Palindromic Fragment-Mediated Single-Chain Amplification: An Innovative Mode for Photoelectrochemical Bioassay

This work reports a strategy for glutathione-loaded liposome-encoded magnetic beads initiated by palindromic fragment-mediated single-chain amplification (PFMSCA) for high-precision quantification of a low-abundance aminoglycoside antibiotic (kanamycin; Kana) by using In₂O₃-ZnIn₂S₄ (IO-ZIS) as a photoactive matrix. In this strategy, a Kana-recognition region, primer-like palindromic fragment, and polymerization/nicking template are reasonably integrated into one oligonucleotide (hairpin HP1) for target recognition, magnetic separation, and target amplification. Upon target Kana introduction, the Kana-aptamer region in HP1 specifically recognizes the Kana and triggers the palindromic tails intramolecular self-hybridization, amplifying a large number of short fragments in the presence of Klenow fragment polymerase and Nt.BbvCI. The as-generated nick fragments act as a linker to introduce the free hairpin HP2-functionalized glutathione-loaded liposomes (HP2-GLL) onto the surface of the hairpin HP3-modified magnetic beads (HP3-MB), constructing liposome-encoded magnetic beads (HP3-MB-nick-HP2-GLL). Following magnetic separation, the detached glutathione-loaded liposomes (GLL) are lysed by treatment with 1% Triton X-100 to release the glutathione within it, which were then detected as an amplified photocurrent at the IO-ZIS-based photoelectrode. Importantly, this method can be readily carried out by using one oligonucleotide to achieve an exponential amplification effect and open new opportunities for advanced development of robust biodetection systems.