Liposomes produced in a pilot scale: production, purification and efficiency aspects

One step membrane incorporation of viral antigens as a vaccine candidate against HIV

Liposomes can been used as potential immunoadjuvants, because they have the ability to elicit both a cellular mediated immune response and a humoral immune response. Studies have shown liposomes to be effective immunopotentiators in hepatitis A and influenza vaccines. For all these purposes, liposomes can be prepared by different methods. After disperging suitable membrane lipids in an aqueous phase and spontaneous formation of multilamellar large vesicles (MLV), mechanical procedures such as ultrasonication, homogenization by a French press or by other high pressure devices and, or extrusion through polycarbonate membranes with defined pore sizes lead to a reduction in size and number of lamellae of the vesicles. A second group of preparation procedures uses suitable detergents, e.g., bile salts or alkylglycosides. A third group of procedures starts with dissolving the lipids in an organic solvent and mixing it with an aqueous phase. The concentration of the organic solvent is then reduced by suitable procedures. Here we present a new technique for the preparation of liposomes with associated membrane proteins, where lipid vesicles are formed immediately after injection into a micellar protein solution. The model membrane protein used for these studies is a truncated recombinant gp41 produced in E. coli. This viral membrane antigen is a possible candidate protein for the establishment of HIV-vaccines. The data presented here, show an efficient and reproducible one step membrane protein encapsulation procedure into liposomes in a closed and sterile containment. We examined encapsulation efficiency, membrane protein conformation and immunogenicity of this possible liposomal vaccine candidate, which can be produced in GMP-compliant quality with the described technique.

Controlled microfluidic encapsulation of cells, proteins, and microbeads in lipid vesicles

Cells have been encapsulated inside lipid vesicles by using a new microfluidic lipid vesicle formulation technique. Lipid vesicles are formulated within minutes without using toxic lipid solvents. The encapsulation efficiency inside the vesicles is controlled by the microfluidic flows. Green fluorescent proteins (GFP), carcinoma cells, and bead encapsulated vesicles have mean diameters of 27.2 mum, 62.4 mum, and 55.9 mum, respectively. The variations of vesicle sizes are approximately 20% for the GFP and cell encapsulated vesicles and approximately 10% for the bead encapsulated vesicles.

GMP production of liposomes--a new industrial approach

A new scalable liposome production system is presented, which is based on the ethanol injection technique. The system permits liposome manufacture regardless of production scale, as scale is determined only by free disposable vessel volumes. Once the parameters are defined, an easy scale up can be performed by just changing the process vessels. These vessels are fully sterilizeable and all raw materials are transferred into the sanitized and sterilized system via 0.2 microm filters to guarantee an aseptic production. Liposome size can be controlled by the local lipid concentration at the injection point depending on process parameters like injection pressure, lipid concentration and injection rate. These defined process parameters are furthermore responsible for highly reproducible results with respect to vesicle diameters and encapsulation rates Compared to other technologies like the film method which is normally followed by size reduction through high pressure homogenization, ultrasonication or extrusion, no mechanical forces are needed to generate homogeneous and narrow distributed liposomes. Another important advantage of this method is the suitability for the entrapment of many different drug substances such as large hydrophilic proteins by passive encapsulation, small amphiphilic drugs by a one step remote loading technique or membrane association of antigens for vaccination approaches.

The preparation of liposomes using compressed carbon dioxide: strategies, important considerations and comparison with conventional techniques

Numerous strategies are currently available for preparing liposomes, although no single method is ideal in every respect. Two methods for producing liposomes using compressed carbon dioxide in either its liquid or supercritical state were therefore investigated as possible alternatives to the conventional techniques currently used. The first technique used modified compressed carbon dioxide as a solvent system. The way in which changes in pressure, temperature, apparatus geometry and solvent flow rate affected the size distributions of the formulations was examined. In general, liposomes in the nano-size range with an average diameter of 200 nm could be produced, although some micron-sized vesicles were also present. Liposomes were characterized according to their hydrophobic drug-loading capacity and encapsulated aqueous volumes. The latter were found to be higher than in conventional techniques such as high-pressure homogenization. The second method used compressed carbon dioxide as an anti-solvent to promote uniform precipitation of phospholipids from concentrated ethanolic solutions. Finely divided solvent-free phospholipid powders of saturated lipids could be prepared that were subsequently hydrated to produce liposomes with mean volume diameters of around 5 microm.

Liposomal Recombinant Human Superoxide Dismutase for the Treatment of Peyronie's Disease: A Randomized Placebo-Controlled Double-Blind Prospective Clinical Study

OBJECTIVE

To demonstrate the efficacy and safety of a topical gel containing liposomally encapsulated recombinant human Superoxide Dismutase (lrhSOD) in the treatment of painful Peyronie's Disease. The theoretical background is that lrhSOD, by scavenging of free oxygen radicals, might interrupt inflammatory cascades and thereby limit further disease progression.

METHODS

In a placebo-controlled randomized clinical trial, 39 patients with Peyronie's Disease and significant pain symptoms were treated with lrhSOD or placebo for a 4 week period. At this time, statistical evaluation of pain resolution was performed as primary study endpoint. Patients then were continued in a cross-over study design to ensure a total of 8 weeks of lrhSOD therapy for all study participants. Pain, plaque and curvature assessment was performed at study entry and every 4 weeks until week 12.

RESULTS

LrhSOD treatment resulted in a statistically significant reduction of pain (p=0.017) compared to placebo already after 4 weeks. At week 12 pain was significantly reduced in 89% of patients who all had received 8 weeks of lrhSOD therapy at that time. Response to other disease parameters was assessed at week 12: plaque size was reduced in 47% of patients, as was plaque consistence in 38%. Penile curvature was improved at 5-30 degrees in 23% of patients. The expected spontaneous disease progression rate of up to 40%, as reported by several investigators, was significantly reduced to <10% under lrhSOD therapy, and patients satisfaction was high, also consequent to the lack of therapy-related side effects observed in the present study.

CONCLUSION

LrhSOD is an easily administrable, safe and effective local therapeutic for the painful phase of Peyronie's Disease.