PEG molecular net-cloth grafted on polymeric substrates and its bio-merits

Covalently Attaching Hollow Silica Nanoparticles on a COC Surface for the Fabrication of a Three-Dimensional Protein Microarray

Compared to traditional two-dimensional (2D) biochips, three-dimensional (3D) biochips exhibit the advantages of higher probe density and detection sensitivity due to their designable surface microstructure as well as enlarged surface area. In the study, we proposed an approach to prepare a 3D protein chip by deposition of a monolayer of functionalized hollow silica nanoparticles (HSNs) on an activated cyclic olefin copolymer (COC) substrate. First, the COC substrate was chemically modified through the photografting technique to tether poly[3-(trimethoxysilyl) propyl methacrylate] (PTMSPMA) brushes on it. Then, a monolayer of HSNs was deposited on the modified COC and covalently attached via a condensation reaction between the hydrolyzed pendant siloxane groups of PTMSPMA and the Si-OH groups of HSNs. The roughness of the COC substrate significantly increased to 50.3 nm after depositing a monolayer of HSNs (ranging from 100 to 700 nm), while it only caused a negligible reduction in the light transmittance of COC. The HSN-modified COC was further functionalized with epoxide groups by a silane coupling agent for binding proteins. Immunoglobulin G could be effectively immobilized on this substrate with the highest immobilization efficiency of 75.2% and a maximum immobilization density of 1.236 μg/cm², while the highest immobilization efficiency on a 2D epoxide group-modified glass slide was only 57.4%. Moreover, immunoassay results confirmed a competitive limit of detection (LOD) (1.06 ng/mL) and a linear detection range (1-100 ng/mL) of the 3D protein chip. This facile and effective approach for fabricating nanoparticle-based 3D protein microarrays has great potential in the field of biorelated detection.

Visible light-induced controlled surface grafting polymerization of hydroxyethyl methacrylate from isopropylthioxanthone semipinacol-terminated organic monolayers

Reaction scheme of the visible light-induced controlled surface grafting polymerization of methacrylate monomers onto organosilane-coated silicon initiated by previously coupled dormant ITXSP groups.

Antibacterial hydrogel coating: Strategies in surface chemistry

Hydrogels have emerged as promising antimicrobial materials due to their unique three-dimensional structure, which provides sufficient capacity to accommodate various materials, including small molecules, polymers and particles. Coating substrates with antibacterial hydrogel layers has been recognized as an effective strategy to combat bacterial colonization. To prevent possible delamination of hydrogel coatings from substrates, it is crucial to attach hydrogel layers via stronger links, such as covalent bonds. To date, various surface chemical strategies have been developed to introduce hydrogel coatings on different substrates. In this review, we first give a brief introduction of the major strategies for designing antibacterial coatings. Then, we summarize the chemical methods used to fix the antibacterial hydrogel layer on the substrate, which include surface-initiated graft crosslinking polymerization, anchoring the hydrogel layer on the surface during crosslinking, and chemical crosslinking of layer-by-layer coating. The reaction mechanisms of each method and matched pretreatment strategies are systemically documented with the aim of introducing available protocols to researchers in related fields for designing hydrogel-coated antibacterial surfaces.

Facile fabrication of shell crosslinked microcapsule by visible light induced graft polymerization for enzyme encapsulation

A strategy to encapsulate enzymes into microcapsule fabricated by visible light-induced graft polymerization using CaCO₃microparticles as template was developed.

Layered Co-Immobilization of β-Glucosidase and Cellulase on Polymer Film by Visible-Light-Induced Graft Polymerization

Exploring a suitable immobilization strategy to improve catalytic efficiency and reusability of cellulase is of great importance to lowering the cost and promoting the industrialization of cellulose-derived bioethanol. In this work, a layered structure with a thin PEG hydrogel as the inner layer and sodium polyacrylate (PAANa) brush as the outer layer was fabricated on low density polyethylene (LDPE) film by visible-light-induced graft polymerization. Two enzymes, β-glucosidase (BG) and cellulase, were separately coimmobilized onto this hierarchical film. As supplementary to cellulase for improving catalytic efficiency, BG was in situ entrapped into the inner PEG hydrogel layer during the graft polymerization from the LDPE surface. After graft polymerization of sodium acrylate on the PEG hydrogel layer was reinitiated, cellulase was covalently attached on the outer PAANa brush layer. Owing to the mild reaction condition (visible-light irradiation and room temperature), the immobilized BG could retain a high activity after the graft polymerization. The immobilization did not alter the optimal pH and temperature of BG or the optimal temperature of cellulase. However, the optimal pH of cellulase shifts to 5.0 after immobilization. Compared with the original activity of single cellulase system and isolated BG/cellulase immobilization system, the dual-enzyme system exhibited 82% and 20% increase in catalytic activity, respectively. The dual-enzyme system could maintain 93% of carboxymethylcellulose sodium salt (CMC) activity after repeating 10 cycles of hydrolysis and 89% of filter paper activity after 6 cycles relative to original activity, exhibiting excellent reusability. This layer coimmobilization system of BG and cellulase on the polymer film displays tremendous potential for practical application in a biorefinery.

Enzymatically cross-linked hydrogels based on a linear poly(ethylene glycol) analogue for controlled protein release and 3D cell culture

Injectable and enzyme-mediated cross-linked hydrogels are promising biomedical materials. However, although poly(ethylene glycol) (PEG) is a popular basic component of synthetic hydrogels, only a few PEG-based enzymatically cross-linked hydrogels have been developed based on branched PEG. Compared with branched PEG, linear PEGs with different molecular weights are readily available and low-cost, while the poor capacity for post-polymerization modifications of linear PEG limited its application on a greater scale. Herein, a linear PEG-based analogue functionalized with multiple phenolic hydroxyl moieties, PEGDA-DTT-HPA, was designed and synthesized via Michael-type polyaddition combined with Steglich esterification. Environmentally friendly hydrogels composed of PEGDA-DTT-HPA were facilely formed under the catalysis of horseradish peroxidase (HRP) in the presence of hydrogen peroxide (H₂O₂). The gelation time and mechanical strengths of hydrogels were found to be adjusted independently by altering the concentrations of HRP and H₂O₂, respectively. The hydrogels were further demonstrated as protein drug and cell carriers using bovine serum albumin (BSA) and lentivirus-mediated LifeAct-EGFP overexpressed human mesenchymal stem cells (hMSCs-LifeAct-EGFP), respectively. The BSA-loaded hydrogel systems exhibited a sustained drug release over 3 weeks; the encapsulated hMSCs showed good viability over all time points assessed. Consequently, the current study opens new avenues for the design of PEG-based injectable hydrogels and the PEGDA-DTT-HPA hydrogel has great potential for applications in drug delivery, 3D cell culture and tissue regeneration.

Cytocompatible Fabrication of Yeast Cells/Fabrics Composite Sheet for Bioethanol Production

Entrapment of living cells into a polymer network has significant potential in various fields such as biomass conversion and tissue engineering. A crucial challenge for this strategy is to provide a mild enough condition to preserve cell viability. Here, a facile and cytocompatible method to entrap living yeast cells into a poly(ethylene glycol) (PEG) network grafting from polypropylene nonwoven fabrics via visible-light-induced surface living graft crosslinking polymerization is reported. Due to the mild reaction conditions and excellent biocompatibility of PEG, the immobilized yeast cells could maintain their viability and proliferate well. The obtained composite sheet has excellent long-term stability and shows no significant efficiency loss after 25 cycles of repeated batch bioethanol fermentation. The immobilized yeast cells exhibit 18.0% higher bioethanol fermentation efficiency than free cells. This strategy for immobilization of living cells with high viability has significant potential application.

Separated Immobilization of Incompatible Enzymes on Polymer Substrate via Visible Light Induced Living Photografting Polymerization

The use of the mixed catalytic system with several enzymes can provide multiple benefits in terms of the cost, simplification of a multistep reaction, and effectiveness of complex chemical reactions. Although study of different enzyme coimmobilization systems has attracted increasing attention in recent years, separately immobilizing enzymes which can not coexist on one support is still one of the great challenges. In this paper, a simple and effective strategy was introduced to separately encapsulate incompatible trypsin and transglutaminase (TGase) into different poly(ethylene glycol) (PEG) network layer grafted on low-density polyethylene (LDPE) film via visible light induced living photografting polymerization. As a proof of concept, this dual-enzyme separately loaded film was used to catalyze the synthesis of a new target antitumor drug LTV-azacytidine. The final results demonstrated that this strategy could maintain higher activities of both enzymes than the mixed coimmobilization method. And the mass spectra analysis results demonstrated that LTV-azacytidine was successfully synthesized. We believe that this facile and mild separately immobilizing incompatible enzyme strategy has great application potential in the field of biocatalysis.

Strong Bioinspired Polymer Hydrogel with Tunable Stiffness and Toughness for Mimicking the Extracellular Matrix

Inspired by the delicate architecture of hyaline articular cartilage, we report on a biomimetic polymer hydrogel that incorporates strong intermolecular hydrogen bonding between urethane-urethane linkages as well as urethane-ester linkages. The resultant hydrogel, containing ≈75% water, can endure a compressive stress up to 56 MPa with a strain of 98%, and exhibit tunable compressive modulus (0.19-1.38 MPa), as well as toughness (3629-28290 J m^-2) within a wide range. The tensile strength and elastic modulus reach as high as 0.56 and 5.5 MPa, respectively. The high stiffness and toughness enable the gel to withstand cyclic compressive loadings without fracturing. Moreover, our hydrogel mimics the extracellular matrices of cartilage and bone tissues and provides biochemical and physical cues that support the three-dimensional proliferation of chondrocytes and osteogenic differentiation of preosteoblasts.

Net-Immobilization of β-glucosidase on Nonwoven Fabrics to Lower the Cost of "Cellulosic Ethanol" and Increase Cellulose Conversions

The main limitation preventing the use of enzymatic cellulosic ethanol in industrial production is its higher cost which is mainly due to the elevated price of β-glucosidase (BG). Herein, we report on a simple strategy for the in-situ encapsulation of BG for repeated cellulosic ethanol production. In this strategy, BG was net-immobilized into a poly(ethylene glycol) (PEG) net-cloth layer on a PP nonwoven fabric by way of the visible light-induced surface controlled/living graft cross-linking polymerization. The visible light and mild reaction conditions could ensure the activity retention of BG during immobilization, while the non-swelling uniform net-mesh formed by living cross-linking polymerization could prevent the leakage of BG effectively (at the immobilization rate of more than 98.6% and the leakage rate of only 0.4%). When the BG-loaded fabric was used in combination with free cellulase (CEL), the results of the catalytic reaction demonstrated that these BG-loaded fabrics could not only give a 40% increase in cellulose conversions but also be reused for more than fifteen batches without losing the activity. These BG-loaded fabrics with characteristics including easy separation, excellent operation stability, a low cost of the polymeric matrix and a simple fabrication process are particularly interesting for a future bio-fuel production strategy.

A Self-Folding Hydrogel In Vitro Model for Ductal Carcinoma

A significant challenge in oncology is the need to develop in vitro models that accurately mimic the complex microenvironment within and around normal and diseased tissues. Here, we describe a self-folding approach to create curved hydrogel microstructures that more accurately mimic the geometry of ducts and acini within the mammary glands, as compared to existing three-dimensional block-like models or flat dishes. The microstructures are composed of photopatterned bilayers of poly (ethylene glycol) diacrylate (PEGDA), a hydrogel widely used in tissue engineering. The PEGDA bilayers of dissimilar molecular weights spontaneously curve when released from the underlying substrate due to differential swelling ratios. The photopatterns can be altered via AutoCAD-designed photomasks so that a variety of ductal and acinar mimetic structures can be mass-produced. In addition, by co-polymerizing methacrylated gelatin (methagel) with PEGDA, microstructures with increased cell adherence are synthesized. Biocompatibility and versatility of our approach is highlighted by culturing either SUM159 cells, which were seeded postfabrication, or MDA-MB-231 cells, which were encapsulated in hydrogels; cell viability is verified over 9 and 15 days, respectively. We believe that self-folding processes and associated tubular, curved, and folded constructs like the ones demonstrated here can facilitate the design of more accurate in vitro models for investigating ductal carcinoma.

Synthesis and characterization of a library of in-situ curing, nonswelling ethoxylated polyol thiol-ene hydrogels for tailorable macromolecule delivery

A transesterfication reaction is used to synthesize tri-thiol-functionalized-ethoxylated polyols that are combined with polyethylene glycol diacrylates to form a biodegradable hydrogel library. Hydrogels display nonswelling equilibration and offer temporal control over material degradation and the release of biomolecules. The demonstrated in vitro biocompatibility makes this a versatile platform that can be used for local drug delivery to volume-constrained anatomical sites.

Synthesis of pH-responsive hydrogel thin films grafted on PCL substrates for protein delivery

A new visible light induced graft polymerization method was utilized to prepare pH-sensitive hydrogel layers covalently attached to polymer substrates for drug delivery.