CoSe2 nanoparticles catalyzed the formation of Cu-BTC polyhedral nanoframes enabling biosensing of endogenous opioid peptides

We describe a point-of-care biosensing platform for the detection of endogenous opioids using an integrated assay. In this system, cobalt–selenium (Co-Se2) nanoparticles catalyze the formation of tunable Cu-BTC metal–organic framework (MOF) nanostructures (Cu-BTC@Co-Sex:1MOFs), which serve as potential biosensing candidates. These Cu-BTC@Co-Sex:1MOFs are functionalized with mono-target (Anti-Met-Enk or Anti-Leu-Enk) and/or dual-target (Anti-Met-Enk/Leu-Enk) antibodies for the selective and simultaneous recognition of Met-Enkephalin (Met-Enk) and Leu-Enkephalin (Leu-Enk). Bovine serum albumin is employed as a blocking agent to minimize nonspecific binding, thereby enhancing the specificity and reproducibility of the biosensor and enabling the detection of Met-Enk and Leu-Enk within clinically relevant concentration ranges. Among various MOF configurations, the Cu-BTC@Co-Se3:1MOFs-based biosensing platform exhibits a broad detection range, 1.0–200.0 pg/mL for Met-Enk and 5.0–300.0 pg/mL for Leu-Enk covering physiological concentration ranges, with limits of detection of 0.81 and 3.64 pg/mL, respectively (S/N = 3). These performance characteristics are primarily attributed to the following: (i) a noticeable difference in isoelectric points between Cu-BTC@Co-Se3:1MOFs (≥8.61) and Anti-Met-Enk-Abs (∼4.94), which facilitates electrostatic interactions for effective antibody incorporation; (ii) the distribution of Co-Se2 nanoparticles within the MOF porous cavities and on the surface, providing a high active surface area (57.4 and 51.6 m2/g), which enables the efficient Anti-Met-Enk-Abs antibody immobilization; and (iii) ester-like bridging between antibody carboxyl groups and metal centers (Cu, Co, and Se) through chemical adsorption interactions. Finally, clinical validation with human serum and artificial mouse cerebrospinal fluid showed recovery rates of 90.6%–96.2%, comparable to those from a standard ELISA kit.