Antifouling Biosensors Research Articles

An Antibiofouling Electrochemical Sensor Consisting of Amphiphilic Copolymer on CNT-COOH Electrodes for Point-of-Care Monitoring of Propofol Blood Concentration in Surgical Patients

The monitoring of propofol (PPF) blood concentration is vital for the safety of intravenous anesthesia. Electrochemical sensors represent a powerful tool for the detection of PPF. Our previous research has demonstrated that CNT-COOH electrodes exhibit advantages in resisting electrochemical fouling from PPF oxidation products. Nevertheless, biofouling remains a critical challenge hindering the clinical transformation of PPF electrochemical sensors. To address this issue, we employed in-situ electrodeposition to deposit zwitterionic sulfobetaine methacrylate (SBMA) and overoxidation polydopamine (OPDA) onto CNT-COOH screen-printed electrodes (SPEs) and proposed an innovative CNT-COOH/OPDA-SBMA (CNT-COOH/OPS) amphiphilic antifouling biosensor. This amphiphilic electrode, featuring both hydrophilic and hydrophobic properties, demonstrated excellent antifouling performance through electrochemical characterization in ex-vivo blood assays, coupled with commendable sensitivity, stability, and selectivity. CNT-COOH/OPS SPEs were also applied in point-of-care monitoring of the PPF blood concentrations in animals and clinical surgical patients and exhibited good accuracy and linearity (Ipa=0.0084c+0.4458, R2=0.995) with a limit of detection of 2.948μM. Further, the electrodes demonstrated a high recovery and the blood concentrations determined by electrochemical detection had robust negative correlation with the depth of anesthesia. Therefore, CNT-COOH/OPS SPEs hold promise as a significant tool in point-of-care monitoring of PPF, offering patients safer and more personalized medical care.

A Nonfouling Electrochemical Biosensor for Protein Analysis in Complex Body Fluids Based on Multifunctional Peptide Conjugated with PEGlyated Phospholipid.

Developing antifouling biosensors capable of performing robustly in complex human body fluids is crucial for biomarker diagnosis and health monitoring. Herein, an antifouling and highly sensitive and stable biosensor was constructed through the self-assembly of the designed conjugates composed of a multifunctional peptide (MP) and PEGylated distearoylphosphatidylethanolamine (DSPE-PEG). The self-assembly capability of the DSPE-PEG-MP was demonstrated clearly through coarse-grained molecular dynamics simulation and transmission electron microscopy, and it can be effectively self-assembled onto the electrode surface modified with gold nanoparticles. The MP was designed to be antifouling and contained a peptide sequence that can specifically bind the target protein Annexin A1 (ANXA1), and the D-type amino acid composition of MP can enhance its resistance to enzymatic hydrolysis. The unique design of MP, in conjugation with the self-assembly capability of the PEGylated phospholipid DSPE-PEG, enabled the biosensor to exhibit excellent antifouling capability and stability in various complex human body fluids. The biosensor was capable of sensitively and selectively quantifying ANXA1 and achieved a limit of detection down to 0.12 pg mL-1. More importantly, the biosensor demonstrated satisfactory accuracy for ANXA1 detection in clinical serum samples, as verified by the enzyme linked immunosorbent assay (ELISA) kits. It is expected that various antifouling biosensors suitable for application in complex biological environments can be constructed by utilizing the strategy of designing similar DSPE-PEG-MP conjugates.

An efficient electrochemical biosensor based on double-conductive hydrogel as antifouling interface for ultrasensitive analysis of biomarkers in complex serum medium

Electrochemical biosensors are suitable for trace detection of biomarkers in serum due to their high sensitivity and fast response time. However, the extensive adsorption of non-specific biomolecules may affect detection results and reduce the operating life of sensors. Herein, an efficient electrochemical biosensor based on double-conductive antifouling hydrogel was developed for ultrasensitive detection of carcinoembryonic antigen (CEA) in serum. Specifically, the antifouling hydrogel was designed with MXene as the conductive framework, and its inherent surface hydrophilicity made it have good antifouling ability. Meanwhile, the introduction of conductive poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) further improved the conductivity and stability and of antifouling hydrogel. Furthermore, the prepared MXene nanosheets exhibited large surface area, which could load a large amount of [Ru(NH3)6]3+ as internal standards. Importantly, the encapsulation of [Ru(NH3)6]3+ in hydrogel can not only eliminate the environmental and instrument errors, but also realize the integration of antifouling and internal standards, thus simplifying the construction process and improving the detection accuracy of the biosensor. Based on this, the proposed signal “on-off” electrochemical antifouling biosensor realized trace detection of CEA in a wide linear range (1 pg/mL ∼ 1 μg/mL), with a detection limit as low as 0.41 pg/mL (3δ/k). This study broadens the application of hydrogels in electrochemical antifouling systems, providing a positive reference for sensitive and accurate determination of biomarkers in serum samples.

Platinum-Selenopeptide Interfaces in Support of High Fidelity Electrochemical Biomarker Quantification in Complex Biological Matrices.

The real world applications of conventional antifouling biosensors based on gold-thiol (Au-S) interfaces are hampered by the progressive competitive displacement of key functionality by ubiquitous biothiols. To overcome this limitation, we introduce here novel platinum-selenium (Pt-Se) interfaces. Thiol displacement tests, antifouling analyses, and density functional theory calculations confirm markedly improved interfacial stability. This was then leveraged through the application of a seleno-multifunctional peptide platform, tailored to the detection of murine double minute 2, in biological samples. A derived amperometric sensing platform exhibited a notably lower detection limit and more accurate target quantification than that supported by analogous Au-S and Pt-S interfaces. We believe that this work broadens the scope of electrochemical sensor construction and holds significant promise for the development of high-fidelity impactful bioassay platforms.

Design of U-shaped peptides with long-lasting antifouling efficacy: Toward a feasible electrochemical aptasensor for robust detection in human serum

BackgroundDeveloping biosensors with antifouling properties is essential for accurately detecting low-concentration biomarkers in complex biological matrix, which is imperative for effective disease diagnosis and treatment. Herein, an antifouling electrochemical aptasensor qualifying for probing targets in human serum was explored based on newly-devised peptides that could form inverted U-shaped structures with long-term stability. ResultsThe inverted U-shaped peptides (U-Pep) with two terminals of thiol groups grafted onto the Au-modified electrode showcase superior antifouling properties in terms of high stability against enzymatic hydrolysis and long acting against biofouling in actual biofluids. The construction of the outlined antifouling electrochemical aptasensor just involved the fabrication of Au-deposited poly(3,4 ethylenedioxythiophene) (Au/PEDOT) modified electrode, followed by one-step co-incubation in the peptides and the aptamer probes with the Au/PEDOT electrode. Taking a typical biomarker of alpha-fetoprotein (AFP) for detection, this elegant antifouling aptasenor demonstrated a nice response for probing the target AFP with a low detection limit of 0.27 pg/mL and a wide linear scope of 1.0 pg/mL to 1.0 μg/mL, and furthermore qualified for assaying of AFP in human serum samples with satisfactory accuracy and feasibility. SignificanceThis engineering strategy of U-Pep with long-lasting antifouling efficacy opens a new horizon for high-performance antifouling biosensors suitable for detection in complex bifluids, and it could spark more inspiration for a follow-up exploration of other featured antifouling biomaterials.

An antifouling electrochemical biosensor using self-signal for Salmonella typhimurium direct detection in food sample

Eating food contaminated by foodborne pathogens can lead to illness. The development of electrochemical sensors for pathogen detection has received widespread attention. However, the analytical performance of electrochemical sensors is inevitably affected by the non-specific adsorption of molecules in the sample. Moreover, the external signal probes might be affected by the complex components in the sample accompanied with signal suppression. This work presents an electrochemical aptasensor for Salmonella typhimurium detection based on the self-signal of poly-xanthurenic acid and the antifouling ability of chondroitin sulfate. The detection time was 60 min. The linear range was from 101 to 107 CFU/mL, and the detection limit was 3 CFU/mL. The biosensors presented good repeatability and storage stability. And the biosensors has been successfully applied in milk and orange juice. This strategy is expected to be applied in the design of other antifouling biosensors, to achieve rapid detection of pathogens and ensure food safety.

A low-fouling electrochemical biosensor based on BSA hydrogel doped with carbon black for the detection of cortisol in human serum

Electrochemical biosensors with high sensitivity can detect low concentrations of biomarkers, but their practical detection applications in complex biological environments such as human serum and sweat are severely limited by the biofouling. Herein, a conductive hydrogel based on bovine serum albumin (BSA) and conductive carbon black (CCB) was prepared for the construction of an antifouling biosensor. The BSA hydrogel (BSAG) was doped with CCB, and the prepared composite hydrogel exhibited good conductivity originated from the CCB and antifouling capability owing to the BSA hydrogel. An antifouling biosensor for the sensitive detection of cortisol was fabricated by drop-coating the conductive hydrogel onto a poly(3,4-ethylenedioxythiophene) (PEDOT) modified electrode and further immobilizing the cortisol aptamer. The constructed biosensor showed a linear range of 100 pg mL−1 - 10 μg mL−1 and a limit of detection of 26.0 pg mL−1 for the detection of cortisol, and it was capable of assaying cortisol accurately in complex human serum. This strategy of preparing antifouling and conductive hydrogels provides an effective way to develop robust electrochemical biosensors for biomarker detection in complex biological media.

Enhanced split-type photoelectrochemical aptasensor incorporating a robust antifouling coating derived from four-armed polyethylene glycol

Antifouling biosensors capable of preventing protein nonspecific adhesion in real human bodily fluids are highly sought-after for precise disease diagnosis and treatment. In this context, an enhanced split-type photoelectrochemical (PEC) aptasensor was developed incorporating a four-armed polyethylene glycol (4A-PEG) to construct a robust antifouling coating, enabling accurate and sensitive bioanalysis. The split-type PEC system involved the photoelectrode and the biocathode, effectively separating signal converter with biorecogniton events. Specifically, the TiO2 electrode underwent sequential modification with ZnIn2S4 (ZIS) and polydopamine (PDA) to form the PDA/ZIS/TiO2 photoelectrode. The cathode substrate was synthesized as a hybrid of N-doped graphene loaded with Pt nanoparticles (NG-Pt), and subsequently modified with 4A-PEG to establish a robust antifouling coating. Following the anchoring of probe DNA (pDNA) on the 4A-PEG-grafted antifouling coating, the biocathode for model target of cancer antigen 125 (CA125) was obtained. Leveraging pronounced photocurrent output of the photoelectrode and commendable antifouling characteristics of the biocathode, the split-type PEC aptasensor showcased exceptional detection performances with high sensitivity, good selectivity, antifouling ability, and potential feasibility.

Robust Electrochemical Biosensors Based on Antifouling Peptide Nanoparticles for Protein Quantification in Complex Biofluids.

Peptides with distinct physiochemical properties and biocompatibility hold significant promise across diverse domains including antifouling biosensors. However, the stability of natural antifouling peptides in physiological conditions poses significant challenges to their viability for sustained practical applications. Herein, a unique antifouling peptide FFFGGGEKEKEKEK was designed and self-assembled to form peptide nanoparticles (PNPs), which possessed enhanced stability against enzymatic hydrolysis in biological fluids. The PNP-coated interfaces exhibited superior stability and antifouling properties in preventing adsorption of nonspecific materials, such as proteins and cells in biological samples. Moreover, a highly sensitive and ultralow fouling electrochemical biosensor was developed through the immobilization of the PNPs and specific aptamers onto the polyaniline nanowire-modified electrode, achieving the biomarker carcinoembryonic antigen detection in complex biofluids with reliable accuracy. This research not only addresses the challenge of the poor proteolytic resistance observed in natural peptides but also introduces a universal strategy for constructing ultralow fouling sensing devices.

Prostate specific antigen quantification in human serum supported by the designed four-in-one octabranched peptides and AgNPs-based signal amplifier

BackgrounIt remains challenging for biosensors to directly detect clinical targets in complex biological media with high selectivity and low fouling. MethodsHerein, an antifouling and ultrasensitive biosensor supported by the designed four-in-one octabranched peptides and signaling amplification strategy of silver nanoparticles (AgNPs) was constructed for prostate specific antigen (PSA) quantification in human serum. Chondroitin sulfate functionalized polyaniline (PANI) nanowires and gold nanoparticles (AuNPs) were electrodeposited onto the electrode in sequence to promote electrons transport, and followed by the attachment of the designed octabranched peptides. Significant findingsThe peptides were specially designed to contain four structural domains, namely anchoring domain (CC), linking domain (PPPP), antifouling domain (EKEKEKE), and recognition domain (HSSKLQK). AgNPs loaded on graphene oxide were assembled onto peptides as a signal amplification strategy. The peptides were specifically sheared off by PSA, resulting in a significantly reduced electrochemical response that can be used to sensitively indicate PSA concentration. The antifouling biosensor exhibited a linear response range from 1 × 10−14 to 1 × 10−6 M, with a low detection limit of 1.33 × 10−15 M. Furthermore, the biosensor was employed to detect PSA in clinical samples based on the four-in-one octabranched peptides, indicating feasibility of the biosensor for early clinical diagnosis.

An antifouling biosensor with dual modality readouts for detection of patulin in complex fruit juice

Herein, an antifouling sensing platform with electrochemical and fluorometric dual-signal readouts is proposed for the reliable detection of patulin (PAT) in orange and apple juice. The incorporation of an antifouling peptide of D-amino acids endows sensing surface with a sustained antifouling capability in complex detection system, effectively preventing nonspecific adsorption at the sensing interface. Moreover, the integration of both electrochemical and fluorescent signal readouts addresses the limitations inherent in each signal channel. And both electrochemical and fluorescent signal readouts would make up for the drawbacks of each signal channel and merge with the benefits of each transduction channel, ensuring mutual complementation of the detection results. In the sensing process, antifouling peptides and PAT-binding aptamers tagged with methylene blue (Mb-Apta) are covalently attached to gold nanoparticles (AuNPs), forming antifouling monolayers and sensing probes, respectively. Subsequently, SiO2-polyamidoamine (SiO2-PAMAM) will integrate with aptamers through electrostatic attraction. In the presence of PAT in the detection system, the Mb-Apta selectively bind with PAT molecules, resulting in Mb near to electrode surface and release SiO2-PAMAM into sample systems. Consequently, noticeable electrochemical and robust aggregation-induced emission (AIE) dual-signals are generated. The combined utilization of both electrochemical and fluorescent signal readouts offers enhanced detection sensitivity and an extended linear range.

Peptide aptamer-based polyaniline-modified amperometric biosensor for L-lysine detection in real serum samples

L-Lysine (L-Lys) quantification in serum using a novel and highly selective amperometric biosensor has been reported. In this study, an efficient, enzyme-free, and simple anti-fouling biosensor was developed based on a self-screened peptide aptamer. A glassy carbon electrode (GCE) was used to construct anti-fouling interfaces by modifying its surface with polyaniline (PANI) polymer. The peptide aptamer, Cys-Pro-Pro-Pro-Pro-Arg-Glu-Asn-Ile-Gln-Arg-Leu-Thr, was then immobilized onto this electrode via an electroactive cysteine linker and its potential in the determination of L-Lys was examined. Under optimised experimental conditions, the peptide-modified electrodes exhibited excellent anti-fouling and electrochemical sensing. The biosensor was effective in resisting biofouling in a wide range of serum samples and amino acid solutions, and its linear range for L-Lys detection ranged from 1 nM to 10 mM, with a comparatively lower detection limit (0.3 nM; S/N = 3). The anti-fouling biosensor could detect L-Lys in real serum samples, and this approach of designing peptide aptamers basedlow-fouling biosensorscan easily be extended to the development of a bio-sensing platform system for a variety of other metabolites.

Phosphorylation of Oligopeptides: Design of Ultra-Hydrophilic Zwitterionic Peptides for Anti-Fouling Detection of Nucleic Acids in Saliva.

The construction of low-fouling biosensors for assaying biomarkers in complex biological samples remains a challenge, and the key limitation is the lack of effective anti-fouling materials. Inspired by the biomimetic process of protein phosphorylation, we herein designed a new phosphorylated peptide modified with the dihydrogen phosphate (-PO4H2) group, which significantly increased the hydrophilicity and anti-fouling capability of the peptide when compared with natural and normal peptides. Molecular simulation (MS) illustrated that, compared with the -COOH and -NH2 groups, the -PO4H2 group formed the most numbers of hydrogen bonds and stronger hydrogen bonds with water molecules. As a result, the PO4H2-oligopeptide was proved by MS to be able to attract the greatest number of water molecules, so as to form a compact layer of H2O to resist further adsorption of nonspecific biomolecules. The modification of electrodes with the designed PO4H2-oligopeptides, in addition to the adoption of neutral peptide nucleic acids (PNAs) as the sensing probes, ensured the fabrication of anti-fouling electrochemical biosensors capable of detecting nucleic acids in complex saliva. The constructed anti-fouling biosensor was able to detect the nucleic acid of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in undiluted saliva, with a wide linear response range (0.01 pM-0.01 μM) and a low limit of detection (LOD) of 3.4 fM (S/N = 3). The phosphorylation of oligopeptides offers an effective strategy to designing ultra-hydrophilic peptides suitable for the construction of promising anti-biofouling biosensors and bioelectronics.

Copolymerization of zwitterionic sulfobetaine and hydrophobic acrylamide based antifouling electrochemical biosensors for detection of CA125 in clinical serum samples

It is crucial to construct antifouling electrochemical biosensors with long-term stability and high sensitivity for the detection of biomarkers in complex biological environments to prevent the unspecific adsorption of proteins and other biomolecules. Herein, a glassy carbon electrode electropolymerization with polyaniline (PANI/GCE) was further modified with a copolymerization (PSN) of zwitterionic sulfobetaine methacrylate (SBMA) and hydrophobic N-isopropyl acrylamide (NIPAM) by simple hydrophobic interaction to construct an antifouling biosensor. PSN forms a stable self-assembled monolayer on the PANI/GCE surface and exhibits good antifouling performance in serum due to the advantages of hydrophobic anchoring and the antifouling performance of zwitterionic polymers. Ascribe to the large specific surface area and excellent conductivity, the present biosensor can detect CA125 in undiluted samples in the range of 0.01–1000 U mL−1 with a limit of detection of 2.7 mU mL−1 (3σ/k). Both with good biocompatibility and biological stability, PSN modified sensing surface realizes a long-term antifouling for 15 days in a buffer solution. The present work provides a simple strategy for the direct analysis of CA125 in human serum without a complicated construction of biosensors, indicating the potential application in clinical diagnosis.

A comparative assessment of a piezoelectric biosensor based on a new antifouling nanolayer and cultivation methods: Enhancing S. aureus detection in fresh dairy products

Ensuring dairy product safety demands rapid and precise Staphylococcus aureus (S. aureus) detection. Biosensors show promise, but their performance is often demonstrated in model samples using non-native pathogens and has never been studied towards S. aureus detection in naturally contaminated samples. This study addresses the gap by directly comparing results taken with a novel piezoelectric biosensor, capable of one-step detection, with four conventional cultivation-based methods. Our findings reveal that this biosensor, based on an antifouling nanolayer-coated biochip, exhibits exceptional resistance to biofouling from unprocessed dairy products and is further capable of specific S. aureus detection. Notably, it performed comparably to Petrifilm and Baird-Parker methods but delivered results in only 30 min, bringing a substantial reduction from the 24 h required by cultivation-based techniques. Our study also highlights differences in the performance of cultivation methods when analyzing artificially spiked versus naturally contaminated foods. These findings underline the potential of antifouling biosensors as efficient reliable tools for rapid, cost-effective, point-of-care testing, enhancing fresh dairy product safety and S. aureus detection.

Electrochemical detection of carcinoembryonic antigen in human serum based on designed anti-fouling and anti-enzymolysis peptides conjugated with silk sericine-inspired beta-homoserine

Zwitterionic peptides with strong water binding ability have drawn much attention in the biomedical diagnosis field as antifouling materials. However, the proteolytic susceptibility of natural peptides in human serum or blood greatly limited their practical application. Herein, inspired by the strong stability and biocompatibility of sericin, an extended zwitterionic peptide containing unnatural β-homoserine (pβ-peptide) was designed to construct antifouling biosensors with enhance stability in complex biological fluids. The molecular dynamic simulation illustrated the strong water binding capability of the pβ-peptide owing to the formation of a large quantity of hydrogen bonds with water. Compared with the electrodes modified with normal peptide, ones modified with the designed peptide demonstrated much stronger antifouling capability and significantly enhanced stability when evaluated in human serum and blood. Furthermore, the constructed biosensor integrating the designed antifouling peptide with carcinoembryonic antigen (CEA) aptamer exhibited a great sensitivity for detecting CEA protein, with a broad linear range of 1.0 fg·mL−1-1.0 ng·mL−1 and a low detection limit of 0.33 fg·mL−1. The biosensor was competent to accurately assay CEA in clinical serum samples when compared with the commonly adopted ELISA method, which indicates a promising potential for practical applications.

Antifouling zwitterionic peptide hydrogel based electrochemical biosensor for reliable detection of prostate specific antigen in human serum

An electrochemical biosensor based on the antifouling zwitterionic peptide hydrogel (CFEFKFC) and the poly(3,4-ethylenedioxythiophene) (PEDOT) was fabricated to accurately detect prostate specific antigen (PSA) in complex human serum. The electrode was modified with the conducting polymer PEDOT and gold nanoparticles (AuNPs) in sequence through electrodeposition, and then the designed zwitterionic peptide hydrogel prepared through self-assembly was immobilized onto the modified electrode surface via the Au–S bond. The zwitterionic peptide hydrogel with cysteine terminal is easy for immobilization onto the gold surface, and it is also suitable for the immobilization of biomolecules such as PSA antibody in this work, through the formation of covalent amide bonds. The peptide hydrogel possessed excellent antifouling property, and it was able to effectively prevent the adsorption of nonspecific proteins, cells and other biomolecules. The developed antifouling biosensor showed a linear response range from 0.1 ng mL−1 to 100 ng mL−1, with a low limit of detection down to 5.6 pg mL−1. These results encourage the wide use of zwitterionic peptide hydrogels as antifouling materials in various sensing and bio-sensing devices.

Alpha-aminoisobutyric acid incorporated peptides for the construction of electrochemical biosensors with high stability and low fouling in serum

An effective strategy to construct low fouling electrochemical biosensors for assaying serum biomarkers was proposed based on specially designed α-aminoisobutyric acid (Aib) incorporated peptides. The Aib-peptides were designed to be of antifouling properties, and at the same to incorporate Aib residues in their interior to enhance the hydrolytic stability. In order to construct the electrochemical biosensor, two kinds of Aib-peptides labelled with biotin were modified on the electrode surface: One with cysteine terminal for easy attachment to the electrode modified with gold nanoparticles, the other with unique terminal peptide sequence for specific binding of immunoglobulin G (IgG), and they were connected through the streptavidin-biotin affinity system. Owing to the interposition of Aib residues, the peptides as well as the constructed biosensors showed excellent antifouling performances and enhanced stability against enzymatic degradation in serum. Furthermore, the IgG biosensor constructed with the Aib-peptides displayed a very low detection limit (29.5 pg mL−1) and a broad linear range (100 pg mL−1 - 10 μg mL−1), and it was able to assay IgG in clinical human sera with decent accuracy and reliability. This strategy provides a new path for the construction of stable antifouling biosensors based on functional peptides for practical biomarker assaying in real clinical samples.

Cell Membrane and V2C MXene-Based Electrochemical Immunosensor with Enhanced Antifouling Capability for Detection of CD44.

The inactive adsorption and interference of biomolecules in electrochemical biosensors is a topic of intense interest. Directly utilizing native cell membranes to endow electrochemical surfaces with antifouling and biocompatible features is a promising strategy, rather than attempting to synthetically replicate complex biological interface properties. In this study, we present a facial and sensitive sandwich-type antifouling immunoassay through platelet membrane/Au nanoparticle/delaminated V2C nanosheet (PM/AuNPs/d-V2C)-modified electrode as the substrate of sensing interface and methylene blue/aminated metal organic framework (MB@NH2-Fe-MOF-Zn) as an electrochemical signal probe. The biosensor perfectly integrates the high conductivity of AuNPs-loaded V2C MXene with the excellent loading property of NH2-Fe-MOF-Zn to improve the electrochemical sensing performance. In addition, the excellent antifouling properties of the homogeneous cell membrane can effectively prevent the non-specific adsorption of model proteins. The obtained antifouling biosensor possesses the capability of ultrasensitive detection of CD44 and CD44-positive cancer cell in complex liquids and exhibits good analytical performance for the analysis of CD44 with a linear range from 0.5 ng/mL to 500 ng/mL. This strategy of developing cell membrane-based biosensing systems with enhanced antifouling capability can be easily expanded to the construction of other complex biosensors, and the advanced biological probes and analytical methods provide a favorable means to accurately quantify biomarkers associated with tumor progression.

D-Amino Acid-Based Antifouling Peptides for the Construction of Electrochemical Biosensors Capable of Assaying Proteins in Serum with Enhanced Stability.

The susceptibility of peptides to proteolytic degradation in human serum significantly hindered the potential application of peptide-based antifouling biosensors for long-term assaying of clinical samples. Herein, a robust antifouling biosensor with enhanced stability was constructed based on peptides composed of d-amino acids (d-peptide) with prominent proteolytic resistance. The electrode was electropolymerized with poly(3,4-ehtylenedioxythiophene) and electrodeposited with Au nanoparticles (AuNPs), and the d-peptide was then immobilized onto the AuNPs, and a typical antibody specific for immunoglobulin M (IgM) was immobilized. Because of the effect of d-amino acids, the d-peptide-modified electrode surface showed prominent antifouling capability and high tolerance to enzymatic hydrolysis. Moreover, the d-peptide-modified electrode exhibited much stronger long-term stability, as well as antifouling ability in human serum than the electrode modified with normal peptides. The electrochemical biosensor exhibited a sensitive response to IgM linearly within the range of 100 pg mL-1 to 1.0 μg mL-1 and a very low detection limit down to 37 pg mL-1, and it was able to detect IgM in human serum with good accuracy. This work provided a new strategy to develop robust peptide-based biosensors to resist the proteolytic degradation for practical application in complex clinical samples.