Native albumin for targeted drug delivery

Albumin conjugates and assemblies as versatile bio-functional additives and carriers for biomedical applications

As the most abundant plasma protein, serum albumin has been extensively studied and employed for therapeutic applications. Despite its direct clinical use for the maintenance of blood homeostasis in various medical conditions, this review exclusively summarizes and discusses albumin-based bio-conjugates and assemblies as versatile bio-functional additives and carriers in biomedical applications. As one of the smallest-sized proteins in the human body, albumin is physiochemically stable and biochemically inert. Moreover, albumin is also endowed with abundant specific binding sites for numerous therapeutic compounds, which also endow it with superior bioactivities. Firstly, due to its small size and binding specificity, albumin alone or its derived assemblies can be utilized as competent drug carriers, which can deliver drugs through the enhanced permeability and retention (EPR) effect or actively target lesion sites through binding with gp60 and secreted protein acidic and rich in cysteine (SPARC) in tumor sites. Furthermore, its biochemical stability and inertness make it a safe and biocompatible coating material for use in biomedical applications. Albumin-based surface modifying additives can be used to functionalize both macro substrates (e.g. surfaces of medical devices or implants) and nanoparticle surfaces (e.g. drug carriers and imaging contrast agents). In this review, we elaborate on the synthesis and applications of albumin-based bio-functional coatings and drug carriers, respectively.

Dual-triggered drug-release vehicles for synergistic cancer therapy

Cancer is a complex and tenacious disease. Drug-delivery systems in combination with multimodal therapy strategies are very promising candidates for cancer theranostic applications. In this study, a new drug-delivery vehicle that combine human serum albumin (HSA)- and poly(sodium 4-styrenesulfonate) (PSS)-coated gold nanorod nanoparticles(GNR/PSS/HSA NPs) was developed for synergistic cancer therapy. Doxorubicin (DOX) was loaded onto GNR/PSS/HSA NPs, by electrostatic and hydrophobic forces, to create multimodal DOX@GNR/PSS/HSA NPs. DOX@GNR/PSS/HSA NPs were found to be highly biocompatible and stable in physiological solutions. Furthermore, GNR/PSS/HSA NPs with or without DOX were designed to exhibit strong absorbance in the near-infrared region and high photothermal conversion efficiency. Therefore, bimodal DOX release from DOX@GNR/PSS/HSA NPs could be triggered by an acidic pH and by near-infrared irradiation after NPs preferentially accumulated at tumor sites, leading to a significant chemotherapeutic effect. Moreover, DOX@GNR/PSS/HSA NPs were designed to be applied during chemo- and photo-thermal combination therapy and exhibited a synergistic anticancer effect that was superior to the effect of monotherapy, from both in vitro and in vivo results. These results suggest that DOX@GNR/PSS/HSA NPs are a strong candidate for a nanoplatform for future antitumor therapeutic strategies.

Stimuli-Responsive Therapeutic Metallodrugs

The success of platinum-based anticancer agents has motivated the exploration of novel metal-based drugs for several decades, whereas problems such as drug-resistance and systemic toxicity hampered their clinical applications and efficacy. Stimuli-responsiveness of some metal complexes offers a good opportunity for designing site-specific prodrugs to maximize the therapeutic efficacy and minimize the side effect of metallodrugs. This review presents a comprehensive and up-to-date overview on the therapeutic stimuli-responsive metallodrugs that have appeared in the past two decades, where stimuli such as redox, pH, enzyme, light, temperature, and so forth were involved. The compounds are classified into three major categories based on the nature of stimuli, that is, endo-stimuli-responsive metallodrugs, exo-stimuli-responsive metallodrugs, and dual-stimuli-responsive metallodrugs. Representative examples of each type are discussed in terms of structure, response mechanism, and potential medical applications. In the end, future opportunities and challenges in this field are tentatively proposed. With diverse metal complexes being introduced, the foci of this review are pointed to platinum and ruthenium complexes.

Tracers for Fluorescence-Guided Surgery: How Elongation of the Polymethine Chain in Cyanine Dyes Alters the Pharmacokinetics of a Dual-Modality c[RGDyK] Tracer

The potential of receptor-mediated fluorescence-based image-guided surgery tracers is generally linked to the near-infrared emission profile and good-manufacturing-production availability of fluorescent dyes. Surprisingly, little is known about the critical interaction between the structural composition of the dyes and the pharmacokinetics of the tracers. In this study, a dual-modality tracer design was used to systematically and quantitatively evaluate the influence of elongation of the polymethine chain in a fluorescent cyanine dye on the imaging potential of a targeted tracer. Methods: As a model system, the integrin marker α_vβ₃ was targeted using arginylglycylaspartisc acid [RGD]-based vectors functionalized with a ¹¹¹In-diethylenetriaminepentaacetic acid (DTPA) chelate and a fluorescent dye: (Cy3-(SO₃)methyl-COOH [emission wavelength (λ_em), 580 nm], Cy5-(SO₃)methyl-COOH [λ_em, 680 nm], or Cy7-(SO₃)methyl-COOH [λ_em, 780 nm]). Tracers were analyzed for differences in photophysical properties, serum protein binding, chemical or optical stability, and signal penetration through tissue. Receptor affinities were evaluated using saturation and competition experiments. In vivo biodistribution (SPECT imaging and percentage injected dose per gram of tissue) was assessed in tumor-bearing mice and complemented with in vivo and ex vivo fluorescence images obtained using a clinical-grade multispectral fluorescence laparoscope. Results: Two carbon-atom-step variations in the polymethine chain of the fluorescent cyanine dyes were shown to significantly influence the chemical and photophysical characteristics (e.g., stability, brightness, and tissue penetration) of the hybrid RGD tracers. DTPA-Cy5-(SO₃)methyl-COOH-c[RGDyK] structurally outperformed its Cy3 and Cy7 derivatives. Radioactivity-based evaluation of in vivo tracer pharmacokinetics yielded the lowest nonspecific uptake and highest tumor-to-background ratio for DTPA-Cy5-(SO₃)methyl-COOH-c[RGDyK] (13.2 ± 1.7), with the Cy3 and Cy7 analogs trailing at respective tumor-to-background ratios of 5.7 ± 0.7 and 4.7 ± 0.7. Fluorescence-based assessment of tumor visibility revealed a similar trend. Conclusion: These findings underline that variations in the polymethine chain lengths of cyanine dyes have a profound influence on the photophysical properties, stability, and in vivo targeting capabilities of fluorescent imaging tracers. In a direct comparison, the intermediate-length dye (Cy5) yielded a superior c[RGDyK] tracer, compared with the shorter (Cy3) and longer (Cy7) analogs.

Organ-based drug delivery

The phenomenal advances in pharmaceutical sciences over the last few decades have led to the development of new therapeutics like peptides, proteins, RNAs, DNAs and highly potent small molecules. Fruitful applications of these therapeutics have been challenged by several anatomical and physiological barriers that limit adequate drug disposition at the site-of-action and by off-target drug distribution to undesired tissues, which together result in the reduced effectiveness and increased side effects of therapeutic agents. As such, the development of drug delivery and targeting systems has been recognised as a cornerstone for future drug development. Research in pharmaceutical sciences is now devoted to tackling delivery challenges through engineering delivery systems that move beyond conventional dosage forms and regimens into state-of-the-art targeted drug delivery tailored toward specific therapeutic needs. Modern drug delivery systems comprise passive and active targeting approaches. While passive targeting relies on the natural course of distribution of drugs or drug carriers in the body, as governed by their physicochemical properties, active targeting often exploits targeting moieties that home preferentially into target tissues. Here, we provide an overview of theories of and approaches to passive and active drug delivery. As the design of drug delivery is dependent on the unique structure of target tissues and organs, we present our discussion in an organ-specific manner with the aim to inspire the development of new strategies for curing disease with high accuracy and efficiency.

Alkyl-Modified Oligonucleotides as Intercalating Vehicles for Doxorubicin Uptake via Albumin Binding

DNA-based drug delivery vehicles have displayed promise for the delivery of intercalating drugs. Here, we demonstrate that oligonucleotides modified with an alkyl chain can bind to human serum albumin, mimicking the natural binding of fatty acids. These alkyl-DNA-albumin complexes display excellent serum stability and are capable of strongly binding doxorubicin. Complexes are internalized by cells in vitro, trafficking to the mitochondria, and are capable of delivering doxorubicin with excellent efficiency resulting in cell death. However, the cellular localization of the delivered doxorubicin, and ultimately the complex efficacy, is dependent on the nature of the linker between the alkyl group and the oligonucleotide.

Impact of albumin based approaches in nanomedicine: Imaging, targeting and drug delivery

A major challenge in the field of nanomedicine is to transform laboratory innovations into commercially successful clinical products. In this campaign, a variety of nanoenabled approaches have been designed and investigated for their role in biomedical applications. The advantages associated with the unique structure of albumin imparts it with the ability to interact with variety of molecules, while the functional groups present on their surface provide base for large number of modifications making it as an ideal nanocarrier system. So far, a variety of albumin based nanoenabled approaches have been intensively exploited for effective diagnosis and personalized medicine, among them some have successfully completed their journey from lab bench to marketed products. This review focuses on the recent most promising advancement in the field of albumin based nanoenabled approaches for various biomedical applications and their potential use in cancer diagnosis and therapy.

Lipophilic siRNA targets albumin in situ and promotes bioavailability, tumor penetration, and carrier-free gene silencing

Clinical translation of therapies based on small interfering RNA (siRNA) is hampered by siRNA's comprehensively poor pharmacokinetic properties, which necessitate molecule modifications and complex delivery strategies. We sought an alternative approach to commonly used nanoparticle carriers by leveraging the long-lived endogenous serum protein albumin as an siRNA carrier. We synthesized siRNA conjugated to a diacyl lipid moiety (siRNA-L₂), which rapidly binds albumin in situ. siRNA-L₂, in comparison with unmodified siRNA, exhibited a 5.7-fold increase in circulation half-life, an 8.6-fold increase in bioavailability, and reduced renal accumulation. Benchmarked against leading commercial siRNA nanocarrier in vivo jetPEI, siRNA-L₂ achieved 19-fold greater tumor accumulation and 46-fold increase in per-tumor-cell uptake in a mouse orthotopic model of human triple-negative breast cancer. siRNA-L₂ penetrated tumor tissue rapidly and homogeneously; 30 min after i.v. injection, siRNA-L₂ achieved uptake in 99% of tumor cells, compared with 60% for jetPEI. Remarkably, siRNA-L₂ achieved a tumor:liver accumulation ratio >40:1 vs. <3:1 for jetPEI. The improved pharmacokinetic properties of siRNA-L₂ facilitated significant tumor gene silencing for 7 d after two i.v. doses. Proof-of-concept was extended to a patient-derived xenograft model, in which jetPEI tumor accumulation was reduced fourfold relative to the same formulation in the orthotopic model. The siRNA-L₂ tumor accumulation diminished only twofold, suggesting that the superior tumor distribution of the conjugate over nanoparticles will be accentuated in clinical situations. These data reveal the immense promise of in situ albumin targeting for development of translational, carrier-free RNAi-based cancer therapies.

In situ preparation of water-soluble ginsenoside Rh2-entrapped bovine serum albumin nanoparticles: in vitro cytocompatibility studies

The present study investigates a simple and convenient one-step procedure for the preparation of bovine serum albumin (BSA)-Rh2 nanoparticles (NPs) at room temperature. In this work, ginsenoside Rh2 was entrapped within the BSA protein to form BSA-Rh2 NPs to enhance the aqueous solubility, stability, and therapeutic efficacy of Rh2. The physiochemical characterization by high-performance liquid chromatography, nuclear magnetic resonance, Fourier transform infrared spectroscopy, field emission transmission electron microscopy, dynamic light scattering, and thermogravimetric analysis confirmed that the prepared BSA-Rh2 NPs were spherical, highly monodispersed, and stable in aqueous systems. In addition, the stability of NPs in terms of different time intervals, pHs, and temperatures (20°C–700°C) was analyzed. The results obtained with different pHs showed that the synthesized BSA-Rh2 NPs were stable in the physiological buffer (pH 7.4) for up to 8 days, but degraded under acidic conditions (pH 5.0) representing the pH inside tumor cells. Furthermore, comparative analysis of the water solubility of BSA-Rh2 NPs and standard Rh2 showed that the BSA nanocarrier enhanced the water solubility of Rh2. Moreover, in vitro cytotoxicity assays including cell viability assays and morphological analyses revealed that Rh2-entrapped BSA NPs, unlike the free Rh2, demonstrated better in vitro cell viability in HaCaT skin cell lines and that BSA enhanced the anticancer effect of Rh2 in A549 lung cell and HT29 colon cancer cell lines. Additionally, anti-inflammatory assay of BSA-Rh2 NPs and standard Rh2 performed using RAW264.7 cells revealed decreased lipopolysaccharide-induced nitric oxide production by BSA-Rh2 NPs. Collectively, the present study suggests that BSA can significantly enhance the therapeutic behavior of Rh2 by improving its solubility and stability in aqueous systems, and hence, BSA-Rh2 NPs may potentially be used as a ginsenoside delivery vehicle in cancer and inflammatory cell lines.

Bovine serum albumin as a nanocarrier for the efficient delivery of ginsenoside compound K: preparation, physicochemical characterizations and in vitro biological studies

Study on the preparation of BSA–CK NPs by a desolvation method and their application as delivery vehicles in cancer and inflammatory cell lines.

A novel Pd(ii) CNO pincer complex of MR (methyl red): synthesis, crystal structure, interaction with human serum albumin (HSA) in vitro and molecular docking

The C–H activation of methyl red (MR) (MR = 2-{[4-(dimethylamino)phenyl]diazenyl}benzoic acid) was achieved by reaction with Pd(OAc)₂under mild conditions.

Albumin nanoparticles for glutathione-responsive release of cisplatin: New opportunities for medulloblastoma

Redox-responsive nanoparticles were synthesized by desolvation of bovine serum albumin followed by disulfide-bond crosslinking with N, N'-Bis (acryloyl) cystamine. Dynamic light scattering and transmission electron microscopy studies revealed spherical nanoparticles (mean diameter: 83nm, polydispersity index: 0.3) that were glutathione-responsive. Confocal microscopy revealed rapid, efficient internalization of the nanoparticles by Daoy medulloblastoma cells and healthy controls (HaCaT keratinocytes). Cisplatin-loaded nanoparticles with drug:carrier ratios of 5%, 10%, and 20% were tested in both cell lines. The formulation with the highest drug:carrier ratio reduced Daoy and HaCaT cell viability with IC₅₀ values of 6.19 and 11.17μgmL^-1, respectively. The differential cytotoxicity reflects the cancer cells' higher glutathione content, which triggers more extensive disruption of the disulfide bond-mediated intra-particle cross-links, decreasing particle stability and increasing their cisplatin release. These findings support continuing efforts to improve the safety and efficacy of antineoplastic drug therapy for pediatric brain tumors using selective nanoparticle-based drug delivery systems.

Factors influencing the fabrication of albumin-bound drug nanoparticles (ABDns): Part II. Albumin-bound carbamazepine nanoparticles (ABCns)

Carbamazepine (CBZ) is a BCS Class II drug with poor solubility profile. In order to improve the physicochemical properties of CBZ, albumin (HSA)-bound CBZ nanoparticles (ABCns) were prepared. Drug-loading studies indicated that monomeric ABCns can be fabricated by self-assembly of anhydrous form III of CBZ and HSA in molar ratios of 1:1 or 2:1 within 0.5 h in phosphate buffer pH 7.4 with particle size in the range of 10-20 nm. Approximately 73-76% of the CBZ was encapsulated within HSA and 20-40% CBZ was released from the ABCns over 8 days. In conclusion, novel ABCns can be fabricated with sustained-release of CBZ for over 8 days which can significantly improve the physicochemical profile of CBZ.

Conjugation of Methotrexate-Amino Derivatives to Macromolecules through Carboxylate Moieties Is Superior Over Conventional Linkage to Amino Residues: Chemical, Cell-Free and In Vitro Characterizations

In this study, we examined the possibility of introducing methotrexate (MTX) to the carboxylate rather than to the ε-amino side chains of proteins. We found that MTX—amino compounds covalently linked to the carboxylate moieties of macromolecules, undergo unusual peptide-bond cleavage, with the release of the MTX amino derivatives from the conjugates. This event takes place at an accelerated rate under acidic conditions, and at a slower rate at physiological pH values. The glutamate portion of MTX is responsible for this behavior, with little or no contribution of the p-aminobenzoate-pteridine ring that is linked to the α-amino side chain of the glutamate. Carboxylate-linked Fmoc-Glu-γ-CONH-(CH₂)₆-NH₂ undergoes hydrolysis in a nearly indistinguishable fashion. A free α carboxylate moiety is essential for this effect. Carboxylate linked Fmoc-glutamic-amide-γ-CONH-(CH₂)₆-NH₂ undergoes no hydrolysis under acidic conditions. Based on these findings, we engineered a cysteine specific MTX containing reagent. Its linkage to bovine serum albumin (BSA) yielded a conjugate with profound antiproliferative efficacy in a MTX-sensitive glioma cell line. In conclusion, carboxylate linked MTX-amino derivatives in particular, and carboxylate linked R-α-GLU-γ amino compounds in general are equipped with‘built-in chemical machinery’ that releases them under mild acidic conditions.

Maghemite-human serum albumin hybrid nanoparticles: towards a theranostic system with high MRI r2* relaxivity

Human Serum Albumin (HSA) is the most abundant plasma protein in human blood, and therefore, it is the material of choice for the development of particulate formulations due to its biodegradable and biocompatible nature. Over the last decade, HSA nanoparticles (NPs) have been prepared mostly using desolvation techniques and evaluated as promising drug carriers. In addition, controlling the particle size has become a primary concern while formulating such nanoparticulate systems. Since many of these HSA-based carrier systems have often demonstrated batch-to-batch fabrication variability, significant efforts have been made to develop and characterize HSA-based NPs featuring a robust and controllable particle size, by using a desolvation/cross-linking-type Divinyl Sulfone (DVS)-mediated nanofabrication method. For this purpose and for global multi-parameter fabrication process optimization, a statistically significant Design of Experiment (DoE, MINITAB® 17 DoE software) methodology has been successfully implemented. It aimed to disclose an optimal set of HSA NP fabrication conditions in order to afford highly reproducible and stable 23.05 ± 5.3 nm-sized DoE-globally optimized core HSA NPs. Due to the use of bifunctional DVS as a cross-linker for the preparation of such DoE-optimized HSA NPs, their surface contains a variety of free functional groups which are available for further second step functional modifications. Moreover, related hybrid organic/inorganic nanosystems consisting of DoE-optimized HSA NPs that encapsulated hydrophilic (NH₄)₂Ce(IV)(NO₃)₆ (Ceric Ammonium Nitrate - CAN) modified γ-Fe₂O₃ NPs (CAN-maghemite or CAN-γ-Fe₂O₃ NPs), which enable medical imaging using magnetic resonance imaging (MRI), have also been fabricated and characterized. The resulting hybrid magnetic NPs are a quite powerful T₂* contrast agent (r₂* of 482 mM^-1 s^-1), which may be used as a powerful dual phase platform for both therapeutic (drug delivery) and diagnostic imaging (MRI) applications.

Utilization of nanoparticle technology in rheumatoid arthritis treatment

Rheumatoid arthritis (RA) is one of the common and severe autoimmune diseases related to joints. This chronic autoimmune inflammatory disease, leads to functional limitation and reduced quality of life, since as there is bone and cartilage destruction, joint swelling and pain. Current advances and new treatment approaches have considerably postponed disease progression and improved the quality of life for many patients. In spite of major advances in therapeutic options, restrictions on the routes of administration and the necessity for frequent and long-term dosing often result in systemic adverse effects and patient non-compliance. Unlike usual drugs, nanoparticle systems are planned to deliver therapeutic agents especially to inflamed synovium, so avoiding systemic and unpleasant effects. The present review discusses about some of the most successful drugs in RA therapy and their side effects and also focuses on key design parameters of RA-targeted nanotechnology-based strategies for improving RA therapies.

Simple bioconjugate chemistry serves great clinical advances: albumin as a versatile platform for diagnosis and precision therapy

Albumin is the most abundant circulating protein in plasma and has recently emerged as a versatile protein carrier for drug targeting and for improving the pharmacokinetic profile of peptide or protein based drugs. Three drug delivery technologies related to albumin have been developed, which include the coupling of low-molecular weight drugs to exogenous or endogenous albumin, conjugating bioactive proteins by albumin fusion technology (AFT), and encapsulation of drugs into albumin nanoparticles. This review article starts with a brief introduction of human serum albumin (HSA), and then summarizes the mainstream chemical strategies of developing HSA binding molecules for coupling with drug molecules. Moreover, we also concisely condense the recent progress of the most important clinical applications of HSA-binding platforms, and specify the current challenges that need to be met for a bright future of HSA-binding.

Development and Validation of a Small Single-domain Antibody That Effectively Inhibits Matrix Metalloproteinase 8

A detrimental role for matrix metalloproteinase 8 (MMP8) has been identified in several pathological conditions, e.g., lethal hepatitis and the systemic inflammatory response syndrome. Since matrix MMP8-deficient mice are protected in the above-mentioned diseases, specific MMP8 inhibitors could be of clinical value. However, targeting a specific matrix metalloproteinase remains challenging due to the strong structural homology of matrix metalloproteinases, which form a family of 25 members in mammals. Single-domain antibodies, called nanobodies, offer a range of possibilities toward therapy since they are easy to generate, express, produce, and modify, e.g., by linkage to nanobodies directed against other target molecules. Hence, we generated small MMP8-binding nanobodies, and established a proof-of-principle for developing nanobodies that inhibit matrix metalloproteinase activity. Also, we demonstrated for the first time the possibility of expressing nanobodies systemically by in vivo electroporation of the muscle and its relevance as a potential therapy in inflammatory diseases.

A dual-fluorescent nano-carrier for delivering photoactive ruthenium polypyridyl complexes

A photo-responsive diagnostic conjugate was generated by loading a photoactive polypyridyl ruthenium complex onto a dual-fluorescent nanocarrier, resulting in photo-induced cytotoxicity.

Human Serum Albumin Conjugated Nanoparticles for pH and Redox-Responsive Delivery of a Prodrug of Cisplatin

Platinum anticancer drugs are particularly in need of controlled drug delivery because of their severe side effects. Platinum(IV) agents are designed as prodrugs to reduce the side effects of platinum(II) drugs; however, premature reduction could limit the effect as a prodrug. In this work, a highly biocompatible, pH and redox dual-responsive delivery system is prepared by using hybrid nanoparticles of human serum albumin (HSA) and calcium phosphate (CaP) for the Pt(IV) prodrug of cisplatin. This conjugate is very stable under extracellular conditions, so that it protects the platinum(IV) prodrug in HSA. Upon reaching the acidic and hypoxic environment, the platinum drug is released in its active form and is able to bind to the target DNA. The Pt-HSA/CaP hybrid inhibits the proliferation of various cancer cells more efficiently than cisplatin. Different cell cycle arrests suggest different cellular responses of the Pt(IV) prodrug in the CaP nanocarrier. Interestingly, this delivery system demonstrates enhanced cytotoxicity to tumor cells, but not to normal cells.

Dragon fruit-like biocage as an iron trapping nanoplatform for high efficiency targeted cancer multimodality imaging

Natural biopolymer based multifunctional nanomaterials are perfect candidates for multimodality imaging and therapeutic applications. Conventional methods of building multimodal imaging probe require either cross-linking manners to increase its in vivo stability or attach a target module to realize targeted imaging. In this study, the intrinsic photoacoustic signals and the native strong chelating properties with metal ions of melanin nanoparticle (MNP), and transferrin receptor 1 (TfR1) targeting ability of apoferritin (APF) was employed to construct an efficient nanoplatform (AMF) without tedious assembling process. Smart APF shell significantly increased metal ions loading (molar ratio of 1:800, APF/Fe(3+)) and therefore improved magnetic resonance imaging (MRI) sensitivity. Moreover, synergistic use of Fe(3+) and APF contributed to high photoacounstic imaging (PAI) sensitivity. AMF showed excellent bio-stability and presented good in vivo multimodality imaging (PET/MRI/PAI) properties (good tumor uptake, high specificity and high tumor contrast) in HT29 tumor because of its targeting property combined with the enhanced permeability and retention (EPR) effect, making it promising in theranostics and translational nanomedicine.

Regulation of BAX/BCL2 gene expression in breast cancer cells by docetaxel-loaded human serum albumin nanoparticles

Today, using nanoparticle-based drug delivery systems has expanded to avoid anticancer side effects. Taxanes are important chemotherapeutic agents in the treatment of metastatic breast cancer. In this study, docetaxel (DTX)-loaded human serum albumin (HSA) nanoparticles (NPs) were prepared and characterized. Drug toxicity of the nanoparticles was measured by MTT assay with different drug concentrations (0.01, 0.1, 0.5, 1 and 5 μM) at different incubation times (24, 48 and 72 h). Expression of BAX/BCL2 mRNA levels was determined by real-time PCR. The size of NPs prepared and used in our study was about 147 nm with surface charge of -29.6 mV. Results obtained from MTT assay showed that 0.5 μM of free drug had 50 % toxicity on MCF-7 cells after 48-h incubation. Real-time PCR results showed an increase in expression of BAX and no change for BCL2. In conclusion, a significant overexpression of BAX gene and changes in BAX/BCL2 ratio were observed for DTX-loaded HSA nanoparticles compared with free DTX and may provide a potential therapy to inhibit anticancer drug resistance.

Structural basis of non-steroidal anti-inflammatory drug diclofenac binding to human serum albumin

Human serum albumin (HSA) is the most abundant protein in plasma, which plays a central role in drug pharmacokinetics because most compounds bound to HSA in blood circulation. To understand binding characterization of non-steroidal anti-inflammatory drugs to HSA, we resolved the structure of diclofenac and HSA complex by X-ray crystallography. HSA-palmitic acid-diclofenac structure reveals two distinct binding sites for three diclofenac in HSA. One diclofenac is located at the IB subdomain, and its carboxylate group projects toward polar environment, forming hydrogen bond with one water molecule. The other two diclofenac molecules cobind in big hydrophobic cavity of the IIA subdomain without interactive association. Among them, one binds in main chamber of big hydrophobic cavity, and its carboxylate group forms hydrogen bonds with Lys199 and Arg218, as well as one water molecule, whereas another diclofenac binds in side chamber, its carboxylate group projects out cavity, forming hydrogen bond with Ser480.

A polyphenylene dendrimer drug transporter with precisely positioned amphiphilic surface patches

The design and synthesis of a polyphenylene dendrimer (PPD 3) with discrete binding sites for lipophilic guest molecules and characteristic surface patterns is presented. Its semi-rigidity in combination with a precise positioning of hydrophilic and hydrophobic groups at the periphery yields a refined architecture with lipophilic binding pockets that accommodate defined numbers of biologically relevant guest molecules such as fatty acids or the drug doxorubicin. The size, architecture, and surface textures allow to even penetrate brain endothelial cells that are a major component of the extremely tight blood-brain barrier. In addition, low to no toxicity is observed in in vivo studies using zebrafish embryos. The unique PPD scaffold allows the precise placement of functional groups in a given environment and offers a universal platform for designing drug transporters that closely mimic many features of proteins.

Curcumin-incorporated albumin nanoparticles and its tumor image

Albumin is an ideal carrier for hydrophobic drugs. This paper reports a facile route to develop human serum albumin (HSA)-curcumin (CCM) nanoparticles, in which β-mercaptoethanol (β-ME) acted as an inducer and CCM acted as a bridge. Fluorescence quenching and conformational changes in HSA-CCM nanoparticles occurred during assembly. Disulfide bonds and hydrophobic interactions may play a key role in assembly. HSA-CCM nanoparticles were about 130 nm in size, and the solubility of CCM increased by more than 500 times. The HSA-CCM nanoparticles could accumulate at the cytoplasm of tumor cells and target the tumor tissues. Therefore, HSA nanoparticles fabricated by β-ME denaturation are promising nanocarriers for hydrophobic substances from chemotherapy drugs to imaging probes.

Bionanotherapeutics: niclosamide encapsulated albumin nanoparticles as a novel drug delivery system for cancer therapy

In this work niclosamide was encapsulated into albumin nanoparticles through a desolvation method to improve its scope of application in cancer therapy.

Interactive association of drugs binding to human serum albumin

Human serum albumin (HSA) is an abundant plasma protein, which attracts great interest in the pharmaceutical industry since it can bind a remarkable variety of drugs impacting their delivery and efficacy and ultimately altering the drug’s pharmacokinetic and pharmacodynamic properties. Additionally, HSA is widely used in clinical settings as a drug delivery system due to its potential for improving targeting while decreasing the side effects of drugs. It is thus of great importance from the viewpoint of pharmaceutical sciences to clarify the structure, function, and properties of HSA–drug complexes. This review will succinctly outline the properties of binding site of drugs in IIA subdomain within the structure of HSA. We will also give an overview on the binding characterization of interactive association of drugs to human serum albumin that may potentially lead to significant clinical applications.

Comparison of binding characterization of two antiviral drugs to human serum albumin

Ribavirin and lamivudine are representatives of antiviral drugs that are widely used to treat viral infections, especially chronic liver disease. To compare binding mechanism and behavior of antiviral drugs with human serum albumin (HSA), we performed fluorescence spectroscopy and X-ray crystallography to investigate the interactions of ribavirin and lamivudine with HSA. Fluorescence spectroscopy showed ribavirin and lamivudine inhibit binding affinity each other. Our results further demonstrated that ribavirin and lamivdudine interaction with HSA could be affected by the presence of other compounds, including the non-steroidal anti-inflammatory drugs, indometacin. X-ray structures revealed that ribavirin and lamivudine bind in IIA subdomain of HSA mainly by forming hydrogen bond and hydrophobic interactions forces. The carboxamido of ribavirin forms hydrogen bonds with Arg222; Hydroxyl group (6) of ribavirin forms hydrogen bond with Arg257. Hydroxyl group (15) of lamivudine forms hydrogen bond with Arg222; amino group (4) of lamivudine forms hydrogen bond with carbonyl of Arg257. Our results reveal the key biochemical and structural characteristics of the HSA interaction with ribavirin and lamivudine, providing guidance for future development of ribavirin- and lamivudine-based compounds and a drug-HSA delivery system.

Kinetics and efficiency of a methyl-carboxylated 5-Fluorouracil-bovine serum albumin adduct for targeted delivery

5-Fluorouracil (5-FU) is a clinically well-established anti-cancer drug effectively applied in chemotherapy, mainly for the treatment of breast and colorectal cancer. Substantial disadvantages are adverse effects, arising from serious damage of healthy tissues, and shortcoming pharmacokinetics due to its low molecular weight. A promising approach for improvement of such drugs is their coupling to suitable carriers. Here, a 5-FU adduct, 5-fluorouracil acetate (FUAc) is synthesized and covalently coupled to bovine serum albumin (BSA) as model carrier molecule. On average, 12 molecules FUAc are bound to one BSA. Circular dichriosm (CD)-spectra of BSA and FUAc-BSA are identical, suggesting no significant conformational differences. FUAc-BSA is tested on T-47D and MDA-MB-231 breast cancer cells. Proliferation inhibition of membrane albumin-binding protein (mABP)-expressing T-47D cells by FUAc-BSA is similar to that of 5-FU and only moderate for MDA-MB-231 cells that lack such expression. Therefore, a crucial role of mABP expression in effective cell growth inhibition by FUAc-BSA is assumed.

A core-shell albumin copolymer nanotransporter for high capacity loading and two-step release of doxorubicin with enhanced anti-leukemia activity

The native transportation protein serum albumin represents an attractive nano-sized transporter for drug delivery applications due to its beneficial safety profile. Existing albumin-based drug delivery systems are often limited by their low drug loading capacity as well as noticeable drug leakage into the blood circulation. Therefore, a unique albumin-derived core-shell doxorubicin (DOX) delivery system based on the protein denaturing-backfolding strategy was developed. 28 DOX molecules were covalently conjugated to the albumin polypeptide backbone via an acid sensitive hydrazone linker. Polycationic and pegylated human serum albumin formed two non-toxic and enzymatically degradable protection shells around the encapsulated DOX molecules. This core-shell delivery system possesses notable advantages, including a high drug loading capacity critical for low administration doses, a two-step drug release mechanism based on pH and the presence of proteases, an attractive biocompatibility and narrow size distribution inherited from the albumin backbone, as well as fast cellular uptake and masking of epitopes due to a high degree of pegylation. The IC50 of these nanoscopic onion-type micelles was found in the low nanomolar range for Hela cells as well as leukemia cell lines. In vivo data indicate its attractive potential as anti-leukemia treatment suggesting its promising profile as nanomedicine drug delivery system.

Regulation of amantadine hydrochloride binding with IIA subdomain of human serum albumin by fatty acid chains

Human serum albumin (HSA) is a major protein component of blood plasma that has been exploited to bind and transport a wide variety of endogenous and exogenous organic compounds. Although anionic drugs readily associate with the IIA subdomain of HSA, most cationic drugs poorly associate with HSA at this subdomain. In this study, we propose to improve the association between cationic drugs and HSA by modifying HSA with fatty acid chains. For our experiments, we tested amantadine hydrochloride, a cationic drug with antiviral and antiparkinsonian effects. Our results suggest that extensive myristoylation of HSA can help stabilize the interaction between amantadine and HSA in vitro. Our X-ray crystallography data further elucidate the structural basis of this regulation. Additionally, our crystallography data suggest that anionic drugs, with a functional carboxylate group, may enhance the association between amantadine and HSA by a mechanism similar to myristoylation. Ultimately, our results provide critical structural insight into this novel association between cationic drugs and the HSA IIA subdomain, raising the tempting possibility to fully exploit the unique binding capacity of HSA's IIA subdomain to achieve simultaneous delivery of anionic and cationic drugs.

The determination and interpretation of the therapeutic index in drug development

A key part of drug discovery and development is the characterization and optimization of the safety and efficacy of drug candidates to identify those that have an appropriately balanced safety-efficacy profile for a given indication. The therapeutic index (TI)--which is typically considered as the ratio of the highest exposure to the drug that results in no toxicity to the exposure that produces the desired efficacy--is an important parameter in efforts to achieve this balance. Various types of safety and efficacy data are generated in vitro and in vivo (in animals and in humans), and these data can be used to predict the clinical TI of a drug candidate at an early stage. However, approaches to systematically and quantitatively compare these types of data and to apply this knowledge more effectively are needed. This article critically discusses the various aspects of TI determination and interpretation in drug development for both small molecule drugs and biotherapeutics.