DNA hydrogels play an increasingly important role in biomedicine and bioanalysis applications. Due to their high programmability, multifunctionality and biocompatibility, they are often used as effective carriers for packing drugs, cells, or other bioactive cargoes in vitro and in vivo. However, the stability of the DNA hydrogels prevents their in‐demand rapid release of cargoes to achieve a full therapeutic effect in time. For bioanalysis, the generation of signals sometimes needs the DNA hydrogel to be rapidly degraded when sensing target molecules. To meet these requirements, stimulus‐responsive DNA hydrogels are designed. By responding to different stimuli, self‐degradable DNA hydrogels can switch from gel to solution for quantitative bioanalysis and precision cargo delivery. This review summarizes the recently developed innovative methods for designing stimuli‐responsive self‐degradable DNA hydrogels and showed their applications in the bioanalysis and biomedicines fields. Challenges, as well as prospects, are also discussed.

Immunotherapy is emerging as a paradigm-shifting modality for treatment cancer. However, systemic administration of immunomodulators is usually accompanied by extra-tumor toxicity and adverse immune effects. Precise delivery of immunomodulators with a highly controllable system may provide a solution for this issue. Here, we developed a photocontrolled DNA nanomedicine for localized delivery of DNA immunomodulators to enhance membrane-targeted photodynamic immunotherapy. Specifically, the DNA nanomedicine is composed of long tandemly repeated functional DNA sequences (PDL1 aptamers and CpG) with a photosensitizer (TMPyP4) inserted into the DNA structure, providing high drug-loading capacity. By blocking the surface PDL1 aptamer with a pHLIP-modified cDNA, the DNA nanomedicine does not induce any obvious immune response and can be specifically delivered and anchored to the tumor membrane. Under localized irradiation, photodynamically generated reactive oxygen species (ROS) causes breakage of DNA sequences, which triggers the collapse of the nanostructure and release of internal DNA immunomodulators. Under localized illumination, photodynamically generated ROS can cause DNA sequence breaks, triggering the collapse of nanostructures and the release of internal DNA immunomodulators thus enhancing membrane-targeted photodynamic immunotherapy. We have demonstrated that the developed DNA nanomedicine can drive efficient immune responses in tumor tissue without perceptibly interfering off-tumor immunity, resulting in efficient antitumor treatment while mitigating systemic toxicity.

Postoperative tumor recurrence and metastases often lead to cancer treatment failure. Here, we develop a local embedded photodynamic immunomodulatory DNA hydrogel for early warning and inhibition of postoperative tumor recurrence. The DNA hydrogel contains PDL1 aptamers that capture and enrich in situ relapsed tumor cells, increasing local ATP concentration to provide a timely warning signal. When a positive signal is detected, local laser irradiation is performed to trigger photodynamic therapy to kill captured tumor cells and release tumor-associated antigens (TAA). In addition, reactive oxygen species break DNA strands in the hydrogel to release encoded PDL1 aptamer and CpG, which together with TAA promote sufficient systemic antitumor immunotherapy. In a murine model where tumor cells are injected at the surgical site to mimic tumor recurrence, we find that the hydrogel system enables timely detection of tumor recurrence by enriching relapsed tumor cells to increase local ATP concentrations. As a result, a significant inhibitory effect of approximately 88.1% on recurrent tumors and effectively suppressing metastasis, offering a promising avenue for timely and effective treatment of postoperative tumor recurrence.