Stimuli-Responsive mRNA Vaccines to Induce Robust CD8+ T Cell Response via ROS-Mediated Innate Immunity Boosting.

The messenger RNA (mRNA) vaccines hold great significance in contagion prevention and cancer immunotherapy. However, safely and effectively harnessing innate immunity to stimulate robust and durable adaptive immune protection is crucial, yet challenging. In this study, we synthesized a library of stimuli-responsive bivalent ionizable lipids (srBiv iLPs) with smart molecular blocks responsive to esterase, H2O2, cytochrome P450, alkaline phosphatase, nitroreductase, or glutathione (GSH), aiming to leverage physiological cues to trigger fast lipid degradation, promote mRNA translation, and induce robust antitumor immunity via reactive oxygen species (ROS)-mediated boosting. After subcutaneous immunization, esterase-responsive vaccine (eBiv-mVac) was rapidly internalized and transported into the draining lymph nodes. It then underwent fast decaging and self-immolative degradation in esterase-rich antigen-presenting cells, releasing sufficient mRNA for antigen translation and massive reactive quinone methides to elevate ROS levels. This resulted in broad activation of innate immunity to boost T cell response, prompting a large number of primed antigen-specific CD8+ T cells to circulate and infiltrate into tumors (>1000-fold versus unvaccinated control), thereby orchestrating innate and adaptive immunity to control tumor growth. Moreover, by further combining our vaccination strategy with immune checkpoint blockade, we demonstrated a synergism that significantly amplified the magnitude and function of antigen-specific CD8+ T cells. This, in turn, caused potent systemic antitumor efficacy and prolonged survival with high complete response rate in xenograft and metastasis models. Overall, our generalized stimuli-responsive mRNA delivery platform promises a paradigm shift in the design of potent vaccines for cancer immunotherapy, as well as effective and precise carriers for gene editing, protein replacement, and cell engineering.

Programmable DNA Tweezer-Actuated SERS Probe for the Sensitive Detection of AFB1.

A DNA tweezer is a dynamic DNA nanomachine that can reversibly switch its state between open and closed. Here, we employed a DNA tweezer for the first time to dynamically control the distance between plasmonic silver nanoparticles (Ag NPs) for a surface enhanced Raman scattering (SERS) biosensing application. Two DNA and 4-nitrothiophenol (4-NTP) modified Ag NPs were linked to the arms of the DNA tweezer (DNA tweezer-Ag NPs probe) by complementary base pairing. Activation of the Raman intensity was achieved by the state transformation of the DNA tweezer-Ag NPs probe from open to closed. The distances between two Ag NPs in open and closed state were 8.1 ± 2.7 nm and 3.2 ± 0.8 nm, respectively. Furthermore, the two Ag NPs were spatially separated in the open state with a low Raman signal, whereas in the closed state, Raman intensity was enhanced because of the proximity of two Ag NPs. The developed biosensing system exhibited a good linear relationship when the concentration of aflatoxin B1 (AFB1) ranged from 1 ng/mL to 0.01 pg/mL, and the limit of detection (LOD) was 5.07 fg/mL. In addition, spike recovery and certificated real foodstuffs were used to examine the feasibility in a real situation. This protocol provides a potential candidate for SERS detection and can be used as a promising technology for biological and chemical sensors.

Catalytic hairpin assembly-assisted lateral flow assay for visual determination of microRNA-21 using gold nanoparticles.

The authors describe an improved lateral flow assay based on (a) the use of catalytic hairpin assembly (CHA), and (b) on signal amplification performed at the interface of gold nanoparticles (AuNPs). The combination of the amplification capability of the CHA reaction and the unique optical properties of AuNPs results in an assay that has a sensitivity that is improved by more than two orders of magnitude. MicroRNA-21 was employed as a model analyte to prove the concept. The presence of microRNA-21 triggers the self-assembly of two hairpin DNAs into double stranded DNA and exposing biotin molecules on the surface of AuNPs. Hence, the target becomes recycled and the signal is strongly amplified. The AuNPs carrying biotin are captured on the test line of the strip to display a red zone. This enables the visual recognition of microRNA without the need for any instrumentation. The fast quantitation of microRNA via the red band intensity is accomplished with the help of software, and the limit of detection is 0.89 pM. The enhanced lateral flow assay was employed to the determination of microRNA-21 in cell extracts and spiked serum samples. Graphical abstract A lateral flow assay for microRNA is described with a detection limit that is improved by two orders of magnitude. It is based on catalytic hairpin assembly (CHA) signal amplification performed at the interface of gold nanoparticles.