Poly(glycidyl methacrylate-co-2-hydroxyethyl methacrylate) Brushes as Peptide/Protein Microarray Substrate for Improving Protein Binding and Functionality

Quantitative Detection of Multiple Cardiovascular Biomarkers by an Antibody Microarray-Based Metal-Enhanced Fluorescence Assay

Accurate detection of multiple cardiovascular biomarkers is crucial for the timely screening of acute coronary syndrome (ACS) and differential diagnosis from acute aortic syndrome (AAS). Herein, an antibody microarray-based metal-enhanced fluorescence assay (AMMEFA) has been developed to quantitatively detect 7 cardiovascular biomarkers through the formation of a sandwich immunoassay on the poly(glycidyl methacrylate-co-2-hydroxyethyl methacrylate)-decorated GNR-modified slide (GNR@P(GMA-HEMA) slide). The AMMEFA exhibits high specificity and sensitivity, the linear ranges span 5 orders of magnitude, and the limits of detection (LODs) of cardiac troponin I (cTnI), heart-type fatty acid binding protein (H-FABP), C-reactive protein (CRP), copeptin, myoglobin, D-Dimer, and N-terminal pro-brain natriuretic peptide (NT-proBNP) reach 0.07, 0.2, 65.7, 0.6, 0.2, 8.3, and 0.3 pg mL-1, respectively. To demonstrate its practicability, the AMMEFA has been applied to quantitatively analyze 7 cardiovascular biomarkers in 140 clinical plasma samples. In addition, the expression levels of cardiovascular biomarkers were analyzed by the least absolute shrinkage and selector operator (LASSO) regression, and the area under receiver operator characteristic curves (AUCs) of healthy donors (HDs), ACS patients, and AAS patients are 0.99, 0.98, and 0.97, respectively.

Development of a peptide microarray-based metal-enhanced fluorescence assay for ultrasensitive detection of multiple matrix metalloproteinase activities by using a gold nanorod-polymer substrate

Matrix metalloproteinases (MMPs) are attractive biomarkers for cancer diagnosis and treatment, while it is still a challenge to precise analysis of MMP activities owing to their very low abundance in the biological samples, especially at the early stages of tumors. Herein, a peptide microarray-based metal-enhanced fluorescence assay (PMMEFA) is proposed to simultaneously detect MMP-1, -2, -3, -7, -9, and -13 activities. The assay involves immobilization of Förster resonance energy transfer dye pair decorated peptides (FRET-peptides) on a poly(glycidyl methacrylate-co-2-hydroxyethyl methacrylate) coated gold nanorod modified glass slide (GNR@P(GMA-HEMA)). To fabricate the GNR@P(GMA-HEMA) slide, GNRs are self-assembled onto an aminated glass slide, and a polymer brush (P(GMA-HEMA)) is grown through a surface-initiated atom transfer radical polymerization reaction (SI-ATRP). Upon the addition of MMPs, the FRET pairs are broken due to the specific cleavage of FRET-peptides by enzymes, resulting in the recovery of fluorescence signals and further enhancement by the MEF of GNRs. The fluorescence recovery degree provides a direct indicator for MMP activity. The PMMEFA exhibits excellent sensitivity, which enables to detect MMP-1, -2, -3, -7, -9, and -13 activities, with low limits of detection (LODs) of 1.7 fg mL-1, 0.3 fg mL-1, 2.0 fg mL-1, 1.8 fg mL-1, 2.2 fg mL-1 and 14.0 fg mL-1, respectively. To substantiate the practicability of PMMEFA, MMP activities were measured in a range of matrices, encompassing cell culture medium, serum, and tumor tissue homogenate, and MMP activities can be detected only in 0.15 μL serum and 0.025 mg tumor tissue.

Surface modification for improving immunoassay sensitivity

Immunoassays are widely performed in many fields such as biomarker discovery, proteomics, drug development, and clinical diagnosis. There is a growing need for high sensitivity of immunoassays to detect low abundance analytes. As a result, great effort has been made to improve the quality of surfaces, on which the immunoassay is performed. In this review article, we summarize the recent progress in surface modification strategies for improving the sensitivity of immunoassays. The surface modification strategies can be categorized into two groups: antifouling coatings to reduce background noise and nanostructured surfaces to amplify the signals. The first part of the review summarizes the common antifouling coating techniques to prevent nonspecific binding and reduce background noise. The techniques include hydrophilic polymer based self-assembled monomers, polymer brushes, and surface attached hydrogels, and omniphobicity based perfluorinated surfaces. In the second part, some common nanostructured surfaces to amplify the specific detection signals are introduced, including nanoparticle functionalized surfaces, two dimensional (2D) nanoarrays, and 2D nanomaterial coatings. The third part discusses the surface modification techniques for digital immunoassays. In the end, the challenges and the future perspectives of the surface modification techniques for immunoassays are presented.

Room-Temperature Self-Healable Blends of Waterborne Polyurethanes with 2-Hydroxyethyl Methacrylate-Based Polymers

The design of self-healing agents is a topic of important scientific interest for the development of high-performance materials for coating applications. Herein, two series of copolymers of 2-hydroxyethyl methacrylate (HEMA) with either the hydrophilic N,N-dimethylacrylamide (DMAM) or the epoxy group-bearing hydrophobic glycidyl methacrylate were synthesized and studied as potential self-healing agents of waterborne polyurethanes (WPU). The molar percentage of DMAM or GMA units in the P(HEMA-co-DMAMy) and P(HEMA-co-GMAy) copolymers varies from 0% up to 80%. WPU/polymer composites with a 10% w/w or 20% w/w copolymer content were prepared with the facile method of solution mixing. Thanks to the presence of P(HEMA-co-DMAMy) copolymers, WPU/P(HEMA-co-DMAMy) composite films exhibited surface hydrophilicity (water contact angle studies), and tendency for water uptake (water sorption kinetics studies). In contrast, the surfaces of the WPU/P(HEMA-co-GMAy) composites were less hydrophilic compared with the WPU/P(HEMA-co-DMAMy) ones. The room-temperature, water-mediated self-healing ability of these composites was investigated through addition of water drops on the damaged area. Both copolymer series exhibited healing abilities, with the hydrophilic P(HEMA-co-DMAMy) copolymers being more promising. This green healing procedure, in combination with the simple film fabrication process and simple healing triggering, makes these materials attractive for practical applications.

Profiling of Multiple Matrix Metalloproteinases Activities in the Progression of Osteosarcoma by Peptide Microarray-Based Fluorescence Assay on Polymer Brush-Coated Zinc Oxide Nanorod Substrate

Peptide microarray provides the ability to miniaturize, parallelize, and automate high-throughput screening substrate specificities of enzymes, profiling of multiple enzyme activities, discovery of disease biomarkers, and development of drugs. Matrix metalloproteinases (MMPs) are demonstrated as important biomarkers of tumor invasion and metastasis. Herein, a peptide microarray-based fluorescence assay is proposed to profile multiple MMPs (MMP-1, MMP-2, MMP-3, MMP-7, MMP-9, and MMP-13) activities in the culture medium of four human osteosarcoma (OS) cells and in the progression of OS by using the mouse-bearing xenograft OSs including U-2OS and Saos-2 human. This method has excellent selectivity and sensitivity, which enables to detect the activities of cellular secreted MMP-1, MMP-2, MMP-3, MMP-7, MMP-9, and MMP-13 with limit of detection downs to 10 pM, 30 pM, 113 pM, 13 pM, 93 pM, and 12 pM, respectively. Furthermore, it is demonstrated that the activity pattern of MMPs is serum closely relevant to the disease progression and type of tumor.

Development of a clinical microarray system for genetic analysis screening

Objectives

Research on the relationship between diseases and genes and the advancement of genetic analysis technologies have made genetic testing in medical care possible. There are various methods for genetic testing, including PCR-based methods and next-generation sequencing; however, screening tests in clinical laboratories are becoming more diverse; therefore, novel measurement systems and equipment are required to meet the needs of each situation. In this study, we aimed to develop a novel microarray-based genetic analysis system that uses a Peltier element to overcome the issues of conventional microarrays, such as the long measurement time and high cost.

Methods

We constructed a microarray system to detect the UDP-glucuronosyltransferase gene polymorphisms UGT1A1*6 and UGT1A1*28 in patients eligible for irinotecan hydrochloride treatment for use in clinical laboratories. To evaluate the performance of the system, the hybridization temperature and reaction time were determined, and the results were compared with those obtained using a conventional hybridization oven.

Results

The hybridization temperature reached its target in 1/27th of the time required by the conventional system. We assessed 111 human clinical samples and found that our results agreed with those obtained using existing methods. The total time for the newly developed device was reduced by 85 min compared to that for existing methods, as the automated DNA microarray eliminates the time that existing methods spend on manual operation.

Conclusions

The surface treatment technology used in our system enables high-density and strong DNA fixation, allowing the construction of a measurement system suitable for clinical applications.

Advances in design of polymer brush functionalized inorganic nanomaterials and their applications in biomedical arena

Grafting of polymer brush (assembly of polymer chains tethered to the substrate by one end) is emerging as one of the most viable approach to alter the surface of inorganic nanomaterials. Inorganic nanomaterials despite their intrinsic functional superiority, their applications remain restricted due to their incompatibility with organic or biological moieties vis-à-vis agglomeration issues. To overcome such a shortcoming, polymer brush modified surfaces of inorganic nanomaterials have lately proved to be of immense potential. For example, polymer brush-modified inorganic nanomaterials can act as efficient substrates/platforms in biomedical applications, ranging from drug-delivery to protein-array due to their integrated advantages such as amphiphilicity, stimuli responsiveness, enhanced biocompatibility, and so on. In this review, the current state of the art related to polymer brush-modified inorganic nanomaterials focusing, not only, on their synthetic strategies and applications in biomedical field but also the architectural influence of polymer brushes on the responsiveness properties of modified nanomaterials have comprehensively been discussed and its associated future perspective is also presented. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Manufacturing and Characterization of Modified Wood with In Situ Polymerization and Cross-Linking of Water-Soluble Monomers on Wood Cell Walls

Fast-growing plantation wood has poor dimensional stability and easily cracks, which limits its application. As wood modification can improve the dimensional stability, strength, and other properties of wood, it has been extensively used. In this study, 2-Hydroxyethyl methacrylate (HEMA) and glyoxal were applied to treat poplar wood (Populus euramevicana cv.I-214) by using vacuum pressure impregnation to improve its dimensional stability. The weight percentage gain (WPG), anti-swelling efficiency (ASE), water absorption rate (WAR), leachability (L), and other properties of modified wood were examined. Results showed that the modifier was diffused into the cell walls and intercellular space and reacted with the wood cell wall after heating to form a stable reticular structure polymer which effectively decreased the hydroxyl content in the wood and blocked the water movement channel; thus, further improving the physical performance of wood. These results were confirmed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR). When the ratio of the modifier was 80:20, the concentration of the modifier was 40%, and the curing temperature was 120 °C, the modified poplar had the best performance, which showed a low WAR (at its lowest 58.39%), a low L (at its lowest 10.44%), and a high ASE (of up to 77.94%).

The Bioanalytical and Biomedical Applications of Polymer Modified Substrates

Polymers with different structures and morphology have been extensively used to construct functionalized surfaces for a wide range of applications because the physicochemical properties of polymers can be finely adjusted by their molecular weights, polydispersity and configurations, as well as the chemical structures and natures of monomers. In particular, the specific functions of polymers can be easily achieved at post-synthesis by the attachment of different kinds of active molecules such as recognition ligand, peptides, aptamers and antibodies. In this review, the recent advances in the bioanalytical and biomedical applications of polymer modified substrates were summarized with subsections on functionalization using branched polymers, polymer brushes and polymer hydrogels. The review focuses on their applications as biosensors with excellent analytical performance and/or as nonfouling surfaces with efficient antibacterial activity. Finally, we discuss the perspectives and future directions of polymer modified substrates in the development of biodevices for the diagnosis, treatment and prevention of diseases.

A multifunctional nanoprobe for real-time SERS monitoring of invasion ability affected by photodynamic therapy

A multifunctional RhB-PLGM@CN nanoprobe was created, in which g-C3N4 played dual pivotal functions in photodynamic therapy (PDT) and monitoring of invasion-related MMP-9 by surface-enhanced Raman spectroscopy. Significantly, using this probe,...

Construction of a Degradation-Free DNA Conjugated Nanoprobe and Its Application in Rapid Field Screening for Sulfur Mustard

Sulfur mustard (SM) is a notorious blistering chemical warfare agent. Rapid field screening for trace SM is of vital significance for the detection of antiterrorism and timely treatment. Here, a visual assay for SM was constructed on the basis of its inhibition for the G-quadruplexes/hemin DNAzyme. Specifically, multiple guanine (G)-rich single stranded oligonucleotides (ssODN) named S1 (80% of G in the total bases), i.e., the precursor for G-quadruplex, which could oxide tetramethylbenzidine (TMB) to its green product, were conjugated on the nonfouling polymer brush grafted magnetic beads (MB@P(C-H)). SM could specifically alkylate the N7 and O6 sites of G in the S1; thus, it failed to form the DNAzyme based signal reporter. It was demonstrated that the nonfouling P(C-H) interface on the magnetic bead (MB) could protect the conjugated ssODN from nuclease degradation, thus ensuring its well sensing performance in complex samples. Under the optimized conditions, this method achieved good sensitivity and selectivity with a limit of detection (LOD) as low as 0.26 μmol L^-1, and the recoveries ranging from 86% to 117% were obtained for different SM spiked real samples. Above all, this method combining low cost and ready operation could be suited for rapid field SM screening in a wide range of environmental matrices.

Thermoresponsive Poly(N,N-diethylacrylamide-co-glycidyl methacrylate) Copolymers and Its Catalytically Active α-Chymotrypsin Bioconjugate with Enhanced Enzyme Stability

Responsive (smart, intelligent, adaptive) polymers have been widely explored for a variety of advanced applications in recent years. The thermoresponsive poly(N,N-diethylacrylamide) (PDEAAm), which has a better biocompatibility than the widely investigated poly(N,N-isopropylacrylamide), has gained increased interest in recent years. In this paper, the successful synthesis, characterization, and bioconjugation of a novel thermoresponsive copolymer, poly(N,N-diethylacrylamide-co-glycidyl methacrylate) (P(DEAAm-co-GMA)), obtained by free radical copolymerization with various comonomer contents and monomer/initiator ratios are reported. It was found that all the investigated copolymers possess LCST-type thermoresponsive behavior with small extent of hysteresis, and the critical solution temperatures (CST), i.e., the cloud and clearing points, decrease linearly with increasing GMA content of these copolymers. The P(DEAAm-co-GMA) copolymer with pendant epoxy groups was found to conjugate efficiently with α-chymotrypsin in a direct, one-step reaction, leading to enzyme-polymer nanoparticle (EPNP) with average size of 56.9 nm. This EPNP also shows reversible thermoresponsive behavior with somewhat higher critical solution temperature than that of the unreacted P(DEAAm-co-GMA). Although the catalytic activity of the enzyme-polymer nanoconjugate is lower than that of the native enzyme, the results of the enzyme activity investigations prove that the pH and thermal stability of the enzyme is significantly enhanced by conjugation the with P(DEAAm-co-GMA) copolymer.

Biosensors and bioassays for determination of matrix metalloproteinases: state of the art and recent advances

Matrix metalloproteinases (MMPs) are closely associated with various physiological and pathological processes, and have been regarded as potential biomarkers for severe diseases including cancer. Accurate determination of MMPs would advance our understanding of their roles in disease progression, and is of great significance for disease diagnosis, treatment and prognosis. In this review, we present a comprehensive overview of the developed bioassays/biosensors for detection of MMPs, and highlight the recent advancement in nanomaterial-based immunoassays for MMP abundance measurements and nanomaterial-based biosensors for MMP activity determination. Enzyme-linked immunosorbent assay (ELISA)-based immunoassays provide information about total levels of MMPs with high specificity and sensitivity, while target-based biosensors measure the amounts of active MMPs, and allow imaging of MMP activities in vivo. For multiplex and high-throughput analysis of MMPs, microfluidics and microarray-based assays are described. Additionally, we put forward the existing challenges and future prospects from our perspective.

Bifunctional polymer brush-grafted coronary stent for anticoagulation and endothelialization

At present, cardiovascular stent intervention faces clinical complications such as delayed endothelialization, late thrombosis and restenosis after implantation. In this work, a kind of bifunctional polymer brush-grafted coronary stent with anticoagulant and endothelial functions was developed. First, a block copolymer brush with zwitterionic structure consisting of sulfoethyl methacrylate (SBMA) and glycidyl methacrylate (GMA) was surface-induced grafted onto the surface of bare metal coronary stent by atom transfer radical polymerization. The diethylenetriamine NONOate (DETA NONOate), acted as nitric oxide (NO) donor to promote endothelialization, was then attached to polyglycidyl methacrylate (PGMA) brush by a reactive epoxy group to produce NO. The process of chemical modification and the release behavior of NO were characterized in detail. Moreover, the results of anticoagulant test, cytotoxicity test, endothelial cells (ECs) proliferation test and animal experiment of this bifunctional polymer brush-grafted coronary stent we proposed indicate that the zwitterion modified and NO supplied bifunctional coatings has good anticoagulant property, no cytotoxicity and significant endothelialization effect. This work opens the door to combine biological activity of NO and anticoagulant effect of zwitterions, which has great potential to address post-operative side effects associated with restenosis and late stent thrombosis.

Photografting and Patterning of Poly(ethylene glycol) Methacrylate Hydrogel on Glass for Biochip Applications

An efficient procedure for chemical initiator-free, in situ synthesis of a functional polyethylene glycol methacrylate (PEG MA) hydrogel on regular glass substrates is reported. It is demonstrated that self-initiated photografting and photopolymerization driven by UV irradiation can yield tens of nanometer-thick coatings of carboxy-functionalized PEG MA on the aldehyde-terminated borosilicate glass surface. The most efficient formulation for hydrogel synthesis contained methyl methacrylic acid (MAA), 2-hydroxyethyl methacrylate (HEMA), and PEG methacrylate (PEG₁₀MA) monomers (1:1:1). The resulting HEMA/PEG₁₀MA/MAA (HPMAA) coatings had a defined thickness in the range from 11 to 50 nm. The physicochemical properties of the synthesized HPMAA coatings were analyzed by combining water contact angle measurements, stylus profilometry, imaging null ellipsometry, and atomic force microscopy (AFM). The latter technique was employed in the quantitative imaging mode not only for direct probing of the surface topography but also for swelling behavior characterization in the pH range from 4.5 to 8.0. The estimated high swelling ratios of the HPMAA hydrogel (up to 3.2) together with its good stability and resistance to nonspecific protein binding were advantageous in extracellular matrix mimetics via patterning of fibronectin (FN) at a resolution close to 200 nm. It was shown that the fabricated FN micropatterns on HPMAA were equally suitable for single-cell arraying, as well as controlled cell culture lasting at least for 96 h.

In Pursuit of Zero 2.0: Recent Developments in Nonfouling Polymer Brushes for Immunoassays

"Nonfouling" polymer brush surfaces can greatly improve the performance of in vitro diagnostic (IVD) assays due to the reduction of nonspecific protein adsorption and consequent improvement of signal-to-noise ratios. The development of synthetic polymer brush architectures that suppress adventitious protein adsorption is reviewed, and their integration into surface plasmon resonance and fluorescent sandwich immunoassay formats is discussed. Also, highlighted is a novel, self-contained immunoassay platform (the D4 assay) that transforms time-consuming laboratory-based assays into a user-friendly and point-of-care format with a sensitivity and specificity comparable or better than standard enzyme-linked immunosorbent assay (ELISA) directly from unprocessed samples. These advancements clearly demonstrate the utility of nonfouling polymer brushes as a substrate for ultrasensitive and robust diagnostic assays that may be suitable for clinical testing, in field and laboratory settings.

Towards precision medicine: the role and potential of protein and peptide microarrays

Although the traditional strategy of developing general medical treatments for heterogeneous patient populations has a well-established track record, the acknowledgment that one-size-does-not-fit-all is pushing health-care to enter a new era of tailored interventions. The advent of precision medicine is fueled by the high-throughput analysis of individual DNA variants and mRNA expression profiles. However, due to the role of proteins in providing a more direct view of disease states than genomics alone, the ability to comprehensively analyze protein alterations and post translational modifications (PTMs) is a necessary step to unravel disease mechanisms, develop novel biomarkers and targeted therapies. Protein and peptide microarrays can play a major role in this frame, due to high-throughput, low sample consumption and wide applicability. Here, their current role and potentialities are discussed through the review of some promising applications in the fields of PTMs analysis, enzyme screening, high-content immune-profiling and the phenotyping of extracellular vesicles.

Proteome microarray technology and application: higher, wider, and deeper

Introduction: Protein microarray is a powerful tool for both biological study and clinical research. The most useful features of protein microarrays are their miniaturized size (low reagent and sample consumption), high sensitivity and their capability for parallel/high-throughput analysis. The major focus of this review is functional proteome microarray. Areas covered: For proteome microarray, this review will discuss some recently constructed proteome microarrays and new concepts that have been used for constructing proteome microarrays and data interpretation in past few years, such as PAGES, M-NAPPA strategy, VirD technology, and the first protein microarray database. this review will summarize recent proteomic scale applications and address the limitations and future directions of proteome microarray technology. Expert opinion: Proteome microarray is a powerful tool for basic biological and clinical research. It is expected to see improvements in the currently used proteome microarrays and the construction of more proteome microarrays for other species by using traditional strategies or novel concepts. It is anticipated that the maximum number of features on a single microarray and the number of possible applications will be increased, and the information that can be obtained from proteome microarray experiments will more in-depth in the future.

Polymer brush interfaces for protein biosensing prepared by surface-initiated controlled radical polymerization

This article discusses protein-binding polymer brushes and the various strategies that can be used to immobilize proteins on these films.

Performance Comparison of Three Chemical Vapor Deposited Aminosilanes in Peptide Synthesis: Effects of Silane on Peptide Stability and Purity

Silicon oxide substrates underwent gas-phase functionalization with various aminosilanes, and the resulting surfaces were evaluated for their suitability as a solid support for solid phase peptide synthesis (SPPS). APTES (3-aminopropyltriethoxysilane), APDEMS (3-aminopropyldiethoxymethylsilane), and APDIPES (3-aminopropyldiisopropylethoxysilane) were individually applied to thermal oxide-terminated silicon substrates via gas-phase deposition. Coated surfaces were characterized by spectroscopic ellipsometry (SE), contact angle goniometry, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and spectrophotometry. Model oligopeptides with 16 residues were synthesized on the amino surfaces, and the chemical stabilities of the resulting surfaces were evaluated against a stringent side chain deprotection (SCD) step, which contained trifluoroacetic acid (TFA) and trifluoromethanesulfonic acid (TFMSA). Functionalized surface thickness loss during SCD was most acute for APDIPES and the observed relative stability order was APTES > APDEMS > APDIPES. Amino surfaces were evaluated for compatibility with stepwise peptide synthesis where complete deprotection and coupling cycles are paramount. Model trimer syntheses indicated that routine capping of unreacted amines with acetic anhydride significantly increased purity as measured by MALDI-MS. An inverse correlation between the amine loading density and peptide purity was observed. In general, peptide purity was highest for the lowest amine density APDIPES surface.

Filter paper grafted with epoxide-based copolymer brushes for activation-free peptide nucleic acid conjugation and its application for colorimetric DNA detection

Epoxide-bearing filter paper was first prepared by surface-initiated reversible addition-fragmentation chain transfer (RAFT) copolymerization of glycidyl methacrylate (GMA) and poly(ethylene glycol)methacrylate (PEGMA). Without the need for activation step, the capture peptide nucleic acid (PNA) probes carrying a C-terminal lysine modification can be directly immobilized on the surface-grafted poly[glycidyl methacrylate-ran-poly(ethylene glycol)methacrylate] (P(GMA-ran-PEGMA)) through ring-opening of epoxide groups in the GMA repeating units by amino groups in the PNA's structure. The success of P(GMA-ran-PEGMA) grafting on the filter paper and subsequent PNA immobilization was confirmed by fluorescence microscopy, Fourier transform-infrared spectroscopy and X-ray photoelectron spectroscopy. Colorimetric detection with signal amplification upon DNA hybridization relies on sandwich-hybridization assay employing another biotinylated PNA strand as a reporter probe together with streptavidin-horseradish peroxidase conjugate (SA-HRP) and o-phenylenediamine (OPD) substrate. It was found that increasing ionic strength during the DNA hybridization step by addition of NaCl can increase the signal intensity, which can be visualized by naked eye. The sensing platform showed the best performance in preventing non-specific adsorption from the non-complementary DNA and discriminating between complementary and single-mismatched targets of at least 50 fmol without the requirement for stringent hybridization or washing condition. This superior ability to suppress non-specific adsorption of non-target DNA as well as other non-DNA components may be explained as a result of hydrophilic PEGMA repeating units in the surface-grafted copolymer.

Uncovering the Binding Specificities of Lectins with Cells for Precision Colorectal Cancer Diagnosis Based on Multimodal Imaging

There is a high desire for novel targets/biomarkers to diagnose and treat colorectal cancer (CRC). Here, an approach starting from a polyacrylamide hydrogel-based lectin microarray is presented to screen the high expression of glycans on the CRC cell surface and to identify new lectin biomarkers for CRC. Three common CRC cell lines (SW480, SW620, and HCT116) and one normal colon cell line (NCM460) are profiled on the microarray with 27 lectins. The experimental results reveal that CRC cells highly express the glycans with d-galactose, d-glucose, and/or sialic acid residues, and Uelx Europaeus Agglutinin-I (UEA-I) exhibits reasonable specificity with SW480 cells. After conjugation of UEA-I with silica-coated NaGdF4:Yb3+, Er3+@NaGdF4 upconversion nanoparticles, the follow-up in vitro and in vivo experiments provide further evidence on that UEA-I can serve as tumor-targeting molecule to diagnose SW480 tumor by multimodal imaging including upconversion luminescence imaging, T1-weighted magnetic resonance imaging, and X-ray computed tomography imaging.

Development of hierarchical Fe3O4 magnetic microspheres as solid substrates for high sensitive immunoassays

Improving the detection sensitivity of enzyme linked immunosorbent assay (ELISA) is of the utmost importance for meeting the demand of early disease diagnosis. In this work, a sensitive solid substrate for ELISA, i.e., hierarchical iron oxide magnetic microspheres, Fe₃O₄@mSiO₂@poly[poly(ethylene glycol) methacrylate-co-glycidyl methacrylate], was developed via a novel surface-initiated photoiniferter-mediated polymerization (SI-PIMP) strategy. The magnetic microspheres consist of a magnetic Fe₃O₄ core that gives a high magnetic response, a 3D backbone, a mesoporous SiO₂ middle layer, that facilitates microsphere stability and provides anchoring sites, and polymer brushes, that serve as an antifouling and oriented antibody immobilization layer. As a result, the as-prepared microspheres possess a high antibody loading capacity, an enhanced detection signal and a dramatically improved sensitivity, resulting in a 25-fold improvement over conventional ELISA solid substrates.

Ultrasensitive Detection of Metal Ions with DNA Nanostructure

In spite of its greatly scientific and technological importance, developing rapid, low cost and sensitive microarray sensors for onsite monitoring heavy metal contamination remains challenging. Here we develop a DNA nanostructured microarray (DNM) with a tubular three-dimensional sensing surface and an ordered nanotopography for rapid and sensitive multiplex detection of heavy metal ions. In our design, DNA tetrahedral-structured probes (TSPs) are used to engineer the sensing interface with spatially resolved and density-tunable sensing spots, improving the micro-confined molecular recognition. Meanwhile, a bubble-mediated shuttle reaction inside the DNM-functionalized microchannel improves the target-capturing efficiency. Thus, the sensitive and selective detection of multiple heavy metal ions (i.e., Hg²⁺, Ag⁺, and Pb²⁺) with this novel DNM biosensor can be achieved within 5 min. Moreover, the detection limit is down to 10, 10, and 20 nM for Hg²⁺, Ag⁺, and Pb²⁺, respectively. Therefore, the DNM biosensor capable of simultaneously detecting multiple heavy metal ions with sensitivity and selectivity shows great potential to be point-of-test devices.

Evaluation of Matrix Metalloproteinase Inhibition by Peptide Microarray-Based Fluorescence Assay on Polymer Brush Substrate and in Vivo Assessment

Matrix metalloproteinases (MMPs) are important biomarkers and potential therapeutic targets of tumor. In this report, a peptide microarray-based fluorescence assay is developed for MMPs inhibitors evaluation through immobilization of biotin-modified peptides on the poly(glycidyl methacrylate-co-2-hydroxyethyl methacrylate) (P(GMA-HEMA)) brush-modified glass slides. After biotin is recognized with cyanine 3 (Cy3)-modified avidin (Cy3-avidin), the microarrays can produce strong fluorescence signal. The biotin moieties detach from microarray, when the biotin-modified peptide substrates are specially cleaved by a MMP, resulting in decreased fluorescence intensity of the microarray. The decreasing level of fluorescence intensity is correlated with the MMP inhibition. Nine known MMP inhibitors against MMP-2 and MMP-9 are evaluated by the assay, and the quantitative determination of inhibitory potencies (half maximal inhibitory concentration) are obtained, which are comparable with the literatures. Two biocompatible fluorogenic peptides containing MMP-specific recognition sequences and FAM/Dabcyl fluorophore-quencher pair are designed as activatable reporter probes for sensing MMP-2 and MMP-9 activities in cell and in vivo. The peptide microarray-based results are well verified by the cell inhibition assay and in vitro fluorescence imaging, and further confirmed by the in vivo imaging of HT-1080 tumor-bearing mice.

Creation of antifouling microarrays by photopolymerization of zwitterionic compounds for protein assay and cell patterning

Nonspecific binding or adsorption of biomolecules presents as a major obstacle to higher sensitivity, specificity and reproducibility in microarray technology. We report herein a method to fabricate antifouling microarray via photopolymerization of biomimetic betaine compounds. In brief, carboxybetaine methacrylate was polymerized as arrays for protein sensing, while sulfobetaine methacrylate was polymerized as background. With the abundant carboxyl groups on array surfaces and zwitterionic polymers on the entire surfaces, this microarray allows biomolecular immobilization and recognition with low nonspecific interactions due to its antifouling property. Therefore, low concentration of target molecules can be captured and detected by this microarray. It was proved that a concentration of 10ngmL^-1 bovine serum albumin in the sample matrix of bovine serum can be detected by the microarray derivatized with anti-bovine serum albumin. Moreover, with proper hydrophilic-hydrophobic designs, this approach can be applied to fabricate surface-tension droplet arrays, which allows surface-directed cell adhesion and growth. These light controllable approaches constitute a clear improvement in the design of antifouling interfaces, which may lead to greater flexibility in the development of interfacial architectures and wider application in blood contact microdevices.

Fast on-Site Visual Detection of Active Ricin Using a Combination of Highly Efficient Dual-Recognition Affinity Magnetic Enrichment and a Specific Gold Nanoparticle Probe

Ricin, a highly toxic protein, is a controlled substance by both the Chemical Weapons Convention (CWC) and the Biological Weapons Convention (BWC). Therefore, fast precaution of potential ricin toxin plays an important role in national security and public safety. Herein, a simple, sensitive, and accurate visual detection of active ricin in complex samples is presented by combining magnetic affinity enrichment with a specific gold nanoparticle (AuNP) probe. In the first step, a dual-recognition magnetic absorbent was fabricated by simultaneously incorporating two different affinity ligands (concanavalin A and galactosamine) on low-foul polymer brushes grafted magnetic beads, which showed remarkable multivalent synergy binding capacity for ricin even under complex interfering environments. Subsequently, a homoadenine-constituted oligodeoxynucleotide named poly(21dA) was conjugated to AuNPs (the poly(21dA)-AuNPs), which served as a specific depurination substrate of active ricin. Coralyne can trigger the intact poly(21dA)-AuNPs aggregate by forming a non-Watson-Crick homoadenine/coralyne complex, but the poly(21dA)-AuNPs after reacting with active ricin failed to form this complex due to the loss of adenines. Based on these facts, active ricin can be detected as low as 12.5 ng mL^-1 with the naked eyes. This detection strategy could be well-applied in various ricin-spiked complex matrices. The features such as ready operation, facile readout, and easy accessibility make the assay a better choice for fast on-site active ricin detection.

Development of Sphere-Polymer Brush Hierarchical Nanostructure Substrates for Fabricating Microarrays with High Performance

In this work, a sphere-polymer brush hierarchical nanostructure-modified glass slide has been developed for fabricating high-performance microarrays. The substrate consists of a uniform 160 nm silica particle-self-assembled monolayer on a glass slide with a postcoated poly(glycidyl methacrylate) (PGMA) brush layer (termed PGMA@3D(160) substrate), which can provide three-dimensional (3D) polymer brushes containing abundant epoxy groups for directly immobilizing various biomolecules. As a typical example, the interactions of three monosaccharides (4-aminophenyl β-d-galactopyranoside, 4-aminophenyl β-d-glucopyranoside, and 4-aminophenyl α-d-mannopyranoside) with two lectins (biotinylated ricinus communis agglutinin 120 and biotinylated concanavalin A from Canavalia ensiformis) have been assessed by PGMA@3D(160) substrate-based carbohydrate microarrays. The carbohydrate microarrays show good selectivity, strong multivalent interaction, and low limit of detection (LOD) in the picomolar range without any signal amplification. Furthermore, the proposed sphere-polymer brush hierarchical nanostructure substrates can be easily extended to fabricate other types of microarrays for DNA and protein detection. PGMA@3D(160) substrate-based microarrays exhibit higher reaction efficiencies and lower LODs (by at least 1 order of magnitude) in comparison to those of two-dimensional microarrays, which are fabricated on planar epoxy substrates, making it a promising platform for bioanalytical and biomedical applications.

Bubble-Mediated Ultrasensitive Multiplex Detection of Metal Ions in Three-Dimensional DNA Nanostructure-Encoded Microchannels

The development of rapid and sensitive point-of-test devices for on-site monitoring of heavy-metal contamination has great scientific and technological importance. However, developing fast, inexpensive, and sensitive microarray sensors to achieve such a goal remains challenging. In this work, we present a DNA-nanostructured microarray (DNM) with a tubular three-dimensional sensing surface and an ordered nanotopography. This microarray enables enhanced molecular interaction toward the rapid and sensitive multiplex detection of heavy-metal ions. In our design, the use of DNA tetrahedral-structured probes engineers the sensing interface with spatially resolved and density-tunable sensing spots that improve the microconfined molecular recognition. A bubble-mediated shuttle reaction was used inside the DNM-functionalized microchannel to improve the target-capturing efficiency. Using this novel DNM biosensor, the sensitive and selective detection of multiple heavy-metal ions (i.e., Hg²⁺, Ag⁺, and Pb²⁺) was achieved within 5 min, the detection limit was down to 10, 10, and 20 nM for Hg²⁺, Ag⁺, and Pb²⁺, respectively. The feasibility of our DNM sensor was further demonstrated by probing heavy-metal ions in real water samples with a direct optical readout. Beyond metal ions, this unique DNM sensor can easily be extended to in vitro bioassays and clinical diagnostics.

Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes

The generation of polymer brushes by surface-initiated controlled radical polymerization (SI-CRP) techniques has become a powerful approach to tailor the chemical and physical properties of interfaces and has given rise to great advances in surface and interface engineering. Polymer brushes are defined as thin polymer films in which the individual polymer chains are tethered by one chain end to a solid interface. Significant advances have been made over the past years in the field of polymer brushes. This includes novel developments in SI-CRP, as well as the emergence of novel applications such as catalysis, electronics, nanomaterial synthesis and biosensing. Additionally, polymer brushes prepared via SI-CRP have been utilized to modify the surface of novel substrates such as natural fibers, polymer nanofibers, mesoporous materials, graphene, viruses and protein nanoparticles. The last years have also seen exciting advances in the chemical and physical characterization of polymer brushes, as well as an ever increasing set of computational and simulation tools that allow understanding and predictions of these surface-grafted polymer architectures. The aim of this contribution is to provide a comprehensive review that critically assesses recent advances in the field and highlights the opportunities and challenges for future work.