Terminal Protection Of Small Molecule-linked DNA Research Articles

Dual-recognition-based determination of ctDNA via the clamping function of peptide nucleic acid and terminal protection of small-molecule-linked DNA.

A new dual-recognition fluorescent biosensor for circulating tumor DNA (ctDNA) detection has been developed, which combines the clamping function of peptide nucleic acid (PNA) and terminal protection of small-molecule-linked DNA (TPSMLD). Taking the tumor-specific E542K mutation and methylation of the PIK3CA gene as the target ctDNA, a low detection limit of 0.3161 pM ctDNA is achieved with good selectivity. This study not only offers a sensitive, selective and accurate ctDNA detection method, but can also be used to detect the target in complex biological samples.

Conjugated cationic polymer-assisted amplified fluorescent biosensor for protein detection via terminal protection of small molecule-linked DNA and graphene oxide

A sensitive and selective protein biosensor was proposed based on cationic conjugated polymer (PFP)-induced signal amplification with the aid of terminal protection of small molecule-linked DNA (TPSMLD) and graphene oxide (GO). The DNA probe labeled with fluorescein (FAM, P2) had a complementary sequence to the small molecule modified single-stranded DNA (P1). Taking streptavidin (SA) as the target protein, P1 labeled with biotin was digested to small nucleotide fragments by exonuclease I (Exo I) without SA. Upon adding PFP to P2-GO complex, weak fluorescence resonance energy transfer (FRET) from PFP to FAM-induced fluorescence signal was observed owing to the equal affinity for P2 and PFP toward GO. In the presence of SA, P1 was protected from the digestion of Exo I due to the specific binding between SA and biotin, releasing P2 from GO surface by hybridization to form double-stranded DNA (dsDNA). In this case, the addition of PFP led to obvious FRET signal because of strong electrostatic interactions between dsDNA and PFP. By monitoring the change of FRET signal, SA could be quantified. Compared to the strategy without PFP, the introduction of PFP showed an enhanced sensitivity with a detection limit of 1.6ngmL−1 for SA detection. Also, folate reporter was detected based on this platform with a good linear relationship, demonstrating the generality of this design.

MoS2 nanosheet-based fluorescent biosensor for protein detection via terminal protection of small-molecule-linked DNA and exonuclease III-aided DNA recycling amplification.

A new MoS2 nanosheet-based fluorescent biosensor for protein detection is developed. This method combines the terminal protection of small-molecule-linked DNA (TPSMLD) and exonuclease III (Exo III)-aided DNA recycling amplification to convert protein assay into the highly sensitive detection of DNA. Taking the streptavidin (SA)-biotin system as a model, a detection limit of 0.67 ng mL(-1) SA is obtained with a good selectivity. The study demonstrated here not only offers simple, sensitive and selective detection method for protein assay, but also will expand the application of the emerging 2D nanomaterials into biological assay.