Abstract
Polymerized liposomes encapsulating L-tryptophan were studied with the aim to characterize them as drug delivery systems for the treatment of several metabolic diseases that need an increased systemic L-tryptophan concentration. polymerized liposomes were obtained by UV irradiation of vesicles containing 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DC8,9PC) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) in a 1:1 molar ratio, in the presence of 10 and 50 mol% of L-tryptophan (respect to total lipid concentration). Polymerization efficiency was studied spectrophotometrically. Also, bilayer packing at the polar head region was followed with the Merocyanine 540 (MC540) and specific interactions in the lipopolymers were studied by FTIR. High L-tryptophan concentrations (50 mol% respect to total lipid concentration) induced a higher amount of six- and nine-unit polymers. This phenomenon was induced because the L-tryptophan located outside the lipid membrane was included in it during the polymerization process and was thus responsible for the better accommodate of the polar head region. This was not possible with the lower amount of L-tryptophan (10 mol%). The stability of lipopolymers with different amounts of L-tryptophan was studied through release profiles. Polymerized liposomes with 50 mol% of L-tryptophan were able to retain around 80% of the amino acid after 24 hours, whereas those with 10 mol % of the amino acid were able to retain 20%. The metabolic activity of the Caco-2 cell line was also studied. Cytotoxic effects were low in the presence of polymerized liposomes, rendering a maximum percentage of cell death of 30%. In summary, this work stresses the relevance of nonspecific drug-polymerized membrane binding on L-tryptophan pharmacological interaction with possible pharmaceutical applications in liposomal drug delivery. Moreover, the absence of significant cytotoxic effects allows the system proposed to be applied in human health.
Highlights
Liposomes, which are useful drug delivery systems, have been used to deliver small molecules [1] and macromolecules such as proteins [2] and DNA [3]. polymerized liposomes can be obtained by a photopolymerization process
Polymerized liposomes encapsulating L-tryptophan were studied with the aim to characterize them as drug delivery systems for the treatment of several metabolic diseases that need an increased systemic L-tryptophan concentration. polymerized liposomes were obtained by UV irradiation of vesicles containing 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DC8,9PC) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) in a 1:1 molar ratio, in the presence of 10 and 50 mol% of L-tryptophan
Bilayer packing at the polar head region was followed with the Merocyanine 540 (MC540) and specific interactions in the lipopolymers were studied by Fourier-transform infrared (FTIR)
Summary
Liposomes, which are useful drug delivery systems, have been used to deliver small molecules [1] and macromolecules such as proteins [2] and DNA [3]. polymerized liposomes can be obtained by a photopolymerization process. Polymerized liposomes can be obtained by a photopolymerization process. Design of lipopolymers relies on two advantages: lipid self-assembly properties and photoactivable bonds in photopolymerizable lipids [6]. Polymerizable lipids contain a diacetylene moiety along their acyl chain. These lipids can be polymerized by UV irradiation to form chains of covalently linked lipids in the bilayer. Packed and properly ordered, diacetylene lipids undergo polymerization via 1,4-addition to form alternating ene-iyne polymer chains upon irradiation with 254 nm light [7]. Lipopolymers can aggregate into a variety of vesicular and non-vesicular assemblies depending on the lipid concentration, structure and processing conditions [8]
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