composition is, PLA-PEG systems will self-assemble into core-shell structures, whereas onion-like and vesicle structures are also found for the PLA-PCB systems. Different morphologies are obtained at different polymer concentrations in both copolymer systems. Simulation results demonstrate that PCB is more stable than PEG in maintaining self-assembled spherical structures of copolymer systems because PLA-PEG forms dumbbell-like structures whereas PLA-PCB is spherical under the same polymer concentration. Although both copolymer systems can self-assemble into core-shell nanoparticles when the block ratio of PLA:PEG or PLA:PCB is 80:20, the core-shell structures of the nanoparticles are quite different. The shell layers formed by PEG in PLA-PEG nanoparticles are inhomogeneous in size because of the amphiphilicity of PEG, whereas the shell layers in PLA-PCB nanoparticles are homogenous because of the strong hydrophilicity of the zwitterionic PCB polymer block.

Effect of elimination on antifouling and pH-responsive properties of carboxybetaine materials

α- and β-substituted methyl carboxybetaine materials are developed to investigate the occurrence of elimination in the ethylene intercharge arm in a harsh basic solution.

Bottom-up fabrication of zwitterionic polymer brushes on intraocular lens for improved biocompatibility

Intraocular lens (IOL) is an efficient implantable device commonly used for treating cataracts. However, bioadhesion of bacteria or residual lens epithelial cells on the IOL surface after surgery causes postoperative complications, such as endophthalmitis or posterior capsular opacification, and leads to loss of sight again. In the present study, zwitterionic polymer brushes were fabricated on the IOL surface via bottom-up grafting procedure. The attenuated total reflection-Fourier transform infrared and contact angle measurements indicated successful surface modification, as well as excellent hydrophilicity. The coating of hydrophilic zwitterionic polymer effectively decreased the bioadhesion of lens epithelial cells or bacteria. In vivo intraocular implantation results showed good in vivo biocompatibility of zwitterionic IOL and its effectiveness against postoperative complications.

Antibacterial Adhesion of Poly(methyl methacrylate) Modified by Borneol Acrylate

Poly(methyl methacrylate) (PMMA) is a widely used biomaterial. But there is still a challenge facing its unwanted bacterial adhesion because the subsequent biofilm formation usually leads to failure of related implants. Herein, we present a borneol-modified PMMA based on a facile and effective stereochemical strategy, generating antibacterial copolymer named as P(MMA-co-BA). It was synthesized by free radical polymerization and studied with different ratio between methyl methacrylate (MMA) and borneol acrylate (BA) monomers. NMR, GPC, and EA, etc., were used to confirm their chemical features. Their films were challenged with Escherichia coli (Gram-negative) and Bacillus subtilis (Gram-positive), showing a BA content dependent antibacterial performance. The minimum effective dose should be 10%. Then in vivo subcutaneous implantations in mice demonstrated their biocompatibilities through routine histotomy and HE staining. Therefore, P(MMA-co-BA)s not only exhibited their unique antibacterial character but also suggested a potential for the safe usage of borneol-modified PMMA frame and devices for further implantation.

Antifouling Electrospun Nanofiber Mats Functionalized with Polymer Zwitterions

In this study, we exploit the excellent fouling resistance of polymer zwitterions and present electrospun nanofiber mats surface functionalized with poly(2-methacryloyloxyethyl phosphorylcholine) (polyMPC). This zwitterionic polymer coating maximizes the accessibility of the zwitterion to effectively limit biofouling on nanofiber membranes. Two facile, scalable methods yielded a coating on cellulose nanofibers: (i) a two-step sequential deposition featuring dopamine polymerization followed by the physioadsorption of polyMPC, and (ii) a one-step codeposition of polydopamine (PDA) with polyMPC. While the sequential and codeposited nanofiber mat assemblies have an equivalent average fiber diameter, hydrophilic contact angle, surface chemistry, and stability, the topography of nanofibers prepared by codeposition were smoother. Protein and microbial antifouling performance of the zwitterion modified nanofiber mats along with two controls, cellulose (unmodified) and PDA coated nanofiber mats were evaluated by dynamic protein fouling and prolonged bacterial exposure. Following 21 days of exposure to bovine serum albumin, the sequential nanofiber mats significantly resisted protein fouling, as indicated by their 95% flux recovery ratio in a water flux experiment, a 300% improvement over the cellulose nanofiber mats. When challenged with two model microbes Escherichia coli and Staphylococcus aureus for 24 h, both zwitterion modifications demonstrated superior fouling resistance by statistically reducing microbial attachment over the two controls. This study demonstrates that, by decorating the surfaces of chemically and mechanically robust cellulose nanofiber mats with polyMPC, we can generate high performance, free-standing nanofiber mats that hold potential in applications where antifouling materials are imperative, such as tissue engineering scaffolds and water purification technologies.

Functionalization of Polydopamine via the Aza-Michael Reaction for Antimicrobial Interfaces

Polydopamine (pDA) coatings afford tremendous versatility due to their capabilities to provide substrate-independent functionalization with a wide range of amine- and thiol-containing molecules. In this work, we developed a new and facile conjugation approach to the formation of β-amino carbonyl linkages between pDA and acrylate/acrylamide molecules via the aza-Michael reaction. Sulfobetaine acrylamide (SBAA), sulfobetaine methacrylate (SBMA), and poly(ethylene glycol) methacrylate (PEGMA) were employed to graft onto pDA films, giving rise to formation of antifouling coatings. Because of the universal adhesive property of pDA, the coating strategy was applied to different substrates, including TiO2, gold, SiO2, Nitinol alloy, polystyrene, and poly(dimethylsiloxane). The variation of surface chemistry and surface wettability upon pDA modification and subsequent conjugation was monitored with X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. Antifouling properties of coatings were challenged by three common Gram-negative and Gram-positive bacteria. Cytocompatibility of the coatings with NIH-3T3 fibroblasts was accessed using MTT assay. The results showed that pDA coatings grafted with SBAA exhibited superhydrophilicity and excellent fouling resistance likely due to the high chemical reactivity of acrylamide, leading to high grafting density. In addition, dual functional coatings containing passive and active antibacterial components were constructed through the in situ deposition of antimicrobial agent, silver nanoparticles, in pDA, followed by the grafting of SBAA for bacterial repellence. The composite coatings allowed reducing adsorption of E. coli by >95%, while killing attached bacteria by up to 98% upon the releasing of Ag(+) ions as measured by inductively coupled plasma mass spectrometry. Consequently, this work paves a new avenue to the grafting strategy to engineer pDA and to the functional bioinspired antifouling interfaces in a substrate-independent fashion.

Surface modification with zwitterionic cysteine betaine for nanoshell-assisted near-infrared plasmonic hyperthermia

Nanoparticles decorated with biocompatible coatings have received considerable attention in recent years for their potential biomedical applications. However, the desirable properties of nanoparticles for in vivo uses, such as colloidal stability, biodistribution, and pharmacokinetics, require further research. In this work, we report a bio-derived zwitterionic surface ligand, cysteine betaine (Cys-b) for the modification of hollow gold-silver nanoshells, giving rise to hyperthermia applications. Cys-b coatings on planar substrates and nanoshells were compared to conventional (11-mercaptoundecyl)tri(ethylene glycol) (OEG-thiol) to investigate their effects on the fouling resistance, colloidal stability, environmental tolerance, and photothermal properties. The results found that Cys-b and OEG-thiol coatings exhibited comparable antifouling properties against bacteria of gram-negative Pseudomonas aeruginosa (P. aeruginosa) and gram-positive Staphylococcus epidermidis (S. epidermidis), NIH-3T3 fibroblasts, and bovine serum albumin. However, when the modified nanoshells were suspended at a temperature of 50°C in aqueous 3M NaCl solutions, shifts in the extinction maximum of the OEG-capped nanoshells with time were observed, while the corresponding spectra of nanoshells capped with Cys-b generally remained unchanged. In addition, when the nanoshells were continuously exposed to NIR irradiation, the temperature of the solution containing nanoshells capped with Cys-b increased to a plateau of 54°C, while that of the OEG-capped nanoshells gradually decreased after reaching a peak temperature. Accordingly, the Cys-b nanoshells were conjugated with anti-HER2 antibodies for targeted delivery to HER2-positive MDA-MB-453 breast cancer cells for hyperthermia treatment. The results showed the selective delivery and effective photothermal cell ablation with the antibody-conjugated Cys-b nanoshells. Therefore, this work demonstrated the promise of bio-derived zwitterionic Cys-b as a stable and biocompatible surface coating for materials in nanomedicine.

Recent advances in cytokine detection by immunosensing

The detection of cytokines in body fluids, cells, tissues and organisms continues to attract considerable attention due to the importance of these key cell signaling molecules in biology and medicine. In this review, we describe recent advances in cytokine detection in the course of ongoing pursuit of new analytical approaches for these trace analytes with specific focus on immunosensing. We discuss recent elegant designs of sensing interface with improved performance with respect to sensitivity, selectivity, stability, simplicity, and the absence of sample matrix effects. Various immunosensing approaches based on multifunctional nanomaterials open novel opportunities for ultrasensitive detection of cytokines in body fluids in vitro and in vivo. Methodologies such as suspension arrays also known as bead assays together with optical fiber-based sensors, on their own or in combination with microfluidic devices will continue to have an important role to address the grand challenge of real-time in vivo multiplex cytokine detection.

Zwitterionic nanocomposite hydrogels as effective wound dressings

Zwitterionic poly(sulfobetaine acrylamide) (pSBAA) nanocomposite hydrogels were synthesized and implemented as effective chronic wound dressings.