A multimer-based SERS aptasensor for highly sensitive and homogeneous assay of carcinoembryonic antigens

Carcinoembryonic antigens (CEAs) are known as one of the most common tumor markers. Their facile and affordable detection is critical for early diagnosis of malignant tumors, especially in resource-constrained settings. Here, we report a novel multimer-based surface-enhanced Raman scattering (SERS) aptasensor for a specific CEA assay. The aptasensor is fabricated through aptamer-assisted self-assembly of silver-coated gold nanoparticles (Au@Ag NPs), and the self-assembled multimeric structure possesses abundant hot-spots to provide high SERS response. When CEA is introduced, the specific recognition of CEA by aptamers will lead to the disassembly of Au@Ag multimers due to the lack of a bridging aptamer between Au@Ag NPs. As a result, the number of hot-spots in the multimeric system is decreased, and the intensity at 1585 cm-1 of the SERS reporter (4-mercaptobenzoic acid, 4-MBA) on the surface of NPs will also be decreased. The Raman intensity is proportional to the logarithm of the concentration of CEA. The detection sensitivity can be down to the pg mL-1 level. The analytical method only needs a droplet of 2 μL of sample, and the detection time is less than 20 min. The multimer-based SERS aptasensor can be applied in sensitive and inexpensive detection of CEA in serum samples.

A simple method to construct a low-cost immunosensor based on a dithiol-functionalized polydopamine platform

A simple and low-cost electrochemical CEA immunosensor was investigated via the self-polymerization of dopamine and a dithiol compound spacer for the covalent immobilization of antibodies. The designed CEA immunosensor exhibited a linear response and a low detection limit.

Substrate-Independent Micropatterning of Polymer Brushes Based on Photolytic Deactivation of Chemical Vapor Deposition Based Surface-Initiated Atom-Transfer Radical Polymerization Initiator Films

Precise microscale arrangement of biomolecules and cells is essential for tissue engineering, microarray development, diagnostic sensors, and fundamental research in the biosciences. Biofunctional polymer brushes have attracted broad interest in these applications. However, patterning approaches to creating microstructured biointerfaces based on polymer brushes often involve tedious, expensive, and complicated procedures that are specifically designed for model substrates. We report a substrate-independent, facile, and scalable technique with which to prepare micropatterned biofunctional brushes with the ability to generate binary chemical patterns. Employing chemical vapor deposition (CVD) polymerization, a functionalized polymer coating decorated with 2-bromoisobutyryl groups that act as atom-transfer radical polymerization (ATRP) initiators was prepared and subsequently modified using UV light. The exposure of 2-bromoisobutyryl groups to UV light with wavelengths between 187 and 254 nm resulted in selective debromination, effectively eliminating the initiation of ATRP. In addition, when coatings incorporating both 2-bromoisobutyryl and primary amine groups were irradiated with UV light, the amines retained their functionality after UV treatment and could be conjugated to activated esters, facilitating binary chemical patterns. In contrast, polymer brushes were selectively grown from areas protected from UV treatment, as confirmed by atomic force microscopy, time-of-flight secondary ion mass spectrometry, and imaging ellipsometry. Furthermore, spatial control over biomolecular adhesion was achieved in three ways: (1) patterned nonfouling brushes resulted in nonspecific protein adsorption to areas not covered with polymer brushes; (2) patterned brushes decorated with active binding sides gave rise to specific protein immobilization on areas presenting polymer brushes; (3) and primary amines were co-patterned along with clickable polymer brushes bearing pendant alkyne groups, leading to bifunctional reactivity. Because this novel technique is independent of the original substrate's physicochemical properties, it can be extended to technologically relevant substrates such as polystyrene, polydimethylsiloxane, polyvinyl chloride, and steel. With further work, the photolytic deactivation of CVD-based initiator coatings promises to advance the utility of patterned biofunctional polymer brushes across a spectrum of biomedical applications.

Multiplexing determination of cancer-associated biomarkers by surface-enhanced Raman scattering using ordered gold nanohoneycomb arrays

AIM

Here, a multiplex surface-enhanced Raman scattering (SERS) based assay for simultaneous quantitation of carcinoembryonic antigen (CEA) and α-fetoprotein (AFP) was developed.

METHODS

SERS tags of nanostars and SERS substrates of nanobowl arrays were functionalized with labeling and capturing antibodies, respectively. In presence of antigens, SERS tags, antigens and SERS substrates formed sandwich structure.

RESULTS

The SERS-based technique showed a wide linear range from 0.5 to 100 ng/ml and detection limits were 0.41 and 0.35 ng/ml for CEA and AFP in phosphate-buffered saline buffer, respectively. Analysis results of clinical serum samples using this technique were similar to that shown in phosphate-buffered saline buffer. The LODs were 0.44 and 0.40 ng/ml for CEA and AFP, respectively. Conclusion: The precision and stability of this analysis technique were satisfactory, meanwhile, no obvious cross-reactivity could be found. What's more, it also suggested that this novel multiplex SERS-based technique could be a simple, specific, reliable, sensitive and multiplexed tool for important diagnostic and prognostic applications.

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.

Visual multiple recognition of protein biomarkers based on an array of aptamer modified gold nanoparticles in biocomputing to strip biosensor logic operations

We developed a strip biosensors array based on aptamer-modified gold nanoparticles as receptors and combined the protein-aptamer binding reaction with the streptavidin-biotin interaction as well as the sandwich format. We found that a series of protein receptors obtained a distinct response pattern to each target protein. Three proteins have been well distinguished with the naked eyes and a portable reader without mutual interference, accompanying with lower limit of detection and wider linear range. A complete set of four elementary logic gates (AND, OR, INH, and NAND) and eight combinative logic gates (AND-OR; AND-INH; OR-INH; INH-NAND; AND-OR-INH; AND-INH-NAND; OR-INH-NAND; AND-OR-INH-NAND) are thoroughly realized using this array, which could eventually be applicable to the keypad-lock system with enhanced complexity in the near future. Moreover, this array shows excellent linear relationships, anti-interference capability, real human serum samples applicability, long-term storage stability and reproducibility. All indicate that this design has very good prospects for development.

A sandwich-type electrochemical immunosensor for carcinoembryonic antigen based on signal amplification strategy of optimized ferrocene functionalized Fe₃O₄@SiO₂ as labels

A sandwich-type electrochemical immunosensor was developed for sensitive detection of carcinoembryonic antigen (CEA) by using ferroferric oxide@silica-amino groups (Fe3O4@SiO2-NH2) as carriers and gold nanoparticles-graphene oxide (GO-AuNPs) as platform. The Fe3O4@SiO2-NH2 surface was used as linked reagents for co-immobilization of ferrocenecarboxylic acid (Fc-COOH) and secondary anti-CEA (Ab2) to prepare the signal probe, and it also could hasten the decomposition of hydrogen peroxide (H2O2) to amplify signals. Differential pulse voltammetry (DPV) was successfully used to quantify CEA. Under the optimized conditions, the designed immunosensor shows an excellent analytical performance wide dynamic response range of CEA concentration from 0.001 ng mL(-1) to 80 ng mL(-1) with a relatively low detection limit of 0.0002 ng mL(-1) (S/N=3), and high specificity and good reproducibility. The proposed immunosensor was successfully used to determine CEA in spiked human serum samples.

A chitosan-Au-hyperbranched polyester nanoparticles-based antifouling immunosensor for sensitive detection of carcinoembryonic antigen

An electrochemical immunosensor was developed for the detection of carcinoembryonic antigen in whole blood, based on the antibiofouling properties of carboxylic acid group functionalized hyperbranched polyester nanoparticles.