Ibuprofen was crystallized from methanol, ethanol, isopropanol, and hexane at similar conditions. Marked differences in crystal habit of the samples obtained from these solvents were observed. The samples crystallized from methanol and ethanol had a polyhedral crystal habit, while those from hexane were needlelike. Those from isopropanol were elongated crystals. X-ray powder diffraction (XPD) and diferential scanning calorimetry (DSC) studies confirmed that these samples were structurally similar, therefore, polymorphic modifications were ruled out. The results showed that crystal habit modification had a great influence on the mechanical properties (compressibility, flow rate, and bulk density) of ibuprofen crystals. Samples obtained from methanol and ethanol exhibited the highest bulk density and the best flow rate, while those from hexane showed the lowest bulk density and the worst flow rate. The samples obtained from ethanol exhibited the best compression force/hardness profiles, and those obtained from hexane produced the softest tablets.
BackgroundProprotein convertase subtilisin/kexin 9 (PCSK9) is an important regulator of low-density lipoprotein receptor (LDLR) and plasma levels of LDL cholesterol (LDL-C). PCSK9 inhibition is an efficient therapeutic approach for the treatment of dyslipidemia. We tested the therapeutic effect of a PCSK9 vaccine on dyslipidemia and atherosclerosis.MethodsLipid film hydration method was used to prepare negatively charged nanoliposomes as a vaccine delivery system. An immunogenic peptide called immunogenic fused PCSK9-tetanus (IFPT) was incorporated on the surface of nanoliposomes using DSPE-PEG-maleimide lipid (L-IFPT) and adsorbed to Alhydrogel® (L-IFPTA+). The prepared vaccine formulation (L-IFPTA+) and empty liposomes (negative control) were inoculated four times with bi-weekly intervals in C57BL/6 mice on the background of a severe atherogenic diet and poloxamer 407 (thrice weekly) injection. Antibody titers were evaluated 2 weeks after each vaccination and at the end of the study in vaccinated mice. Effects of anti-PCSK9 vaccination on plasma concentrations of PCSK9 and its interaction with LDLR were determined using ELISA. To evaluate the inflammatory response, interferon-gamma (IFN-γ)- and interleukin (IL)-10-producing splenic cells were assayed using ELISpot analysis.ResultsL-IFPTA+ vaccine induced a high IgG antibody response against PCSK9 peptide in the vaccinated hypercholesterolemic mice. L-IFPTA+-induced antibodies specifically targeted PCSK9 and decreased its plasma consecration by up to 58.5% (− 164.7 ± 9.6 ng/mL, p = 0.0001) compared with the control. PCSK9-LDLR binding assay showed that generated antibodies could inhibit PCSK9-LDLR interaction. The L-IFPTA+ vaccine reduced total cholesterol, LDL-C, and VLDL-C by up to 44.7%, 51.7%, and 19.2%, respectively, after the fourth vaccination booster, compared with the control group at week 8. Long-term studies of vaccinated hypercholesterolemic mice revealed that the L-IFPTA+ vaccine was able to induce a long-lasting humoral immune response against PCSK9 peptide, which was paralleled by a significant decrease of LDL-C by up to 42% over 16 weeks post-prime immunization compared to control. Splenocytes isolated from the vaccinated group showed increased IL-10-producing cells and decreased IFN-γ-producing cells when compared with control and naive mice, suggesting the immune safety of the vaccine.ConclusionsL-IFPTA+ vaccine could generate long-lasting, functional, and safe PCSK9-specific antibodies in C57BL/6 mice with severe atherosclerosis, which was accompanied by long-term therapeutic effect against hypercholesterolemia and atherosclerosis.
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