Work

Is Bioorthogonal Pretargeting Superior to Conventional Targeted Photosensitizers? A Comparative Study of Chlorin Delivery Using Biotin Vectors

Year: 2026

Type: preprint

Abstract: Bioorthogonal pretargeting offers a modular approach to targeted photodynamic therapy (PDT), but its advantages over conventional ligand-photosensitizer conjugates remain insufficiently explored. Here, we aimed to directly compare preformed biotin-containing conjugates with sequential biotin-mediated bioorthogonal delivery. DFT calculations were used to guide the design of new tetrazine dienes with tuned electronic properties for inverse-electron-demand Diels-Alder (IEDDA) chemistry. The selected tetrazines were synthesized and paired with BCN- and s-TCO-functionalized chlorin photosensitizers, and their reactivity was characterized by second-order rate constants and photophysical measurements. In vitro, sequential pretargeting produced substantially higher intracellular fluorescence than administration of preformed 1:1 ligation products; however, this advantage did not translate into enhanced photodynamic activity. Moreover, neither accumulation nor PDT efficacy consistently correlated with SLC5A6 expression in SMVT-high SK-BR-3 versus SMVT-low MDA-MB-231 cells. Free-biotin competition produced heterogeneous, combination-dependent effects, indicating that SMVT is unlikely to be the sole determinant of uptake.

Source: ChemRxiv

DOI: 10.26434/chemrxiv.15008548/v1