Impact of albumin on drug delivery--new applications on the horizon

Photo-Based Nanomedicines Using Polymeric Systems in the Field of Cancer Imaging and Therapy

The use of photo-based nanomedicine in imaging and therapy has grown rapidly. The property of light in converting its energy into different forms has been exploited in the fields of optical imaging (OI) and phototherapy (PT) for diagnostic and therapeutic applications. The development of nanotechnology offers numerous advantages to overcome the challenges of OI and PT. Accordingly, in this review, we shed light on common photosensitive agents (PSAs) used in OI and PT; these include fluorescent and bioluminescent PSAs for OI or PT agents for photodynamic therapy (PDT) and photothermal therapy (PTT). We also describe photo-based nanotechnology systems that can be used in photo-based diagnostics and therapies by using various polymeric systems.

Pharmaceutical Technology Innovation Strategy Based on the Function of Blood Transport Proteins as DDS Carriers for the Treatment of Intractable Disorders and Cancer

Blood transport proteins are biogenic molecules with unique and interesting inherent characteristics that make up living organisms. As the utilization of their inherent characteristics can be a groundbreaking strategy to resolve and improve several clinical problems, attempts have been made to develop pharmaceutical and biomedical preparations based on blood transport proteins for the treatment and diagnosis of disorders. Among various blood transport proteins, we focus on the immense potential of hemoglobin and albumin to serve as carriers of biomedical gases (oxygen and carbon monoxide) and anticancer agents (low-molecular compounds and antisense oligodeoxynucleotides), respectively, for the development of innovative drug delivery systems (DDS) to treat intractable disorders and solid cancers. In this review, I introduce the pharmaceutical technology, strategies, and application of DDS carriers that have been designed on the basis of the structure and function of hemoglobin and albumin. In addition, the prospect of using hemoglobin and albumin as materials for DDS carriers is discussed.

Potentials of nanotechnology in treatment of methicillin-resistant Staphylococcus aureus

Abuse of antibiotics has led to the emergence of drug-resistant pathogens. Methicillin-resistant Staphylococcus aureus (MRSA) was reported just two years after the clinical use of methicillin, which can cause severe infections with high morbidity and mortality in both community and hospital. The treatment of MRSA infection is greatly challenging since it has developed the resistance to almost all types of antibiotics. As such, it is of great significance and importance to develop novel therapeutic approaches. The fast development of nanotechnology provides a promising solution to this dilemma. Functional nanomaterials and nanoparticles can act either as drug carriers or as antibacterial agents for antibacterial therapy. Herein, we aim to provide a comprehensive understanding of the drug resistance mechanisms of MRSA and discuss the potential applications of some functionalized nanomaterials in anti-MRSA therapy. Also, the concerns and possible solutions for the nanomaterials-based anti-MRSA therapy are discussed.

Live long and active: Polypeptide-mediated assembly of antibody variable fragments

Antibodies possess multiple biologically relevant features that have been engineered into new therapeutic formats. Two examples include the adaptable specificity of their variable (Fv) region and the extension of plasma circulation times through their crystallizable (Fc) region. Since the invention of the single chain variable fragment (scFv) in 1988, antibody variable regions have been re-engineered into a wide variety of multifunctional nanostructures. Among these strategies, peptide-mediated self-assembly of variable regions through heterologous expression has become a powerful method to produce homogenous, functional biomaterials. This manuscript reviews recent reports of antibody fragments assembled through fusion with peptides and proteins, including elastin-like polypeptides (ELPs), collagen-like polypeptides (CLPs), albumin, transmembrane proteins, leucine zippers, silk protein, and viruses. This review further discusses the current clinical status of engineered antibody fragments and challenges to overcome.

Characterization of binding between model protein GA-Z and human serum albumin using asymmetrical flow field-flow fractionation and small angle X-ray scattering

Protein-based drugs often require targeted drug delivery for optimal therapy. A successful strategy to increase the circulation time of the protein in the blood is to link the therapeutic protein with an albumin-binding domain. In this work, we characterized such a protein-based drug, GA-Z. Using asymmetrical flow field-flow fractionation coupled with multi-angle light scattering (AF4-MALS) we investigated the GA-Z monomer-dimer equilibrium as well as the molar binding ratio of GA-Z to HSA. Using small angle X-ray scattering, we studied the structure of GA-Z as well as the complex between GA-Z and HSA. The results show that GA-Z is predominantly dimeric in solution at pH 7 and that it binds to monomeric as well as dimeric HSA. Furthermore, GA-Z binds to HSA both as a monomer and a dimer, and thus, it can be expected to stay bound also upon dilution following injection in the blood stream. The results from SAXS and binding studies indicate that the GA-Z dimer is formed between two target domains (Z-domains). The results also indicate that the binding of GA-Z to HSA does not affect the ratio between HSA dimers and monomers, and that no higher order oligomers of the complex are seen other than those containing dimers of GA-Z and dimers of HSA.

Biomolecular Densely Grafted Brush Polymers: Oligonucleotides, Oligosaccharides and Oligopeptides

In this Minireview, we describe synthetic polymers densely functionalized with sequence-defined biomolecular sidechains. We focus on synthetic brush polymers of oligonucleotides, oligosaccharides, and oligopeptides, prepared via graft-through polymerization from biomolecule functionalized monomers. The resulting structures are brush polymers wherein a biomolecular graft is positioned at each monomer backbone unit. We describe key synthetic milestones, identify synthetic opportunities, and highlight recent advances in the field, including biological applications.

One-pot thiol-amine bioconjugation to maleimides: simultaneous stabilisation and dual functionalisation

Maleimide chemistry is widely used in the site-selective modification of proteins. However, hydrolysis of the resultant thiosuccinimides is required to provide robust stability to the bioconjugates. Herein, we present an alternative approach that affords simultaneous stabilisation and dual functionalisation in a one pot fashion. By consecutive conjugation of a thiol and an amine to dibromomaleimides, we show that aminothiomaleimides can be generated extremely efficiently. Furthermore, the amine serves to deactivate the electrophilicity of the maleimide, precluding further reactivity and hence generating stable conjugates. We have applied this conjugation strategy to peptides and proteins to generate stabilised trifunctional conjugates. We propose that this stabilisation-dual modification strategy could have widespread use in the generation of diverse conjugates.

Human Serum Albumin Binds Native Insulin and Aggregable Insulin Fragments and Inhibits Their Aggregation

The purpose of this study was to investigate whether Human Serum Albumin (HSA) can bind native human insulin and its A13–A19 and B12–B17 fragments, which are responsible for the aggregation of the whole hormone. To label the hormone and both hot spots, so that their binding positions within the HSA could be identified, 4-(1-pyrenyl)butyric acid was used as a fluorophore. Triazine coupling reagent was used to attach the 4-(1-pyrenyl)butyric acid to the N-terminus of the peptides. When attached to the peptides, the fluorophore showed extended fluorescence lifetimes in the excited state in the presence of HSA, compared to the samples in buffer solution. We also analyzed the interactions of unlabeled native insulin and its hot spots with HSA, using circular dichroism (CD), the microscale thermophoresis technique (MST), and three independent methods recommended for aggregating peptides. The CD spectra indicated increased amounts of the α-helical secondary structure in all analyzed samples after incubation. Moreover, for each of the two unlabeled hot spots, it was possible to determine the dissociation constant in the presence of HSA, as 14.4 µM (A13–A19) and 246 nM (B12–B17). Congo Red, Thioflavin T, and microscopy assays revealed significant differences between typical amyloids formed by the native hormone or its hot-spots and the secondary structures formed by the complexes of HSA with insulin and A13–A19 and B12–B17 fragments. All results show that the tested peptide-probe conjugates and their unlabeled analogues interact with HSA, which inhibits their aggregation.

[68Ga]ABY-028: an albumin-binding domain (ABD) protein-based imaging tracer for positron emission tomography (PET) studies of altered vascular permeability and predictions of albumin-drug conjugate transport

Background

Albumin is commonly used as a carrier platform for drugs to extend their circulatory half-lives and influence their uptake into tissues that have altered permeability to the plasma protein. The albumin-binding domain (ABD) protein, which binds in vivo to serum albumin with high affinity, has proven to be a versatile scaffold for engineering biopharmaceuticals with a range of binding capabilities. In this study, the ABD protein equipped with a mal-DOTA chelator (denoted ABY-028) was radiolabeled with gallium-68 (⁶⁸Ga). This novel radiotracer was then used together with positron emission tomography (PET) imaging to examine variations in the uptake of the ABD-albumin conjugate with variations in endothelial permeability.

Results

ABY-028, produced by peptide synthesis in excellent purity and stored at − 20 °C, was stable for 24 months (end of study). [⁶⁸Ga]ABY-028 could be obtained with labeling yields of > 80% and approximately 95% radiochemical purity. [⁶⁸Ga]ABY-028 distributed in vivo with the plasma pool, with highest radioactivity in the heart ventricles and major vessels of the body, a gradual transport over time from the circulatory system into tissues and elimination via the kidneys. Early [⁶⁸Ga]ABY-028 uptake differed in xenografts with different vascular properties: mean standard uptake values (SUV_mean) were initially 5 times larger in FaDu than in A431 xenografts, but the difference decreased to 3 after 1 h. Cutaneously administered, vasoactive nitroglycerin increased radioactivity in the A431 xenografts. Heterogeneity in the levels and rates of increases of radioactivity uptake was observed in sub-regions of individual MMTV-PyMT mammary tumors and in FaDu xenografts. Higher uptake early after tracer administration could be observed in lower metabolic regions. Fluctuations in the increased permeability for the tracer across the blood-brain-barrier (BBB) direct after experimentally induced stroke were monitored by PET and the increased uptake was confirmed by ex vivo phosphorimaging.

Conclusions

[⁶⁸Ga]ABY-028 is a promising new tracer for visualization of changes in albumin uptake due to disease- and pharmacologically altered vascular permeability and their potential effects on the passive uptake of targeting therapeutics based on the ABD protein technology.

Evaluation of the In Vitro Stability of Stimuli-Sensitive Fatty Acid-Based Microparticles for the Treatment of Lung Cancer

The fatty acid-based microparticles containing iron oxide nanoparticles and paclitaxel (PAX) are a viable proposition for the treatment of lung cancer. The microparticles inhaled as a dry powder can be guided to selected locations using an external magnetic field, and when accumulated there, the active compound release can be triggered by local hyperthermia. However, this general strategy requires that the active compound is released from microparticles and can reach the targeted cells before microparticles are removed. Isothermal titration calorimetry was used to demonstrate that the components of microparticles were released and transferred to albumins and lipid bilayers. The morphology of the measured particulates was studied with scanning electron microscopy and dynamic light scattering. To determine the cytotoxicity of microparticles, cell culture studies were done. It has been shown that the transfer efficiency depends predominantly on the fatty acid composition of microparticles, which, together with the active ingredient, accumulate predominantly in membrane structures after being released from microparticles and before entering the cytoplasm. The release process is sufficient; hence, paclitaxel-loaded microparticles effectively suppressed the proliferation of A549 human lung epithelial cells of malignant origin (IC₅₀ values for both lauric acid-based and myristic/palmitic-based microparticles containing paclitaxel were below 0.375 μg/mL), while reference microparticles were noncytotoxic.

Cyclic RGD-Functionalized closo-Dodecaborate Albumin Conjugates as Integrin Targeting Boron Carriers for Neutron Capture Therapy

Cyclic RGD (cRGD) peptide-conjugated boronated albumin was developed to direct toward integrin α_vβ_3, which overexpresses on many cancer cells. A stepwise conjugation of c[RGDfK(Mal)] and maleimide-conjugated closo-dodecaborate (MID) to bovine serum albumin (BSA) afforded cRGD-MID-BSA, which was noncytotoxic toward both U87MG and A549 cells. As compared with l-BPA, selective antitumor activity of cRGD-MID-BSA toward U87MG cells overexpressing integrin α_vβ₃ was identified after thermal neutron irradiation. In vivo fluorescence live imaging of Cy5-conjugated cRGD-MID-BSA and MID-BSA revealed that both cRGD-MID-BSA and MID-BSA similarly reached the maximum accumulation during 8-12 h after injection. The selective accumulation and retention of Cy5-cRGD-MID-BSA was more pronounced than Cy5-MID-BSA after 24 h. An in vivo boron neutron capture therapy (BNCT) study revealed that the cRGD peptide ligand combination enhanced accumulation of MID-BSA into tumor cells in U87MG xenograft models. The significant tumor growth suppression was observed in U87MG xenograft models at a dose of 7.5 mg [¹⁰B]/kg after neutron irradiation.

SARS-CoV-2 Bound Human Serum Albumin and Systemic Septic Shock

The emergence of the COVID-19 virus and the subsequent pandemic have driven a great deal of research activity. The effects of COVID-19 are caused by the severe respiratory syndrome coronavirus 2 (SARS-CoV-2) and it is the underlying actions of SARs-CoV-2 virions on the endothelial glycocalyx that we consider here. One of the key factors in COVID-19 infection is its almost unique age-related profile, with a doubling in mortality every 10 years after the age of 50. The endothelial glycocalyx layer is essential in maintaining normal fluid homeostasis, but is fragile and prone to pathophysiological damage. It is physiologically significant in capillary microcirculation and in fluid distribution to the tissues. Human serum albumin (HSA), the most abundant protein in plasma, is created in the liver which also maintains its concentration, but this reduces by 10-15% after 50 years of age. HSA transports hormones, free fatty acids and maintains oncotic pressure, but SARS-CoV-2 virions bind competitively to HSA diminishing its normal transport function. Furthermore, hypoalbuminemia is frequently observed in patients with such conditions as diabetes, hypertension, and chronic heart failure, i.e., those most vulnerable to SARS-CoV-2 infection. Hypoalbuminemia, coagulopathy, and vascular disease have been linked in COVID-19 and have been shown to predict outcome independent of age and morbidity. Hypoalbuminemia is also known factor in sepsis and Acute respiratory distress syndrome (ARDS) occurs when fluids build-up in the alveoli and it is associated with sepsis, whose mechanism is systemic, being associated with the fluid and logistic mechanisms of the circulation. Glycocalyx damage is associated with changes plasma protein concentration, particularly HSA and blockage of albumin transport can produce the systemic symptoms seen in SARS-CoV-2 infection and sepsis. We therefore conclude that albumin binding to SARS-CoV-2 virions may inhibit the formation of the endothelial glycocalyx by inhibition of albumin transport binding sites. We postulate that albumin therapy to replace bound albumin might alleviate some of the symptoms leading to sepsis and that clinical trials to test this postulation should be initiated as a matter of urgency.

Ternary Nanocomplexes of Metallic Nanoclusters and Recombinant Peptides for Fluorescence Imaging and Enhanced Gene Delivery

The efficient carrier design for transferring therapeutic genes into target cells as well as tracking the delivered agents has attracted lots of attention in the field of DNA-based therapeutics. Here, we demonstrate this concept by a fast and facilitated method using BSA gold nanocluster (BSA AuNcs) conjugated with chimeric peptide with ability of DNA binding/packaging, endosome disruption and cell nuclear localization. An extensive characterization of photoluminescence properties, electrophoresis mobility and size distribution of the nanocarrier demonstrating the stable complexes composed of plasmid DNA, chimeric peptide and BSA AuNcs were successfully formed through electrostatic interactions. In the hybrid complexes, chimeric peptide could effectively decrease the cytotoxicity of AuNcs as well as enhance internalization of plasmid harboring firefly luciferase gene into HEK 293 T. The designed nanocarrier could be a promising vector in gene delivery systems for improved theranostics applications.

In vivo synthesis of triple-loaded albumin conjugate for efficient targeted cancer chemotherapy

The development of selective anticancer drugs avoiding side effects met in the course of almost all current treatments is of major interest for cancer patients. Here, we report on a novel β-glucuronidase-responsive drug delivery system allowing the in vivo synthesis of triple-loaded albumin conjugate. Following intravenous administration, the glucuronide prodrug reacts in the blood stream with the cysteine-34 residue of circulating albumin through thio-Michael addition, enabling the bioconjugation of three Monomethylauristatin E (MMAE) molecules to the plasmatic protein. The albumin conjugate then accumulates in malignant tissues where tumor-associated β-glucuronidase triggers the selective release of the whole transported drugs. By operating this way, the trimeric glucuronide prodrug produces remarkable anticancer activity on orthotopic MIA PaCa-2 pancreatic tumors, leading to dramatic reduction or even remission of tumors (3/8 mice).

Palmitic acid-modified bovine serum albumin nanoparticles target scavenger receptor-A on activated macrophages to treat rheumatoid arthritis

Palmitic acid-modified bovine serum albumin (PAB) was synthetized and found to own remarkable scavenger receptor-A (SR-A) targeting ability in vitro and in vivo, through which activated macrophages took up PAB nanoparticles (PAB NPs) 9.10 times more than bovine serum albumin nanoparticles (BSA NPs) and PAB NPs could delivery anti-inflammatory drugs celastrol (CLT) to inflamed tissues more effectively than BSA NPs. Compared with chondroitin sulfate modified BSA NPs targeting activated macrophages via CD44, PAB NPs show a more prominent targeting effect whether in vivo or in vitro. And PAB also demonstrated excellent biosafety compared to maleylated BSA, a known SR-A ligand that was lethal in our study. Furthermore, in adjuvant-induced arthritis rats, CLT-PAB NPs significantly improved disease pathology at a lower CLT dose with high safety, compared with CLT-BSA NPs. In addition, compared with the existing ligands with SR-A targeting due to strong electronegativity, the enhanced electronegativity and introduced PA are both important for the SR-A targeting effect of PAB. Therefore, PAB provides a novel direction for the treatment of rheumatoid arthritis and design of new ligands of SR-A.

Functionalisation of a heat-derived and bio-inert albumin hydrogel with extracellular matrix by air plasma treatment

Albumin-based hydrogels are increasingly attractive in tissue engineering because they provide a xeno-free, biocompatible and potentially patient-specific platform for tissue engineering and drug delivery. The majority of research on albumin hydrogels has focused on bovine serum albumin (BSA), leaving human serum albumin (HSA) comparatively understudied. Different gelation methods are usually employed for HSA and BSA, and variations in the amino acid sequences of HSA and BSA exist; these account for differences in the hydrogel properties. Heat-induced gelation of aqueous HSA is the easiest method of synthesizing HSA hydrogels however hydrogel opacity and poor cell attachment limit their usefulness in downstream applications. Here, a solution to this problem is presented. Stable and translucent HSA hydrogels were created by controlled thermal gelation and the addition of sodium chloride. The resulting bio-inert hydrogel was then subjected to air plasma treatment which functionalised its surface, enabling the attachment of basement membrane matrix (Geltrex). In vitro survival and proliferation studies of foetal human osteoblasts subsequently demonstrated good biocompatibility of functionalised albumin hydrogels compared to untreated samples. Thus, air plasma treatment enables functionalisation of inert heat-derived HSA hydrogels with extracellular matrix proteins and these may be used as a xeno-free platform for biomedical research or cell therapy.

Aggregate Removal Nanofiltration of Human Serum Albumin Solution Using Nanocellulose-Based Filter Paper

This study is dedicated to the rapid removal of protein aggregates and viruses from plasma-derived human serum albumin (HSA) product to reduce the risk of viral contamination and increase biosafety. A two-step filtration approach was implemented to first remove HSA aggregates and then achieve high model virus clearance using a nanocellulose-based filter paper of different thicknesses, i.e., 11 μm (prefilter) and 22 μm (virus filter) at pH 7.4 and room temperature. The pore size distribution of these filters was characterized by nitrogen gas sorption analysis. Dynamic light scattering (DLS) and size-exclusion high performance liquid chromatography (SE-HPLC) were performed to analyze the presence of HSA aggregates in process intermediates. The virus filter showed high clearance of a small-size model virus, i.e., log₁₀ reduction value (LRV) > 5, when operated at 3 and 5 bar, but a distinct decrease in LRV was detected at 1 bar, i.e., LRV 2.65–3.75. The throughput of HSA was also dependent on applied transmembrane pressure as was seen by Vmax values of 110 ± 2.5 L m⁻² and 63.6 ± 5.8 L m⁻² at 3 bar and 5 bar, respectively. Protein loss was low, i.e., recovery > 90%. A distribution of pore sizes between 40 nm and 60 nm, which was present in the prefilter and absent in the virus filter, played a crucial part in removing the HSA aggregates and minimizing the risk of virus filter fouling. The presented results enable the application of virus removal nanofiltration of HSA in bioprocessing as an alternative to virus inactivation methods based, e.g., on heat treatment.

Efficient drug and gene delivery to liver fibrosis: rationale, recent advances, and perspectives

Liver fibrosis results from chronic damages together with an accumulation of extracellular matrix, and no specific medical therapy is approved for that until now. Due to liver metabolic capacity for drugs, the fragility of drugs, and the presence of insurmountable physiological obstacles in the way of targeting, the development of efficient drug delivery systems for anti-fibrotics seems vital. We have explored articles with a different perspective on liver fibrosis over the two decades, then collected and summarized the information by providing corresponding in vitro and in vivo cases. We have discussed the mechanism of hepatic fibrogenesis with different ways of fibrosis induction in animals. Furthermore, the critical chemical and herbal anti-fibrotics, biological molecules such as micro-RNAs, siRNAs, and growth factors, which can affect cell division and differentiation, are mentioned. Likewise, drug and gene delivery and therapeutic systems on in vitro and in vivo models are summarized in the data tables. This review article enlightens recent advances in emerging drugs and nanocarriers and represents perspectives on targeting strategies employed in liver fibrosis treatment.

Efficacy and safety of nanoparticle albumin-bound paclitaxel as neoadjuvant chemotherapy in HER2-negative breast cancer

CONTEXT

Nanoparticle albumin-bound paclitaxel (Nab-PTX) is a form of paclitaxel bound to albumin nanoparticles and is used widely in a neoadjuvant setting for patients with breast cancer.

AIMS

We conducted a retrospective study to compare the efficacy and safety of Nab-PTX to PTX as neoadjuvant chemotherapy for patients with operable HER2-negative breast cancer.

SETTINGS AND DESIGN

In total, 50 patients were enrolled. Nab-PTX was administered in the study group, and PTX was administered in the control group.

SUBJECTS AND METHODS

The clinical response and safety profile were recorded. The expression of secreted protein acidic rich in cysteine (SPARC) in tumor tissue was examined.

STATISTICAL ANALYSIS

The efficacy and safety analyses were computed using SPSS statistical software. Multiple logistic regression analysis was performed to evaluate the exploratory variables (age, stage, estrogen receptor, partial response, and SPARC expression) for the pathological complete response (pCR), and Fisher's exact test was performed to evaluate the relationship between SPARC and pCR.

RESULTS

Both groups of patients achieved a good clinical response. The pCR rate for the Nab-PTX regimen was significantly higher than that for the PTX regimen. The most common adverse events were neutropenia, peripheral sensory neuropathy, arthralgia, and myalgia. In 68% of cases in the Nab-PTX group, high SPARC expression was observed.

CONCLUSIONS

As neoadjuvant therapy, the Nab-PTX regimen has advantages over conventional taxane regimen in patients with HER2-negative breast cancer. With this regimen, a high pCR rate was achieved with a good safety profile.

Protein-Based Nanoparticles as Drug Delivery Systems

Nanoparticles have been extensively used as carriers for the delivery of chemicals and biomolecular drugs, such as anticancer drugs and therapeutic proteins. Natural biomolecules, such as proteins, are an attractive alternative to synthetic polymers commonly used in nanoparticle formulation because of their safety. In general, protein nanoparticles offer many advantages, such as biocompatibility and biodegradability. Moreover, the preparation of protein nanoparticles and the corresponding encapsulation process involved mild conditions without the use of toxic chemicals or organic solvents. Protein nanoparticles can be generated using proteins, such as fibroins, albumin, gelatin, gliadine, legumin, 30Kc19, lipoprotein, and ferritin proteins, and are prepared through emulsion, electrospray, and desolvation methods. This review introduces the proteins used and methods used in generating protein nanoparticles and compares the corresponding advantages and disadvantages of each.

Nanoscopic Characterization of Stearic Acid Release from Bovine Serum Albumin Hydrogels

The release behavior of 16-doxyl stearic acid (16-DSA) from hydrogels made from bovine serum albumin (BSA) is characterized. 16-DSA serves as a model tracer molecule for amphiphilic drugs. Various hydrogel preparation procedures are tested and the fatty acid release from the different gels is compared in detail. These comparisons reach from the macroscopic level, the viscoelastic behavior via rheological characterization to changes on the nanoscopic level concerning the secondary structure of the protein during gelation through infrared (ATR-IR) spectroscopy. 16-DSA-BSA interaction via continuous wave electron paramagnetic resonance (CW EPR) spectroscopy in addition gives a nanoscopic view of small molecule-hydrogel interaction. The combined effects of fatty acid concentration, hydrogel incubation time, and gelation procedures on release behavior are studied via CW EPR spectroscopy and dynamic light scattering (DLS) measurements, which provide deep insight on the interaction of 16-DSA with BSA hydrogels and the nature and size of the released components, respectively. It is found that the release rate of the fatty acid from BSA hydrogels depends on and can thus be tuned through its loading percentage, duration of hydrogel formation and the type of gelation methods. All of the results confirm the potential of these gels as delivery hosts in pharmaceutical applications allowing the sustained release of drug.

Poly(propylene imine) dendrimers can bind to PEGylated albumin at PEG and albumin surface: Biophysical examination of a PEGylated platform to transport cationic dendritic nanoparticles

Cationic dendrimers are considered one of the best drug transporters in the body. However, in order to improve their biocompatibility, modification of them is required to reduce toxicity. In this way, many dendrimers may lose their original properties, for example, anticancer. To improve biocompatibility of dendrimers, it is possible to complex them with albumin, as is done very often in drug delivery. However, the interaction of dendrimers with albumin can lead to protein structure disruption or no complexation at all. Therefore, the investigation of the interaction between cationic poly-(propylene imine) dendrimers and polyethylene glycol (PEG)-albumin by fluorescence, circular dichroism, small angle X-ray scattering (SAXS), and transmission electron microscopy was carried out. Results show that cationic dendrimers bind to PEGylated albumin at PEG and albumin surfaces. The obtained results for 5k-PEG indicate a preferential binding of the dendrimers to PEG. For 20k-PEG binding of dendrimers to PEG and protein could induce a collapse of the PEG chain onto the protein surface. This opens up new possibilities to the use of PEGylated albumin as a platform to carry dendrimers without changing the albumin structure and improve the pharmacokinetic properties of dendrimers without further modification.

A novel nanoparticle-based theranostic agent targeting LRP-1 enhances the efficacy of neoadjuvant radiotherapy in colorectal cancer

Neoadjuvant radiotherapy has become an important therapeutic option for colorectal cancer (CRC) patients, whereas complete tumor response is observed only in 20-30% patients. Therefore, the development of diagnostic probe for radio-resistance is important to decide an optimal treatment timing and strategy for radiotherapy-resistant CRC patients. In this study, using the patient-derived xenograft (PDX) mouse model established with a radio-resistant CRC tumor tissue, we found low-density lipoprotein receptor-related protein-1 (LRP-1) as a radio-resistant marker protein induced by initial-dose radiation in radio-resistant CRC tumors. Simultaneously, we discovered a LRP-1 targeting peptide in a radio-resistant CRC PDX through in vivo peptide screening. We next engineered the theranostic agent made of human serum albumin nanoparticles (HSA NPs) containing 5-FU for chemo-radiotherapy and decorating LRP-1-targeting peptide for tumor localization, Cy7 fluorophore for diagnostic imaging. The nanoparticle-based theranostic agent accurately targeted the tumor designated by LRP-1 responding radiation and showed dramatically improved therapeutic efficacy in the radio-resistant PDX model. In conclusion, we have identified LRP-1 as a signature protein of radio-resistant CRC and successfully developed LRP-1-targeting HSA-NP containing 5-FU that is a novel theranostic tool for both diagnostic imaging and neoadjuvant therapy of CRC patients. This approach is clinically applicable to improve the effectiveness of neo-adjuvant radiotherapy and increase the ratio of complete tumor response in radio-resistant CRC.

Turning weakness into strength: Albumin nanoparticle-redirected amphotericin B biodistribution for reducing nephrotoxicity and enhancing antifungal activity

As the gold standard treatment for invasive fungal infection, amphotericin B (AmB) is limited by its severe nephrotoxicity. It has been shown that AmB complex with albumin in vivo forms a sub-10 nm nanocomplex within kidney excretion size range and eventually induces the nephrotoxicity. This study presents an approach to take advantage of the "weakness" of such unique interaction between AmB and albumin to form AmB nanocomplex beyond the size range of kidney excretion. Herein, a novel strategy was developed by directly assembling molecular BSA into larger-sized nanostructures with the reconstructed intermolecular disulfide bond and hydrophobic interaction. The rich binding sites of AmB within BSA nanostructures enabled the efficient AmB loading and forming nanoparticle (AmB-NP) which exceeds the size range of kidney excretion (~ 60 nm). We found nanoassembly with BSA redirected biodistribution of AmB with a 2.8-fold reduction of drug accumulation in the kidney and significantly improved its renal impairment in mice. Furthermore, we found that nanoassembly with BSA significantly increased the biodistribution of AmB in brain and endowed it 100-folds increase in pharmacological effect against meningoencephalitis caused by common fungal pathogen Cryptococcus neoformans. Together, this study not merely overcomes the nephrotoxicity of AmB using its "weakness" by a nanoassembly method, and provides a new strategy for reducing toxicity of drugs with high albumin binding rate in vivo.

Carbonic Anhydrase-IX Guided Albumin Nanoparticles for Hypoxia-mediated Triple-Negative Breast Cancer Cell Killing and Imaging of Patient-derived Tumor

Triple-Negative Breast Cancer (TNBC) is considered as the most onerous cancer subtype, lacking the estrogen, progesterone, and HER2 receptors. Evaluating new markers is an unmet need for improving targeted therapy against TNBC. TNBC depends on several factors, including hypoxia development, which contributes to therapy resistance, immune evasion, and tumor stroma formation. In this study, we studied the curcumin analogue (3,4-Difluorobenzylidene Curcumin; CDF) encapsulated bovine serum albumin (BSA) nanoparticle for tumor targeting. For tumor targeting, we conjugated Acetazolamide (ATZ) with CDF and encapsulated it in the BSA to form a nanoparticle (namely BSA-CDF-ATZ). The in vitro cytotoxicity study suggested that BSA-CDF-ATZ is more efficient when compared to free CDF. The BSA-CDF-ATZ nanoparticles showed significantly higher cell killing in hypoxic conditions compared to normoxic conditions, suggesting better internalization of the nanoparticles into cancer cells under hypoxia. Fluorescent-dye labeled BSA-CDF-ATZ revealed higher cell uptake of the nanoparticle compared to free dye indicative of better delivery, substantiated by a high rate of apoptosis-mediated cell death compared to free CDF. The significantly higher tumor accumulation and low liver and spleen uptake in TNBC patient-derived tumor xenograft models confirm the significant potential of BSA-CDF-ATZ for targeted TNBC imaging and therapy.

Redox- and MMP-2-sensitive drug delivery nanoparticles based on gelatin and albumin for tumor targeted delivery of paclitaxel

Tumor-responsive nanocarriers are highly valuable and demanded for smart anticancer drug delivery, where a quick release of chemotherapeutic drugs in tumors is preferred. Herein, a redox and MMP-2 sensitive nanoparticle has been designed for targeted delivery of PTX. Bovine serum albumin as a targeting ligand and gelatin as a hydrophilic carrier and MMP-2 sensitive reagent were used to construct the nanoparticles. Disulfide containing prodrug (PTX-SS-COOH) was grafted to the sulfhydryl modified gelatin to form the redox sensitive amphiphilic polymer. The nanoparticles were formed by self-assembly of amphiphilic polymer and BSA covering. Furthermore the modified sulfhydryl group on the gelatin can form a disulfide bond by self-crosslinking in the air, which endows the nanoparticle with a stable structure. The nanoparticle was sensitive to changes in MMP-2 concentration and redox potential, resulting in multiple responsive drug delivery to the tumor microenvironment. We further verified the anticancer effect of the nanoparticles both in vitro and in vivo, the nanoparticle (BSA/Gel-SS-PTX/PTX-SS-COOH NPs) demonstrated an excellent anticancer efficiency.

The Minimal Effect of Linker Length for Fatty Acid Conjugation to a Small Protein on the Serum Half-Life Extension

Conjugation of serum albumin or one of its ligands (such as fatty acid) has been an effective strategy to prolong the serum half-lives of drugs via neonatal Fc receptor (FcRn)–mediated recycling of albumin. So far, fatty acid (FA) has been effective in prolonging the serum half-lives for therapeutic peptides and small proteins, but not for large therapeutic proteins. Very recently, it was reported a large protein conjugated to FA competes with the binding of FcRn with serum albumin, leading to limited serum half-life extension, because primary FA binding sites in serum albumin partially overlap with FcRn binding sites. In order to prevent such competition, longer linkers between FA and the large proteins were required. Herein, we hypothesized that small proteins do not cause substantial competition for FcRn binding to albumin, resulting in the extended serum half-life. Using a small protein (28 kDa), we investigated whether the intramolecular distance in FA-protein conjugate affects the FcRn binding with albumin and serum half-life using linkers with varying lengths. Unlike with the FA-conjugated large protein, all FA-conjugated small proteins with different linkers exhibited comparable the FcRn binding to albumin and extended serum half-life.

Recombinant Peptide Production Platform Coupled with Site-Specific Albumin Conjugation Enables a Convenient Production of Long-Acting Therapeutic Peptide

The number of therapeutic peptides for human treatment is growing rapidly. However, their development faces two major issues: the poor yield of large peptides from conventional solid-phase synthesis, and the intrinsically short serum half-life of peptides. To address these issues, we investigated a platform for the production of a recombinant therapeutic peptide with an extended serum half-life involving the site-specific conjugation of human serum albumin (HSA). HSA has an exceptionally long serum half-life and can be used to extend the serum half-lives of therapeutic proteins and peptides. We used glucagon-like-peptide 1 (GLP-1) as a model peptide in the present study. A “clickable” non-natural amino acid—p-azido-l-phenylalanine (AzF)—was incorporated into three specific sites (V16, Y19, and F28) of a GLP-1 variant, followed by conjugation with HSA through strain-promoted azide–alkyne cycloaddition. All three HSA-conjugated GLP-1 variants (GLP1_16HSA, GLP1_19HSA, and GLP1_28HSA) exhibited comparable serum half-lives in vivo. However, the three GLP1_HSA variants had different in vitro biological activities and in vivo glucose-lowering effects, demonstrating the importance of site-specific HSA conjugation. The platform described herein could be used to develop other therapeutic peptides with extended serum half-lives.

Protein modification by thiolactone homocysteine chemistry: a multifunctionalized human serum albumin theranostic

As the most abundant protein with a variety of physiological functions, albumin has been used extensively for the delivery of therapeutic molecules. Thiolactone chemistry provides a powerful tool to prepare spin-labeled albumin-based multimodal imaging probes and therapeutic agents. We report the synthesis of a tamoxifen homocysteine thiolactone derivative and its use in thiol-'click' chemistry to prepare multi-functionalized serum albumin. The released sulfhydryl group of the homocysteine functional handle was labeled with a nitroxide reagent to prepare a spin-labeled albumin-tamoxifen conjugate confirmed by MALDI-TOF-MS, EPR spectroscopy, UV-vis and fluorescent emission spectra. This is the basis for a novel multimodal tamoxifen-albumin theranostic with a significant (dose-dependent) inhibitory effect on the proliferation of malignant cells. The response of human glioblastoma multiforme T98G cells and breast cancer MCF-7 cells to tamoxifen and its albumin conjugates was different in tumor cells with different expression level of ERα in our experiments. These results provide further impetus to develop a serum protein for delivery of tamoxifen to cancer cells.

Versatile Impact of Serum Proteins on Ruthenium(II) Polypyridyl Complexes Properties - Opportunities and Obstacles

Ruthenium(II) polypyridyl complexes have been extensively studied for the past few decades as promising anticancer agents. Despite the expected intravenous route of administration, the interaction between Ru(II) polypyridyl compounds and serum proteins is not well characterized and vast majority of the available literature data concerns determination of the binding constant. Ru-protein adducts can modify the biological effects of the Ru complexes influencing their cytotoxic and antimicrobial activity as well as introduce significant changes in their photophysical properties. More extensive research on the interaction between serum proteins and Ru(II) polypyridyl complexes is important for further development of Ru(II) polypyridyl compounds towards their application in anticancer therapy and diagnostics and can open new opportunities for already developed complexes.

Study of HSA interactions with arachidonic acid using spectroscopic methods revealing molecular dynamics of HSA-AA interactions

The interaction between human serum albumin (HSA) and arachidonic acid (AA) as an unsaturated fatty acid were investigated in the present study using methods including UV-VIS spectrophotometry, fluorescence and circular dichroism (CD) spectroscopy, lifetime measurements, fluorescence anisotropy measurements and visual molecular dynamics (MD). The thermodynamic parameters were assessed from HSA thermal and chemical denaturation in the presence and absence of AA. From the thermal denaturation, the Tm and ΔG˚(298K) magnitudes obtained were 327.7 K and 88 kJ/mol, respectively, for HSA alone, and 323.4 K and 85 kJ/mol, respectively, following treatment with a 10 µM AA concentration. The same manner of reduction in Gibbs free energy as a criterion of protein stability was achieved during chemical denaturation by urea in the presence of AA. The present study investigates HSA binding nature through MD approaches, and the results indicated that the binding affinity of AA to the subdomain IIA of HSA is greater compared with that of subdomain IIIA. Although the HSA regular secondary structure evaluation by CD exhibited a minor change following incubation with AA, its tertiary structure revealed an observable fluctuation. Thus, it appears that the interaction between AA and HSA requires minor instability and partial structural changes.

Curcumin Delivery Mediated by Bio-Based Nanoparticles: A Review

Todays, nano-pharmaceutics is emerging as an important field of science to develop and improve efficacy of different drugs. Although nutraceuticals are currently being utilized in the prevention and treatment of various chronic diseases such as cancers, a number of them have displayed issues associated with their solubility, bioavailability, and bio-degradability. In the present review, we focus on curcumin, an important and widely used polyphenol, with diverse pharmacological activities such as anti-inflammatory, anti-carcinogenic, anti-viral, etc. Notwithstanding, it also exhibits poor solubility and bioavailability that may compromise its clinical application to a great extent. Therefore, the manipulation and encapsulation of curcumin into a nanocarrier formulation can overcome these major drawbacks and potentially may lead to a far superior therapeutic efficacy. Among different types of nanocarriers, biological and biopolymer carriers have attracted a significant attention due to their pleiotropic features. Thus, in the present review, the potential protective and therapeutic applications of curcumin, as well as different types of bio-nanocarriers, which can be used to deliver curcumin effectively to the different target sites will be discussed.

Albumin-driven disassembly of lipidic nanoparticles: the specific case of the squalene-adenosine nanodrug

In the field of nanomedicine, nanostructured nanoparticles (NPs) made of self-assembling prodrugs emerged in the recent years with promising properties. In particular, squalene-based drug nanoparticles have already shown their efficiency through in vivo experiments. However, a complete pattern of their stability and interactions in the blood stream is still lacking. In this work we assess the behavior of squalene-adenosine (SQAd) nanoparticles - whose neuroprotective effect has already been demonstrated in murine models - in the presence of fetal bovine serum (FBS) and of bovine serum albumin (BSA), the main protein of blood plasma. Extensive physicochemical characterizations were performed using Small Angle Neutron Scattering (SANS), cryogenic transmission electron microscopy (Cryo-TEM), circular dichroism (CD), steady-state fluorescence spectroscopy (SSFS) and isothermal titration calorimetry (ITC) as well as in silico by means of ensemble docking simulations with human serum albumin (HSA). Significant changes in the colloidal stability of the nanoparticles in the presence of serum albumin were observed. SANS, CD and SSFS analyses demonstrated an interaction between SQAd and BSA, with a partial disassembly of the nanoparticles in the presence of BSA and the formation of a complex between SQAd and BSA. The interaction free energy of SQAd nanoparticles with BSA derived from ITC experiments, is about -8 kcal mol^-1 which is further supported in silico by ensemble docking simulations. Overall, our results show that serum albumin partially disassembles SQAd nanoparticles by extracting individual SQAd monomers from them. As a consequence, the SQAd nanoparticles would act as a circulating reservoir in the blood stream. The approach developed in this study could be extended to other soft organic nanoparticles.

Biomolecular study and conjugation of two para-aminobenzoic acid derivatives with serum proteins: drug binding efficacy and protein structural analysis

Two aminobenzoic acid derivatives DAB-0 and DAB-1 showed distinct biological properties on murine bladder cancer (BCa) cell line MB49-I. In contrast to DAB-1, DAB-0 does not possess any anti-inflammatory activity and is less toxic. Furthermore, DAB-0 does not interfere with INFγ-induced STAT1 activation and TNFα-induced IκB phosphorylation, while DAB-1 does. In order to rationalize these results, the binding efficacy of DAB-0 and DAB-1 with serum proteins such a human serum albumin (HSA), bovine serum albumin (BSA) and beta-lactoglobulin (β-LG) was investigated in aqueous solution at physiological pH. Multiple spectroscopic methods and thermodynamic analysis were used to determine the binding efficacy of DAB-0 and DAB-1 with serum proteins. Drug-protein conjugation was observed via through ionic contacts. DAB-1 forms stronger adducts than DAB-0, while β-LG shows more affinity with the order of stability β-LG > BSA > HSA. The stronger complexation of DAB-1 with serum proteins might account for its biological potential and transport in the blood. The binding efficacy ranged from 40 to 60%. Major alterations of protein secondary structures were detected upon drug complexation. Serum proteins are capable of delivering DAB-1 in vitro.Communicated by Ramaswamy H. Sarma.

Development of Meloxicam-Human Serum Albumin Nanoparticles for Nose-to-Brain Delivery via Application of a Quality by Design Approach

The aim of this study was to optimize the formulation of meloxicam (MEL)-containing human serum albumin (HSA) nanoparticles for nose-to-brain via a quality by design (QbD) approach. Liquid and dried formulations of nanoparticles containing Tween 80 and without the surfactant were investigated. Various properties, such as the Z-average, zeta potential, encapsulation efficacy (EE), conjugation of MEL and HSA, physical stability, in vitro dissolution, in vitro permeability, and in vivo plasma and brain distribution of MEL were characterized. From a stability point of view, a solid product (Mel-HSA-Tween) is recommended for further development since it met the desired critical parameters (176 ± 0.3 nm Z-average, 0.205 ± 0.01 PdI, -14.1 ± 0.7 mV zeta potential) after 6 months of storage. In vitro examination showed a significantly increased drug dissolution and permeability of MEL-containing nanoparticles, especially in the case of applying Tween 80. The in vivo studies confirmed both the trans-epithelial and axonal transport of nanoparticles, and a significantly higher cerebral concentration of MEL was detected with nose-to-brain delivery, in comparison with intravenous or per os administration. These results indicate intranasal the administration of optimized MEL-containing HSA formulations as a potentially applicable "value-added" product for the treatment of neuroinflammation.

Tumor Targeting Chemo- and Photodynamic Therapy Packaged in Albumin for Enhanced Anti-Tumor Efficacy

PURPOSE

Combination therapy for tumors is an important and promising strategy to improve therapeutic efficiency. This study aims at combining tumor targeting, chemo-, and photodynamic therapies to improve the anti-tumor performance.

PATIENTS AND METHODS

Human serum albumin (HSA), as a nontoxic and biodegradable drug carrier, was used to load hydrophobic photosensitizers (mono-substituted β-4-pyridyloxy phthalocyanine zinc, mPPZ) by a dilution-incubation-purification (DIP) strategy to form molecular complex HSA:mPPZ. This complex was cross-linked as nanoparticles, and then chemotherapy drug doxorubicin (DOX) was adsorbed into the nanoparticles to achieve combined photodynamic therapy and chemotherapy. Next, the surface of the obtained composite was modified by a tumor surface receptor (urokinase receptor) targeting agent (ATF-HSA) using a noncovalent method to obtain the final product (ATF-HSA@HSA:mPPZ:DOX nanoparticles, AHmDN).

RESULTS

AHmDN exhibited strong stability, remarkable cytotoxicity and higher uptake to tumor cells. Cell imaging analysis indicated that DOX was separated from AHmDN and uniformly distributed in cell nucleus while mPPZ localized in cytoplasm. The PDT activity of all the samples had been confirmed by the detection of intracellular ROS. In animal experiments, AHmDN was demonstrated to have a prominent tumor-targeting effect using a 3D imaging system. In addition, the enhanced antitumor effect of AHmDN in tumor-bearing mice was also been observed. Importantly, the tumor-targeting effect of such nanoparticles lasted for about 14 days after one injection.

CONCLUSION

These albumin nanoparticles with combined functions of tumor targeting, chemotherapy and photodynamic therapy can highly enhance the anti-tumor effect. This drug delivery system can be applied to package other hydrophobic photosensitizers and chemotherapy drugs for improving therapeutic efficacy to tumors.