What to Consider When Selecting Lipids for Drug Delivery or Pharmaceutical Applications

Posted on October 01, 2019


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There are a lot of different things to consider when selecting the right lipids or lipid mixture for your drug delivery or pharmaceutical project. Avanti is here to help you get the very best results from your research, with the purest possible lipids. Keep reading for some of the most important things to think about before placing your order.

Phase Transition Temperature

Phase transition temperature, or the temperature required to induce a change in the lipid physical state from the ordered gel phase—where the hydrocarbon chains are fully extended and closely packed—to the disordered liquid crystalline phase, can drastically affect your research.

A lot of things can impact the phase transition temperature, like the hydrocarbon length, unsaturation, charge, and headgroup species. Essentially, as the hydrocarbon length increases, more energy is needed to disrupt the ordered packing—causing the phase transition temperature to increase. Whereas introducing a double bond to the acyl group puts a kink in the chain, which requires a lower temperature.

Being able to control the transition temperature could prove very useful when developing something new. For example, a high temperature means that the packaging won’t leak before you’re ready to use it. However, if leaky packaging during use would benefit your project, you’d want a lower temperature. Also keep in mind that using a high temperature lipid when filtration is necessary could be difficult.

Stability

The long-term stability, or shelf life, of a product containing lipids can be determined by the lipid species used in the formulation. For example, the more unsaturated a compound is, the easier the product is to oxidize—this leads to a shorter shelf life. Lipids from biological sources like egg, bovine, or soybean typically have significant levels of polyunsaturated fatty acids. This makes them inherently less stable than synthetic lipid compounds.

If you’re looking for the greatest stability in terms of oxidation, saturated lipids are the way to go. They do, however, have a much higher transition temperature, which could present other difficulties in formulation. If unsaturation is necessary, try to keep the degree of unsaturation as low as possible.

A common problem with lipid products is stability issues due to hydrolytic degradation. Aqueous formulations of drug products can be less stable, because the presence of excess or bulk water leads to rapid hydrolytic degradation 3n lipid preparations.

Stabilizing membranes has been a popular subject of research for a long time, with the bulk of the research being aimed at stabilizing intact liposomes in the dry powder form. This way, they retain their trapped internal contents when they’re reconstituted.

Charge

A lot of biological membranes carry a net negative charge on their surface, which is generally imparted by anionic phospholipid species in the membrane. This charge can provide a special function for the membrane—for example, numerous steps of blood coagulation cascade require a lipid membrane.

The assembling of protein aggregates on the surface of platelets requires a negatively charged surface. Problems can arise because in some systems, the charge requirement has to be satisfied along with the system specificity for particular species.

Lipid Mixtures

In a lot of cases, a single lipid species doesn’t have the perfect physical properties necessary for a particular system, nor does it accurately mimic the natural system it’s designed to copy or replace. A lot of these scenarios can be satisfied using a complex lipid mixture. In fact, many commercially available coagulation reagents (which contained crude brain extracts) are being replaced by synthetic lipid blends. This results in increased stability due to the reproducibility of synthetic blends.

Another perk of using complex lipid mixtures is that it doesn’t require very much additional effort when it comes to sample preparation. In fact, a supplier will often pre-blend the mixture to the user’s specifications and provide a ready-to-use product if the quantity of the lipid blend is enough. For more things to consider when planning for your next project, contact Avanti Polar Lipids today.