Current Pharmaceutical Design - Volume 21, Issue 14, 2015

Human serum albumin (HSA) is the most important carrier of exogenous and endogenous molecules in human plasma. Understanding and characterizing the interaction of drugs with HSA has attracted enormous research interests from decades. The nature and magnitude of these bindings have direct consequence on drug delivery, pharmacokinetics, pharmacodynamics, therapeutic efficacy and drug designing. An overview of HSA and antibacterial/ anti-cancer ligands interaction is the need of the hour as these drugs together constitute more than half of the total drug consumption in the world. In this review, the information on the number of binding sites, binding strength, the nature of binding interactions and the location of binding sites of such drugs on the HSA are summarised. The effect of such drugs on the overall conformation, stability and function of HSA is also reviewed. This review will help to gain useful insights into the significance of the binding of anti-bacterial and anti-cancer drugs with plasma protein and the effect of binding on its overall distribution and pharmacological activities.

Human serum albumin (HSA) is one of the major carrier proteins in the body and constitutes approximately half of the protein found in blood plasma. It plays an important role in lipid metabolism, and its ability to reversibly bind a large variety of pharmaceutical compounds makes it a crucial determinant of drug pharmacokinetics and pharmacodynamics. This review deals with one of the protein’s major binding sites “Sudlow I” which includes a binding pocket for the drug warfarin (WAR). The binding nature of this important site can be characterized by measuring the spectroscopic changes when a ligand is bound. Using several drugs, including WAR, and other drug-like molecules as ligands, the results emphasize the nature of Sudlow I as a flexible binding site, capable of binding a variety of ligands by adapting its binding pockets. The high affinity of the WAR pocket for binding versatile molecular structures stems from the flexibility of the amino acids forming the pocket. The binding site is shown to have an ionization ability which is important to consider when using drugs that are known to bind in Sudlow I. Several studies point to the important role of water molecules trapped inside the binding site in molecular recognition and ligand binding. Water inside the protein’s cavity is crucial in maintaining the balance between the hydrophobic and hydrophilic nature of the binding site. Upon the unfolding and refolding of HSA, more water molecules are trapped inside the binding site which cause some swelling that prevents a full recovery from the denatured state. Better understanding of the mechanism of binding in macromolecules such as HSA and other proteins can be achieved by combining experimental and theoretical studies which produce significant synergies in studying complex biochemical phenomena.

Human serum albumin (HSA) is the major plasma protein with vital functions acting as depot and career for many endogenous (fatty acids, bilirubin, etc.) and exogenous substances (drugs, nutrients, etc.) in the blood. Binding to HSA controls the free, active concentration of the drug and may affect considerably the overall pharmacodynamic and pharmacokinetic profile. Studies on drug – protein binding are important from both theoretical and practical point of view as they allow better understanding of the processes underlying drug disposition and elimination and the effect of several pathological states or co-administered drugs on drug delivery and efficacy. The present review focuses on the current state of drug – HSA binding studies. The major functions and consequences of drug – protein binding are described. The X-ray structure of HSA is discussed focusing on the location and the architecture of the primary drug and fatty acids binding sites. Some of the most commonly used methods for drug – HSA binding assay are presented together with examples for their application. The most extensive studied topics in the area are discussed including quantitative characterization of drug – HSA complexation, identification of the binding sites, stereoselectivity of drug – HSA interactions, and thermodynamic characterization of the binding process. A short section is devoted to in silico prediction of drug – HSA binding as an important step in drug design and development.

Human serum albumin (HSA) is the most abundant protein in plasma, and plays multiple roles in physiology, including as a carrier protein for endogenous and exogenous compounds. Recent studies provide new evidences to support the enzymatic activities of HSA and new molecular insights for such activities. Here, the structural features and enzymatic characteristics of HSA are reviewed.

Human serum albumin (HSA) represents an important determinant of plasma oncotic pressure and a relevant factor that modulates fluid distribution between the body compartments. Moreover, HSA (i) represents the depot and transporter of several compounds, both endogenous and exogenous, (ii) affects the pharmacokinetics of many drugs, (iii) regulates chemical modifications of some ligands, (iv) shows (pseudo-)enzymatic properties, (v) inactivates some toxic compounds, and (vi) displays anti-oxidant properties. HSA binding and (pseudo-)enzymatic properties are regulated competitively, allosterically, and by covalent modifications. While competitive inhibition of HSA binding properties is evident, allosteric mechanisms and covalent modifications affecting HSA reactivity are less clear. In several pathological conditions in which free heme-Fe levels increase, the buffering capacity of plasma hemopexin is overwhelmed and most of heme-Fe binds to the fatty acid site 1 of HSA. HSA-heme-Fe displays globin-like properties; in turn, heme-Fe modulates competitively and allosterically HSA binding and reactivity properties. Remarkably, heme-Fe-mediated HSA properties are time-dependent, representing a case for “chronosteric effects”. Here, we review the drug-based modulation of (i) heme-Fe-recognition by HSA and (ii) heme-Fe-mediated reactivity.

To date, many potent metal-based anticancer drugs have been developed and many drug delivery systems have been exploited to improve the targeting and decrease the side effects of anticancer drugs. Human serum albumin (HSA) binding contributes significantly to the discovery of new drug candidates because binding of drugs to HSA strongly influences their pharmacokinetic behaviour. Moreover, HSA is widely used in the clinical setting as a drug delivery system due to its potential for improving targeting while decreasing the side effects of drugs. This review not only provides a brief outline of the properties of HSA carriers but also provides an overview of the binding and anticancer characteristics of platinum-/ruthenium-based anticancer drugs to HSA that may guide the rational designing and development of metal-based drugs and HSA-based carriers for clinical applications.

Human serum albumin (HSA) regulates the transport and availability of numerous chemical compounds and molecules in the blood vascular system. While previous HSA research has found that HSA interacts with specific varieties of ligands, new research efforts aim to expand HSA’s ability to interact with more different drugs in order to improve the delivery of various pharmacological drugs. This review will cover fatty acid chain and posttranslational modifications of HSA that potentially modulate how HSA interacts with various pharmacological drugs, including glycation, cysteinylation, S-nitrosylation, S-transnitrosation and S-guanylation.

Human serum albumin (HSA), a major transport protein component in blood plasma, has been reported recently to play many important roles in pharmacotherapeutics development. Owing to its promising intrinsic binding capability of drug molecules, HSA offers favorable characteristics and can be directly used as its monomeric formula or can be fabricated into protein based nanoparticle platforms to realize the effective delivery of therapeutic molecules into targeted diseases areas. In addition, HSA can also serve as a protein stabilizer or environment-responsive moieties to hybridize with the functional materials including polymers or inorganic nanoparticles through the covalent reactions or electrostatic interactions, and can thus greatly alter the relevant biological distribution and pharmacokinetic behavior to improve their therapeutic efficacy. By right, extensive studies have been conducted to develop HSA-conjugated pharmacotherapeutic agents toward effective in vitro and in vivo diseases diagnosis and treatment. The current review gives an in-detail account of the latest progresses of HSA-based carriers as functional protein materials, mainly with respect to its conjugation types, formulation aspects, and importantly their promising applications towards enhanced drug delivery and medical diagnosis.

Albumin has been used as a popular material for carrying imaging probes and/or drugs to provide efficient biomedical imaging and therapy. It is considered as an ideal material for in vivo applications, because albumin is naturally abundant in serum to show non-toxicity and non-immunogenicity. In addition, based on the convenience of chemical modifications, it is widely used for the delivery of diverse molecules including chemicals, proteins/peptides, and oligonucleotides. Albumin nanoparticles carrying these molecules have shown improved pharmacokinetic properties by providing longer circulation time and more disease-specific accumulation, and they are emerging as a promising carrier system for in vivo imaging and therapy. Constant efforts to improve the properties of albumin nanoparticles have led to a great progress in medical application, and recent examples of market approval and success are brightening the prospect of albumin-based nanocarrier formulations in the future. This article will summarize the developments in albumin nanocarriers for biomedical imaging and targeted drug delivery. This review will give an account of the different applications of albumin carriers with examples of some recent innovative works.

Fusion proteins have been well-studied and widely applied in biopharmaceutics. Albumin fusion proteins are simple to construct, easy to purify, and stable to formulate. One main application of fusion protein is to extend the plasma half-life of therapeutic proteins and peptides. Albiglutide for diabetes treatment is the first albumin fusion protein drug approved by FDA. Balugrastim and other albumin fusion proteins have been evaluated in clinical trials. Taking advantage of the physiological functions of albumin, albumin fusion proteins can also been applied to act on an essential intracellular target and carry fatty acid-modified drugs. This novel approach makes it possible to co-deliver two different types of drug to one tumor cell for synergistic cytotoxicity.

Human serum albumin (HSA) is an abundant protein in blood and tissue fluids and has been used as a carrier for drug delivery. HSA can improve the pharmacokinetic profiles of drugs, such as extending the blood half-life of existing drugs and reducing toxic side effects. At the same time, more and more molecular imaging probes conjugated or fused with HSA have been studied to achieve higher specificity and better pharmacokinetic performance. These molecular probes can be attached to HSA covalently or non-covalently. They can also be fused with HSA as a fusion protein or coupled with HSA in vivo. Importantly, HSA conjugated probes have been applied to many imaging modalities such as the single photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), positron emission tomography (PET) and optical imaging alone or in combination with more than one modality. Besides in vivo molecular imaging, HSA conjugated probes can be used for molecular therapeutics, image-guided therapy, such as photodynamic imaging and photodynamic therapy (PDI/PDT). Some potential problems also need to be considered when using of HSA based probe strategy which are discussed in detail in the paper. Overall, HSA based probe design represents a very useful and powerful strategy for developing more molecular probes for theranostics of diseases.