Polarity-switchable photoelectrochemical biosensors: applied materials, advances, and mechanisms

Polarity-switchable photoelectrochemical (PS-PEC) biosensors have emerged as a powerful platform for highly sensitive and selective detection of diverse analytes. By dynamically reversing photocurrent direction upon target binding, PS-PEC strategies overcome limitations of traditional signal-on/off approaches, offering self-calibration, enhanced reliability, and resistance to interference. Recent advances in photoelectrode design, including semiconductor heterojunctions, plasmonic composites, and nanozyme-based hybrids, combined with selective recognition elements such as molecularly imprinted polymers, antibodies, aptamers, and enzymes, have significantly improved light harvesting, charge separation, and target specificity. This review systematically summarizes the mechanisms, amplification strategies, engineered electrode materials, and detection performance of PS-PEC biosensors. Applications in biomedical diagnostics, environmental monitoring, and food safety are highlighted, along with current challenges and future perspectives toward portable, multifunctional, and intelligent sensing devices.