Optical UVA biosensor platform for high-throughput testing of UV blockers.

UVR is a major public health concern, linked to skin cancer, eye damage, immune suppression, and premature aging. Yet, despite decades of innovation, the gold standard for sunscreen evaluation, sun protection factor and UVA protection factor testing in human volunteers, remains empirical, ethically questionable, and highly variable. In this study, we present an assay for UVA radiation assessment, a high-throughput, cell-based biosensor that luminesces in response to UVA exposure (320-400 nm). Assay for UVA radiation assessment-transgenic human cells express a membrane-anchored, photocleavable PhoCl domain fused to the tetracycline repressor and viral activator VP16, with nuclear export signals that ensure minimal basal activity. Upon UVA illumination, PhoCl cleavage liberates tetracycline repressor-VP16, which translocates to the nucleus and activates a tetracycline-responsive reporter. This molecular design enables sensitive detection of 365 nm and 395 nm light with up to 100-fold induction. By combining precision, reproducibility, and ethical advantages, assay for UVA radiation assessment establishes a powerful platform for the high-throughput testing of UV blockers and offers a transformative alternative to in vivo UVA protection factor assessment.