Intelligent Metal Carbonyl Metal-Organic Framework Nanocomplex for Fluorescent Traceable H2 O2 -Triggered CO Delivery

The recognized therapeutic benefits from carbon monoxide (CO) have caused booming attention to develop a CO therapy for various major diseases, such as cancer. However, the controlled release of CO gas and the monitoring of the CO release are vitally important to the on-demand CO administration for a safe and efficient therapy, but greatly challenging. In this work, a new CO-releasing nanocomplex was constructed by the adsorption and coordination of manganese carbonyl ([MnBr(CO)₅ ], abbreviated as MnCO) with a Ti-based metal-organic framework (Ti-MOF) to realize an intratumoral H₂ O₂ -triggered CO release and real-time CO release monitoring by fluorescence imaging. A high CO prodrug loading capacity (0.532 g MnCO per gram Ti-MOF) is achieved due to the high surface area of Ti-MOF, and the intracellular H₂ O₂ -triggered CO release from the MnCO@Ti-MOF is realized to enable the nanocomplex selectively release CO in tumor cells and kill tumor cells rather than normal cells. Particularly significant is that the real-time fluorescence imaging monitoring of the CO release is realized based on an annihilation effect of the fluorescence after MnCO loading into Ti-MOF and an activation effect of the fluorescence after CO release from Ti-MOF. The quantitative relationship between the fluorescence intensity and the released CO amount is established in great favor of guiding on-demand CO administration. The results demonstrate the advantage of versatile MOFs for high efficient CO delivery and monitoring, which is critical for the improvement of the effectiveness of future therapeutic application.

Monitoring pH-triggered drug release from radioluminescent nanocapsules with X-ray excited optical luminescence

One of the greatest challenges in cancer therapy is to develop methods to deliver chemotherapy agents to tumor cells while reducing systemic toxicity to noncancerous cells. A promising approach to localizing drug release is to employ drug-loaded nanoparticles with coatings that release the drugs only in the presence of specific triggers found in the target cells such as pH, enzymes, or light. However, many parameters affect the nanoparticle distribution and drug release rate, and it is difficult to quantify drug release in situ. In this work, we show proof-of-principle for a "smart" radioluminescent nanocapsule with an X-ray excited optical luminescence (XEOL) spectrum that changes during release of the optically absorbing chemotherapy drug, doxorubicin. XEOL provides an almost background-free luminescent signal for measuring drug release from particles irradiated by a narrow X-ray beam. We study in vitro pH-triggered release rates of doxorubicin from nanocapsules coated with a pH-responsive polyelectrolyte multilayer using HPLC and XEOL spectroscopy. The doxorubicin was loaded to over 5% by weight and released from the capsule with a time constant in vitro of ∼36 days at pH 7.4 and 21 h at pH 5.0, respectively. The Gd₂O₂S:Eu nanocapsules are also paramagnetic at room temperature with similar magnetic susceptibility and similarly good MRI T₂ relaxivities to Gd₂O₃, but the sulfur increases the radioluminescence intensity and shifts the spectrum. Empty nanocapsules did not affect cell viability up to concentrations of at least 250 μg/mL. These empty nanocapsules accumulated in a mouse liver and spleen following tail vein injection and could be observed in vivo using XEOL. The particles are synthesized with a versatile template synthesis technique which allows for control of particle size and shape. The XEOL analysis technique opens the door to noninvasive quantification of drug release as a function of nanoparticle size, shape, surface chemistry, and tissue type.