Adsorption of human serum albumin on the chrysotile surface: a molecular dynamics and spectroscopic investigation

Unveiling the Modification of Esterase-like Activity of Serum Albumin by Nanoplastics and Their Cocontaminants

Nanoplastics and other cocontaminants have raised concerns due to their widespread presence in the environment and their potential to enter the food chain. The harmful effects of these particles depend on various factors, such as nanoparticle size, shape, surface charge, and the nature of the cocontaminants involved. On entering the human body, human serum albumin (HSA) molecules bind and transport these particles in the blood system. The esterase-like activity of HSA, which plays a role in metabolizing drug/toxic compounds, was taken as a representative to portray the effects of these particles on HSA. Polystyrene nanoplastics (PSNPs) with different surface functionalization (plain (PS), amine (PS-NH2), and carboxy (PS-COOH)), different sizes (100 and 500 nm), and PS with cocontaminant metformin hydrochloride (Met-HCl), a widely used antidiabetic drug, were investigated in this study. Fluorescence emission spectra of HSA revealed that PS-NH2 exhibits a greater effect on protein conformation, smaller NPs have a greater influence on protein structure than larger NPs, and Met-HCl lowers PSNPs' affinity for HSA by coating the surface of the NPs, which may result in direct NP distribution to the drug's target organs and toxicity. Circular dichroism spectra also supported these results in terms of secondary structural changes. Esterase activity of HSA was inhibited by all the particles (except Met-HCl) by competitive inhibition as concluded from constant Vmax and increasing Km. Greater reduction in enzyme activity was observed for PS-NH2 among functionalizations and for 100 nm PS among sizes. Furthermore, Met-HCl lowers the inhibitory impact of PSNPs on HSA since the drug binds weakly to HSA, and so they can serve as a vector delivering PSNPs to their target organs, resulting in serious implications.

Isolation and characterization of microplastics from skin care products; interactions with albumin proteins and in-vivo toxicity studies on Artemia salina

Skincare products are a significant source of primary microplastics (MPs). This study isolates and characterizes microplastic from two skin care products: face wash (FW-MPs) and face scrub (FS-MPs). Microplastics extracted were around 660 µm in size. The extracted MPs, designated as unground MPs (UG-MPs), were smooth surface and spherical. Ground ones were denoted as the ground MPs (G-MPs) that varied in size and surface shape. G-MPs interacted with bovine serum albumin (BSA) and human serum albumin (HSA). BSA adsorption on FW-MPs was 29%, whereas HSA adsorption was 47%. Contrarily, FS-MPs displayed 17% and 31%. Fluorescence spectroscopy and FE-SEM images showed HSA adsorption on G-MPs was greater than BSA. G-MP interaction changed the life cycle of Artemia salina. UV-Vis and fluorescence spectroscopy were used to study protein adsorption and desorption on G-MPs. A. salina treated to 2.5 mg/mL G-MPs delayed hatching and development and internalized microplastics in the gut at 144 h exposure.

Nanoplastics alter the conformation and activity of human serum albumin

Nanoplastics finds its presence in most of the consumer products. Their chance of coming in contact with human cells and components is rampant. This study focuses on the interaction of polystyrene nanoplastics (PSNPs) with human serum albumin (HSA), ultimately causing structural and functional properties of the protein. Fluorescence and UV-Visible spectroscopic studies reported that PSNPs form a spontaneous ground-state complex with HSA, by hydrogen bonding, van der waal's, and hydrophobic force of attraction. This causes changes in the environment around major aromatic amino acids, especially tryptophan-214, which has a strong affinity with PSNPs. Further docking analysis confirmed hydrophobic interactions between PSNPs and aromatic amino acids in subdomain IIA of HSA. A shift in amide bands in HSA, as determined by FTIR analysis confirmed the disturbances in its secondary structure followed by reordering which will lead to the unfolding of HSA. Besides, PSNPs reduce the esterase activity of HSA by competitive inhibition. This molecular-level information such as binding energy, binding site, binding forces, reversible or irreversible binding, and structural changes of protein will shed light on the extent of toxicity in humans. This study will emphasize the urgent need for regulation of the use of nanoplastics (NPs) in consumer products, as well as the need for more research to determine the fate of NPs in the biological system.

Minerals in biology and medicine

Natural minerals ('stone drugs') have been used in traditional Chinese medicines for over 2000 years, but there is potential for modern-day use of inorganic minerals to combat viral infections, antimicrobial resistance, and for other areas in need of new therapies and diagnostic aids. Metal and mineral surfaces on scales from milli-to nanometres, either natural or synthetic, are patterned or can be modified with hydrophilic/hydrophobic and ionic/covalent target-recognition sites. They introduce new strategies for medical applications. Such surfaces have novel properties compared to single metal centres. Moreover, 3D mineral particles (including hybrid organo-minerals) can have reactive cavities, and some minerals have dynamic movement of metal ions, anions, and other molecules within their structures. Minerals have a unique ability to interact with viruses, microbes and macro-biomolecules through multipoint ionic and/or non-covalent contacts, with potential for novel applications in therapy and biotechnology. Investigations of mineral deposits in biology, with their often inherent heterogeneity and tendency to become chemically-modified on isolation, are highly challenging, but new methods for their study, including in intact tissues, hold promise for future advances.

Confining a Protein-Containing Water Nanodroplet inside Silica Nanochannels

Incorporation of biological systems in water nanodroplets has recently emerged as a new frontier to investigate structural changes of biomolecules, with perspective applications in ultra-fast drug delivery. We report on the molecular dynamics of the digestive protein Pepsin subjected to a double confinement. The double confinement stemmed from embedding the protein inside a water nanodroplet, which in turn was caged in a nanochannel mimicking the mesoporous silica SBA-15. The nano-bio-droplet, whose size fits with the pore diameter, behaved differently depending on the protonation state of the pore surface silanols. Neutral channel sections allowed for the droplet to flow, while deprotonated sections acted as anchoring piers for the droplet. Inside the droplet, the protein, not directly bonded to the surface, showed a behavior similar to that reported for bulk water solutions, indicating that double confinement should not alter its catalytic activity. Our results suggest that nanobiodroplets, recently fabricated in volatile environments, can be encapsulated and stored in mesoporous silicas.

BSA/HSA ratio modulates the properties of Ca(2+)-induced cold gelation scaffolds

An effective tissue engineering approach requires adjustment according to the target tissue to be engineered. The possibility of obtaining a protein-based formulation for the development of multivalent tunable scaffolds that can be adapted for several types of cells and tissues is explored in this work. The incremental substitution of bovine serum albumin (BSA) by human serum albumin (HSA), changing the scaffolds' hydrophilic/hydrophobic ratio, on a previously optimized scaffold formulation resulted in a set of uniform porous scaffolds with different physical properties and associated cell proliferation profile along time. There was a general trend towards an increase in hydrophilicity, swelling degree and in vitro degradation of the scaffolds with increasing replacement of BSA by HAS. The set of BSA/HSA scaffolds presented distinct values for the storage (elastic) modulus and loss factor which were similar to those described for different native tissues such as bone, cartilage, muscle, skin and neural tissue. The preferential adhesion and proliferation of skin fibroblasts on the BSA25%HSA75% and HSA100% scaffolds, as predicted by their viscoelastic properties, demonstrate that the BSA/HSA scaffold formulation is promising for the development of scaffolds that can be tuned according to the tissue to be repaired and restored.

Computational studies of the binding mechanisms of fullerenes to human serum albumin

Fullerene and its derivatives show promising prospects for applications in a vast array of biological systems. A key aspect concerning their biomedical applications is how they interact with proteins from molecular levels, which is still poorly understood. In the current study, we investigated the structural and thermodynamic basis of the interactions between two pharmacologically relevant fullerene derivatives and human serum albumin (HSA) using molecular docking, molecular dynamics simulations, and binding free energy calculations. Our results demonstrate that fullerenes steadily bind with HSA at the interfacial cavity formed by subdomains IIA and IIIA. In agreement with available experimental data, our simulations show that the global structure of HSA becomes more compact in the presence of fullerene, while local structural dynamics of the binding cavity behaves diversely depending on the chemical properties of bound fullerenes. Binding free energy calculations confirmed that the interactions between fullerenes and HSA are dominantly stabilized by van der Waals forces and they further allowed the identification of key residues involved in fullerene binding. The structural and energetic insights obtained from this work may help for the development of fullerene-based drug delivery devices and therapeutic agents with improved biological profile.

Adsorption of bovine serum albumin onto synthetic Fe-doped geomimetic chrysotile

Synthetic stoichiometric and Fe-doped geomimetic chrysotile nanocrystals represent a reference standard to investigate the health hazard associated with mineral asbestos fibres. Experimental evidence suggests that the generation of reactive oxygen species and other radicals, catalysed by iron ions at the fibre surface, plays an important role in asbestos-induced cytotoxicity and genotoxicity. In this study, structural modification of bovine serum albumin (BSA) adsorbed onto synthetic chrysotile doped with different amounts of Fe has been investigated by Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA) and analytical pyrolysis coupled with gas chromatography-mass spectrometry. FT-IR data evidenced a marked increase in disordered structures like random coil and β-turn of BSA-nanocrystal adduct with 0.52 wt% of Fe doped. The TGA profile of the BSA revealed that its interaction with the synthetic chrysotile surface was strongly affected by the substitution of Fe into the chrysotile structure. The 2,5-diketopiperazine yields, formed upon thermal degradation of the polypeptide chain (pyrolysis-gas chromatography), changed when the BSA was adsorbed on the nanofibres. In general, results suggested that minute amount (less than 1 wt%) of Fe doping in chrysotile affected the protein-nanofibre interactions, supporting the role that this element may play in asbestos toxicity. The catalytic role of iron and the consequent unfolding of protein due to the structural surface modification of nanofibres were also evaluated.

Surface topography effects in protein adsorption on nanostructured carbon allotropes

We report a molecular dynamics (MD) simulation study of protein adsorption on the surface of nanosized carbon allotropes, namely single-walled carbon nanotubes (SWNT) considering both the convex outer surface and the concave inner surface, together with a graphene sheet for comparison. These systems are chosen to investigate the effect of the surface curvature on protein adsorption at the same surface chemistry, given by sp(2) carbon atoms in all cases. The simulations show that proteins do favorably interact with these hydrophobic surfaces, as previously found on graphite which has the same chemical nature. However, the main finding of the present study is that the adsorption strength does depend on the surface topography: in particular, it is slightly weaker on the outer convex surfaces of SWNT and is conversely enhanced on the inner concave SWNT surface, being therefore intermediate for flat graphene. We additionally find that oligopeptides may enter the cavity of common SWNT, provided their size is small enough and the tube diameter is large enough for both entropic and energetic reasons. Therefore, we suggest that proteins can effectively be used to solubilize in water single-walled (and by analogy also multiwalled) carbon nanotubes through adsorption on the outer surface, as indeed experimentally found, and to functionalize them after insertion of oligopeptides within the cavity of nanotubes of appropriate size.

A hydrophobic gold surface triggers misfolding and aggregation of the amyloidogenic Josephin domain in monomeric form, while leaving the oligomers unaffected

Protein misfolding and aggregation in intracellular and extracellular spaces is regarded as a main marker of the presence of degenerative disorders such as amyloidoses. To elucidate the mechanisms of protein misfolding, the interaction of proteins with inorganic surfaces is of particular relevance, since surfaces displaying different wettability properties may represent model systems of the cell membrane. Here, we unveil the role of surface hydrophobicity/hydrophilicity in the misfolding of the Josephin domain (JD), a globular-shaped domain of ataxin-3, the protein responsible for the spinocerebellar ataxia type 3. By means of a combined experimental and theoretical approach based on atomic force microscopy, Fourier transform infrared spectroscopy and molecular dynamics simulations, we reveal changes in JD morphology and secondary structure elicited by the interaction with the hydrophobic gold substrate, but not by the hydrophilic mica. Our results demonstrate that the interaction with the gold surface triggers misfolding of the JD when it is in native-like configuration, while no structural modification is observed after the protein has undergone oligomerization. This raises the possibility that biological membranes would be unable to affect amyloid oligomeric structures and toxicity.

Molecular modelling of protein adsorption on the surface of titanium dioxide polymorphs

This paper reports a molecular modelling study of the adsorption of protein subdomains with unlike secondary structures on different surfaces of ceramic titanium dioxide (TiO(2)), forming a passivating film on titanium biomaterials that provides the interface between the bulk metal and the physiological environment, affecting its biocompatibility and performance. Using molecular dynamics methods, we study the effect of the nanoscale structure of the common TiO(2) polymorphs (rutile, anatase and brookite) on the adsorption of an albumin subdomain and on two connected fibronectin modules, respectively containing α-helices and β-sheets. We find that the larger protein subdomain shows a stronger adsorption, as expected because of its size, but also that the three surfaces behave differently. In particular, brookite shows the weakest adsorption, whereas anatase leads to the strongest intrinsic adsorption, in particular for the fibronectin modules. Moreover, the simulations indicate a significant conformational change of the adsorbed protein subdomains with extensive surface nanopatterning. These results show that classical molecular dynamics methods can provide useful information about the influence of nanostructure and topology on protein physisorption at a fixed surface chemistry.

Disentangling protein-silica interactions

We present the results of modelling studies aimed at the understanding of the interaction of a 7 nm sized water droplet containing a negatively charged globular protein with flat silica surfaces. We show how the droplet interaction with the surface depends on the electrostatic surface charge, and that adhesion of the droplet occurs when the surface is negatively charged as well. The key role of water and of the charge-balancing counter ions in mediating the surface-protein adhesion is highlighted. The relevance of the present results with respect to the production of bioinorganic hybrids via encapsulation of proteins inside mesoporous silica materials is discussed.