PubMed · 5980769
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K Navrátil. 1966. [Spofavit. (Dragée)].. https://pubmed.ncbi.nlm.nih.gov/5980769/
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Liposomes due to their biphasic characteristic and diversity in design, composition and construction, offer a dynamic and adaptable technology for enhancing drug solubility. Starting with equimolar egg-phosphatidylcholine (PC)/cholesterol liposomes, the influence of the liposomal composition and surface charge on the incorporation and retention of a model poorly water soluble drug, ibuprofen was investigated. Both the incorporation and the release of ibuprofen were influenced by the lipid composition of the multi-lamellar vesicles (MLV) with inclusion of the long alkyl chain lipid (dilignoceroyl phosphatidylcholine (C24PC)) resulting in enhanced ibuprofen incorporation efficiency and retention. The cholesterol content of the liposome bilayer was also shown to influence ibuprofen incorporation with maximum ibuprofen incorporation efficiency achieved when 4 micromol of cholesterol was present in the MLV formulation. Addition of anionic lipid dicetylphosphate (DCP) reduced ibuprofen drug loading presumably due to electrostatic repulsive forces between the carboxyl group of ibuprofen and the anionic head-group of DCP. In contrast, the addition of 2 micromol of the cationic lipid stearylamine (SA) to the liposome formulation (PC:Chol - 16 micromol:4 micromol) increased ibuprofen incorporation efficiency by approximately 8%. However further increases of the SA content to 4 micromol and above reduced incorporation by almost 50% compared to liposome formulations excluding the cationic lipid. Environmental scanning electron microscopy (ESEM) was used to dynamically follow the changes in liposome morphology during dehydration to provide an alternative assay of liposome stability. ESEM analysis clearly demonstrated that ibuprofen incorporation improved the stability of PC:Chol liposomes as evidenced by an increased resistance to coalescence during dehydration. These finding suggest a positive interaction between amphiphilic ibuprofen molecules and the bilayer structure of the liposome.
Estradiol-3-benzoate (EB), an ester derivative of the main oestrogen hormone estradiol, was chemically modified and bound to poly(alpha,beta-(N-2-hydroxyethyl-DL-aspartamide))-poly(alpha,beta-(N-2-aminoethyl-DL-aspartamide)) copolymer (PAHA). EB was first converted to estradiol-3-benzoate-17-(benzotriazole-1-carboxylate), which readily reacted with amino groups in PAHA affording the polymer-drug conjugate PAHA-EB. In PAHA-EB estradiol moiety was covalently bound to the polymeric carrier by carbamate linkage, through non-toxic ethylenediamine spacer. The synthesized compound is a potential hydrosoluble estradiol prodrug.
Poly(vinyl alcohol) (PVA) microspheres containing cyclodextrin (CD) were obtained by chemical cross-linking with glutaraldehyde of an acidified mixture solution of PVA and alpha-, beta- or gamma-CD. The amount of linked CD in microspheres, estimated by tetrazolium blue method, decreases in the order beta- > gamma- > alpha-CD. The dimensions of PVA/gamma-CD microspheres are much higher than those of PVA/alpha- and beta-CD. The cross-linking density of microspheres was estimated by the amount of iodine retained by the polymer matrix. The pore size as well as the porous volume of PVA/CD microspheres decrease significantly on increasing the amount of glutaraldehyde, but are enough large to permit the access of drugs to the CD cavity. In order to test the PVA/CD microsphere inclusion ability, the microspheres were packed in a glass column and the liquid chromatographic behaviour by isocratic elution of different drugs or typical organic compounds, taken as model drugs, was investigated.