S100B is a clinically important biomarker for traumatic brain injury and neurodegenerative diseases, necessitating the development of sensitive and reliable analytical methods for its determination in complex biological fluids susceptible to potential biofouling and electroactive interference. Herein, we report a robust antifouling photoelectrochemical (PEC) immunoassay based on a self-assembled peptide hydrogel-engineered Au/SCN/PCN-222 photocathode for sensitive S100B detection. The Au/SCN/PCN-222 photocathode integrates sulfur-doped carbon nitride (SCN) quantum dots and Au nanoparticles with the porphyrinic metal–organic framework PCN-222, serving as the signal transduction element with enhanced light absorption and improved charge transfer, thereby increasing the cathodic photocurrent response. To address nonspecific adsorption and biofouling, a self-assembled Fmoc-FF-GG-EK-EK-EK peptide hydrogel was engineered on the photocathode surface, forming a highly hydrated, charge-balanced three-dimensional interface that effectively suppresses biofouling while enabling efficient antibody immobilization. Upon specific recognition of S100B, immune complex formation increases interfacial steric hindrance and suppresses charge transfer, resulting in a concentration-dependent decrease in photocurrent. The proposed PEC immunoassay exhibited high sensitivity, excellent antifouling performance, and good selectivity, enabling reliable analysis in complex biological matrices. This work establishes a general peptide hydrogel-based interfacial engineering strategy for antifouling PEC bioanalysis, providing a versatile and robust platform for biomarker detection.
Feng Xu, Yaoyao Xiao, Gaochao Fan et al.· Analytical Chemistry· 0 citations
The precise detection of biomarkers in complex biofluids remains a significant challenge for electrochemical biosensors, largely due to the nonspecific adsorption of proteins and other molecules. While zwitterionic peptides offer excellent antifouling properties, their typical linear architectures are prone to protease hydrolysis, compromising performance and limiting practical use. To overcome this limitation, we engineered a linear peptide through structural modulation, stabilizing it into a hairpin-shaped conformation by introducing two disulfide-directed bridges, and designated it as the hairpin-shaped antifouling peptide (HAP). This structural modulation maintains its inherent antifouling properties while the conferred conformational constraints significantly enhance its resistance to enzymatic hydrolysis. Based on this HAP, an antifouling electrochemical biosensor was constructed, which effectively resists nonspecific adsorption while maintaining high enzymatic stability, enabling the direct detection of carbohydrate antigen 15-3 (CA15-3) in human serum with a detection limit of 2.64 mU·mL-1. Importantly, the HAP-based biosensor demonstrates reliability on par with commercial enzyme-linked immunosorbent assay methods and successfully discriminates between healthy individuals and cancer patients. With its high accuracy and capacity for direct detection, the platform offers a promising strategy for analyzing cancer biomarkers in serum, potentially enabling more timely and effective clinical diagnosis and treatment.
Shuyu Jiang, Shicheng Liu, Zhen Song et al.· Analytical Chemistry· 0 citations
The reliable electrochemical detection of immunoglobulin G (IgG) in complex biological fluids is severely hampered by nonspecific protein fouling and enzymatic degradation. Inspired by natural lasso peptides, we engineer a multifunctional lasso-like peptide (LaP) composed entirely of D-amino acids that uniquely integrates a terminal cysteine anchoring domain, a zwitterionic antifouling segment, and a specific IgG recognition segment into a single topology-constrained architecture. The covalently closed lasso topology sterically restricts protease access to cleavage-sensitive peptide bonds, while the all-D-amino acid backbone is inherently invisible to naturally occurring proteases. Together, these features provide dual physical and stereochemical protection while preserving the conformational freedom of the recognition domain for efficient target binding. Compared with a branched peptide (BrP) of identical sequence, the LaP-modified interface exhibits markedly superior resistance to nonspecific protein adsorption in undiluted serum. Molecular dynamics simulations reveal that the lasso constraint induces a superficial, low-affinity binding pose toward carboxypeptidase Y (CPY), whereas BrP penetrates deeply into the enzyme active pocket. Consequently, the LaP-based biosensor shows negligible signal change after CPY treatment, whereas BrP loses most of its activity. The LaP/AuNPs/PANI electrochemical biosensor achieves excellent selectivity and maintains its analytical performance even in complex serum matrices. This work establishes a paradigm for designing topology-constrained, multifunctional peptide interfaces that overcome the longstanding trade-off between biofouling and enzymatic degradation, opening new avenues for high-fidelity electrochemical biosensing in complex biological matrices.
