Location and partition coefficients of anti-inflammatory drugs in EPC liposomes. A fluorescence quenching study using n-(9-anthroyloxy)-stearic probes

• Type: Article in International Scientific Journal
• Date: 2001

Authors

de Castro, B (Author) FCUP; Gameiro, P (Author) FCUP; Lima, JLFC (Author) FFUP; Matos, C (Author) Other; Reis, S (Author) FFUP

Journal

Title: Colloids and Surfaces A: Physicochemical and Engineering Aspects

Vol. 190

Pages: 205-212

ISSN: 0927-7757

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 22 Citations

Scopus - 30 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: P-000-T84

DOI: 10.1016/s0927-7757(01)00680-x

Abstract (EN): Steady-state fluorescence quenching of a series of n-(9-anthroyloxy) stearic acids (n-AS, n = 2, 6, 9 and 12) was used to investigate the location of two anti-inflammatory drugs, namely indomethacin and acemetacin, in multilamellar and unilamellar egg phosphatidylcholine liposomes (EPC) at two pH values (7.4 and 5.0). The quenching properties were also used in determining quantitatively the partition coefficient of both drugs in multilamellar and unilamellar EPC vesicles, at pH 7.4 using a 12-AS probe. All n-AS probes were quenched by both drugs and the relative quenching efficiencies are in the order 2-AS < 6-AS < 9-AS < 12-AS. At pH 5.0, the apparent Stern-Volmer constant values, k(q)(app), were always higher than those obtained at pH 7.4. The partition coefficients determined at pH 7.4 lead q to higher values for acemetacin than for indomethacin, especially for multilamellar liposomes (MLVs) and are identical, within experimental error, to those obtained by other methods. The observation that the k app values q increase with the depth of the probe (larger n) for both drugs at pH 7.4 suggests that the anti-inflammatory drugs can reach the inner part of the bilayer, probably with the negative carboxyl group anchored near the choline of the phospholipid headgroup, and with the rest of the molecule buried deeply in the membrane and aligned with the phospholipid aliphatic tails. Quenching of 12-AS is larger in MLVs than in LUVs, which can be related to the different packing of the lipids in these structures, and also to the different drug penetrations in the bilayer.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 8