Chemical Modifications of Porous Carbon Nanospheres Obtained from Ubiquitous Precursors for Targeted Drug Delivery and Live Cell Imaging

Cost-effective anti-cancer drug delivery vehicles that can ensure controlled and targeted transportation of drug molecules are pertinent to modern day biomedical applications. Minimally toxic 9–13 nm diameter porous carbon nanospheres (PNs) were synthesized by oxidative cutting of porous carbon matrices (PCs) obtained by carbonization of pasture grass, human hair and sucrose. Among them, the grass-derived PNs (PN-G) with superior surface area, porosity and graphitic content demonstrate a significant loading of the drug both by chemical binding and physisorption. Polyethylenimine (PEI) and folic acid (FA) functionalization maintain therapeutic efficacy of the drug doxorubicin (DOX) to the targeted folate receptor (FR) overexpressed human cervical cancer cells (HeLa) and human breast cancer cells (MDA-MB-231) through receptor mediated endocytosis whereas FR deficient normal cells (human embryonic kidney 293) exhibit substantially lower endocytosis under identical conditions. Moreover, upon loading cell-impermeable propidium iodide (PI), the PNs display superior activity toward near-infrared (NIR) live cell imaging in HeLa cells whereby due to a higher binding affinity of PI with the nucleic acids, the PI-to-PN energy transfer quenched fluorescence is recovered. This dual functionality of controlled and targeted drug delivery and photobleaching resistant live cell imaging by the cost-effective PNs has larger implications in nanomedicine research and technology. Porous carbon nanospheres derived from abundant resources act as highly efficient and cost-effective nanocarriers for targeted anticancer drug delivery and live cell imaging

Maneuvering the Physical Properties and Spin States To Enhance the Activity of La–Sr–Co–Fe–O Perovskite Oxide Nanoparticles in Electrochemical Water Oxidation

Perovskite oxides have attracted considerable attention as durable electrocatalysts for metal–air batteries and fuel cells due to their precedence in oxygen electrocatalysis in spite of the complexities involved with their crystal structure, spin states, and physical properties. Here we report optimization of the activity of a model perovskite system La_1–<i>x</i>Sr_<i>x</i>Co_1–<i>y</i>Fe_<i>y</i>O_3−δ (LSCF; <i>x</i> = 0.301, <i>y</i> = 0.298, and δ = 0.05–0.11) toward electrochemical water oxidation (OER) by altering the calcination temperature of the nonaqueous sol–gel synthesized nanoparticles (NPs). Our results show that improved OER activity is the result of a synergism between its morphology, surface area, electrical conductivity, and spin state of the active transition metal site. With an e_g orbital occupancy of 1.26, the interconnected ∼90 nm LSCF NPs prepared at 975 °C (LSCF-975) outperforms the other distinguishable LSCF morphologies, requiring 440 mV overpotential to achieve 10 mA/cm², a performance comparable to the best-performing perovskite oxide electrocatalysts. While the interconnected NP morphology increases the propensity of electronic conduction across crystalline grain boundaries, the morphology-tuned high spin Co³⁺ ions increases the probability of binding reaction intermediates at the available surface sites. Density functional theory based work function modeling further demonstrates that LSCF-975 is the most favorable OER catalyst among others in terms of a moderate work function and Fermi energy level facilitating the adsorption and desorption of reaction intermediates