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Factors Limiting The Production Of Liposomes

Pharmaceutical industry prognosticators recognize that liposomes will play an increasingly important role in the development of new drugs for the foreseeable future, due to the unique drug-delivery advantages these designer entities offer. With a heterogenous bilayer encapsulating an aqueous interior core, liposomes are ideal vesicles for the delivery of pharmacological payloads consisting of a hydrophilic compound contained within the aqueous core. Advantages include reduced toxicity, greater therapeutic index of the drug in question, and enhanced duration and/or frequency of drug delivery.

The Emerging Importance of Liposome Technology

Drug makers are not limited to hydrophilic active pharmaceutical ingredient (API) moieties, however, as amphiphilic and lipophilic compounds can alternatively be tucked into the vesicle’s lipid bilayers. In either case, these custom-made sub-cellular structures are ideal for delivering payloads directly to target cells, knocking on the proverbial cell membrane “door,” and gaining entry into the inner sanctum of the cell through its own protective semipermeable cytoplasmic membrane. Once inside, or perched within the cell’s lipid bilayer, the payload (immunological, chemotoxic or virtually anything else) can be released to maximum effect.

Oncology, especially, has benefitted from advances in liposomal drug delivery. Potent chemotherapeutic payloads can now be targeted directly at aberrant cells, improving the drug’s anti-cancer activity, and helping to limit collateral damage to adjacent healthy cells and tissues. The old chemotherapy paradigm can perhaps be characterized as reliant on carpet-bombing the body, with little regard for the risks posed by friendly fire. Liposomes allow oncologists to send in “laser-guided missiles” to take out carefully identified, “painted” targets. Thus, even crowded “neighborhoods” are spared, while the “bad guys” are taken out.

Liposomes Drug Delivery System Benefits

The usefulness of liposomes as drug delivery systems is not restricted to oncology, though. Their enhanced pharmacokinetic properties are also being harnessed to deliver drugs, nutrients, vaccines, hormones (insulin), peptides and other bioactives. Liposomes are typically superior to free drugs due to their ability to resist gastrointestinal degradation and avoid rapid elimination.

They’re the ultimate controlled- or sustained-release drug delivery vehicles, offering superior stability and enhanced targeting. Issues surrounding the chemical and physical stability of liposomes have been viewed as limitations in the past, as they affect shelf stability. However, various methods have been explored to overcome this challenge, including lyophilization with a suitable cryoprotectant, and subsequent reconstitution before clinical use.

Of course, achieving these vesicles involves overcoming significant technical challenges by drug developers. Chief among these challenges is the issue of controlling size and distribution. Numerous methods exist. Some involve multi-step processes that include spontaneous assembly under bulk mixing conditions, followed by extrusion or sonication to achieve the appropriate tiny particle size and relatively tight size distributions.

Microfluidics Is the Superior Technology

These methods are generally complex, inefficient and time-consuming. However, microfluidics has emerged as a superior technology that gives manufacturers precise control over the lipid hydration process. Various methods employing this technology have been devised to achieve micro to nanoscale liposomes with admirably tight particle size distributions. Of course, uniform particle size distributions are crucial to the success of any drug-manufacturing endeavor, as particle size uniformity within a given dose is a key determinant of predictable, uniform dosing.

Specifically, continuous-flow microfluidics is emerging as the superior liposome manufacturing technology, especially when nanoparticles are desired. As noted in a 2009 article, “The self-assembly in microfluidics can be controlled by varying liquid flow rates, ratios of cross-flows and the composition and concentration of lipids, resulting in tunable sizes, and narrower size distributions.”

Thus, continuous microfluidics provides the ability to carefully control parameters related to the generation of specific liposome characteristics. Most development processes will focus on successful encapsulation of the compound of interest. Optimization of liposomal encapsulation is possible using the right processes and equipment. When it comes to optimal equipment, we believe Microfluidics Microfluidizer® microencapsulation technology is second to none.

Microfluidizer® Excels at Microencapsulation and Nanoencapsulation

Our unique, proprietary fixed-geometry interaction chamber is at the heart of every Microfluidics Microfluidizer® machine. This advanced technology enables process engineers to achieve vanishingly small particle sizes, with uniform particle size distributions, often within a single pass. Efficient encapsulation rates are achieved using this high-pressure homogenization featuring controlled shear rates and precise temperature control.

Precise shearing ensures tight particle size distributions and enhanced process efficiency. Even better, the Microfluidics family of machines has been designed to facilitate seamless scale-up from lab, to pilot, to full production runs. Microfluidizer® technology sets the pharmaceutical industry standard for the successful, efficient achievement of any number of crucial drug development/manufacturing processes, including: nanoemulsions, dispersions, nanoencapsulation and cell disruption.

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