The effect of chelation of three alkaline earth metals (Ca, Sr, and Ba) by polyphosphates on the pH and viscosity of the solution is examined and correlated to the phosphate glass properties. Also, the impact of the polyphosphate average degree of polymerization (D(p)) as well as the type and amount of chelated divalent cation on the degradation rate of the chains is studied. Subsequently, the number of divalent cations required for polyphosphate chain agglomeration to form a coacervate, and the resulting composition of these coacervates, was investigated. A decrease in polyphosphate solution pH during chelation was routinely obtained, with a sudden shift in the rate of pH drop occurring around a divalent cation/phosphorus molar ratio of 0.18. Longer chains or cations with a smaller ionic radius accelerated the rate of D(p) reduction. The number of divalent cations required for coacervation depends on different variables such as the polyphosphate concentration, the D(p), and the type of divalent cation. The formed coacervate retains the D(p) of polyphosphate originally used for coacervation, and the resulting Ca/P molar ratio depends largely on the amount of calcium being used during coacervation. Overall, this article helps one to understand the coacervation of polyphosphates in order to exploit their potential as a biomaterial.
A cellulose nanocrystal liquid crystalline suspension was mixed with monomers and confined to a capillary tube. After photopolymerization, a fiber with a single-domain concentric chiral nematic structure throughout the length of the fiber was obtained.
Cutaneous leishmaniasis is caused by different species of Leishmania parasites and its available treatments have not yet provided a strong consistent result. The weak response of current chemotherapeutics is due to their deficient effects on stealth parasites inside macrophages, rapid clearance from the site of action and systemic side effects in high doses. Liposomal formulation of anti-leishmanial drugs could overcome these problems. In this study, different liposomal formulations of three famous anti-leishmanial drugs: Glucantime®, miltefosine and paromomycin were prepared by a modified freeze-drying double emulsion method. Liposome size, zeta potential and encapsulation efficiency were evaluated, and their imaging was carried out by means of atomic force microscopy. Three formulations were evaluated in vivo by subcutaneous injection into skin lesions caused by Leishmania major in BALB/c mice. Encapsulation efficiency of prepared liposomes was up to 90%; however, they inherited a bimodal size distribution that caused their encapsulation efficiency to decrease to 50% during filtering sterilization. Besides, the effect of surface charge was significant on preparation procedure, size and encapsulation efficiency. All three formulations reduced amastigote counts and lesion size but only miltefosine-loaded formulations had significant therapeutic effects compared with control group (p < 0.05).
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