Efficient Hydrogen Generation from Ammonia Borane Hydrolysis on a Tandem Ruthenium-Platinum-Titanium Catalyst.

Hydrolysis of ammonia borane (NH3BH3, AB) involves multiple undefined steps and complex adsorption and activation, so single or dual sites are not enough to rapidly achieve the multi-step catalytic processes. Designing multi-site catalysts is necessary to enhance the catalytic performance of AB hydrolysis reactions but revealing the matching reaction mechanisms of AB hydrolysis is a great challenge. In this work, we propose to construct RuPt-Ti multi-site catalysts to clarify the multi-site tandem activation mechanism of AB hydrolysis. Experimental and theoretical studies reveal that the multi-site tandem mode can respectively promote the activation of NH3BH3 and H2O molecules on the Ru and Pt sites as well as facilitate the fast transfer of *H and the desorption of H2 on Ti sites at the same time. RuPt-Ti multi-site catalysts exhibit the highest turnover frequency (TOF) of 1293 min-1 for AB hydrolysis reaction, outperforming the single-site Ru, dual-site RuPt and Ru-Ti catalysts. This study proposes a multi-site tandem concept for accelerating the dehydrogenation of hydrogen storage material, aiming to contribute to the development of cleaner, low-carbon, and high-performance hydrogen production systems.

Tandem activated photodynamic and chemotherapy: Using pH-Sensitive nanosystems to realize different tumour distributions of photosensitizer/prodrug for amplified combination therapy.

Photodynamic therapy (PDT) combined with hypoxia-activated prodrugs to overcome hypoxia environment has been recently explored as a promising clinical modality for cancer therapy. Nevertheless, delivering these two therapeutic agents together to different tumour areas that possess a number of biological barriers remains a considerable challenge. Herein, we used the semiconducting polyelectrolyte-based zwitterionic photosensitizer (PFNS) to modify the surface of upconversion nanoparticles (NPs) and prepare near-infrared (NIR) light-responsive PDT agents (UCNP@PFNS). A pH-sensitive Mn-Ca3(PO4)2 (MnCaP) layer was further coated onto UCNP@PFNS with the hypoxia-activated prodrug AQ4N incorporated inside. The final nanocomposites exhibited a diameter of 73 nm with high stability in the blood and a remarkably enhanced permeability and retention (EPR) effect in tumours. Importantly, when these nanoparticles reached the tumour site, the acidic tumour microenvironment (pH 6.5-6.8) decomposed the MnCaP layer, releasing both UCNP@PFNS (30 nm) and AQ4N. The relatively small size of UCNP@PFNS and AQ4N satisfied the different distribution requirements in tumour and achieved a high therapeutic effect, thereby reaching an inhibition rate of as high as 83%. In addition, Mn2+ ions can be released during the decomposition of CaP, leading to a significantly increased magnetic resonance (MR) signal in the tumour site. Overall, we report a nanoparticle guided by MRI and fluorescence imaging possesses of tandem active pattern of PDT and chemotherapy, which is promising for future clinical diagnosis and treatment.

Magnetic Tandem Apoptosis for Overcoming Multidrug-Resistant Cancer.

Multidrug resistance (MDR) is a leading cause of failure in current chemotherapy treatment and constitutes a formidable challenge in therapeutics. Here, we demonstrate that a nanoscale magnetic tandem apoptosis trigger (m-TAT), which consists of a magnetic nanoparticle and chemodrug (e.g., doxorubicin), can completely remove MDR cancer cells in both in vitro and in vivo systems. m-TAT simultaneously activates extrinsic and intrinsic apoptosis signals in a synergistic fashion and downregulates the drug efflux pump (e.g., P-glycoprotein) which is one of the main causes of MDR. The tandem apoptosis strategy uses low level of chemodrug (in the nanomolar (nM) range) to eliminate MDR cancer cells. We further demonstrate that apoptosis of MDR cancer cells can be achieved in a spatially selective manner with single-cell level precision. Our study indicates that nanoscale tandem activation of convergent signaling pathways is a new platform concept to overcome MDR with high efficacy and specificity.