In vivo and in vitro systems were employed to investigate the biocompatibility of two forms of calcined mesoporous silica microparticles, MCM41-cal and SBA15-cal, with ventricular myocytes. These particles have potential clinical use in delivering bioactive compounds to the heart. Ventricular myocytes were isolated from 6 to 8 week male Wistar rats. The distribution of the particles in ventricular myocytes was investigated by transmission electron microscopy and scanning electron microscopy. The distribution of particles was also examined in cardiac muscle 10 min after intravenous injection of 2.0 mg/mL MCM41-cal. Myocyte shortening and the Ca 2+ transient were determined following exposure to 200 μg/mL MCM41-cal or SBA15-cal for 10 min. Within 10 min of incubation at 25 C, both MCM41-cal and SBA15-cal were found attached to the plasma membrane, and some particles were observed inside ventricular myocytes. MCM41-cal was more abundant inside the myocytes than SBA15-cal. The particles had a notable affinity to mitochondrial membranes, where they eventually settled. Within 10 min of intravenous injection (2.0 mg/mL), MCM41-cal traversed the perivascular space, and some particles entered ventricular myocytes and localized around the mitochondrial membranes. The amplitude of shortening was slightly reduced in myocytes superperfused with MCM41-cal or SBA15-cal. The amplitude of the Ca 2+ transient was significantly reduced in myocytes superperfused with MCM41-cal but was only slightly reduced with SBA15-cal. Overall, the results show reasonable bioavailability and biocompatibility of MCM41-cal and SBA15-cal with ventricular myocytes.
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