Bovine serum albumin: A generalist in Biochemistry

Introduction

Among the widespread types of biomolecules used for targeted delivery, albumin protein has attracted attention of researchers for its selective delivery capabilities, nontoxicity, and nonimmunogenicity. Up to now, various types of albumin protein have been isolated, including ovalbumin (OVA) (derived from egg white), human serum albumin (HSA), bovine serum albumin (BSA), and rat serum albumin (RSA) and have been used for different biomedical applications.

Among them, BSA is a serum albumin protein. Bovine serum albumin is one of the cow’s milk and beef proteins that can escape from the intestinal barrier and thus induce the formation of anti-bovine serum albumin antibodies. Like humans, BSA is widely used for drug delivery because of its abundance, biocompatibility, biodegradability, nontoxicity, and non-immunogenicity. Furthermore, BSA is accepted in drug delivery systems (DDSs) because of the water-solubility improvement of prodrugs, low cost, and proper delivery properties.

Chemical property

BSA is described as a globular non-glycoprotein with a molecular weight close to 66 430. It is made of 583 amino acid residues and has 17 cystine residues (8 disulphides bridges and 1 free thiol group). BSA is easily cross-linkable and highly soluble. Its structure is not fully known, but it is structurally similar to human serum albumin, which is due to the identity of the sequences. The isoelectric point of BSA is approximately 4,7–5, and it has applications in the biotechnological field as a blocking agent, enzymatic stabilizer, and tissue culture feeder.

Uses

BSA is widely used in tissue engineering and for various pharmaceutical applications. Bovine serum albumin is inexpensive as it is readily available and is harvested from the blood, and it is also a byproduct of the cattle industry. BSA is a highly stable and biochemically inert substance that causes enhanced signals in enzyme-linked immune-histochemical, immunosorbent, and immunoblotting assays. Bovine serum albumin fibres are prepared without the presence of a cross-linker and using an electrospinning procedure. The fibres are biodegradable and biocompatible and show promising biomechanical properties. During diabetic wound healing, the BSA fibres demonstrate evidence of proliferation and new blood vessel formation with decreased capillary length.

Drug delivery

For example, a study is used from these advantages for BSA NP-based delivery of tacrolimus to reduce its kidney uptake/distribution and functional nephrotoxicity. The results showed the initial burst release followed by sustained release and reduced functional nephrotoxicity. Similar initial phases of rapid decrease in tacrolimus concentration for Prograf (as control) and drug–BSA NPs and slower decline and delayed blood clearance with increased circulation time for drug–BSA NPs were also reported. The possible immunologic response developed against BSA in vivo could limit its clinical applications and encourage substitution with other albumins (particularly HSA).

Attachment studies

Bovine serum albumin (BSA) is suitable for attachment studies because of its high stability, availability at high purity, and water solubility. Solution pH affects BSA adsorption as BSA's isoelectric point (IEP) is at pH 4.5–5.0. Therefore, the protein is negatively charged at neutral pH and positively charged under acidic conditions. The three domains of BSA with varying surface charge density influence BSA adsorption on charged surfaces. For instance, negatively charged amino acids (glutamic acid, aspartic acid) and positively charged residues (lysine, histidine) on BSA can result in attachment to both positively and negatively charged surfaces. At pH values above the IEP of the protein, adsorption was observed on negatively charged surfaces due to electrostatic interactions with positively charged amino acid residues. In addition, BSA adsorption is a pH-dependent phenomenon, whereby maximum protein adsorption is observed near the IEP, with decreasing adsorption observed at pH above or below the IEP. BSA adsorbs to a variety of surfaces such as titanium powder, TiO2, clays, polymers, and oxide minerals as measured by spectrophotometric measurements, colorimetric estimation, and various spectroscopic techniques including NMR, fluorescence, circular dichroism, and FTIR-spectroscopy.

References

[1] Mahdi Karimi. “Albumin nanostructures as advanced drug delivery systems.” Expert Opinion on Drug Delivery 13 11 (2016): 1609–1623.

[2] Hanna Debiec. “Early-childhood membranous nephropathy due to cationic bovine serum albumin.” New England Journal of Medicine 364 22 (2011): 2101–10.

[3] Hanh T M Phan. “Investigation of Bovine Serum Albumin (BSA) Attachment onto Self-Assembled Monolayers (SAMs) Using Combinatorial Quartz Crystal Microbalance with Dissipation (QCM-D) and Spectroscopic Ellipsometry (SE).” PLoS ONE (2015): e0141282.

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