Albumin in Formulation
In the past there has been a varied range of formulations for albumin . Plasma sourced human serum albumin was utilized initially. However, there has been a change in the field towards the utilization of chemically defined (recombinant) human serum albumin .
This change comes from the fact that the recombinant product is considered favorable because of its factors such as: the lack of animal material used, assured supply, greater purity, the lack of host-derived proteases, great homogeneity, a higher free thiol content, the lack of known or unknown human pathogens, consistency from batch to batch, and the existence of a reputable regulatory pathway.
Albumin in formulation has been reported to prevent:
- Surface adsorption
And to improve:
- Lyophilized cake formation
- Dissolving properties of API from lyophilized powder
The comprehensive mechanistic reasons for why albumin has these characteristics are not always delved into when producing formulations. Most often the outcome will be variable, and not easily assigned to one particular characteristic. Below details the mechanistic elements of albumin into four categories to allow for a discussion of the purposes of albumin in formulations.
Perceived Mechanisms of Albumin in Formulation
The Oxidation Protection Capability of Albumin
Stemming from the free thiol moiety of cysteine 34, this unpaired cysteine residue, present at its reduced form, can become oxidized rather than the API when put under oxidative stress . The thiol of cysteine 34 is located in a gap in the albumin protein which protects it greatly from the solvent, and specifically to larger molecules.
Therefore, the cysteine 34 of albumin has a particularly lesser reactivity, which is why its purpose is as a scavenger of mostly greatly reactive oxidation species such as radicals, instead of being a common oxygen scavenger.
Moreover, cysteine 34 does not easily become oxidized which means it can be handled without any particular protection during the steps of the formulation process. The free thiol content of commercial albumin can change according to the production process and source which is important to consider.
Commonly, the sources of recombinant have a greater free thiol content as opposed to plasma sourced albumin. The increased free thiol content is due to the recombinant material being supported by albumin, which is completely minimized at the beginning of decontamination and the purification utilized being more of a careful method than what is used for human-derived albumin.
The Surface Covering Ability of Albumin
The qualities of albumin mean that it is predisposed to coat both hydrophobic and hydrophilic surfaces . In the past, albumin has been utilized to coat surfaces of medical instruments to expand their biocompatibility.
Studies have found that spontaneously formed albumin coverage is in the order of a single albumin molecule in height, and only 1-2 mg of albumin is necessary to coat 1 m² of surface. This characteristic can be beneficial in low dose and high potency drugs, where the dose could be challenging to manage because of its surface adsorption when production, handling, and storage are underway.
An additional outcome of albumin coating surfaces is that this effect can hinder surface-induced unfolding and API aggregation events.
The Direct Interaction Ability of Albumin
The structure of albumin seems to have been created for a surplus of binding configurations to briefly and non-covalently accommodate hydrophobic, charged, minor and greater molecules.
The promiscuous quality of albumin’s binding properties has led to many accounts of APIs binding to albumin. They often bind in either a simple 1:1 ratio, or in other more convoluted ratios. This quality can impact various outcomes on the formulation.
For example, by direct binding, albumin can increase the solubility of molecules that are taxing to solubilize in other respects, or reduce harmful interactions of molecules that could allow unfolding and aggregation .
There are also reports of albumin being able to bind to the unconcealed hydrophobic end of growing fibrils, which diminishes their spreading.
The Indirect Interaction Ability of Albumin
Albumin has a positive second viral coefficient, this property describes the fact that albumin will try to avoid interacting with itself in solution . This characteristic is effectively what creates the oncotic pressure in blood.
This effect also causes a second potentially stabilizing characteristic of albumin. Albumin can reduce the general transportation and versatility of other materials present in the solution as it spreads throughout the solution uniformly.
The decreased flexibility of the entities in the formulation can result in the greater stability of these entities. The outcome of this, when used in formulation, is not simple to envisage or describe. However, SAXS has demonstrated that co-formulated proteins have a smaller flexibility when they are formulated with albumin, even if there is no particular direct interaction.
Using Albumin in Formulation
The four effects described above each require various amounts of albumin in order to become apparent:
- Surface adsorption: ≈0.1mg albumin/mL 0.1-2 mg/mL
- Direct interaction: According to the concentration of API and ratio, ≈0.5-2 mol albumin/mol API
- Indirect interaction and anti-oxidation (also seen in lyophilizing): ≥10-20 mg albumin/mL (in the solution before freeze-drying)
Recombinant human serum albumin from Albumedix is delivered as a liquid form, with the albumin being at a 20% concentration and ready to use. A comprehensive outline for retracting material from the container is available in a step by step guide that can be provided.
Due to the high concentration of the albumin substance, an easy addition/dilution of the liquid albumin is generally viable and can be comfortably carried out in formulation studies, and greater large scale production.
A quick addition of the albumin sometimes is not possible in an R&D environment to accomplish the greater concentrations of point 3. In the event of this, a lyophilizing step can be utilized. If lyophilizing is carried out, it is helpful to add the albumin to the solution before lyophilizing, as the albumin can shield the API during the dissolving, lyophilizing (cake building), and freezing processes.
If there are any further questions around using Albumedix albumin products, there are a team of dedicated albumin formulation scientists who are on hand to guide and support the utilization of albumin for formulation purposes.
References and Further Reading
- Fanali, G., di Masi A., Trezza V., Marino M., Fasano M., Ascenzi P.; Human Serum Albumin: From Bench to Bedside. Mol Aspects Med (2012) 33 209-290.
- Hawe A., Freiss W.; Formulation Development for Hydrophobic Therapeutic Proteins. Pharmaceutical Dev Tech (2007) 12 223-237.
- Tarelii E., Mire-Sluis A., Tivnann H.A., Bolgiano B., Crane D.T., Gee C., et all.; Recombinant Human Albumin as a Stabilizer for Biological Materials and the Preparation of International Reference Reagents. Biologicals (1998) 26 331-346.
- Roche M., Rondeau P., Singh N.R., Tarnus E., Bourdon E.; The Antioxidant Properties of Serum Albumin. FEBS Lett (2008) 582 1783-1787.
- Kowalcyzńska H.M., Nowak-Wyrzkowska M., Szczepankiewicz A.A., Dobkowski J., Dyda, M., Kamiński, J., Kolos R.; Albumin Adsorption on Unmodified and Sulfonated Polystyrene Surfaces, in Relation to Cell-Substratum Adhesion. Coll Surfaces Biointerfaces (2011) 84 536-544.
- Milojevic J., Esposito V., Das R., Melacini G.; Understanding the Molecular Basis for the Inhibition of the Alzheimer’s Aß-Peptide Oligomerization by Human Serum Albumin Using Saturation Transfer Difference and Off-Resonance Relaxation NMR Spectroscopy. JACS (2007) 129 4282-4290.
- Ma Y., Acosta D.M., Whitney J.R., Podgornik, R., Steinmetz, N.F., French, R.H., Parsegian V.A.; Determination of the Second Viral Coefficient of Bovine Serum Albumin Under Varying pH and Ionic Strength by Composition-Gradient Multi-Angle Static Light Scattering. J Biol Phys (2015) 41 85-97.
About Albumedix Ltd.
Too many people battle with diseases that keep them from living a full life. Healthcare professionals work hard every day to provide these people with better therapies. Together with partners, Albumedix utilize its albumin-based drug enhancing products and technologies to enable the development of more effective treatments.
With more than 30 years of experience, we are proud to be recognized as the world leader in recombinant human albumin products and technologies.
As the highest quality recombinant human albumin products ever developed, Albumedix enables the effective formulation of otherwise hard-to-stabilize drugs, cell therapies, and vaccines.
Our albumin-based technologies offer new ways of optimizing drug dosing and enhancing therapeutic performance by increasing the half-life, payload capacity, and tissue specific delivery of active pharmaceutical agents. This results in simpler treatment regimens, better performance, and, ultimately, improved patient outcomes.
Albumedix is headquartered in Nottingham, UK, with both research and large-scale manufacturing facilities. We are all committed to improving patient quality of life and are just as passionate about albumin and albumin-enabled therapies today as we were when we started 30 years ago.
Sponsored Content Policy: News-Medical.net publishes articles and related content that may be derived from sources where we have existing commercial relationships, provided such content adds value to the core editorial ethos of News-Medical.Net which is to educate and inform site visitors interested in medical research, science, medical devices and treatments.