Investigation of an Escherichia coli environmental benchmark for waterborne pathogens in agricultural watersheds in Canada

Canada's National Agri-Environmental Standards Initiative sought to develop an environmental benchmark for low-level waterborne pathogen occurrence in agricultural watersheds. A field study collected 902 water samples from 27 sites in four intensive agricultural watersheds across Canada from 2005 to 2007. Four of the sites were selected as reference sites away from livestock and human fecal pollution sources in each watershed. Water samples were analyzed for Campylobacter spp., Salmonella spp., Escherichia coli O157:H7, Cryptosporidium spp., Giardia spp., and the water quality indicator E. coli. The annual mean number of pathogen species was higher at agricultural sites (1.54 ± 0.07 species per water sample) than at reference sites (0.75 ± 0.14 species per water sample). The annual mean concentration of E. coli was also higher at agricultural sites (491 ± 96 colony-forming units [cfu] 100 mL(-1)) than at reference sites (53 ± 18 cfu 100 mL(-1)). The feasibility of adopting existing E. coli water quality guideline values as an environmental benchmark was assessed, but waterborne pathogens were detected at agricultural sites in 80% of water samples with low E. coli concentrations (<100 cfu 100 mL(-1)). Instead, an approach was developed based on using the natural background occurrence of pathogens at reference sites in agricultural watersheds to derive provisional environmental benchmarks for pathogens at agricultural sites. The environmental benchmarks that were derived were found to represent E. coli values lower than geometric mean values typically found in recreational water quality guidelines. Additional research is needed to investigate environmental benchmarks for waterborne pathogens within the context of the "One World, One Health" perspective for protecting human, domestic animal, and wildlife health.

Expression of DeltaF508 CFTR in normal mouse lung after site-specific modification of CFTR sequences by SFHR

The development of gene targeting strategies for specific modification of genomic DNA in human somatic cells has provided a potential gene therapy for the treatment of inherited diseases. One approach, small fragment homologous replacement (SFHR), directly targets and modifies specific genomic sequences with small fragments of exogenous DNA (400-800 bp) that are homologous to genomic sequences except for the desired modification. This approach has been effective for the in vitro modification of exon 10 in the cystic fibrosis transmembrane conductance regulator (CFTR) gene in human airway epithelial cells. As another step in the development of SFHR for gene therapy, studies were carried out to target and modify specific genomic sequences in exon 10 of the mouse CFTR (mCFTR) in vivo. Small DNA fragments (783 bp), homologous to mCFTR except for a 3-bp deletion (DeltaF508) and a silent mutation which introduces a unique restriction site (KpnI), were instilled into the lungs of normal mice using four different DNA vehicles (AVE, LipofectAMINE, DDAB, SuperFect). Successful modification was determined by PCR amplification of DNA or mRNA-derived cDNA followed by KpnI digestion. The results of these studies showed that SFHR can be used as a gene therapy to introduce specific modifications into the cells of clinically affected organs and that the cells will express the new sequence.

An innovative topical drug formulation for wound healing and infection treatment: in vitro and in vivo investigations of a povidone-iodine liposome hydrogel

BACKGROUND

In topical wound treatment, the combination of anti-infectious therapy and a healing-promoting moisturization has not been accomplished yet.

OBJECTIVE

Evaluation of a new topical drug consisting of a povidone-iodine (PVP-I) liposome hydrogel allowing for both antiseptic and moist treatment.

METHODS

Pharmaceutical formulation of a complex of PVP-I (3%) and phosphatidylcholine in a hydrogel. In vitro, interaction of the complex with relevant micro-organisms was analysed by electron microscopy. Antimicrobial activity was investigated using Staphylococcus aureus in a suspension test. Tissue toxicity was examined by an explantation test in a rodent model. A randomized clinical study on efficacy and tolerability in wound healing was carried out on 35 patients with mesh grafts in parallel groups (PVP-I liposome hydrogel vs. Bactigras) for proof of concept in humans.

RESULTS

A direct interaction of the PVP-I liposomes with micro-organisms by attachment to the cell surface was documented. A significantly better microbicidal activity and tissue tolerability of the PVP-I liposome hydrogel compared to conventional PVP-I formulations was shown. The results of the clinical study, especially measurements of neo-epithelization per time and transplant loss, demonstrate significant differences in favour of the PVP-I liposome hydrogel.

CONCLUSION

The novel PVP-I liposome hydrogel combines microbicidal and wound healing activities resulting in enhanced epithelization.

Nuclear transport of oligonucleotides in HepG2-cells mediated by protamine sulfate and negatively charged liposomes

PURPOSE

The aim of this study was to characterize the intracellular fate and nuclear uptake kinetics of oligonucleotides (ON) that were complexed with protamine sulfate (PS) and negatively charged liposomes at different ratios of ON to PS.

METHODS

Double-fluorescence labelling of ON and liposomal lipid was applied to simultaneously monitor the interaction as well as the individual fate of active agent and carrier upon intracellular delivery using confocal laser scanning microscopy (CLSM). A DNA-analogue of a 68-mer intramolecular double-stranded RNA:DNA-hybridoligonucleotide (chimeraplasts) with unmodified phosphate backbone was employed. This construct was condensed with PS and coated with a liposomal formulation (AVE-3 = artificial viral envelope).

RESULTS

PS-ON complexes and AVE -3-coated complexes with a defined composition were very effective in nuclear transport of ON for a ON:PS charge ratio of 1:3. Nucleus:cytosol fluorescence ratios peaked at about 10 hrs and started to decrease again at 21 hrs.

CONCLUSIONS

AVE associates with PS-condensed ON, and this complex is able to be taken up by cells and to deliver ON to the nucleus. PS-ON complexes are released from the liposomal formulation, mainly as an extranuclear enzymatic degradation of the liposomal phospholipids. The results of the kinetic analysis can be used to optimize transfection protocols with ON in HepG2 cells.

Nuclear gene targeting using negatively charged liposomes

Oligonucleotides are a very useful tool to control gene activity. Oligos work by complementary base-pairing with target sequences either in the nucleus or in the cytosol (Zelphati, O., Szoka, F.C., Jr., 1996. Liposomes as a carrier for intracellular delivery of antisense oligonucleotides: a real or magic bullet? J. Contr. Rel. 41, 99-119). In a new approach using chimeric oligonucleotides (Yoon, K., Cole Strauss, A., Kmiec, E.B., 1996. Targeted gene correction of episomal DNA in mammalian cells mediated by a chimeric RNA-DNA oligonucleotide. Proc. Natl. Acad. Sci. USA 93, 2071-2076) conversion of single base mutations with help of intranuclear repair mechanisms maybe an advantageous method to cure genetic diseases which are based on single point mutations. These chimeric oligonucleotides are constructed in a way that they form an intramolecular double strand of DNA and modified RNA-bases. We used a fluorescent labelled pure 68-mer DNA-analogue of a chimeric oligonucleotides to follow the intracellular fate of these kind of genetic material. The oligos were complexed with protamine sulfate and coated with three different liposomal formulations. The AVE-3 formulation shows enhanced properties compared to a classical neutral and negatively charged formulation. Nuclear localisation of oligos could only be observed with the AVE-3 formulation. Furthermore only the negatively charged liposome formulations interact with the protamine-complexed oligonucleotides.

Simulated lung transfection by nebulization of liposome cDNA complexes using a cascade impactor seeded with 2-CFSME0-cells

The aim of this study was to devise a simulation aerosol system for quasirealistic gene transfection that could eventually be used to study the characteristics of aerosol delivery, stability, delivery efficiency, and expression efficacy of gene products. It consisted of (1) a PARI aerosol generator and PARI LL jet; (2) an Andersen cascade impactor with a calibrated vacuum pump, fitted with a glass "throat," nebulizer in which stages were seeded with pulmonary cells of interest (e.g., 2-CFSME0-); and (3) a hot room set to 37 degrees C and approximately 70% relative humidity. Cell viability remained at 95% to 99%. A prostaglandin G/H synthase (PGH)- and a human alpha 1-antitrypsin (AAT)-expressing plasmid, respectively, driven by a cytomegalovirus promoter (pCMV4-PGH, pCMV4-AAT) and a heat-insensitive placental alkaline phosphatase (PAP)-expressing plasmid driven by a Rous sarcoma virus promoter (pRSV-PAP) were employed; cationic liposomes consisted of N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethylammonium chloride/dioleoylphosphatidylethanolamine (DOTMA/DOPE) or 3 beta-[N-(N',N'-dimethylaminoethane)-carbamoyl]-cholesterol/DOPE (DC-Chol/ DOPE). The fluorescent dye Toto-1 was used to visualize aerosol distribution and to monitor cellular uptake. Alternatively, pCMV4-PGH deposited onto impactor stages covered with nitrocellulose membranes was hybridized with random primer-32P-radiolabeled pCMV4-PGH and autoradiographed. The mass median aerodynamic diameter (MMAD) of the plasmid, liposomes, and liposome-plasmid complexes and their effect on the mass output were monitored. A majority of gene product was delivered to stages 1 through 5, corresponding to an area ranging from the pharynx to the terminal bronchi, excluding the alveolar space. A corresponding, although very low, transfection of cells with pRSV-PAP was found, with the majority of transfected cells on stages 4 and 5. The MMAD was significantly affected by the presence of the DNA constructs alone or by DNA constructs complexed with cationic liposomes; the control phosphate buffered saline (PBS) MMAD of 2.3 microns increased to 3.5 microns for DC-Chol liposomes and 4.5 microns for the DC-Chol/PGH complex; DOTMA-based liposomes and liposome DNA complexes precipitated during aerosolization. Mass output was reduced for cationic liposomes from 0.61 g/min (PBS control) to 0.35 g/min. Large plasmid (pRSV-PAP, 10.1 kb) was more rapidly degraded by aerosolization than smaller plasmid (pCMV4-AAT, 6.2 kb) although complexation with cationic liposomes provided some protection in both cases.

Malaria circumsporozoite protein inhibits protein synthesis in mammalian cells

Native Plasmodium circumsporozoite (CS) protein, translocated by sporozoites into the cytosol of host cells, as well as recombinant CS constructs introduced into the cytoplasm by liposome fusion or transient transfection, all lead to inhibition of protein synthesis in mammalian cells. The following findings suggest that this inhibition of translation is caused by a binding of the CS protein to ribosomes. (i) The distribution of native CS protein translocated by sporozoites into the cytoplasm as well as microinjected recombinant CS protein suggests association with ribosomes. (ii) Recombinant CS protein binds to RNase-sensitive sites on rough microsomes. (iii) Synthetic peptides representing the conserved regions I and II-plus of the P.falciparum CS protein displace recombinant CS protein from rough microsomes with dissociation constants in the nanomolar range. (iv) Synthetic peptides representing region I from the P.falciparum CS protein and region II-plus from the P.falciparum, P.berghei or P.vivax CS protein inhibit in vitro translation. We propose that Plasmodium manipulates hepatocyte protein synthesis to meet the requirements of a rapidly developing schizont. Since macrophages appear to be particularly sensitive to the presence of CS protein in the cytosol, inhibition of translation may represent a novel immune evasion mechanism of Plasmodium.

Effect of dose and release rate on pulmonary targeting of liposomal triamcinolone acetonide phosphate

PURPOSE

To demonstrate the importance of dose and drug release rate for pulmonary targeting of inhaled glucocorticoids using an animal model of intrapulmonary drug deposition.

METHODS

Liposomes composed of 1,2-distearoyl phosphatidylcholine (DSPC), 1,2-distearoyl phosphatidylglycerol (DSPG) and triamcinolone acetonide phosphate (TAP) or liposomes containing triamcinolone acetonide (TA) were prepared by a mechanical dispersion method followed by extrusion through polycarbonate membranes. Encapsulation efficiency was assessed after size exclusion gel chromatography by reverse phase HPLC. The effect of liposome size (200 nm and 800 nm) on the release kinetics of water-soluble encapsulated material was determined in vitro at 37 degrees C using 6-carboxyfluorescein as a marker and Triton X-100 (0.03%) as a leakage inducer. To investigate the relationship between drug release and pulmonary targeting, 100 micrograms/kg of TAP in 800 nm liposomes was delivered to male rats by intratracheal instillation (IT) and the results compared to data for 100 micrograms/kg TA liposomes (recently shown to exhibit a rapid drug release under sink conditions) and to previous studies reported for an equal dose of TAP in solution and TAP in 200 nm (1). Pulmonary targeting was assessed by simultaneously monitoring glucocorticoid receptor occupancy over time in lung and liver using an ex vivo receptor binding assay as a pharmacodynamic measure of glucocorticoid action. To assess the effect of dose on pulmonary targeting experiments were performed using 2.5, 7.5, 25, 100, and 450 micrograms/kg of TAP in 800 nm liposomes.

RESULTS

The in vitro efflux of 6-carboxyfluorescein from (DSPC:DSPG) liposomes after exposure to Triton-X was biexponential. The terminal half-lives of 3.7 h and 9.0 h for the 200 nm and 800 nm liposomes, respectively, demonstrated that larger liposomes promote slower release of encapsulated water-soluble solute while previous results already indicated that encapsulation of lipophilic TA does not result in sustained release. Pulmonary targeting, defined as the difference between cumulative lin and liver receptor occupancies was most pronounced for the 800 nm liposomes (370%xh), followed by the 200 nm preparation (150%xh). No targeting was observed for TAP in solution (30%xh) or the rapid releasing TA liposome preparation. Correspondingly, the mean pulmonary effect time (MET) increased from 2.4-3.0 hr for TA liposomes or TAO in solution to 5.7 h and > 6.2 h for TAP in 200 nm and in 800 nm liposomes, respectively. Escalating doses of TAP encapsulated in 800 nm liposomes revealed a distinct bell shaped relationship between the TAP dose and pulmonary targeting with a maximum occurring at 100 micrograms/kg (370%xh).

CONCLUSIONS

The in vivo data presented here confirm that pulmonary residence time and dose affect the extent of lung targeting of glucocorticoids delivered via the lung.

[Molecular effects of a microbicidal substance on relevant microorganisms: electron microscopic and biochemical studies on povidone-iodine]

The microbicidal activity of the broad spectrum antimicrobial agent povidone-iodine is due to the strong oxidizing effects of free iodine on functional groups of amino acids, nucleotides and double bonds of unsaturated fatty acids. While the chemical mechanism of action of PVP-iodine is well understood, the actual sequence of events on the cellular and molecular level that causes rapid cell death has not been fully understood. The aim of this study was to elucidate effects of povidone-iodine on cell ultrastructure by electron microscopy and to monitor changes in enzyme activity and nucleotide efflux. Staphylococcus aureus, E. coli and C. albicans, medically relevant gram-positive, gram-negative and yeast micro-organisms, served as models. In the presence of povidone-iodine, rapid partitioning of the cytoplasm and pronounced coagulation of nuclear material was noted. Especially C. albicans exhibited a rapid, dose-dependent "loosening" of the cell wall; cells remained intact without lysis, rupture or wall breakage. Changes in beta-galactosidase and nucleotide concentrations were measured in E. coli. A rapid and dose-dependent loss of cellular beta-galactosidase activity was found, with no increase in the supernatant; loss of cellular nucleotides corresponded with an increase in the supernatant. Electron microscopy and biochemical observations support the conclusion that povidone-iodine interacts with cell walls of micro-organisms causing pore formation or generating solid-liquid interfaces at the lipid membrane level which lead to loss of cytosol material, in addition to enzyme denaturation. The chemical mechanism of action explains the fact that povidone-iodine does never generate resistance in micro-organisms.

Molecular effects of povidone-iodine on relevant microorganisms: an electron-microscopic and biochemical study

The aim of this study was to elucidate the effects of povidone-iodine (PVP-I) on cell ultrastructure by electron microscopy and to monitor changes in enzyme activity and nucleotide efflux. Staphylococcus aureus, Escherichia coli and Candida albicans, medically relevant gram-positive, gram-negative and yeast microorganisms, served as models. In the presence of PVP-I, rapid partitioning of the cytoplasm and pronounced coagulation of nuclear material was noted. E. coli and S. aureus showed no major structural wall damage. C. albicans exhibited a rapid, dose-dependent 'loosening' of the cell wall; cells remained intact without lysis, rupture or wall breakage. Changes in beta-galactosidase and nucleotide concentrations were measured in E. coli. A rapid and dose-dependent loss of cellular beta-galactosidase activity was found, with no increase in the supernatant; loss of cellular nucleotides corresponded with an increase in the supernatant. Electron-microscopic and biochemical observations support the conclusion that PVP-I interacts with cell walls of microorganisms causing pore formation or generating solid-liquid interfaces at the lipid membrane level which lead to loss of cytosol material, in addition to enzyme denaturation.

Povidone-iodine liposomes--an overview

In recent years, liposomes have been increasingly explored as novel drug delivery systems, and several liposome-based drug products have been approved in Europe, the USA and Japan. Depending on size, composition and surface characteristics, liposomes interact specifically with biological structures. Liposomal drug products provide a topical activity at the desired locus of action and are deemed more effective and less toxic than conventional drug formulations. The combination of povidone-iodine (PVP-I) and liposomes unites the exceptional microbicidal activity of the antiseptic substance with the excellent tolerability and lack of immunogenicity of liposomes; in addition, liposomes provide a moist molecular film for the wound environment. The multilamellar vesicles act as microreservoirs hence prolonging the release of the active ingredient. Although no commercial product for repeated application on the eye is currently available, PVP-I has been used in ophthalmology not only for pre- and postoperative antisepsis, but also for the treatment of bacterial and viral conjunctivitis and for prophylaxis against ophthalmia neonatorum. For these indications, liposomal formulations with 2.5 and 5.0% PVP-I were developed. These eye drops are isotonic with tear fluid at pH 6. First in vitro tests demonstrated an excellent antimicrobial efficacy, and a placebo-controlled clinical study on volunteers showed a very good local tolerability. A study on rabbits demonstrated positive results of the PVP-I liposome eye drops compared to placebo and the broadspectrum antibiotic Polyspectran in a standardized model of Staphylococcus aureus deep eye infection. The other aim is a well-tolerated liposomal PVP-I hydrogel for improved antiseptic wound treatment with moisturizer. It has been reported that liposomes are enriched at the wound bottom for direct action against infection and support of wound healing. An animal study on the efficacy and tolerability of different formulations of a hydrogel with PVP-I liposomes in deep dermal burn wounds has indicated an outstanding quality of wound healing with smooth granulation tissue, less inflammation, less wound contraction and no hyperkeratotic reactivity, especially with the 3% PVP-I liposome formulation.

Physicochemical properties and in vitro toxicity of cationic liposome cDNA complexes

The purpose of this study was to elucidate the interaction of cationic liposomes and plasmid cDNA by examining their ultrastructure, zeta potential, stability in aqueous media and protection from DNaseI digestion; their potential for hemolysis and platelet aggregation was evaluated as it may serve as an in vitro toxicity screen. Liposomes consisting of N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTMA) or 3 beta-[N-(N',N'-dimethylaminoethane)-carbamoyl]-cholesterol (DC-Chol) and dioleylphosphatidylethanolamine (DOPE) were complexed with plasmid constructs of ovine prostaglandin G/H synthase (pCMV4-PGH) or human alpha 1-antitrypsin (pCMV4-AAT) at lipid:plasmid (L/P) ratios of 3:1-8:1 (w/w). The electron micrographs showed bead-like attachment of liposomes to cDNA and coating of plasmid strands. The zeta potential showed isoelectric points at L/P ratios of 3.5-4 (DOTMA/DOPE) and 5.5-6.5, corresponding to a pKa of 6.45 (DC-Chol/DOPE). Liposome cDNA complexes were stable in water, saline and 5% dextrose for 48 h, but precipitated instantaneously in PBS. An increase in the L/P ratio corresponded with increased protection from DNaseI digestion. DOTMA/DOPE liposomes alone were highly hemolytic and DC-Chol/DOPE liposomes moderately hemolytic; hemolysis was abolished by cDNA complexation, with the exception of very high (> or = 7:1) L/P ratios. Both liposomes alone and cDNA complexes caused transient serum turbidity, while none caused platelet aggregation. It was concluded that current cationic lipid cDNA formulations are metastable and appear to have very little if any toxicity with respect to hemolytic potential and untoward interaction with other blood components.

Pulmonary targeting of liposomal triamcinolone acetonide phosphate

PURPOSE

To explore the use of triamcinolone acetonide phosphate liposomes as a pulmonary targeted drug delivery system.

METHODS

Triamcinolone acetonide phosphate liposomes composed of 1,2-distearoyl phosphatidylcholine and 1,2-distearoyl phosphatidyl glycerol and triamcinolone acetonide 21-phosphate dipotassium salt were prepared by dispersion and extruded through polycarbonate membranes. Encapsulation efficiency and in vitro stability at 37 degrees C were assessed after size exclusion chromatography. TAP liposomes (TAP-lip) or TAP in solution (TAP-sol) were delivered to rats either by intratracheal instillation (IT) or intravenous (IV) administration. Pulmonary targeting was assessed by simultaneous monitoring of glucocorticoid receptor occupancy over time in lung (local organ) and liver (systemic organ) using an ex vivo receptor binding assay as a pharmacodynamic measure of glucocorticoid action.

RESULTS

In vitro studies in different fluids over 24 hours, showed that more than 75% of the TAP remained encapsulated in liposomes. Cumulative pulmonary effects after IT administration of TAP-lip were 1.6 times higher than liver receptor occupancy. In contrast, there was no difference in the pulmonary and hepatic receptor occupancy time profiles when TAP was administered intratracheally as a solution. No preferential lung targeting was observed when TAP-lip was administered IV. As indicated by the mean effect times, lung receptor occupancy was sustained only when TAP-lip was administered IT.

CONCLUSIONS

Intratracheal administration of TAP-lip provided sustained receptor occupancy, and increased pulmonary targeting which was superior to IT administration of TAP-sol or IV administration of TAP-lip. The use of liposomes may represent a valuable approach to optimize sustained delivery of glucocorticoids to the lungs via topical administration.

Water dynamics and population pressure in the Nepalese Himalayas

The authors investigate the impact of water shortages, especially water for irrigation, on development in Nepal. "The problems associated with hydropower development will be illustrated by using the Kulekhani watershed project as a case study." The possible future effects on food supplies and health are discussed.

Assessment of glucocorticoid lung targeting by ex-vivo receptor binding studies in rats

Triamcinolone acetonide (TA, 22 micrograms) was given to rats by intravenous (i.v.) injection or intratracheal (IT) instillation. Free glucocorticoid receptors were monitored over time in liver and lung using an ex-vivo receptor binding technique. After i.v. administration of a TA solution, the reduction of free receptors over time was very similar in lung and liver (AUCLung = 280 +/- 47% h; AUCLiver = 320 +/- 76% h). Intratracheal instillation of the same solution produced time profiles which mirrored those of i.v. injection (AUCLung = 260 +/- 41% h; AUCLiver = 330 +/- 50% h). The lack of lung targeting was also reflected in the failure to show any significant difference in the pulmonary targeting factor T (AUCLung/AUCLiver) between i.v. (T = 0.84 +/- 0.18) and IT (T = 0.78 +/- 0.03) administration. In contrast, a certain degree of lung specificity was observed after IT instillation of a glucocorticoid suspension (22 micrograms; AUCLung = 160 +/- 135% h; AUCLiver = 65 +/- 91% h, T = 2.3 +/- 0.5) as indicated by significant differences in T between i.v. injection and IT instillation (p = 0.038). The method presented provides a means of simultaneously assessing pulmonary and systemic effects after different forms and routes of administration and might be of value in further studying multiple aspects of inhalation glucocorticoid therapy.

(Patho)physiologic pathways to drug targeting: artificial viral envelopes

The goal of this study was to exploit molecular recognition of cell surface receptors by viral surface glycoproteins as a means for the selective intracellular delivery of macromolecules. To accomplish this, artificial viral envelopes (AVE) resembling the human immunodeficiency virus-1 (HIV-1) were designed as a model system. Recombinant HIV-1 surface glycoprotein gp160 (HIV-1 rgp160) was inserted in the artificial envelope by a two-step detergent dialysis process. The artificial HIV-1 envelope recognized the CD4 cell surface receptor. FITC-dextran and ricin A were employed as model macromolecules as they cannot passively diffuse across cell membranes. Selective transfer of FITC-dextran encapsulated in HIV-1 rgp160 AVE into a CD4-positive cell line (REX-1B) versus a CD4-negative cell line (KG-1) was demonstrated. Ricin A at concentrations as low as 2 ng/ml arrested cell growth of CD4-positive MOLT-4 cells, whereas 8 ng/ml ricin A in solution had no effect on cell growth. The arrest of cell growth was reverted in the presence of excess anti-gp120 monoclonal antibody. Naked envelopes (without HIV-1 rgp160 inserted) were also found to interact with cells and transfer material, although less efficiently and in a non-specific manner. Viral mimicry using AVE may be a means for targeted intracellular delivery of peptides, proteins, enzymes, toxins, oligodeoxynucleotides, gene constructs, and other non-diffusive, labile or toxic macromolecules.

Pharmacokinetics of detirelix following intratracheal instillation and aerosol inhalation in the unanesthetized awake sheep

The unanesthetized awake sheep was employed as large animal model for the determination of bioavailability and pharmacokinetics following the pulmonary instillation of the decapeptide detirelix. After intratracheal administration of a 80 micrograms/kg dose, the average t1/2 of elimination was 9.8 +/- 1.3 hours (n = 5) which was similar to the elimination kinetics of a 30 micrograms/kg i.v. dose (7.2 +/- 2.9 hours). Mean residence time (MRT) was prolonged to 10.3 +/- 2.0 hours vs. 2.7 +/- 0.8 hours i.v., and mean absorption time (MAT) was calculated to be 7.5 +/- 1.8 hours. Maximum plasma levels (cmax) of 9.2 ng/ml were reached after 2 hours. The average bioavailability was 9.8 +/- 3.9% of the dose. The pharmacokinetic profile was found to be similar after aerosol administration. It was concluded that detirelix was absorbed systemically when administered by pulmonary instillation or aerosolization and that the unanesthetized awake sheep is a suitable model to study resulting drug profiles.

Targeting of liposomes to cells expressing CD4 using glycosylphosphatidylinositol-anchored gp120. Influence of liposome composition on intracellular trafficking

To test the concept that glycosylphosphatidylinositol (GPI)-anchored proteins might be useful as targeting molecules for liposomes, we engineered a GPI-anchored form of gp120 from human immunodeficiency virus type 1 (termed gp120DAF) using the GPI signal of decay-accelerating factor (DAF). We show that (i) purified gp120DAF spontaneously inserts into liposome membranes via the GPI anchor; (ii) liposomes bearing gp120DAF bind specifically to cells expressing CD4, the cellular receptor for gp120; and (iii) the receptor-bound liposomes are internalized and recycle in Chinese hamster ovary cells. To test whether the lipid composition of the liposome affects any of these processes, we compared small unilamellar liposomes containing only phosphatidylcholine and cholesterol in a 7:1 molar ratio with artificial viral envelopes that mimic the lipid composition of human immunodeficiency virus type 1. We show that when tagged with gp120DAF, both liposome preparations bind specifically to cells expressing CD4, and both are endocytosed. However, artificial viral envelope liposomes are transported to late endosomes or lysosomes in the cell interior, whereas phosphatidylcholine:cholesterol liposomes are confined to a population of vesicles that remain close to the plasma membrane. Since the binding and internalization of both liposome preparations are mediated by the same receptor, we conclude that the lipid composition of the liposome profoundly influences the subsequent intracellular trafficking of the liposome-receptor complex.

The new frontier: gene and oligonucleotide therapy

Gene and oligonucleotide therapy are emerging as clinically viable therapeutic regimens for genetic, neoplastic, and infectious diseases. Approaches include insertion of human genes in viral vectors including recombinant retrovirus, adenovirus, adeno-associated virus, and herpes simplex virus-1, or recombinant bacterial plasmids. Viral vectors transfect cells directly; plasmid DNA is delivered with the help of cationic liposomes (lipofection), polylysine conjugates, gramicidin S, artificial viral envelopes or other such intracellular carriers. Major areas of interest include replacement of the cystic fibrosis transmembrane regulator gene and the alpha 1-antitrypsin gene; arrest of human immunodeficiency virus infection; and reversal of tumorigenicity and cancer immunization, among others. Oligonucleotide therapy is principally focusing on the same areas, although the approach is to halt DNA transcription or messenger RNA translation with code-blocking triple-helix-forming or "antisense" oligomers. Contributions from the pharmaceutical sciences are expected in pharmaceutical chemistry, drug delivery systems design, analytical chemistry, and biopharmaceutics.

Pulmonary effects of chronic exposure to liposome aerosols in mice

Administering liposome-encapsulated drugs by aerosols could be a feasible way of targeting drugs to the lung, specifically to pulmonary alveolar macrophages (AM). In the mouse model, we characterized uptake of carboxyfluorescein- (CF-) labeled liposomes by AM in vivo after acute inhalation of liposome aerosols, and the effects of chronic exposure to liposome aerosols on lung histology and AM function. Mice were placed in a nose-only exposure module and exposed to liposome or saline aerosols for 1 h per day, 5 days per week, for 4 weeks. Five mice of both the experimental and control groups were removed weekly and their lungs examined. Liposomes were made from hydrogenated soy phosphatidylcholine (HSPC) at 50 mg/mL. In vivo uptake of liposomes by AM was documented by fluorescence microscopy and flow cytometry of bronchoalveolar lavage (BAL). A consistent amount of 1-3 micrograms of lipid inhaled per dosing per mouse was estimated from fluorescence measurements. Addition of Triton X-100 to BAL caused a significant increase in fluorescence intensity, indicating that liposomes remained intact in the lung for a period of time. The chronic inhalation study showed no histologic changes of the lung or untoward effects on the general health or survival of animals. AM phagocytic function, intracellular killing, and fatty acid composition were not affected. Transmission electron microscopy and morphometry (computerized image analysis) of AM likewise showed no alterations as a result of the treatment. It was concluded that AM uptake of liposomes delivered by aerosol was operant in vivo. This finding validates the concept of alveolar macrophage-directed delivery of liposome-encapsulated agents to the lung via inhalation. It was also concluded that chronic liposome aerosol inhalation in mice produced no untoward effects on survival, histopathology, and macrophage function. These data confirm and extend prior findings regarding the functional and morphologic interactions of liposomes with AM in vitro (Gonzalez-Rothi et al., Exp. Lung Res. 17:687-705, 1991).

Nebulization of liposomes. III. The effects of operating conditions and local environment

Multilamellar liposomes (MLV) of saturated phosphatidylcholine and dipalmitoyl phosphatidylglycerol (DPPG) (9:1 mole ratio) containing 5,6-carboxyfluorescein (CF) were prepared and extruded through 1.0-micron polycarbonate membranes. Diluted aqueous dispersions were aerosolized for a total of 80 min using a Collison nebulizer under a variety of conditions. The effects of air pressure, temperature, buffer osmotic strength, and pH on nebulized liposome dispersions were studied. Changes in air pressure produced large changes in the percentage release of CF and ranged from 1.3% (4 psig) to 88.2% (50 psig) after 80 min of nebulization. The temperature of the nebulizer dispersions dropped during experiments. The extent of the temperature drop varied according to the air pressure used and ranged from 5 degrees C (4 psig) to 11 degrees C (greater than or equal to 30 psig). The temperature of dispersions caused no increase in CF release until the gel-to-liquid crystalline transition temperature was exceeded (54.6 degrees C), whereupon a 20% increase in leakage was observed after 80 min of nebulization. Aerosol mass output was relatively unaffected by the starting temperature of experiments when conducted within the ambient temperature range. Leakage from the liposomes was increased in hypotonic solution but decreased in hypertonic solutions. At a buffer pH of 2.85 the percentage leakage of CF was increased approximately 18% compared to that at pH 7.2 and pH 10.75. Results show that the stability of liposomes composed of saturated phosphatidylcholine and DPPG (9:1 mole ratio) is affected by the operating and environmental conditions under which aerosolization takes place, with air pressure having the greatest effect.

Artificial viral envelopes containing recombinant Human Immunodeficiency Virus (HIV) gp160

An artificial viral envelope was constructed, resembling the human immunodeficiency virus (HIV) envelope with respect to ultrastructure, size, phospholipid profile and lipid:cholesterol ratio. Recombinant HIV surface protein gp160 was anchored in the outer surface of the envelope membrane using a double detergent dialysis. The envelopes remained physically stable for several months. Immunolabeling with anti-gp160/41 monoclonal antibody revealed surface insertion and availability of gp160 for binding. Cell fusion and cytosolic transfer of the encapsulated fluorescent marker FITC-dextran was demonstrated. Flow cytometry indicated more efficient transfer of the fluorescent marker to cells which were approximately 60% CD4+ (REX-1B), relative to cells which were only approximately 18% CD4+ (KG-1). However, plain lipid envelopes without gp160 fused very efficiently with both cell types, indicating their potential usefulness as "fusogenic liposomes". Complete artificial viral envelopes may serve as subunit vaccines, and receptor-targeted delivery systems for drugs, toxins and genetic constructs.

Lipophilic N-acylpyrazinamide derivatives: synthesis, physicochemical characterization, liposome incorporation, and in vitro activity against Mycobacterium avium-intracellulare

N-acetyl-(2), N-caproyl-(3), N-capryl-(4) and N-palmitoyl-pyrazinamide (5) were synthesized by reacting pyrazinamide (1) with acetic anhydride to prepare (2), or by reacting (1) in chloroform with the corresponding acid chlorides to prepare (3-5). Products were identified by high resolution mass spectroscopy, elemental analysis, and 1H NMR. Melting points, enthalpies of fusion, solubility and octanol-water partition coefficients were determined. Hydrolysis of (2) indicated a pseudo first-order, pH-dependent degradation reaction. Apparent half life times of degradation ranged from 74.2 hours at pH 3 to 5.4 hours at pH 7.34. Derivative (5) was incorporated in liposomes consisting of soy phosphatidylcholine and dipalmitoylphosphatidylglycerol (7:3 molar ratio). The in vitro susceptibility of Mycobacterium avium-intracellulare (MAI) to the liposomal compound containing (5) was tested. MAI was susceptible to (5) at concentrations of 12.5-25 micrograms/ml, although MAI is not susceptible to the parent drug (1). Thus, a new class of antimycobacterial agents with physicochemical properties suitable for stable incorporation within liposomes and high antibiotic efficacy against MAI is presented.

Liposomes and pulmonary alveolar macrophages: functional and morphologic interactions

In vitro toxicity of liposomes and their functional and morphologic interactions with rat pulmonary alveolar macrophage (AMs) were investigated using viability (trypan blue exclusion), phagocytic and killing activity (uptake and digestion of live S. cerevisiae), surface adherence, respiratory burst (nitro-blue tetrazolium reduction), and morphometry (computerized image analysis) as indicators. Liposome stability in physiologic solutions and uptake of liposome-encapsulated carboxyfluorescein (CF) by AMs was assessed by fluorescence spectroscopy and microscopy. Liposomes made from saturated phospholipids and cholesterol were stable, whereas liposomes consisting of unsaturated phospholipids without cholesterol lost 30% to 40% of their content over 24 h. However, CF uptake was highest with unsaturated phospholipid preparations, whereas uptake of the three other formulations was comparable. Although liposome exposure did not affect macrophage viability, a reduction in the number of phagocytizing macrophages to 73% of control was noted after 24-h incubation with the highest lipid concentration tested (10 mumol/ml). Phagocytic killing was similar under all circumstances observed. The fraction of intracellularly killed yeast ranged from 32% to 42% for both control and experimental samples. An increase in cell surface area from 166.1 +/- 39.9 microns 2 on day O (n = 709) to 196.3 +/- 57.6 microns 2 on day 1 (n = 516) and 211.2 +/- 48.0 microns 2 on day 4 (n = 834) was observed after liposome treatment. The corresponding average cell areas of control samples did not change during the observation period. There was no net cell loss of adherence from monolayers as determined by protein assay. The respiratory burst, indicating generation of intracellular superoxide, was also similar--84% to 92% of experimental and control cells under all conditions showed a strong nitro-blue tetrazolium reduction. In summary, in vitro exposure of AMs to large concentrations of liposomes, although producing an increase in macrophage size, was not associated with aberrant macrophage morphologic features, function, or toxicity for the parameters examined.

Acute effects of liposome aerosol inhalation on pulmonary function in healthy human volunteers

Administering liposome-encapsulated drugs by aerosol is a feasible way of targeting drugs to the lungs. Prior to clinical application of aerosolized liposomes as drug carriers, their relative safety must be established. We evaluated the effects of inhaling nondrug-containing liposomes (15 and 150 mg of lipid per milliliter) for 1 h on pulmonary function and on oximetry in ten healthy nonsmoking volunteers. Spirometry was performed prior to and at intervals after inhalation, and subjects were monitored with pulse oximetry. Liposome inhalation was well tolerated, and no oxygen desaturation, decrements in pulmonary function, or side effects were noted. We conclude that inhalation of small particle aerosols of SPC liposomes produces no acute deleterious effects on pulmonary function in healthy subjects.

Nebulization of liposomes. II. The effects of size and modeling of solute release profiles

A series of carboxyfluorescein (CF)-containing multilamellar vesicle (MLV) dispersions was prepared and extruded through polycarbonate membranes ranging in size from 0.2 to 5 microns. Vesicle dispersions were nebulized for 80 min using a Collison nebulizer, and the release of CF was monitored during nebulization. Solute retention was dependent upon the size of the vesicles and leakage ranged from 7.9 +/- 0.4% (N = 3) for vesicles extruded through 0.2-microns filters to 76.8 +/- 5.9% (N = 3) for liposomes that were not filtered. Solute release profiles obtained over greater than or equal to 420-min nebulization periods conformed to a two-compartment kinetic model and exhibited a "fast" initial phase (k1 = 0.052 +/- 0.0043) followed by a "slow" terminal phase (k2 = 0.0034 +/- 0.00018). The results show that CF retention can be increased by nebulizing small vesicles and modeling suggests that the rate of CF leakage from the bilayers is faster than from the core of the liposomes.

Sensitive liquid chromatography assay for the determination of amikacin in human plasma

A selective LC method with on-line post-column derivatization is described for the determination of amikacin in biological fluids. Chromatography was performed on a reversed-phase column, using pentane sulphonic acid as an ion-pairing reagent. For the analysis of biological fluids, amikacin and the internal standard tobramycin were extracted using an ion exchanger (Sephadex). Following complete removal of plasma proteins, the aminoglycosides were eluted with alkaline sodium sulphate solution and injected into the chromatograph. After chromatographic separation the eluent was mixed with the derivatization reagent (o-phthalaldehyde and mercaptoethanol in borate buffer pH 10.4) in a reaction coil at 50 degrees C. Detection was performed by fluorescence (excitation: 340 nm, emission: 418 nm). The overall run time was 8 min, at a flow rate of 1.2 ml min-1. The limit of quantification was 25 ng ml-1 for amikacin in plasma.

Evidence for generation of a large amount of nitric oxide-like vascular smooth muscle relaxant by cholesterol-rich neutrophils

To determine the effect of cholesterol incorporation on the ability of neutrophils to generate superoxide radicals and nitric oxide-like vasorelaxant material, isolated human neutrophils were incubated with cholesterol-rich liposomes, which increased total cholesterol content by 141% and esterified cholesterol content by 523%. Cholesterol loading resulted in 5 to 7 fold increase in cytosolic calcium in resting as well as in PMA or f-MLP-stimulated cells, but a marked (P less than 0.01) reduction in both PMA- and f-MLP-stimulated superoxide radical generation by these cells. Nitric oxide-like activity measured as relaxation of rat aortic rings was more pronounced (P less than 0.02) in cholesterol-rich than in cholesterol-poor cells. The greater relaxation of aortic rings in response to cholesterol-rich neutrophils was observed in rings with or without intact endothelium, and was potentiated by superoxide dismutase and inhibited by oxyhemoglobin as well as L-NMMA, thus suggesting that the vasorelaxant material was nitric oxide. The greater generation of nitric oxide by cholesterol-rich neutrophils occurs perhaps in response to increased cytosolic calcium.

Nebulization of liposomes. I. Effects of lipid composition

A series of multilamellar liposome dispersions was prepared from lipids of soy phosphatidylcholine or hydrogenated soy phosphatidylcholine containing from 0 to 30 mol% of either cholesterol, stearylamine, or dipalmitoyl phosphatidylglycerol. The liposome dispersions were aerosolized with a Collison nebulizer for 80 min at an output flow rate of 4.7 liters of air/min. The effects of nebulization on the vesicles were determined by monitoring the release of encapsulated 5,6-carboxylfluorescein (CF) from dispersions containing approximately 200 micrograms of total CF, of which 93.1 +/- 2.4% (N = 18) was initially encapsulated. In all experiments CF was released from the liposomes while being aerosolized, and this ranged from a mean of 12.7 +/- 3.8 to 60.9 +/- 1.9% of the encapsulated CF, depending upon the lipid composition. The lipid concentration in the dispersions did not affect the rate or percentage release of CF over a range of approximately 0.5 to 50 mg per nebulized dispersion. If liposomes are to be used as drug carriers in an inhalation aerosol a lipid composition should be employed which will minimize the release of encapsulated drug caused by nebulization.

Binding of daunomycin to acidic phospholipids

Apparent binding affinity and capacity of daunomycin to the acidic phospholipids cardiolipin, phosphatidylglycerol, phosphatidic acid, phosphatidylserine and phosphatidylinositol, and the neutral zwitterion phosphatidylcholine were estimated via extraction of the drug with and without lipids into the organic phase of a biphasic organic-aqueous system (Folch) at various pH values. Total extraction was highest at pH 8.50 (approximately 70% of total drug at 1 mumole/3.6 mL concentration), medium at pH 2.77 (approximately 50%) and lowest at pH 6.55 (approximately 20%). Extraction was highly specific in the presence of all phospholipids except phosphatidylcholine at pH 6.55, and specific for cardiolipin and phosphatidylglycerol at pH 2.77. However, there was no phospholipid-specific extraction at pH 8.50. Apparent binding affinity decreased in the order phosphatidic acid much greater than phosphatidylserine greater than phosphatidylinositol greater than phosphatidylglycerol much greater than cardiolipin. No specific extraction was detectable in the presence of the zwitterionic phosphatidylcholine. However, cardiolipin was the only phospholipid with two binding sites per daunomycin molecule, whereas all others have only one binding site per daunomycin molecule.

Prevention of nonspecific lysis in liposomal and erythrocyte immunoassay systems by small lipid vesicles and erythrocyte ghosts

Large unilamellar liposomes prepared by the reverse-phase evaporation method (REVs) were made immunoreactive by incorporating dinitrophenylaminocaproyl-phosphatidylethanolamine (DNP-Cap-PE) or 8-(3-carboxypropyl)-theophylline-dipalmitoylphosphatidylethanolamine (Th-DPPE) into the phospholipid bilayer. Specific lysis in the presence of anti-DNP-BSA and goat anti-theophylline serum respectively, was induced by adding guinea pig serum as source for complement to these liposomes. However, specific lysis was found to be compromised by high levels of nonspecific lysis as monitored by the release of the fluorescent aqueous-space marker 6-carboxyfluorescein. Nonspecific lysis could be prevented without affecting specific lysis by pretreatment of complement or incubation of the reaction mixture with small unilamellar liposomes (SUVs). SUVs of various lipid compositions produced the desired effect; however, when the fraction of negative charge in the SUVs was increased to 30 mol%, specific lysis was inhibited as well. In a similar assay system consisting of hemolysin-sensitized sheep red blood cells it was also found that nonspecific lysis could be inhibited by addition of erythrocyte ghosts to the incubation medium, although specific lysis was somewhat depressed. However, SUVs or REVs of a composition similar to sheep erythrocytes were ineffective indicating a more selective nature of complement-mediated immunoreaction with erythrocyte membranes than with synthetic bilayer membranes.

A radiolabel and electron microscopy study of the interaction of liposomes with synaptosomal membranes

The quantitative and qualitative interaction of liposomes with synaptosomes isolated from rat brain was examined using radiolabeled phospholipids and electron microscopy. Liposomes were prepared by sonication and detergent dialysis. Binding (adsorption) of radiolabeled phospholipid to synaptosomes was saturable when liposomes were in the liquid-crystalline state, were electrically neutral (egg-phosphatidylcholine), or carried increasing fractions (10:2 and 10:4 molar ratio) of negatively charged phosphatidic acid. Analysis using the Langmuir isotherm equation indicated a biphasic adsorption behavior. Adsorption increased with increasing temperature (4 degrees C and 37 degrees C). Binding was nonsaturable when liposomes were positively charged with stearylamine or composed of dimyristoylphosphatidylcholine and phosphatidylinositol (10:2 molar ratio). Due to the latter composition's solid state at 4 degrees C, temperature dependency was inverse. Electron micrographs revealed disc-shaped areas of adsorption that were free of integral membrane particles which appeared to form a condensed layer surrounding the areas of liposome adsorption. Following interaction with stearylamine-containing liposomes the vesicular structure of synaptosomes appeared largely destroyed. It is concluded that both liposome surface charge and membrane fluidity determine the extent of interaction with biological membranes.

Asbestos fibres introduce trace metals into streamwater and sediments

Based on a case study in the Sumas River, it is demonstrated that asbestos fibres, which were introduced by a massive landslide, have altered the water quality and sediment conditions in the downstream section of the river. Asbestos fibres, because of their small size, are readily transported and resuspended i in stream systems. Associated with the fibres are high quantities of Ni, Cr, Co and Mn which occur as contaminations and isomorphic substitutions in most asbestos materials. A direct link between discharge, asbestos fibre and Ni concentrations was demonstrated in the water. Trace metal values in the sediments decrease with distance from the point source but the concentrations 20 km downstream of the slide are still significantly higher than levels at a control station unaffected by the slide. Asbestos fibres leach in acid media, and Mg and trace metals are removed. The process and rates were illustrated on the basis of laboratory experiments using organic acids. Since the pH in the streamwater is decreasing from 8.4 to 7.1 in the downstream direction, trace metals release is of concern.

The use of a new radioactive-iodine labeled lipid marker to follow in vivo disposition of liposomes: comparison with an encapsulated aqueous space marker

The in vivo disposition of multilamellar liposomes extruded at 0.6 micrometers (PC/DPPA/CH/ alpha-T = 4:1:5:0.1 molar ratio) when injected i.v. into mice has been examined utilizing a novel iodinatable phospholipid derivative as a lipid phase marker (p-hydroxybenzamidine phosphatidylethanolamine: 125I-BPE) and compared to that using 14C-inulin as an aqueous phase marker. At times up to 5 h post-dose the disposition of both markers was essentially identical with the exception of blood and intestine, where 125I-BPE levels were consistently higher than 14C-inulin levels. At time intervals from 5-72 h post-dose 125I-BPE levels in all the organs examined were lower than those of 14C-inulin. These differences in the behaviour of the two labels may be explained in terms of exchange of the iodinated lipids, excretion of released inulin and long term metabolism of the lipid marker. We conclude tha 125I-BPE is a useful marker for following liposome disposition in short-term studies particularly in view of the easily quantifiable nature of gamma-radioactivity which obviates the need for sample preparation.