Construction Of Telomerase-triggered DNA Nanoprobes For Diagnosis And Therapy

Telomerase is a specialized reverse transcriptase that can maintain genomic stability and cell viability by adding telomeric repeats to the 3'end of telomeres.Due to its high expression in more than 85%of cancer cells and almost absence in normal cells,telomerase is considered as an important diagnostic and prognostic cancer biomarker.Rapid and sensitive detections of telomerase activity can contribute to cancer diagnosis and anticancer drugs screening.Telomerase-activated cancer therapy can greatly enhance specificity.Recently,DNA nanoprobes have attracted more attention due to its programmability and stimuli-responsiveness.Based on the biological function of telomerase and unique properties of DNA probes,we designed a telomerase-triggered DNA walker for telomerase activity sensing and a telomerase-activated drug releasing nanoprobe for cancer therapy,including the following parts:?1?We designed a telomerase-triggered three-dimensional DNA walker consisting of a superhairpin structure with a bulged loop in the stem as the walking strand and dye-labeled tracks for ultrasensitive detection of telomerase activity.In the presence of telomerase,the primers in the stem of the superhairpin structure were elongated and triggered internal strand displacement,thus activating the superhairpin structure.Thus,the DNA walker could step along the track via enzymatic cleavage for signal amplification.The telomerase-triggered DNA walker was further applied to various cancer lines with high sensitivity and selectivity,and a low detection limit of telomerase activity was realized to be equivalent to 90 cells?L^-1 for He La cells.This telomerase-triggered DNA walker provides a new concept on signal transduction for telomerase detection and is anticipated to stimulate interest in DNA nanomachine design for bioanalysis.?2?A DNA-based composite nanoprobe with tandem responses to tumor microenvironment was constructed and used in cancer treatment.The triple-layered composite nanoprobe was stepwise fabricated with a telomerase-responsive functional gold nanoparticle inner,a p H-sensitive MOF filling and H₂O₂-responsive coordination complexes of Fe³⁺and eigallocatechin gallate?EGCG?as the shell.Under tumor microenvironment,the shell was dissociated by endogenous H₂O₂ and simultaneously produced highly reactive hydroxyl radicals by Fenton reaction.Meanwhile,the released EGCG could down-regulate the expression of P-glycoprotein which was responsible for drug efflux.After the dissociation of the framework by protons,telomerase could trigger the release of the drug intercalated in the nicked molecule beacon.By integrating confined drug release,inhibited efflux pump,and chemodynamic therapy,the all-in-one chemotherapy strategy was identified with enhanced therapeutic efficacy in drug resistant cancer cells.This work presents a significant example of the tandem responsive to tumor microenvironment and telomerase-triggered drug releasing strategy,and shows great potential in multiple therapies.