Thermoresponsive Polymeric Nanolenses Magnify the Thermal Sensitivity of Single Upconverting Nanoparticles

Thermal-Responsive Gel-Based Overheat Limiter Enabled Intelligent Photothermal Therapy

Uncontrolled and excessive photothermal heating in photothermal therapy (PTT) inevitably causes thermal damage to surrounding normal tissues, severely limiting the universality and safety of PTT. To address this issue, an intelligent cooling thermal-responsive (ICTR) gel containing poly(N-isopropylacrylamide-co-acrylamide) (P(NIPAM-AM))microgel is applied onto the skin to realize intelligent PTT, which can avoid excessive heating and accidental injury. The high near-infrared (NIR) light transmittance (> 95%) of the ICTR gel ensures effective light delivery at low temperatures, while the refractive index of the P(NIPAM-AM) microgel increases remarkably when the temperature exceeds a predetermined threshold, resulting in progressively enhanced light scattering and weakened photothermal conversion. In animal studies, the negative feedback regulation of ICTR gel on light transmittance and photothermal heating allows the photothermal temperature in the lesion site to be stabilized within the effective therapeutic range (45 °C) while ensuring that the skin surface temperature does not exceed 35 °C. Compared with the severe skin thermal damage found in the histological staining of mice skin receiving conventional PTT, the mice skin receiving the ICTR gel-enabled intelligent PTT remains in good condition. This study establishes an intelligent and universal paradigm for PTT thermal regulation, which is of great significance for achieving safe and effective PTT.

Microlens-Assisted Light-Scattering Imaging of Plasmonic Nanoparticles at the Single Particle Level

We present a microlens-assisted imaging approach to record the scattering light of plasmonic nanoparticles at the single particle level. The microlens can significantly enhance the backscattering of visible light from individual plasmonic nanoparticles by several dozen folds, and single gold nanoparticles with a diameter as low as 60 nm can be imaged under a conventional optical microscope. This can benefit from a significant increase in the scattering intensity afforded by the microlens, meaning that the imaging of gold nanoparticles at a high temporal resolution (up to 5000 Hz) can be achieved, which is fast enough to record single particle adhesion events on the substrate. This research presents a fast and efficient means of acquiring scattering light from plasmonic nanoparticles, which has great potential to develop plasmonic nanoparticle-based biosensors and investigate a wide range of plasmonic nanoparticle-based fast interaction processes.

Hot Brownian Motion of Thermoresponsive Microgels in Optical Tweezers Shows Discontinuous Volume Phase Transition and Bistability

Microgels are soft microparticles that often exhibit thermoresponsiveness and feature a transformation at a critical temperature, referred to as the volume phase transition temperature. Whether this transformation occurs as a smooth or as a discontinuous one is still a matter of debate. This question can be addressed by studying individual microgels trapped in optical tweezers. For this aim, composite particles are obtained by decorating  Poly-N-isopropylacrylamide (pNIPAM) microgels with iron oxide nanocubes. These composites become self-heating when illuminated by the infrared trapping laser, performing hot Brownian motion within the trap. Above a certain laser power, a single decorated microgel features a volume phase transition that is discontinuous, while the usual continuous sigmoidal-like dependence is recovered after averaging over different microgels. The collective sigmoidal behavior enables the application of a power-to-temperature calibration and provides the effective drag coefficient of the self-heating microgels, thus establishing these composite particles as potential micro-thermometers and micro-heaters. Moreover, the self-heating microgels also exhibit an unexpected and intriguing bistability behavior above the critical temperature, probably due to partial collapses of the microgel. These results set the stage for further studies and the development of applications based on the hot Brownian motion of soft particles.

Nanoparticle-Based Drug Delivery Systems Targeting Tumor Microenvironment for Cancer Immunotherapy Resistance: Current Advances and Applications

Cancer immunotherapy has shown impressive anti-tumor activity in patients with advanced and early-stage malignant tumors, thus improving long-term survival. However, current cancer immunotherapy is limited by barriers such as low tumor specificity, poor response rate, and systemic toxicities, which result in the development of primary, adaptive, or acquired resistance. Immunotherapy resistance has complex mechanisms that depend on the interaction between tumor cells and the tumor microenvironment (TME). Therefore, targeting TME has recently received attention as a feasibility strategy for re-sensitizing resistant neoplastic niches to existing cancer immunotherapy. With the development of nanotechnology, nanoplatforms possess outstanding features, including high loading capacity, tunable porosity, and specific targeting to the desired locus. Therefore, nanoplatforms can significantly improve the effectiveness of immunotherapy while reducing its toxic and side effects on non-target cells that receive intense attention in cancer immunotherapy. This review explores the mechanisms of tumor microenvironment reprogramming in immunotherapy resistance, including TAMs, CAFs, vasculature, and hypoxia. We also examined whether the application of nano-drugs combined with current regimens is improving immunotherapy clinical outcomes in solid tumors.