Hybrid lipoplex co-delivering siPD-L1/miR-140-5p reverses T cell exhaustion via post-transcriptional regulation for in situ photothermal vaccination

Mild photothermal therapy (MPTT) can generate an in situ vaccine by releasing tumor-associated antigens (TAAs), yet its efficacy is often compromised by the concomitant upregulation of programmed cell death ligand 1 (PD-L1) in tumor cells, leading to T cell exhaustion and adaptive immune resistance. Although small interfering RNA (siRNA) targeted to the coding sequence (CDS) can degrade PD-L1 mRNA, the structural variations of mRNA in the 3' untranslated region (3'-UTR) can stabilize the transcript and impair siRNA efficacy. Thus, an effective PD-L1 blockade remains challenging, which requires the combination of targets to both CDS and 3'-UTR for post-transcriptional regulation. Herein, we developed a lipoplex hybridized with gold nanoflowers (AuNFs/RLS, AR) to generate an in situ vaccine through a local MPTT, which co-delivered silencing PD-L1 siRNA (siPD-L1) and microRNA-140-5p (miR-140-5p) (AR/si/mi). It promoted dendritic cell maturation, enhanced TAA uptake, and robust local immune priming. Approximately 90% inhibition of PD-L1 mRNA was achieved using the AR/si/mi system. In murine bilateral melanoma models, intratumoral administration of hybrid lipoplexes not only ablated primary tumors (95.8% inhibition) but also elicited systemic antitumor immunity, effectively suppressing untreated distant tumors (99.6% inhibition). This combination treatment mitigated MPTT-induced PD-L1 upregulation and alleviated T cell exhaustion. Collectively, these findings demonstrate a synergistic strategy that enhances photothermal immunotherapy through the co-delivery of siRNA and miRNA to suppress PD-L1, enabling potent and systemic antitumor responses.