Biomedical subjects

A Urtti

Publications and source records attributed to A Urtti.

At least 55 records · Page 3Linked to original sources

PubMed1997

Characterization of paracellular and aqueous penetration routes in cornea, conjunctiva, and sclera.

PURPOSE: To characterize quantitatively the paracellular permeation routes in rabbit cornea, conjunctiva, and sclera using polyethylene glycol (PEG) oligomers. METHODS: Corneal, conjunctival, and scleral tissues from New Zealand white rabbits were tested individually in a modified two-chamber Ussing apparatus with the mixture of PEGs with mean molecular weights 200, 400, 600, and 1000 in glutathione bicarbonated Ringer's solution buffer on the donor side of the chamber. The samples and standards were analyzed with high-performance liquid chromatography-thermospray mass spectrometry method. The pore sizes and the pore densities of the corneal and conjunctival epithelia were calculated using an effusion-like approach. RESULTS: The conjunctival and scleral tissues were 15 to 25 times more permeable than the cornea and the molecular size affected the conjunctival permeability less than that of the cornea. The palpebral and bulbar conjunctivas had equal permeabilities. The scleral permeability was approximately half of that in the conjunctiva and approximately 10 times more than in the cornea. The conjunctival epithelia had 2 times larger pores and 16 times higher pore density than the cornea. The total paracellular space in the conjunctiva was estimated to be 230 times greater than that in the cornea. CONCLUSIONS: The conjunctival epithelium, due to its higher membrane permeability and larger absorptive and intercellular space surface areas, is the most viable route for ocular delivery of peptides and oligonucleotides.

Absorption↗

PubMed1996

Interaction of liposomes with human skin in vitro--the influence of lipid composition and structure.

Liposomes have been suggested as a vehicle for dermal and transdermal drug delivery, but the knowledge about the interaction between lipid vesicles and human skin is poor. Therefore, we visualized liposome penetration into the human skin by confocal laser scanning microscopy (CLSM) in vitro. Liposomes were prepared from phospholipids in different compositions and labeled with a fluorescent lipid bilayer marker, N-Rh-PE (L-alpha-phosphatidylethanolamine-N-lissamine rhodamine B sulfonyl). Fluorescently labelled liposomes were not able to penetrate into the granular layers of epidermis. However, the fluorescence from liposome compositions containing DOPE (dioleylphosphatidyl ethanolamine) was able to penetrate deeper into the stratum corneum than that from liposomes without DOPE. Pretreatment of skin with unlabeled liposomes containing DOPE or lyso-phosphatidyl choline (lyso-PC) enhanced the subsequent penetration of the fluorescent markers, N-Rh-PE and sulforhodamine B into the skin, suggesting possible enhancer activity, while most liposomes did not show such enhancement. Resonance energy transfer (RET) and calcein release assay between stratum corneum lipid liposomes (SCLLs) and the phospholipid vesicles suggested that the liposomes containing DOPE may fuse or mix with skin lipids in vitro and loosen the SCLL bilayers, respectively. Among the factors not affecting stratum corneum penetration were: negative charge, cholesterol inclusion and acyl chain length of the phospholipids. In conclusion, fusogenicity of the liposome composition appears to be a prerequisite for the skin penetration.

Drug Carriers↗

PubMed1996

Hydroxypropyl-beta-cyclodextrin increases aqueous solubility and stability of anandamide.

Anandamide (arachidonylethanolamide; AEA) is an endogenous ligand for the cannabinoid receptor and its pharmacological effects are under intensive study. However, AEA has a low aqueous solubility and stability which may restrict its use and may eventually endanger the reliability of the obtained results. In the present study, it was found that AEA forms inclusion complexes with cyclodextrins (CDs), resulting in greater aqueous solubility and stability of AEA as AEA/CD complex. Aqueous solubility increased 1 000 to 30 000-fold, depending on the type of CD (10% solution) used. The half-life of AEA in aqueous hydroxypropyl-beta-cyclodextrin solution (10%) at 50 degree C was 2.9 years. These results suggest that CD-technology will be a very useful method to overcome the solubility and stability problems of AEA.

2-Hydroxypropyl-beta-cyclodextrin↗

PubMed1996

Effects of topical anandamides on intraocular pressure in normotensive rabbits.

A series of anandamide-type compounds were synthesized and studied for their effect on the intraocular pressure (IOP) of normotensive pigmented rabbits. Each test compound was dissolved in an aqueous 2-hydroxypropyl-beta-cyclodextrin solution and administered (31.25 - 62.5 micrograms) unilaterally to the eye. The most promising anandamides caused a statistically significant reduction of IOP in treated eyes, usually preceded by an initial transient elevation of IOP, compared to saline controls. In the contralateral untreated eyes, only a marginal or short hypotensive response was observed. Indomethacin pre-treatment (12.5 mg, s.c.) eliminated the IOP response to administered anandamides and arachidonic acid.

Administration, Topical↗

PubMed1996

Accumulation of bisphosphonates in the aorta and some other tissues of healthy and atherosclerotic rabbits.

Clodronate, etidronate, and pamidronate are highly hydrophilic bisphosphonates used for the treatment of bone resorption and hypercalcemia. They also inhibit the development of experimental atherosclerosis without influencing serum cholesterol level. We studied the distribution and the accumulation of the carbon 14-labeled bisphosphonates in the aorta and some other tissues of healthy rabbits and in rabbits with diet-induced atherosclerosis. After intravenous injection, clodronate and pamidronate disappeared from circulation more slowly in atherosclerotic than in healthy rabbits, and the drug concentrations in the peripheral tissues were generally lower in atherosclerotic than in healthy animals. At 24 hours after dosing in healthy rabbits, the mean aorta to plasma ratios of clodronate, etidronate, and pamidronate were, respectively, 2.4 to 2.8, 2.4 to 4.0, and 8.6 to 10. The corresponding ratios in atherosclerotic rabbits were, respectively, 13 to 22, 1.5 to 2.2, and 13 to 24. Seven days after the injection the mean clodronate concentration in the aortas of healthy rabbits was 0.5% to 0.9% of the dose given per tissue weight, and the concentration in those of atherosclerotic animals was 3.8% to 5.2% of the dose given per tissue weight. The results indicate that hydrophilic bisphosphonates, known to inhibit the atherogenesis, concentrate markedly in the aortas of healthy and atherosclerotic rabbits.

Analysis of Variance↗

PubMed1996

Modified beta-cyclodextrin (SBE7-beta-CyD) with viscous vehicle improves the ocular delivery and tolerability of pilocarpine prodrug in rabbits.

The complexation of pilocarpine prodrug, O,O'-dipropionyl-(1,4-xylylene) bispilocarpate, with various beta-cyclodextrin (beta-CyD) derivatives was studied by the phase solubility method. The effects of coadministered sulphobutyl ether beta-CyD (SBE7-beta-CyD) with and without poly(vinyl alcohol) (PVA) on the miotic response and eye irritation of the prodrug were investigated in pigmented rabbits. The pilocarpine prodrug formed 1:1 inclusion complexes with variably substituted sulphobutyl ether derivatives of beta-CyD (SBE4-beta-CyD and SBE7-beta-CyD), and 1:1 and 1:2 complexes with hydroxypropyl-beta-CyD (HP-beta-CyD) at pH 7-4. Coadministered SBE7-beta-CyD eliminated the eye irritation due to the pilocarpine prodrug, but also decreased the miotic response. Ocular absorption of the prodrug was improved by increasing the viscosity of prodrug/SBE7-beta-CyD solution with PVA without inducing any eye irritation. Eye irritation due to viscous prodrug/SBE7-beta-CyD solutions was comparable with isotonic NaCl solution. We conclude that administration of pilocarpine prodrug in viscous SBE7-beta-CyD solution decreases substantially eye irritation while ocular absorption is not affected.

Animals↗

PubMed1995

Comparison of enzymatic hydrolysis of pilocarpine prodrugs in human plasma, rabbit cornea, and butyrylcholinesterase solutions.

Various bispilocarpic acid diesters (double prodrugs of pilocarpine) were synthesized, and their in vitro esterase catalyzed hydrolysis was evaluated in diluted human plasma, rabbit cornea homogenate, and specific butyrylcholinesterase solution. The structural changes greatly affected the rate of enzymatic hydrolysis of the prodrugs. Bispilocarpic acid with 2 cyclopropane substituents was the most stable derivative, whereas bispilocarpic acid with 2 cyclobutane substituents was the most labile derivative. The charged bispilocarpic acid diester hydrolyzed more slowly than the unchanged form. Comparison of the results obtained from different plasma and cornea homogenate batches is difficult because of the variety of the enzyme systems involved. This variety also makes comparing the results between different laboratories difficult.

Animals↗

PubMed1995

Macrophage-like RAW 264 cell line and time-resolved fluoroimmunoassay (TRFIA) as tools in screening drug effects on cytokine secretion.

A screening system was set up to study the effects of drugs on cytokine secretion by macrophages in vitro. The system is based on the murine macrophage-like cell line RAW 264, which can be activated with lipopolysaccharide (LPS) to produce cytokines. The responsiveness of the RAW 264 cells was outlined by challenging them with different concentrations of LPS for 6 or 24 h. Substantial time- and dose-dependent increases were recorded for interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6) and tumour necrosis factor alpha (TNF alpha) secretions. A general procedure was established to construct time-resolved fluoroimmunoassays (TRFIA) from commercial immunochemicals produced originally for enzyme immunoassays. Practical measuring ranges of the non-competitive assays were 100 pg/ml-10 ng/ml for IL-1 beta and TNF alpha and 10 pg/ml 5 for IL-6 and IL-5. The interleukin-5 (IL-5) assay was set up for unrelated human studies, but the others were used in the characterization of RAW 264 cytokine secretion. An immunosuppressive effect with dexamethasone phosphate could be achieved and recorded in the model system. Thus, the system offers a simple and easy-to-use model for screening immunomodulatory effects of drugs on the cytokine secretion of macrophages.

Animals↗

PubMed1995

Effect of liposomal and free bisphosphonates on the IL-1 beta, IL-6 and TNF alpha secretion from RAW 264 cells in vitro.

PURPOSE: In order to evaluate the possible antiinflammatory action of bisphosphonates, the effect of the drugs on the secretion of proinflammatory cytokines (IL-1 beta, IL-6 and TNF alpha) from macrophages was studied. Liposomes or high concentration of extracellular calcium was used to enhance the intracellular delivery of bisphosphonates. METHODS: RAW 264 cells were used as macrophage model, and they were induced with lipopolysaccharide to produce the cytokines. The cytokine concentrations in the culture supernatants were measured with time-resolved fluoroimmunoassay. RESULTS: As a free drug, clodronate and pamidronate, but not etidronate, inhibited LPS-stimulated secretion of the cytokines from macrophage-like RAW 264 cells. Low concentrations of pamidronate, however, induced the IL-6 secretion, and the cytokine inhibitory action at the higher concentrations of pamidronate was attributed to cytotoxicity of the compound. The cytokine induction or toxic effects were not observed with clodronate or etidronate. When the drugs were encapsulated in negatively charged unilamellar liposomes, the inhibitory potency of both clodronate and etidronate enhanced by a factor of 10-20, while that of pamidronate was not increased. The complex formation of bisphosphonates with extracellular calcium, although enhancing the uptake of the compounds by macrophages, did not considerably increase their cytokine inhibitory potency. CONCLUSIONS: Bisphosphonates have inhibitory action on cytokine secretion by macrophages. The non-cytotoxic cytokine inhibition by liposome encapsulated clodronate could be beneficial in local inflammatory diseases, where the inflammation is sustained by the excessive amounts of inflammatory cytokines produced by activated macrophages.

Animals↗

PubMed1995

Hydroxypropyl-beta-cyclodextrin increases the aqueous solubility and stability of pilocarpine prodrugs.

PURPOSE: The effects of 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD) on the aqueous solubility and stability of two lipophilic bispilocarpine prodrugs were investigated at pH 7.4. METHODS: The solubility of prodrugs was studied by phase-solubility method (0-72.5 mM HP-beta-CD). The stability of one of the prodrugs was investigated as a function of temperature (40 degrees C-70 degrees C) and HP-beta-CD concentration (0-72.5 mM). The apparent rate constants (k1, k2) for degradation of prodrug in 1:1 and 1:2 inclusion complexes and apparent stability constants (K1:1, K1:2) were calculated by the curve-fitting method. RESULTS: The phase-solubility diagrams were classified as Ap-type and the apparent stability constants (K1:1, K1:2) for 1:1- and 1:2-inclusion complexes were calculated to be 143-815 M-1 and 29-825 M-1, respectively. The stability of prodrug increased as a function of HP-beta-CD concentration over the studied temperature range. The shelf-life (t90%, calculated by the Arrhenius equation) of the prodrug in 72.5 mM HP-beta-CD solution increased 5.1-fold and 6.1-fold at 25 degrees C and 4 degrees C, respectively. CONCLUSIONS: The solubility of the prodrugs was shown to increase markedly in phase-solubility studies. The degradation rate of prodrug in stability studies was shown to be slower in the 1:2-complex than in the 1:1-complex and the relative amounts of complex species were found to be dependent on CD concentration.

2-Hydroxypropyl-beta-cyclodextrin↗

PubMed1995

Ocular absorption and irritation of pilocarpine prodrug is modified with buffer, polymer, and cyclodextrin in the eyedrop.

The influence of buffer, viscosity and cyclodextrin on the ocular absorption and irritation of a pilocarpine prodrug, O,O'-dipropionyl-(1,4-xylylene) bispilocarpic acid diester, was studied in albino rabbits. The prodrug solutions, equivalent to 0.5% pilocarpine, were prepared in 0, 10, 20, 50, or 75 mM citrate buffer at pH 5.0. Viscosity of the solutions (20, 50 or 115 cP) was modified with hydroxypropyl methylcellulose. 2-hydroxypropyl-beta-cyclodextrin (HPCD) was included at concentrations 5, 10 and 15% (w/v). The formulations were compared to a commercial pilocarpine eyedrop (1.7%). Ocular irritation was graded in a double-masked experiment and miosis was used as a bioassay for pilocarpine delivery to the iris. The prodrug showed decreased peak and prolonged duration of miosis compared to pilocarpine, but it caused ocular irritation. Increasing buffer strength decreased and elevated viscosity intensified the miotic response and irritation by the pilocarpine prodrug. HPCD decreased both the ocular delivery of pilocarpine and the irritation by the prodrug, but the net effect was positive. Thus, administering 1.0% of pilocarpine as a prodrug with 15% (w/v) HPCD, the irritation was at the same level with the commercial pilocarpine eyedrop, but the ocular delivery was substantially improved. In conclusion, the ocular delivery of the pilocarpine prodrug may be enhanced in relation to its local irritation by properly combining buffer, viscosity and HPCD.

2-Hydroxypropyl-beta-cyclodextrin↗

PubMed1995

Sulfobutyl ether beta-cyclodextrin (SBE-beta-CD) in eyedrops improves the tolerability of a topically applied pilocarpine prodrug in rabbits.

The effects of a novel, modified beta-cyclodextrin (SBE4-beta-CD; a variably substituted sulfobutyl ether with an average degree of substitution of four) on eye irritation and miotic response of an ophthalmically applied pilocarpine prodrug, O,O'-dipropionyl-(1,4-xylylene) bispilocarpate, in albino rabbits were studied. Compared to the commercial pilocarpine eyedrop solution (163 mM, equivalent to 3.4% pilocarpine), 12-24 mM pilocarpine prodrug solutions (equivalent to 0.5-1.0% pilocarpine, respectively) decreased peak miotic intensity (Imax) and increased the time to reach peak (tmax), but did not significantly affect values for the area under the miosis versus time curves (AUC), i.e. 12-24 mM pilocarpine prodrug appeared to be equivalent to 163 mM pilocarpine. Ocularly applied 12-24 mM pilocarpine prodrug solutions, however, were more irritating than a commercial pilocarpine eyedrop solution. Coadministered SBE4-beta-CD significantly decreased the eye irritation of the pilocarpine prodrug solutions. Coadministered SBE4-beta-CD did not affect the miotic response of prodrug solution when the molar ratio of SBE4-beta-CD to prodrug was low. However, increasing the molar ratio of SBE4-beta-CD to prodrug decreased the Imax and AUC values. The results show that eye irritation of the pilocarpine prodrug is prevented by levels of SBE4-beta-CD that do not affect the apparent ocular absorption of the prodrug.

Absorption↗

PubMed1995

Ophthalmic arachidonylethanolamide decreases intraocular pressure in normotensive rabbits.

Arachidonylethanolamide (AEA) was the first anandamide to be identified as an endogenous ligand for the cannabinoid receptor of porcine brain. Since cannabinoids have shown some value in the reduction of ocular hypertension, the title compound was evaluated in normotensive rabbits as a possible topically applied agent for reducing intraocular pressure. AEA was dissolved in an aqueous solution of 2-hydroxy-propyl-beta-cyclodextrin. Single eyedrops (25 microliters) containing 3.13, 6.25, 31.25, 62.5 or 125.0 micrograms of AEA were instilled unilaterally into eyes of normotensive albino and pigmented rabbits. The intraocular pressures (IOPs) of these rabbits were then measured at fixed time intervals. The effect of AEA on IOP in treated and untreated (contralateral) eyes was similar in both types of rabbits. Administration of 31.25 micrograms of AEA caused an immediate IOP reduction in the treated eyes. AEA doses of 62.5 micrograms caused an initial increase and subsequent decrease of IOP in the treated eyes. In the untreated eyes, a marginal ocular hypotensive response of limited duration occurred immediately after administration of AEA at doses 31.25 or 62.5 micrograms. A significant increase (without subsequent decrease below baseline) in IOP occurred in treated eyes after a dose of 125.0 micrograms. The lowest dose (3.13 micrograms) did not have an effect on IOP. This study constitutes the first published demonstration that topical, unilateral administration of AEA significantly decreases IOP in normotensive albino and pigmented rabbits. Although the mechanism of action by which this compound produces its hypotensive effect in the eye is not known, the results suggest that AEA may prove useful in the investigation of glaucoma therapy.

Animals↗

PubMed1994

Cationic liposomes improve stability and intracellular delivery of antisense oligonucleotides into CaSki cells.

Antisense oligonucleotides (ODNs) are promising novel therapeutic agents against viral infections and cancer. However, problems with their inefficient delivery and inadequate stability have to be solved before they can be used in therapy. To circumvent these obstacles, a wide variety of improvements, including phosphorothioate ODNs and liposomes as a carrier system, have been developed. This study was designed to compare the effects of two cationic liposomes on the intracellular delivery and stability of ODNs in CaSki cell cultures. Also the stability of 3'-end phosphorothioate ODNs were investigated. The 3'-modification neither had any effect on the delivery, nor protected the ODNs against degradation. The cellular delivery and stability of ODNs was improved with both cationic liposomes, but a cationic liposomal preparations containing dimethyldioctadecylammonium bromide and dioleoylphosphatidylethanolamine (DDAB/DOPE) was more efficient than commercially available N-(1-(2,3-dioleoyloxy)propyl)-N,N,N-trimethylammoniummethylsulf ate (DOTAP). The improved cellular delivery was largely due to the stabilization of ODNs by cationic liposomes. The improved stability in the culture medium indicates that the cationic liposomes per se protect the ODNs from enzymatic degradation. Indeed, intact ODNs were found in the cytoplasm and nucleus only when delivered by cationic liposomes.

Base Sequence↗

PubMed1994

Oligonucleotide-cationic liposome interactions. A physicochemical study.

Cationic liposomes are effective in delivering antisense oligonucleotides into cells in culture, but their interactions with the oligonucleotides are poorly understood. We studied the aggregation and fusion reactions during the formation of cationic lipid/oligonucleotide complexes in solution and their interactions with lipid bilayers. Phosphorothioate oligonucleotides (15-mer) were complexed with cationic liposomes composed of dimethyldioctadecylammonium bromide (DDAB) and dioleoylphosphatidylethanolamine (DOPE) at 8:15 molar ratio or of a commercial formulation DOTAP (N-(1-(2,3-dioleoyloxy)propyl)-N,N,N-trimethylammoniummethylsul fate), at different ratios with apparent -/+ charge ratios of 0.03-5.6. Mean size of the complexes increased with -/+ ratio so that at charge ratios 0.4-2.0 the size increased by at least an order magnitude due to the oligonucleotide induced aggregation. Resonance energy transfer experiments showed that in addition to aggregation oligonucleotides induced fusion of cationic liposomes, but the fusion was rate-controlled by the initial aggregation step. Rate constants for oligonucleotide induced aggregation were dependent on lipid concentration and were in the range of (0.2-1).10(7) M-1 s-1 and (1-10).10(7) M-1 s-1 for DDAB/DOPE and DOTAP, respectively. Increase in oligonucleotide concentration induced the aggregation and fusion until at high -/+ ratios electrostatic repulsion of negative surfaces inhibited further aggregation and fusion. DOTAP/oligonucleotide complexes did not induce leakage of calcein from neutral EPC liposomes, but did cause leakage at -/+ charge ratios of < 0.7 and > 2.0 from EPC/DOPE liposomes. Also at -/+ charge ratios below 0.8 DOTAP/oligonucleotide complexes induced leaking from negatively charged DPPC/DPPG liposomes. These results indicate that either phosphatidylethanolamine or negative charge are required in the cell membrane for fusion of cationic liposome-oligonucleotide complexes. The ratio of oligonucleotide to cationic lipid is critical in determining the physicochemical properties of the mixture.

Cations↗

PubMed1994

Clodronate (dichloromethylene bisphosphonate) inhibits LPS-stimulated IL-6 and TNF production by RAW 264 cells.

Effect of liposome-encapsulated and free clodronate on the IL-6 and TNF production by macrophages was studied using RAW 264 cell line as a macrophage model, and dissociation-enhanced lanthanide fluoroimmunoassay (DELFIA) for analysis of secreted cytokines. LPS-stimulated RAW 264 cells proved to produce notable amounts of these two cytokines, and DELFIA was sensitive and reliable method for analysis. Liposome-encapsulated clodronate inhibited the production of both cytokines, IL-6 being affected more than TNF, and the effect was mostly due to the drug itself, not to liposomal lipid. More than ten times higher concentration of free clodronate than liposomal clodronate was needed to inhibit cytokine production. This is the first report on the cytokine inhibitory property of clodronate, and the results support the idea of the use of liposomal clodronate as a macrophage suppressive agent in autoimmune diseases.

Animals↗

PubMed1994

Cationic liposomes mediated delivery of antisense oligonucleotides targeted to HPV 16 E7 mRNA in CaSki cells.

The "high risk" types 16 and 18 of human papillomavirus (HPV) are involved in the etiology of genital squamous cell carcinoma. The early genes 6 and 7 (E6-E7) of these viruses code for the major transforming proteins, capable of inducing cell transformation alone or acting synergistically with other oncogenes. Antisense oligonucleotides, recently applied to inhibit the functions of a number of cellular and viral proteins, might provide the basis for a new therapeutic strategy against HPV-induced malignancies. We studied the proliferation of CaSki cells by the MTT assay after their exposure to HPV 16 E7 mRNA antisense oligonucleotides with and without cationic liposomes (containing dimethyldioctadecylammonium bromide DDAB, and dioleylphosphatidylethanolamine, DOPE). Unmodified oligonucleotides (either 12- or 23-mers) did not have any effect on either CaSki cell proliferation or morphology when compared with the untreated cells. The cellular uptake of oligonucleotides was significantly enhanced by the cationic liposomes as assessed by confocal laser scanning microscopy (CLSM). The cationic liposomes were toxic to the cells as demonstrated by the reduced cell number and altered cell morphology. Only a slight reduction of the cell proliferation was seen when antisense 12-mer was protected from its 3'- and 5'-ends with thiolate and FITC, respectively. Both the 12- and the 23-mers with the cationic liposomes inhibited cell proliferation, the inhibitory effect being longer with the 23-mer. Overall, the MTT assay was less sensitive than light microscopy to reveal the toxic effects on CaSki cells. The results suggest that antisense oligonucleotides targeted to HPV 16 E7 mRNA can be introduced into CaSki cells with cationic liposomes.

Base Sequence↗

PubMed1994

Liquid chromatography determination of liposome components using a light-scattering evaporative detector.

Analysis of liposomal components is important in stability testing of formulations. An LC method for the analysis of liposomal components cholesterol, phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine and their lyso-forms was developed. The method uses a light-scattering evaporative detector and isocratic mobile phase. In addition, components of pH-sensitive liposomes, cholesterylhemisuccinate and cationic lipid dimethyldioctadecylammonium bromide used in transfections were determined by the method. The separations were carried out on a Spherisorb S5 NH2 cartridge column or Zorbax NH2 column (25 cm x 4.6 mm, 5 microns particle size). The mobile phase consisted of acetonitrile-methanol-ammonium acetate solution (pH 4.8, 0.1 M) (52:32:16, v/v/v) at a flow rate of 2 ml min-1. Detection limits were 1.3-8.0 micrograms ml-1 depending on the lipid. The precision (RSD) of the method was 1.5-3.3% for lipid standard solutions at 50 micrograms ml-1 concentration and 2.0-11.8% for lipids analyzed from liposome suspensions.

Chromatography, Liquid↗