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ABSTRACT: The ability of cell-penetrating peptides (CPPs) to deliver a range of membrane-impermeable molecules into living cells makes them attractive potential vehicles for therapeutics. However, in vivo, the efficiency of CPP delivery to the cytosol remains unsatisfactory owing to endosomal entrapment and/or systemic toxicity, which severely restrict their bioavailability and efficacy in in vivo applications. In this study, we developed a series of novel chimeras consisting of various numbers of d- and l-arginine residues and investigated their cellular uptake behaviors and systemic toxicities. We demonstrated that the intracellular distribution, uptake efficiency, and systemic toxicity of these oligoarginines were all significantly affected by the number of d-arginine residues in the peptide sequence. We also found that a hybrid peptide, (rR)(3)R(2), possessed low systemic toxicity, high uptake efficiency, and, remarkably, achieved efficient cytosolic delivery not only in cultured cells but also in living tissue cells in mice after intravenous injection, implying that this heterogeneous motif might have promising applications in the delivery of cargoes of small sizes directed to cytosolic targets in vivo. Our studies into the uptake mechanism of (rR)(3)R(2) indicate that its cellular uptake was not affected by pharmacological or physical inhibitors of endocytosis but by the elimination of the membrane potential, suggesting that (rR)(3)R(2) does not enter the cells via endocytosis but rather through direct membrane translocation driven by the membrane potential. The results here might provide useful guidelines for the design and application of CPPs in drug delivery.
Journal of Controlled Release 07/2012; 162(2):286-94. · 5.73 Impact Factor
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ABSTRACT: The remarkable ability of cell-penetrating peptides (CPPs) to deliver cell-impermeable compounds into living cells makes them attractive transporters for use in biology and medicine. Despite their highly efficient cellular uptake, CPPs consisting of natural amino acids always suffer from degradation and endosomal entrapment, thereby greatly limiting their application in vivo. Here, we describe the preparation of novel CPPs incorporating α-aminoxy acid residues and their cellular uptake behavior. We demonstrate that introducing α-aminoxy acids into the backbones of CPPs enhances their diffuse cytosolic distribution after direct membrane translocation. We also reveal a hybrid peptide, consisting of D-α-aminoxy acids and L-α-amino acids, that achieves efficient diffuse distribution in the cytosol, is stable toward serum, and possesses low cytotoxicity, thus making it a possible vector candidate for in vivo applications. Our results confirm that α-aminoxy acids are useful building blocks when designing novel CPPs possessing favorable properties.
ChemBioChem 12/2011; 13(1):73-9. · 3.94 Impact Factor
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Yilong Ma
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ABSTRACT: A relatively simple potentiometric pCO2 gas-sensing microelectrode is described. It is based on an ion-exchanger pH electrode, has a 2- to 5-μm tip, and has an air gap which is formed by means of hydrophobic treatments. The microelectrode exhibits a linear response in the range 10−4–10−2m with a Nernstain slope of 59 to 62 mV/decade at 25°C. Ninety-five percent of the steady-state response time is about 20–30 s at the flow system when the concentration of sodium bicarbonate in buffer solution (pH 4.5) suddenly shifts from 0.2 to 2 mm and the lifetime is longer than 1 week.
Analytical Biochemistry 186(1):74-77. · 3.00 Impact Factor
