Surface conjugation of zwitterionic polymers to inhibit cell adhesion and protein adsorption

Current status, challenges and prospects of antifouling materials for oncology applications

Targeted therapy has become crucial to modern translational science, offering a remedy to conventional drug delivery challenges. Conventional drug delivery systems encountered challenges related to solubility, prolonged release, and inadequate drug penetration at the target region, such as a tumor. Several formulations, such as liposomes, polymers, and dendrimers, have been successful in advancing to clinical trials with the goal of improving the drug's pharmacokinetics and biodistribution. Various stealth coatings, including hydrophilic polymers such as PEG, chitosan, and polyacrylamides, can form a protective layer over nanoparticles, preventing aggregation, opsonization, and immune system detection. As a result, they are classified under the Generally Recognized as Safe (GRAS) category. Serum, a biological sample, has a complex composition. Non-specific adsorption of chemicals onto an electrode can lead to fouling, impacting the sensitivity and accuracy of focused diagnostics and therapies. Various anti-fouling materials and procedures have been developed to minimize the impact of fouling on specific diagnoses and therapies, leading to significant advancements in recent decades. This study provides a detailed analysis of current methodologies using surface modifications that leverage the antifouling properties of polymers, peptides, proteins, and cell membranes for advanced targeted diagnostics and therapy in cancer treatment. In conclusion, we examine the significant obstacles encountered by present technologies and the possible avenues for future study and development.

Zwitterion mediated anti-protein adsorption on polypropylene mesh to reduce inflammation for efficient hernia repair

The effectiveness of polypropylene (PP) mesh is often compromised by severe inflammation. Engineering anti-inflammatory coatings has significant implications for PP mesh to repair unwanted hernias. Here, we presented a facile strategy to develop an anti-fouling coating consisting of zwitterionic poly(carboxybetaine methacrylate) (PCBMA), which could prohibit protein adsorption to endow PP mesh with anti-inflammatory efficacy. The incorporation of PCBMA coating had little impact on the raw features of PP mesh. While the modified mesh PCBMA-PP possessed noticeable hydrophilicity increase and surface charge reduction. The excellent lubricity and surface stability enabled PCBMA-PP to exhibit superior anti-fouling capacity, thus efficiently inhibiting the adsorption of proteins. In vivo experiments showed that incorporating the PCBMA layer could provide PP meshes with outstanding anti-inflammatory effects and tissue compatibility for repairing hernias.

Advances in surface modifications of the silicone breast implant and impact on its biocompatibility and biointegration

Silicone breast implants are commonly used for cosmetic and oncologic surgical indications owing to their inertness and being nontoxic. However, complications including capsular contracture and anaplastic large cell lymphoma have been associated with certain breast implant surfaces over time. Novel implant surfaces and modifications of existing ones can directly impact cell-surface interactions and enhance biocompatibility and integration. The extent of foreign body response induced by breast implants influence implant success and integration into the body. This review highlights recent advances in breast implant surface technologies including modifications of implant surface topography and chemistry and effects on protein adsorption, and cell adhesion. A comprehensive online literature search was performed for relevant articles using the following keywords silicone breast implants, foreign body response, cell adhesion, protein adsorption, and cell-surface interaction. Properties of silicone breast implants impacting cell-material interactions including surface roughness, wettability, and stiffness, are discussed. Recent studies highlighting both silicone implant surface activation strategies and modifications to enhance biocompatibility in order to prevent capsular contracture formation and development of anaplastic large cell lymphoma are presented. Overall, breast implant surface modifications are being extensively investigated in order to improve implant biocompatibility to cater for increased demand for both cosmetic and oncologic surgeries.

Impact of Membrane Modification and Surface Immobilization Techniques on the Hemocompatibility of Hemodialysis Membranes: A Critical Review

Despite significant research efforts, hemodialysis patients have poor survival rates and low quality of life. Ultrafiltration (UF) membranes are the core of hemodialysis treatment, acting as a barrier for metabolic waste removal and supplying vital nutrients. So, developing a durable and suitable membrane that may be employed for therapeutic purposes is crucial. Surface modificationis a useful solution to boostmembrane characteristics like roughness, charge neutrality, wettability, hemocompatibility, and functionality, which are important in dialysis efficiency. The modification techniques can be classified as follows: (i) physical modification techniques (thermal treatment, polishing and grinding, blending, and coating), (ii) chemical modification (chemical methods, ozone treatment, ultraviolet-induced grafting, plasma treatment, high energy radiation, and enzymatic treatment); and (iii) combination methods (physicochemical). Despite the fact that each strategy has its own set of benefits and drawbacks, all of these methods yielded noteworthy outcomes, even if quantifying the enhanced performance is difficult. A hemodialysis membrane with outstanding hydrophilicity and hemocompatibility can be achieved by employing the right surface modification and immobilization technique. Modified membranes pave the way for more advancement in hemodialysis membrane hemocompatibility. Therefore, this critical review focused on the impact of the modification method used on the hemocompatibility of dialysis membranes while covering some possible modifications and basic research beyond clinical applications.

Polycarboxybetaine-Based Hydrogels for the Capture and Release of Circulating Tumor Cells

Circulating tumor cells (CTCs) are indicators for the detection, diagnosis, and monitoring of cancers and offer biological information for the development of personalized medicine. Techniques for the specific capture and non-destructive release of CTCs from millions of blood cells remain highly desirable. Here, we present a CTC capture-and-release system using a disulfide-containing poly(carboxybetaine methacrylate) (pCB) hydrogel. The non-fouling characteristic of pCB prevents unwanted, nonspecific cell binding, while the carboxyl functionality of pCB is used for the conjugation of anti-epithelial cell adhesion molecule (anti-EpCAM) antibodies for the capture of CTCs. The results demonstrated that the anti-EpCAM-conjugated pCB hydrogel captured HCT116 cells from blood, and the capture ratio reached 45%. Furthermore, the captured HCT116 cells were released within 30 min from the dissolution of the pCB hydrogel by adding cysteine, which breaks the disulfide bonds of the crosslinkers. The cells released were viable and able to grow. Our system has potential in the development of a device for CTC diagnosis.

Fabrication of Low-Fouling Surfaces on Alkyne-Functionalized Poly-(p-xylylenes) Using Click Chemistry

A facial, versatile, and universal method that breaks the substrate limits is desirable for antifouling treatment. Thin films of functional poly-p-xylylenes (PPX) that are deposited using chemical vapor deposition (CVD) provide a powerful platform for surface immobilization of molecules. In this study, we prepared an alkyne-functionalized PPX coating on which poly (sulfobetaine methacrylate-co-Az) could be conjugated via click chemistry. We found that the conjugated polymers were very stable and inhibited cell adhesion and protein adsorption effectively. The same conjugation strategy could also be applied to conjugate azide-containing poly (ethylene glycol) and poly (NIPAAm). The results indicate that our method provides a simple and robust tool for fabricating antifouling surfaces on a wide range of substrates using CVD technology of functionalized poly (p-xylylenes) for biosensor, diagnostics, immunoassay, and other biomaterial applications.

Coupled Monte Carlo and Molecular Dynamics Simulations on Interfacial Properties of Antifouling Polymer Membranes

We use molecular simulation to study the wetting behavior of antifouling polymer-tethered membranes. We obtain the interfacial properties (e.g., contact angle) of water at various temperatures for five polymer membranes, including a base polysulfone (PSF) membrane and four other PSF membranes grafted with antifouling polymers (two poly(ethylene glycol) (PEG) tethers and two zwitterionic tethers). We implement a coupled Monte Carlo (MC)/molecular dynamics (MD) approach to determine the interface potentials of water on the membrane surfaces in an efficient manner. Within this method, short MC and MD simulations are performed in cycles to collect the surface excess free energy of a thin water film on polymer membrane surfaces. Simulation results show that the grafting of zwitterionic tethers provides a more significant enhancement in the hydrophilicity of the PSF membrane than that of the PEG tethers. Water completely wets the surface of zwitterionic polymer membranes.

Surface modifications to enhance osseointegration-Resulting material properties and biological responses

As life expectancy and the age of the general population increases so does the need for improved implants. A major contributor to the failure of implants is poor osseointegration, which is typically described as the direct connection between bone and implant. This leads to unnecessary complications and an increased burden on the patient population. Modification of the implant surfaces through novel techniques, such as varying topography and/or applying coatings, has become a popular method to enhance the osseointegration capability of implants. Recent research has shown that particular surface features influence how bone cells interact with a material; however, it is unknown which exact features achieve optimal bone integration. In this review, current methods of modifying surfaces will be highlighted, and the resulting surface characteristics and biological responses are discussed. Review of the current strategies of surface modifications found that many coating types are more advantageous when used in combination; however, finding a surface modification that utilizes the mutual beneficial effects of important surface characteristics while still maintaining commercial viability is where future challenges exist.

Conjugation of Polysulfobetaine via Poly(pyrogallol) Coatings for Improving the Antifouling Efficacy of Biomaterials

Antifouling treatment is critical to certain biomedical devices for their functions and patients' life. Facial, versatile, and universal coating methods to conjugate antifouling materials on a wide variety of biomaterials are beneficial for the fabrication of low-fouling biomedical devices. We developed a simple one-step coating method for surface conjugation of zwitterionic poly(sulfobetaine) via deposition of self-polymerized pyrogallol (PG). Poly(pyrogallol) could deposit copolymers of sulfobetaine methacrylate and aminoethyl methacrylate (pSBAE) on various biomaterials. pSBAE coatings inhibited as high as 99.8% of the adhesion of L929 cells and reduced protein adsorption significantly. The resistance against L929 cell adhesion was increased with increasing coating time and was positively correlated with the surface hydrophilicity and film thickness. Such a coating was robust to resist harsh sterilization conditions and stable for long-term storage in phosphate-buffered saline. We expect that the simple low-fouling pSBAE coating is applicable to the manufacture of medical devices.

Antifouling Surfaces Enabled by Surface Grafting of Highly Hydrophilic Sulfoxide Polymer Brushes

Antifouling surfaces are important in a broad range of applications. An effective approach to antifouling surfaces is to covalently attach antifouling polymer brushes. This work reports the synthesis of a new class of antifouling polymer brushes based on highly hydrophilic sulfoxide polymers by surface-initiated photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. The sulfoxide polymer brushes are able to effectively reduce nonspecific adsorption of proteins and cells, demonstrating remarkable antifouling properties. Given the outstanding antifouling behavior of the sulfoxide polymers and versatility of surface-initiated PET-RAFT technology, this work presents a useful and general approach to engineering various material surfaces with antifouling properties, for potential biomedical applications in areas such as tissue engineering, medical implants, and regenerative medicine.

Interface of Phospholipid Polymer Grafting Layers to Analyze Functions of Immobilized Oligopeptides Involved in Cell Adhesion

The aim of this study was to design a material surface for use in the analysis of the behavior of biomolecules at the interface of direct cell contact. A superhydrophilic surface was prepared with poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), which was grafted onto a substrate with controlled polymer chain density. An arginine-glycine-aspartic acid (RGD) peptide was immobilized at the surface of the polymer graft surface (PMPC-RGD surface). Initial adhesion of the cells to this substrate was observed. The PMPC-RGD surface could enable cell adhesion only through RGD peptide-integrin interactions. The density and movability of the RGD peptide at the terminal of the graft PMPC chain and the orientation of the RGD peptide affected the density of adherent cells. Thus, the PMPC graft surface may be a good candidate for a new platform with the ability to immobilize biomolecules to a defined position and enable accurate analysis of their effects on cells.

Zwitterionic Polymer Coating Suppresses Microglial Encapsulation to Neural Implants In Vitro and In Vivo

For brain computer interfaces (BCI), the immune response to implanted electrodes is a major biological cause of device failure. Bioactive coatings such as neural adhesion molecule L1 have been shown to improve the biocompatibility, but are difficult to handle or produce in batches. Here, a synthetic zwitterionic polymer coating, poly(sulfobetaine methacrylate) (PSBMA) is developed for neural implants with the goal of reducing the inflammatory host response. In tests in vitro, the zwitterionic coating inhibits protein adsorption and the attachment of fibroblasts and microglia, and remains stable for at least 4 weeks. In vivo two-photon microscopy on CX3CR1-GFP mice shows that the zwitterionic coating significantly suppresses the microglial encapsulation of neural microelectrodes over a 6 h observation period. Furthermore, the lower microglial encapsulation on zwitterionic polymer-coated microelectrodes is revealed to originate from a reduction in the size but not the number of microglial end feet. This work provides a facile method for coating neural implants with zwitterionic polymers and illustrates the initial interaction between microglia and coated surface at high temporal and spatial resolution.

Zwitterionic Unimolecular Micelles with pH and Temperature Response: Enhanced In Vivo Circulation Stability and Tumor Therapeutic Efficiency

Circulation stability in vivo and stimuli-responsiveness under a tumor microenvironment of the polymeric prodrug micellar drug delivery systems are very critical to improve the tumor therapeutic efficiency. In this study, a series of polyamidoamine (PAMAM)-graft-poly(2-(diethylamino) ethyl methacrylate) (PDEAEMA)-block-poly(betaine sulfonate) (PSBMA) (PDS) unimolecular micelles were prepared via atom transfer radical polymerization. PAMAM served as a hydrophobic core to load the drug, the PDMAEMA segment was a middle layer to provide both thermo- and pH-sensitivity, whereas the PSMBA shell layer was used to improve the stability of the unimolecular micelles. The PDS exhibited a spherical structure with the size of 10-20 nm at pH 7.4. PDS micelles had excellent stability to resist the large volume liquid dilution. Moreover, it exhibited excellent stability in a complex biological microenvironment because of a superhigh antiprotein adhesion capacity of the PSBMA shell layer compared with PAMAM micelles. Drug release studies confirmed that the DOX can remain in the PDS micelles at pH 7.4 and 37 °C, whereas it can rapidly be released when the pH decreases to 5.0 and/or the temperature increases to 40 °C. In vitro studies suggested that the PDS drug delivery system can effectivity induce apoptosis and inhibit the proliferation of cancer cells. In vivo studies suggested that the PDS micelles prolonged the circulation time, decreased the side effects, and increased the antitumor efficacy. Therefore, the prepared PDS micelles are a potential anticancer drug delivery carrier for cancer therapy.

Biologically Functional Ultrathin Films Made of Zwitterionic Block Copolymer Micelles

We report the preparation of ultrathin coatings of zwitterionic block copolymer micelles and a comparison of their protein adsorption, adhesiveness, and antibacterial properties. Zwitterionic block copolymer micelles were obtained through pH-induced self-assembly of poly[3-dimethyl(methacryloyloxyethyl)ammonium propanesulfonate- b-2-(diisopropylamino)ethyl methacrylate] (βPDMA- b-PDPA) at pH 7.5. βPDMA- b-PDPA micelles with zwitterionic βPDMA-corona and pH-responsive PDPA-core were then used as building blocks to prepare layer-by-layer (LbL) assembled multilayer films together with hyaluronic acid (HA), tannic acid (TA), or poly(sodium 4-styrenesulfonate) (PSS). Protein adsorption tests showed that 3-layer βPDMA- b-PDPA micelles/HA films were the most effective to reduce the adhesion of BSA, lysozyme, ferritin, and casein. In contrast, βPDMA- b-PDPA micelles/TA films were the most attractive surfaces for protein adsorption. Bacterial antiadhesive tests against a model Gram-negative bacterium, Escherichia coli, and a model Gram-positive bacterium, Staphylococcus aureus, were in good agreement with the protein adsorption properties of the films. The differences in the antiadhesive properties between these three different film systems are discussed within the context of chemical nature and the functional chemical groups of the polyanions, layer number, and surface morphology of the films. Multilayers were found to lose their antiadhesiveness in the long term. However, by taking advantage of the pH-responsive hydrophobic micellar cores, we show that an antibacterial agent could be loaded into the micelles and multilayers could exhibit antibacterial activity in the long term especially at moderately acidic conditions. In contrast to antiadhesive properties, no significant differences were recorded in the antibacterial properties between the different film types.

Blood-Compatible Surfaces with Phosphorylcholine-Based Polymers for Cardiovascular Medical Devices

For the acquisition of blood-compatible materials, various hydrophilic polymers for surface modification have been examined. Among them, polymers with a representative phospholipid polar group, the phosphorylcholine (PC) group, are a successful example. These polymers were designed from inspiration of the cell membrane surface and provide protein adsorption resistance even following contact with plasma. This important property is based on the unique hydration state of water molecules surrounding hydrated polymer; in other words, water molecules weakly interact with the polymers and maintain their favorable cluster structure through hydrogen bonding. These polymers are not only hydrophilic, but also electrically neutral, important characteristics which make hydrogen bonding with water molecules less likely to occur and avoid hydrophobic interactions. Phosphorylcholine groups and other zwitterionic structures are significant as hydrophilic functional groups meeting these important requirements. In this review, blood compatibility of a polymer having a PC group is introduced in relation to its hydration structure, followed by a description of the applications of this polymer to cardiovascular medical devices.

Sulfobetaine methacrylate hydrogel-coated anti-fouling surfaces for implantable biomedical devices

BACKGROUND

Zwitterionic molecules have been widely studied as coating materials for preparing anti-fouling surfaces because they possess strong hydration properties that can resist non-specific protein adsorption. Numerous studies on surface modification using zwitterionic molecules have been investigated, such as electrochemically mediated and photoinitiated radical polymerization. However, these methods have some limitations, including multi-step process, difficulties in producing thick and dense layers as well as the requirement of extra facilities. In this study, we report a novel zwitterionic hydrogel-coating method via Fenton reaction for the preparation of anti-fouling surfaces.

METHODS

Sulfobetaine methacrylate (SBMA) hydrogel was coated on polyurethane (PU) by polymerization of SBMA molecules via the Fenton reaction. The coated surfaces were characterized by the measurements of water contact angle, SEM and XPS. The anti-fouling properties of the modified surfaces were evaluated by reductions of fibrinogen absorption and cell (human dermal fibroblasts, hDFBs) adhesion.

RESULTS

SBMA hydrogel layers were coated on the PU substrates and these layers have a high affinity for water. The hydrogel coatings were highly stable for 7 days, without a significant change in surface wettability. Importantly, the hydrogel-coated PU substrates decrease 80% of surface-adsorbed fibrinogen and surface-attached hDFBs (compared with uncoated PU substrates), indicating the excellent anti-fouling activities of modified surfaces.

CONCLUSIONS

The hydrogel-coated PU surfaces prepared by Fenton reaction with anti-fouling properties could have potential uses for implantable biomedical devices.

Vapor deposition of polyionic nanocoatings for reduction of microglia adhesion

Polyionics have great potential in improving the performance of neural probes by regulating microglial response. With the shrinkage of microelectrode size and increase in device complexity, challenges arise during liquid-based synthesis of polyionic compounds on neural probes. Nanocoatings of polyionics, with highly crosslinked bulk structure and abundant ionic functional groups on the surface, were synthesized using a process combining chemical vapor deposition and free radical polymerization. Both conformal surface engineering of neural microelectrodes and facile tailoring of surface ionic composition was achieved using this single-step vapor-based method. Adhesion of microglia was reduced on all the polyionic modified surfaces after a seven-day in vitro test, and polyionics with mixed charges presented much lower microglial adhesion than surfaces with single charges. Laminin adsorption on polyionics with mixed charges was significantly reduced due to the surface electrical neutrality and the enhanced wettability. These findings provide valuable information towards the development of neural probes with enhanced biocompatibility and signal stability.

Development of Antifouling Hyperbranched Polyglycerol Layers on Hydroxyl Poly-p-xylylene Coatings

Antifouling surfaces that are resistant to protein adsorption and cell adhesion are desirable for many biomedical devices, such as diagnostic devices, biosensors, and implants. In this study, we developed an antifouling hyperbranched polyglycerol (hPG) surface on hydroxyl poly-p-xylylene (PPX-OH). PPX-OH was deposited via chemical vapor deposition (CVD), and an hPG film was then developed via the ring-opening reaction of glycidol. The hPG film greatly reduced the adhesion of L929 cells and platelets as well as protein adsorption. The addition of alkenyl groups in the hPG layer allows the conjugation of biomolecules, such as peptides and biotin, and elicits specific biological interactions. Since the CVD deposition of PPX-OH could be applied to most types of materials, our approach makes it possible to decorate an antifouling hPG film on most types of materials. Our method could be applied to biosensors, diagnostics, and biomedical devices in the future.

Zwitterionic sulfobetaine polymer-immobilized surface by simple tyrosinase-mediated grafting for enhanced antifouling property

Introducing antifouling property to biomaterial surfaces has been considered an effective method for preventing the failure of implanted devices. In order to achieve this, the immobilization of zwitterions on biomaterial surfaces has been proven to be an excellent way of improving anti-adhesive potency. In this study, poly(sulfobetaine-co-tyramine), a tyramine-conjugated sulfobetaine polymer, was synthesized and simply grafted onto the surface of polyurethane via a tyrosinase-mediated reaction. Surface characterization by water contact angle measurements, X-ray photoelectron spectroscopy and atomic force microscopy demonstrated that the zwitterionic polymer was successfully introduced onto the surface of polyurethane and remained stable for 7days. In vitro studies revealed that poly(sulfobetaine-co-tyramine)-coated surfaces dramatically reduced the adhesion of fibrinogen, platelets, fibroblasts, and S. aureus by over 90% in comparison with bare surfaces. These results proved that polyurethane surfaces grafted with poly(sulfobetaine-co-tyramine) via a tyrosinase-catalyzed reaction could be promising candidates for an implantable medical device with excellent bioinert abilities.

STATEMENT OF SIGNIFICANCE

Antifouling surface modification is one of the key strategy to prevent the thrombus formation or infection which occurs on the surface of biomaterial after transplantation. Although there are many methods to modify the surface have been reported, necessity of simple modification technique still exists to apply for practical applications. The purpose of this study is to modify the biomaterial's surface by simply immobilizing antifouling zwitterion polymer via enzyme tyrosinase-mediated reaction which could modify versatile substrates in mild aqueous condition within fast time period. After modification, pSBTA grafted surface becomes resistant to various biological factors including proteins, cells, and bacterias. This approach appears to be a promising method to impart antifouling property on biomaterial surfaces.

Protein Resistant Polymeric Biomaterials

Toward improving implantable medical devices as well as diagnostic performance, the development of polymeric biomaterials having resistance to proteins remains a priority. Herein, we highlight key strategies reported in the recent literature that have relied upon improvement of surface hydrophilicity via direct surface modification methods or with bulk modification using surface modifying additives (SMAs). These approaches have utilized a variety of techniques to incorporate the surface hydrophilization agent, including physisorption, hydrogel network formation, surface grafting, layer-by-layer (LbL) assembly and blending base polymers with SMAs. While poly(ethylene glycol) (PEG) remains the gold standard, new alternatives have emerged such as polyglycidols, poly(2-oxazoline)s (POx), polyzwitterions, and amphiphilic block copolymers. While these new strategies provide encouraging results, the need for improved correlation between in vitro and in vivo protein resistance is critical. This may be achieved by employing complex protein solutions as well as strides to enhance the sensitivity of protein adsorption measurements.

Biofunctionalization of surfaces using polyelectrolyte multilayers

Biomaterials play a central role in modern strategies in regenerative medicine and tissue engineering to restore the structure and function of damaged or dysfunctional tissue and to direct cellular behavior. Both biologically derived and synthetic materials have been extensively explored in this context. However, most materials when implanted into living tissue initiate a host response. Modern implant design therefore aims to improve implant integration while avoiding chronic inflammation and foreign body reactions, and thus loss of the intended implant function. Directing these processes requires an in-depth understanding of the immunological processes that take place at the interface between biomaterials and the host tissue. The physicochemical properties of biomaterial surfaces (charge, charge density, hydrophilicity, functional molecular domains, etc.) are decisive, as are their stiffness, roughness and topography. This review outlines specific strategies, using polyelectrolyte multilayers to modulate the interactions between biomaterial surfaces and biological systems. The described coatings have the potential to control the adhesion of proteins, bacteria and mammalian cells. They can be used to decrease the risk of bacterial infections occurring after implantation and to achieve better contact between biological tissue and implants. In summary, these results are important for further development and modification of surfaces from different medical implants.

Low-fouling and functional poly(carboxybetaine) coating via a photo-crosslinking process

Antifouling modification technology is developed for many biomedical applications such as blood-contact devices and biosensors.

Measuring the Surface-Surface Interactions Induced by Serum Proteins in a Physiological Environment

In this work, we applied total internal reflection microscopy (TIRM) to directly measure the interactions between three different kinds of macroscopic surfaces: namely bare polystyrene (PS) particle and bare silica surface (bare-PS/bare-silica), PS particle and silica surfaces both coated with bovine serum albumin (BSA) (BSA-PS/BSA-silica), and PS particle and silica surfaces both modified with polyethylene glycol (PEG) (PEG-PS/PEG-silica) polymers, in phosphate buffer solution (PBS) and fetal bovine serum (FBS). Our results showed that in PBS, all the bare-PS, BSA-PS, and PEG-PS particles were irreversibly deposited onto the bare silica surface or surfaces coated either with BSA or PEG. However, in FBS, the interaction potentials between the particle and surface exhibited both free-diffusing particle and stuck particle profiles. Dynamic light scattering (DLS) and elliposmeter measurements indicated that there was a layer of serum proteins adsorbed on the PS particle and silica surface. TIRM measurement revealed that such adsorbed serum proteins can mediate the surface-surface interactions by providing additional stabilization under certain conditions, but also promoting bridging effect between the two surfaces. The measured potential profile of the stuck particle in FBS thus was much wider than in PBS. These quantitative measurements provide insights that serum proteins adsorbed onto surfaces can regulate surface-surface interactions, thus leading to unique moving behavior and stability of colloidal particles in the serum environment.

Zwitterionic polymer brushes via dopamine-initiated ATRP from PET sheets for improving hemocompatible and antifouling properties

A low-fouling zwitterionic surface strategy has been proven to be promising and effective for repelling nonspecific adsorption of proteins, cells and bacteria, which may eventually induce adverse pathogenic problems such as thrombosis and infection. Herein, a multi-step process was developed by a combination of mussel-inspired chemistry and surface-initiated atom transfer radical polymerization (SI-ATRP) technique for improving hemocompatible and anti-biofouling properties. Polyethylene terephthalate (PET) sheets were first treated with dopamine, and then the bromoalkyl initiators were immobilized on the poly(dopamine) functionalized surfaces, followed by surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) of 2-(dimethylamino) ethyl methacrylate (DMAEMA) monomer. Subsequently, the resulting PET sheets were ring-opening reacted with 1,3-propiolactone (PL) and 1,3-propanesultone (PS) to afford polycarboxybetaine and polysulfobetaine brushes, respectively. Characterizations of the PET sheets were undertaken by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), atomic force microscope (AFM), water contact angle (WCA) measurements, and X-ray photoelectron spectroscopy (XPS) analysis, respectively. The conversion rates of PDMAEMA to polyzwitterions were evaluated by XPS analysis. The remained PDMAEMA(weak cationic) and formed zwitterions(neutral) would form a synergetic antifouling and antibacterial surface. Hemocompatible and anti-biofouling properties were evaluated by total adsorption of protein as well as the adhesion of platelet, cell and bacterium. Zwitterionic polymer brushes grafted PET sheets showed outstanding hemocompatibility featured on reduced platelet adhesion and repelled protein adsorption. Meanwhile, the grafted PET sheets exerted excellent anti-biofouling property characterized by the resisted adhesion of Escherichia coli and 3T3 cells. In summary, zwitterionic polymer brushed modified PET sheets have a great potential for biomedical applications.

Controlling cell adhesion using layer-by-layer approaches for biomedical applications

Controlling the adhesion of mammalian and bacterial cells at the interfaces between synthetic materials and biological environments is a real challenge in the biomedical fields such as tissue engineering, antibacterial coating, implantable biomaterials and biosensors. The surface properties of materials are known to profoundly influence the adhesion processes. To mediate the adhesion processes, polymeric coatings have been used to functionalize surfaces to introduce diverse physicochemical properties. The polyelectrolyte multilayer films built via the layer-by-layer (LbL) method, introduced by Moehwald, Decher, and Lvov 20years ago, has led to significant developments ranging from the fundamental understanding of cellular processes to controlling cell adhesion for biomedical applications. In this review, we focus our attention on the modification of surface physicochemical properties, using the LbL approach, to construct films which can either promote or inhibit mammalian/bacterial cell adhesion. We also discuss the emerging field of multifunctional surfaces capable of responding to specific cellular activity but being inert to the others.

Effective tumor-targeted delivery of etoposide using chitosan nanoparticles conjugated with folic acid and sulfobetaine methacrylate

FA–CS(VP-16)-g-PSBMA nanoparticles were synthesized and showed effective tumor-targeting properties and promising anti-tumor capacity in vivo.

Cell resistant zwitterionic polyelectrolyte coating promotes bacterial attachment: an adhesion contradiction

Polymers of various architectures with zwitterionic functionality have recently been shown to effectively suppress nonspecific fouling of surfaces by proteins and prokaryotic (bacteria) or eukaryotic (mammalian) cells as well as other microorganisms and environmental contaminants.

Measurements of long-range interactions between protein-functionalized surfaces by total internal reflection microscopy

Understanding the interaction between protein-functionalized surfaces is an important subject in a variety of protein-related processes, ranging from coatings for biomedical implants to targeted drug carriers and biosensors. In this work, utilizing a total internal reflection microscope (TIRM), we have directly measured the interactions between micron-sized particles decorated with three types of common proteins concanavalin A (ConA), bovine serum albumin (BSA), lysozyme (LYZ), and glass surface coated with soy proteins (SP). Our results show that the protein adsorption greatly affects the charge property of the surfaces, and the interactions between those protein-functionalized surfaces depend on solution pH values. At pH 7.5-10.0, all these three protein-functionalized particles are highly negatively charged, and they move freely above the negatively charged SP-functionalized surface. The net interaction between protein-functionalized surfaces captured by TIRM was found as a long-range, nonspecific double-layer repulsion. When pH was decreased to 5.0, both protein-functionalized surfaces became neutral and double-layer repulsion was greatly reduced, resulting in adhesion of all three protein-functionalized particles to the SP-functionalized surface due to the hydrophobic attraction. The situation is very different at pH = 4.0: BSA-decorated particles, which are highly charged, can move freely above the SP-functionalized surfaces, while ConA- and LYZ-decorated particles can only move restrictively in a limited range. Our results quantify these nonspecific kT-scale interactions between protein-functionalized surfaces, which will enable the design of surfaces for use in biomedical applications and study of biomolecular interactions.

Surface modification of intraocular lenses with hyaluronic acid and lysozyme for the prevention of endophthalmitis and posterior capsule opacification

Posterior capsule opacification is one of the complications of cataract surgery caused by the adhesion and reproduction of residual human lens epithelial cells (HLECs) on the posterior capsule.

Multifunctional REDV-conjugated zwitterionic polycarboxybetaine–polycaprolactone hybrid surfaces for enhanced antibacterial activity, anti-thrombogenicity and endothelial cell proliferation

Multifunctional PCL hybrid surfaces are developed by grafting of REDV–zwitterionic polycarboxybetaine conjugates via surface-initiated ATRP.

Conjugation of monocarboxybetaine molecules on amino-poly-p-xylylene films to reduce protein adsorption and cell adhesion

A surface that resists protein adsorption and cell adhesion is highly desirable for many biomedical applications such as blood-contact devices and biosensors. In this study, we fabricated a carboxybetaine-containing surface and evaluated its antifouling efficacy. First, an amine-containing substrate was created by chemical vapor deposition of 4-aminomethyl-p-xylylene-co-p-xylylene (Amino-PPX). Aldehyde-ended carboxybetaine molecules were synthesized and conjugated onto Amino-PPX. The carboxybetaine-PPX surface greatly reduced protein adsorption and cell adhesion. The attachment of L929 cells on the carboxybetaine-PPX surface was reduced by 87% compared to the cell adhesion on Amino-PPX. Furthermore, RGD peptides could be conjugated on carboxybetaine-PPX to mediate specific cell adhesion. In conclusion, we demonstrate that a surface decoration with monocarboxybetaine molecules is useful for antifouling applications.

Peptide-modified zwitterionic porous hydrogels for endothelial cell and vascular engineering

Hydrogels allow control of gel composition and mechanics, and permit incorporation of cells and a wide variety of molecules from nanoparticles to micromolecules. Peptide-linked hydrogels should tune the basic polymer into a more bioactive template to influence cellular activities. In this study, we first introduced the generation of 2D poly-(sulfobetaine methacrylate [SBMA]) hydrogel surfaces. By incorporating with functional peptide RGD and vascular endothelial growth factor-mimicking peptide KLTWQELYQLKYKG (QK) peptides, endothelial cells attached to the surface well and proliferated in a short-term culturing. However, the mechanical property, which plays a crucial role directing the cellular functions and supporting the structures, decreased when peptides graft onto hydrogels. Manipulating the mechanical property was thus necessary, and the most related factor was the monomer concentration. From our results, the higher amount of SBMA caused greater stiffness in hydrogels. Following the 2D surface studies, we fabricated 3D porous hydrogels for cell scaffolds by several methods. The salt/particle leaching method showed a more reliable way than gas-foaming method to fabricate homogeneous and open-interconnected pores within the hydrogel. Using the salt/particle leaching method, we can control the pore size before leaching. Morphology of endothelial cells within scaffolds was also investigated by scanning electron microscopy, and histological analysis was conducted in vitro and in vivo to test the biocompatibility of SB hydrogel and its potential as a therapeutic reagent for ischemic tissue repair in mice.

Modulation of the stemness and osteogenic differentiation of human mesenchymal stem cells by controlling RGD concentrations of poly(carboxybetaine) hydrogel

In vitro modulation of the differentiation status of mesenchymal stem cells (MSCs) is important for their application to regenerative medicine. We suggested that the morphology and differentiation states of MSCs could be modulated by controlling the cell affinity of a substrate. The objective of this study was to investigate the effects of surface bio-adhesive signals on self-renewal and osteogenic differentiation of MSCs using a low-fouling platform. Cell-resistant poly(carboxybetaine) hydrogel was conjugated with 5 μM or 5 mM of cell-adhesive arginine-glycine-aspartic acid (RGD) peptides in order to control the cells' affinity to the substrate. Human mesenchymal stem cells (hMSCs) were cultured on the RGD-modified poly(carboxybetaine) hydrogel and then the cells' states of stemness and osteogenic differentiation were evaluated using reverse-transcriptase polymerase chain reaction. The hMSCs formed three-dimensional spheroids on the 5 μM RGD substrate, while cells on the 5 mM RGD substrate exhibited spreading morphology. Furthermore, cells on the 5 μM RGD hydrogel maintained a better stemness phenotype, while the hMSCs on the 5 mM RGD hydrogel proliferated faster and underwent osteogenic differentiation. In conclusion, the stemness of hMSCs was best maintained on a low RGD surface, while osteogenic differentiation of hMSCs was enhanced on a high RGD surface.

Nanoscale engineering of low-fouling surfaces through polydopamine immobilisation of zwitterionic peptides

We report a versatile approach for the design of substrate-independent low-fouling surfaces via mussel-inspired immobilisation of zwitterionic peptides. Using mussel-inspired polydopamine (PDA) coatings, zwitterionic glutamic acid- and lysine-based peptides were immobilised on various substrates, including noble metals, metal oxides, polymers, and semiconductors. The variation of surface chemistry and surface wettability upon surface treatment was monitored with X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. Following peptide immobilisation, the surfaces became more hydrophilic due to the strong surface hydration compared with PDA-coated surfaces. The peptide-functionalised surfaces showed resistance to human blood serum adsorption and also effectively prevented the adhesion of gram-negative and gram-positive bacteria (i.e., Escherichia coli and Staphylococcus epidermidis) and mammalian cells (i.e., NIH 3T3 mouse embryonic fibroblast cells). The versatility of mussel-inspired chemistry combined with the unique biological nature and tunability of peptides allows for the design of low-fouling surfaces, making this a promising coating technique for various applications.