Fluorescence study of the interaction between albumin and layered double hydroxides

Layered double hydroxides nanoparticles (LDH-NP) are increasingly studied for biomedical applications. Nevertheless, their interaction with biomolecules such as proteins needs further exploration for an effective application. In this work, the adsorption of bovine serum albumin (BSA) on LDH-NP and the conformation changes of the protein upon adsorption were characterized using fluorescence spectroscopy. First, the quenching of tryptophan residues of BSA by chloride-intercalated LDH-NP was explored and the BSA adsorption capacity of LDH-NP were determined. Then, the structural conformation of the protein was analyzed by fluorescence spectroscopy (including synchronous, polarization and quenching studies) at different surface coverages. Finally, the proclivity of adsorbed BSA molecules to assemble as amyloid fibril was evaluated. Due to the positive charging and low curvature of LDH-NP, BSA molecules were strongly adsorbed, which produced a quenching of the protein fluorescence and a large adsorption capacity. The effect on BSA conformation was dependent on surface coverage (SC): at low values ,t he tryptophan residues were in more hydrophobic environments and more accessible to quenchers than al high ones. At low SC, there is space between the BSA molecules to spread on the surface, which led to a conformation change. Contrarily, the native conformation around tryptophan residues of BSA was preserved at high SC due to the tight packing of the adsorbed protein molecules. As a result, BSA molecules are stabilized against the formation of amyloid fibrils at high SC, while at low SC they present a similar fibrillation than free BSA.

Nanoinformatics based insights into the interaction of blood plasma proteins with carbon based nanomaterials: Implications for biomedical applications

In the past three decades, interest in using carbon-based nanomaterials (CBNs) in biomedical application has witnessed remarkable growth. Despite the rapid advancement, the translation of laboratory experimentation to clinical applications of nanomaterials is one of the major challenges. This might be attributed to poor understanding of bio-nano interface. Arguably, the most significant barrier is the complexity that arises by interplay of several factors like properties of nanomaterial (shape, size, surface chemistry), its interaction with suspending media (surface hydration and dehydration, surface reconstruction and release of free surface energy) and the interaction with biomolecules (conformational change in biomolecules, interaction with membrane and receptor). Tailoring a nanomaterial that minimally interacts with protein and lipids in the medium while effectively acts on target site in biological milieu has been very difficult. Computational methods and artificial intelligence techniques have displayed potential in effectively addressing this problem. Through predictive modelling and deep learning, computer-based methods have demonstrated the capability to create accurate models of interactions between nanoparticles and cell membranes, as well as the uptake of nanomaterials by cells. Computer-based simulations techniques enable these computational models to forecast how making particular alterations to a material's physical and chemical properties could enhance functional aspects, such as the retention of drugs, the process of cellular uptake and biocompatibility. We review the most recent progress regarding the bio-nano interface studies between the plasma proteins and CBNs with a special focus on computational simulations based on molecular dynamics and density functional theory.

Layered double hydroxides and their tailored hybrids/composites: Progressive trends for delivery of natural/synthetic-drug/cosmetic biomolecules

Layered double hydroxides (LDHs) are well-known and important class of hydrotalcite-type anionic clays (HTs) materials that are cost-effective with additional advantages of facile synthesis, composition, tenability, and reusability. These convincing characteristics are liable for their applications in various fields related to energy, environment, catalysis, biomedical, and biotechnology. HTs/LDHs are generally synthesized from low cost abundantly available chemical precursors through the aqueous synthetic pathways under mild reaction conditions. These materials can be termed green materials based on their non-toxic nature, availability of precursors, facile and low-cost production using aqueous medium conditions with less hazardous effluents. Diverse and fascinating characteristics have been attributed to HTs/LDHs like anion exchange ability, surface basicity, biocompatibility, controlled release of the anion specific area, porosity, easy surface modification, and pH dependent biodegradability. Hence, HTs/LDHs and their modified and/or functionalized nanohybrids/nanocomposites are reported as the potential drug delivery carriers with a capability to stabilize the susceptible bioactive molecules, may enhance the solubility of poorly soluble drugs along with controlled drug/bioactive molecule release and delivery. These clay and bioactive hybrid materials have good biocompatibility, less cytotoxicity, and better site-targeting with improved cellular uptake than that of free parent biomolecules. These lamellar solids of micro/nanostructure are compatible, host-guest materials and able to fabricate with drugs/cosmeceutical/bio- or synthetic polymers without any change in their molecular structure and reactivity along with improvement in their stabilities. Other important features are facile synthesis, basicity, high stability with easy storage, and efficient administration with low bio-toxicity. This study enlightens the applications of HTs/LDHs along with their hybrids/composites in the field of drug/cosmeceutical/gene delivery systems of natural/synthetic biomolecules.

Blood Compatibility of Drug-Inorganic Hybrid in Human Blood: Red Blood Cell Hitchhiking and Soft Protein Corona

A drug-delivery system consisting of an inorganic host-layered double hydroxide (LDH)-and an anticancer drug-methotrexate (MTX)-was prepared via the intercalation route (MTX-LDH), and its hematocompatibility was investigated. Hemolysis, a red blood cell counting assay, and optical microscopy revealed that the MTX-LDH had no harmful toxic effect on blood cells. Both scanning electron microscopy and atomic force microscopy exhibited that the MTX-LDH particles softly landed on the concave part inred blood cells without serious morphological changes of the cells. The time-dependent change in the surface charge and hydrodynamic radius of MTX-LDH in the plasma condition demonstrated that the proteins can be gently adsorbed on the MTX-LDH particles, possibly through protein corona, giving rise to good colloidal stability. The fluorescence quenching assay was carried out to monitor the interaction between MTX-LDH and plasma protein, and the result showed that the MTX-LDH had less dynamic interaction with protein compared with MTX alone, due to the capsule moiety of the LDH host. It was verified by a quartz crystal microbalance assay that the surface interaction between MTX-LDH and protein was reversible and reproducible, and the type of protein corona was a soft one, having flexibility toward the biological environment.

Role of the Protein Corona in the Colloidal Behavior of Microplastics

Microparticles of polyethylene and polypropylene are largely found in aquatic environments because they are the most produced and persistent plastic materials. Once in biological media, they are covered by a layer of molecules, the so-called corona, mostly composed of proteins. A yeast protein extract from Saccharomyces cerevisiae was used as a protein system to observe interactions in complex biological media. Proteins, acting as surfactants and providing hydrophilic surfaces, allow the dispersion of highly hydrophobic particles in water and stabilize them. After 24 h, the microplastic quantity was up to 1 × 10¹¹ particles per liter, whereas without protein, no particles remained in solution. Label-free imaging of the protein corona by synchrotron radiation deep UV fluorescence microscopy (SR-DUV) was performed. In situ images of the protein corona were obtained, and the adsorbed protein quantity, the coverage rate, and the corona heterogeneity were determined. The stability kinetics of the microplastic suspensions were measured by light transmission using a Turbiscan analyzer. Together, the microscopic and kinetics results demonstrate that the protein corona can very efficiently stabilize microplastics in solution provided that the protein corona quality is sufficient. Microplastic stability depends on different parameters such as the particle's intrinsic properties (size, density, hydrophobicity) and the protein corona formation that changes the particle wettability, electrostatic charge, and steric hindrance. By controlling these parameters with proteins, it becomes possible to keep microplastics in and out of solution, paving the way for applications in the field of microplastic pollution control and remediation.

Biomaterials Based on Organic Polymers and Layered Double Hydroxides Nanocomposites: Drug Delivery and Tissue Engineering

The development of biomaterials has a substantial role in pharmaceutical and medical strategies for the enhancement of life quality. This review work focused on versatile biomaterials based on nanocomposites comprising organic polymers and a class of layered inorganic nanoparticles, aiming for drug delivery (oral, transdermal, and ocular delivery) and tissue engineering (skin and bone therapies). Layered double hydroxides (LDHs) are 2D nanomaterials that can intercalate anionic bioactive species between the layers. The layers can hold metal cations that confer intrinsic biological activity to LDHs as well as biocompatibility. The intercalation of bioactive species between the layers allows the formation of drug delivery systems with elevated loading capacity and modified release profiles promoted by ion exchange and/or solubilization. The capacity of tissue integration, antigenicity, and stimulation of collagen formation, among other beneficial characteristics of LDH, have been observed by in vivo assays. The association between the properties of biocompatible polymers and LDH-drug nanohybrids produces multifunctional nanocomposites compatible with living matter. Such nanocomposites are stimuli-responsive, show appropriate mechanical properties, and can be prepared by creative methods that allow a fine-tuning of drug release. They are processed in the end form of films, beads, gels, monoliths etc., to reach orientated therapeutic applications. Several studies attest to the higher performance of polymer/LDH-drug nanocomposite compared to the LDH-drug hybrid or the free drug.

Surface modification of two-dimensional layered double hydroxide nanoparticles with biopolymers for biomedical applications

Layered double hydroxides (LDHs) are appealing nanomaterials for (bio)medical applications and their potential is threefold. One can gain advantage of the structure of LDH frame (i.e., layered morphology), anion exchanging property towards drugs with acidic character and tendency for facile surface modification with biopolymers. This review focuses on the third aspect, as it is necessary to evaluate the advantages of polymer adsorption on LDH surfaces. Beside the short discussion on fundamental and structural features of LDHs, LDH-biopolymer interactions will be classified in terms of the effect on the colloidal stability of the dispersions. Thereafter, an overview on the biocompatibility and biomedical applications of LDH-biopolymer composite materials will be given. Finally, the advances made in the field will be summarized and future research directions will be suggested.

Multivalent ACE2 engineering-A promising pathway for advanced coronavirus nanomedicine development

The spread of coronavirus diseases has resulted in a clarion call to develop potent drugs and vaccines even as different strains appear beyond human prediction. An initial step that is integral to the viral entry into host cells results from an active-targeted interaction of the viral spike (S) proteins and the cell surface receptor, called angiotensin-converting enzyme 2 (ACE2). Thus, engineered ACE2 has been an interesting decoy inhibitor against emerging coronavirus infestation. This article discusses promising innovative ACE2 engineering pathways for current and emerging coronavirus therapeutic development. First, we provide a brief discussion of some ACE2-associated human coronaviruses and their cell invasion mechanism. Then, we describe and contrast the individual spike proteins and ACE2 receptor interactions, highlighting crucial hotspots across the ACE2-associated coronaviruses. Lastly, we address the importance of multivalency in ACE2 nanomedicine engineering and discuss novel approaches to develop and achieve multivalent therapeutic outcomes. Beyond coronaviruses, these approaches will serve as a paradigm to develop new and improved treatment technologies against pathogens that use ACE2 receptor for invasion.

Photochemical Consideration in the Interactions between Blood Proteins and Layered Inorganic Materials

Interactions between layered double hydroxide (LDH) nanomaterials and plasma proteins according to their particle size and surface charge were evaluated. The LDHs with different particle size (150, 350 and 2000 nm) were prepared by adjusting hydrothermal treatment and urea hydrolysis and subsequent organic coating with citrate, malite and serite was applied to control the surface charge (ζ-potential: −15, 6 and 36 mV). Adsorption isotherms and Stern–Volmer plots for fluorescence quenching indicated that the human blood plasma had weak interactions toward all the types of LDHs. The adsorption isotherms did not show significant differences in the size and surface charges, while the fluorescence quenching ratio increased with the increase in the surface charge, implying that electrostatic interaction played a major role in their interactions. The fluorescence quenching of three types of plasma proteins (human serum albumin, γ-globulin and fibrinogen) by the surface charge-controlled LDHs suggested that the proteins adsorbed on the LDHs with a single layer and additional proteins were weakly adsorbed to surround the LDHs with adsorbed proteins. It was concluded that the LDH nanomaterials are fairly compatible for blood components due to the protein corona while the electrostatic interaction can affect their interaction with the proteins.

Scratching the Surface of the Protein Corona: Challenging Measurements and Controversies

This Review aims to provide a systematic analysis of the literature regarding ongoing debates in protein corona research. Our goal is to portray the current understanding of two fundamental and debated characteristics of the protein corona, namely, the formation of mono- or multilayers of proteins and their binding (ir)reversibility. The statistical analysis we perform reveals that these characterisitics are strongly correlated to some physicochemical factors of the NP-protein system (particle size, bulk material, protein type), whereas the technique of investigation or the type of measurement (in situ or ex situ) do not impact the results, unlike commonly assumed. Regarding the binding reversibility, the experimental design (either dilution or competition experiments) is also shown to be a key factor, probably due to nontrivial protein binding mechanisms, which could explain the paradoxical phenomena reported in the literature. Overall, we suggest that to truly predict and control the protein corona, future efforts should be directed toward the mechanistic aspects of protein adsorption.

Two-dimensional biomaterials: material science, biological effect and biomedical engineering applications

To date, nanotechnology has increasingly been identified as a promising and efficient means to address a number of challenges associated with public health. In the past decade, two-dimensional (2D) biomaterials, as a unique nanoplatform with planar topology, have attracted explosive interest in various fields such as biomedicine due to their unique morphology, physicochemical properties and biological effect. Motivated by the progress of graphene in biomedicine, dozens of types of ultrathin 2D biomaterials have found versatile bio-applications, including biosensing, biomedical imaging, delivery of therapeutic agents, cancer theranostics, tissue engineering, as well as others. The effective utilization of 2D biomaterials stems from the in-depth knowledge of structure-property-bioactivity-biosafety-application-performance relationships. A comprehensive summary of 2D biomaterials for biomedicine is still lacking. In this comprehensive review, we aim to concentrate on the state-of-the-art 2D biomaterials with a particular focus on their versatile biomedical applications. In particular, we discuss the design, fabrication and functionalization of 2D biomaterials used for diverse biomedical applications based on the up-to-date progress. Furthermore, the interactions between 2D biomaterials and biological systems on the spatial-temporal scale are highlighted, which will deepen the understanding of the underlying action mechanism of 2D biomaterials aiding their design with improved functionalities. Finally, taking the bench-to-bedside as a focus, we conclude this review by proposing the current crucial issues/challenges and presenting the future development directions to advance the clinical translation of these emerging 2D biomaterials.

Detection of Circulating Serum Protein Biomarkers of Non-Muscle Invasive Bladder Cancer after Protein Corona-Silver Nanoparticles Analysis by SWATH-MS

Because cystoscopy is expensive and invasive, a new method of detecting non-invasive muscular bladder cancer (NMIBC) is needed. This study aims to identify potential serum protein markers for NMIBC to improve diagnosis and to find treatment approaches that avoid disease progression to a life-threatening phenotype (muscle-invasive bladder cancer, MIBC). Here, silver nanoparticles (AgNPs, 9.73 ± 1.70 nm) as a scavenging device together with sequential window acquisition of all theoretical mass spectra (SWATH-MS) were used to quantitatively analyze the blood serum protein alterations in two NMIBC subtypes, T1 and Ta, and they were compared to normal samples (HC). NMIBC’s analysis of serum samples identified three major groups of proteins, the relative content of which is different from the HC content: proteins implicated in the complement and coagulation cascade pathways and apolipoproteins. In conclusion, many biomarker proteins were identified that merit further examination to validate their useful significance and utility within the clinical management of NMIBC patients.

Complexity of the Nano-Bio Interface and the Tortuous Path of Metal Oxides in Biological Systems

Metal oxide nanoparticles (NPs) have received a great deal of attention as potential theranostic agents. Despite extensive work on a wide variety of metal oxide NPs, few chemically active metal oxide NPs have received Food and Drug Administration (FDA) clearance. The clinical translation of metal oxide NP activity, which often looks so promising in preclinical studies, has not progressed as rapidly as one might expect. The lack of FDA approval for metal oxide NPs appears to be a consequence of the complex transformation of NP chemistry as any given NP passes through multiple extra- and intracellular environments and interacts with a variety of proteins and transport processes that may degrade or transform the chemical properties of the metal oxide NP. Moreover, the translational models frequently used to study these materials do not represent the final therapeutic environment well, and studies in reduced preparations have, all too frequently, predicted fundamentally different physico-chemical properties from the biological activity observed in intact organisms. Understanding the evolving pharmacology of metal oxide NPs as they interact with biological systems is critical to establish translational test systems that effectively predict future theranostic activity.

Nanocomposite-based dual enzyme system for broad-spectrum scavenging of reactive oxygen species

A broad-spectrum reactive oxygen species (ROS)-scavenging hybrid material (CASCADE) was developed by sequential adsorption of heparin (HEP) and poly(L-lysine) (PLL) polyelectrolytes together with superoxide dismutase (SOD) and horseradish peroxidase (HRP) antioxidant enzymes on layered double hydroxide (LDH) nanoclay support. The synthetic conditions were optimized so that CASCADE possessed remarkable structural (no enzyme leakage) and colloidal (excellent resistance against salt-induced aggregation) stability. The obtained composite was active in decomposition of both superoxide radical anions and hydrogen peroxide in biochemical assays revealing that the strong electrostatic interaction with the functionalized support led to high enzyme loadings, nevertheless, it did not interfere with the native enzyme conformation. In vitro tests demonstrated that ROS generated in human cervical adenocarcinoma cells were successfully consumed by the hybrid material. The cellular uptake was not accompanied with any toxicity effects, which makes the developed CASCADE a promising candidate for treatment of oxidative stress-related diseases.

Effects of Surface Protein Adsorption on the Distribution and Retention of Intratumorally Administered Gold Nanoparticles

The heterogeneous distribution of delivery or treatment modalities within the tumor mass is a crucial limiting factor for a vast range of theranostic applications. Understanding the interactions between a nanomaterial and the tumor microenvironment will help to overcome challenges associated with tumor heterogeneity, as well as the clinical translation of nanotheranostic materials. This study aims to evaluate the influence of protein surface adsorption on gold nanoparticle (GNP) biodistribution using high-resolution computed tomography (CT) preclinical imaging in C57BL/6 mice harboring Lewis lung carcinoma (LLC) tumors. LLC provides a valuable model for study due to its highly heterogenous nature, which makes drug delivery to the tumor challenging. By controlling the adsorption of proteins on the GNP surface, we hypothesize that we can influence the intratumoral distribution pattern and particle retention. We performed an in vitro study to evaluate the uptake of GNPs by LLC cells and an in vivo study to assess and quantify the GNP biodistribution by injecting concentrated GNPs citrate-stabilized or passivated with bovine serum albumin (BSA) intratumorally into LLC solid tumors. Quantitative CT and inductively coupled plasma optical emission spectrometry (ICP-OES) results both confirm the presence of particles in the tumor 9 days post-injection (n = 8 mice/group). A significant difference is highlighted between citrate-GNP and BSA-GNP groups (** p < 0.005, Tukey's multiple comparisons test), confirming that the protein corona of GNPs modifies intratumoral distribution and retention of the particles. In conclusion, our investigations show that the surface passivation of GNPs influences the mechanism of cellular uptake and intratumoral distribution in vivo, highlighting the spatial heterogeneity of the solid tumor.

Layered double hydroxide-based antioxidant dispersions with high colloidal and functional stability

Highly stable antioxidant dispersions were designed on the basis of ring-opened ellagic acid (EA) intercalated into MgAl-layered double hydroxide (LDH) nanoparticles. The morphology of the composite was delicately modified with ethanolic washing to obtain EtOH-EA-LDH with a high specific surface area. The colloidal stability was optimized by surface functionalization with positively charged polyelectrolytes. Polyethyleneimine (PEI), protamine sulfate (PS) and poly(acrylamide-co-diallyl dimethyl ammonium chloride) (PAAm-co-DADMAC) was adsorbed onto the surface of the oppositely charged EtOH-EA-LDH leading to charge neutralization and overcharging at appropriate doses. Formation of adsorbed polyelectrolyte layers provided remarkable colloidal stability for the EtOH-EA-LDH. Modification with PEI and PAAm-co-DADMAC outstandingly improved the resistance of the particles against salt-induced aggregation with a critical coagulation concentration value above 1 M, while only limited stability was achieved by covering the nanoparticles with PS. The high antioxidant activity of EtOH-EA-LDH was greatly preserved upon polyelectrolyte coating, which was proved in the scavenging of radicals in the test reaction applied. Hence, an active antioxidant nanocomposite of high drug dose and remarkable colloidal stability was obtained to combat oxidative stress in systems of high electrolyte concentrations.

ZnAl nano layered double hydroxides for dual functional CRISPR/Cas9 delivery and enhanced green fluorescence protein biosensor

Evaluation of the effect of different parameters for designing a non-viral vector in gene delivery systems has great importance. In this manner, 2D crystals, precisely layered double hydroxides, have attracted the attention of scientists due to their significant adjustability and low-toxicity and low-cost preparation procedure. In this work, the relationship between different physicochemical properties of LDH, including pH, size, zeta potential, and synthesis procedure, was investigated and optimized for CRISPR/Cas9 delivery and reverse fluorescence response to the EGFP. In this manner, ZnAl LDH and ZnAl HMTA LDH were synthesized and characterized and applied in the HEK-293 cell line to deliver CRISPR/Cas9. The results were optimized by different characterizations as well as Gel Electrophoresis and showed acceptable binding ability with the DNA that could be considered as a promising and also new gold-standard for the delivery of CRISPR/Cas9. Also, the relationship of the presence of tertiary amines (in this case, hexamethylenetetramine (HMTA) as the templates) in the structure of the ZnAl LDH, as well as the gene delivery application, was evaluated. The results showed more than 79% of relative cell viability in most of the weight ratios of LDH to CRISPR/Cas9; fully quenching the fluorescence intensity of the EGFP/LDH in the presence of 15 µg mL-1 of the protoporphyrins along with the detection limit of below 2.1 µg mL-1, the transfection efficiency of around 33% of the GFP positive cell for ZnAl LDH and more than 38% for the ZnAl LDH in the presence of its tertiary amine template.

Anti prostate cancer therapy: Aptamer-functionalized, curcumin and cabazitaxel co-delivered, tumor targeted lipid-polymer hybrid nanoparticles

Prostate cancer (PC) is the most common type of newly diagnosed malignancy in men. Combined chemotherapy has been shown to be an effective strategy for the treatment of PC therapy. Lipid-polymer hybrid nanoparticles (LPNs) are core-shell nanoparticles composed of a polymer core and a lipid shell, which are reported to provide significant advantages for combined PC therapy. This study synthesized an aptamer conjugated ligand and designed an aptamer-functionalized, curcumin (CUR) and cabazitaxel (CTX) co-delivered LPNs (APT-CUR/CTX-LPNs). APT-CUR/CTX-LPNs had a mean size of 121.3 ± 4.2 nm and a positive surface charge (23.5 ± 2.6 mV). Both CUR and CTX were sustained released from LPNs. Aptamer-functionalized APT-CUR/CTX-LPNs exhibited good cell inhibition ability, high tumor accumulation, and remarkable tumor inhibition efficiency at the drug ratio of 2:5 (CUR:CTX). The novel LPNs offers great promise for the double drugs delivery to the prostate cancer cells and tumor xenograft in vivo, showing the potential of synergistic combination therapy for prostate cancer.

A Simple Method to Determine Critical Coagulation Concentration from Electrophoretic Mobility

Critical coagulation concentration (CCC) is a key parameter of particle dispersions, since it provides the threshold limit of electrolyte concentrations, above which the dispersions are destabilized due to rapid particle aggregation. A computational method is proposed to predict CCC values using solely electrophoretic mobility data without the need to measure aggregation rates of the particles. The model relies on the DLVO theory; contributions from repulsive double-layer forces and attractive van der Waals forces are included. Comparison between the calculated and previously reported experimental CCC data for the same particles shows that the method performs well in the presence of mono and multivalent electrolytes provided DLVO interparticle forces are dominant. The method is validated for particles of various compositions, shapes, and sizes.

A closer look into the physical interactions between lipid membranes and layered double hydroxide nanoparticles

Layered double hydroxide nanoparticles (LDH-NPs) constitute promising nanocarriers for drug and gene delivery. Although their cell internalization has been studied, the interaction between LDH-NPs and biological membrane models, such as giant unilamellar vesicles (GUVs), remains unexplored. These vesicles are widely-used membrane models that allow minimizing the complexity and uncertainty associated with biological systems to study the physical interactions in the absence of cell metabolism effects. With such an approach the physicochemical properties of the membrane can be differentiated from the biological functionalities involved in cell internalization and the membrane-mediated internalization can be directly understood. In this work, we describe for the first time the interaction of LDH-NPs with freestanding negatively charged POPC:POPS GUVs by fluorescence microscopy. The experiments were performed with fluorescein labeled LDH-NPs of about 100 nm together with different fluorophores in order to evaluate the NPs interactions with the vesicles as well as their impact on the membrane morphology and permeability. Positively charged LDH-NPs are electrostatically accumulated at the GUVs membrane, altering its lateral phospholipid distribution and increasing the stiffness and permeability of the membrane. The adsorption of albumin (LDH@ALB) or polyacrylic acid (LDH@PA) passivates the surface of LDH-NPs eliminating long-range electrostatic attraction. The absence of membrane-mediated internalization of either LDH@ALB or LDH@PA, represents an advantage in the use of LDH-NPs as drug or nucleic acids nanocarriers, because suitable functionalization will allow an optimal cell targeting.

Regulating Protein Corona Formation and Dynamic Protein Exchange by Controlling Nanoparticle Hydrophobicity

Physiochemical properties of engineered nanoparticles (NPs) play a vital role in nano-bio interactions, which are critical for nanotoxicity and nanomedicine research. To understand the effects of NP hydrophobicity on the formation of the protein corona, we synthesized four gold NPs with a continuous change in hydrophobicity ranging from -2.6 to 2.4. Hydrophobic NPs adsorbed 2.1-fold proteins compared to hydrophilic ones. Proteins with small molecular weights (<50 kDa) and negatively charge (PI < 7) constituted the majority of the protein corona, especially for hydrophobic NPs. Moreover, proteins preferred binding to hydrophilic NPs (vitronectin and antithrombin III), hydrophobic NPs (serum albumin and hemoglobin fetal subunit beta), and medium hydrophobic NPs (talin 1 and prothrombin) were identified. Besides, proteins such as apolipoprotein bound to all NPs, did not show surface preference. We also found that there was a dynamic exchange between hard protein corona and solution proteins. Because of such dynamic exchanges, protein-bound NPs could expose their surface in biological systems. Hydrophilic NPs exhibited higher protein exchange rate than hydrophobic NPs. Above understandings have improved our capabilities to modulate protein corona formation by controlling surface chemistry of NPs. These will also help modulate nanotoxicity and develop better nanomedcines.

Finely crafted quasi-core–shell gadolinium/layered double hydroxide hybrids for switching on/off bimodal CT/MRI contrasting nanodiagnostic platforms

Quasi core–shell structure of LDH platetes and Gd(OH)₃ nanorods were synthesized to control water approach to Gd(OH)₃ depending on pH.

Cyclodextrin supramolecular inclusion-enhanced pyrene excimer switching for highly selective detection of RNase H

Here, we report a novel fluorescence method for the highly selective and sensitive detection of RNase H by combining the use of a dual-pyrene-labeled DNA/RNA duplex with supramolecular inclusion-enhanced fluorescence. Initially, the probe is in the "off" state due to the rigidness of the double-stranded duplex, which separates the two pyrene units. In the presence of RNase H, the RNA strand of the DNA/RNA duplex will be hydrolyzed, and the DNA strand transforms into a hairpin structure, bringing close the two pyrene units which in turn enter the hydrophobic cavity of a γ-cyclodextrin. As a result, the pyrene excimer emission is greatly enhanced, thereby realizing the detection of RNase H activity. Under optimal conditions, RNase H detection can be achieved in the range from 0.08 to 4 U/mL, with a detection limit of 0.02 U/mL.

High and long-term antibacterial activity against Escherichia coli via synergy between the antibiotic penicillin G and its carrier ZnAl layered double hydroxide

Antibiotic-resistant bacterial infections are a global health problem. A commonly-used antibiotic Penicillin G was incorporated into ZnAl-layered double hydroxides (PNG/LDH) with a varied amount of PNG. PNG/LDH nanocomposites were well characterized in structure and composition using elemental analysis, X-ray diffraction pattern, Fourier transform infrared spectroscopy and TEM images, revealing that PNG were mostly adsorbed on the LDH surfaces at a lower PNG loading but some were intercalated into LDH interlayers at a higher PNG loading. The typical release profile of PNG and Zn²⁺ from PNG/LDH was a quick release, followed by a sustainable slow release. The antibacterial tests against Escherichia coli demonstrated that PNG/LDH with a suitable composition synergistically improved bacterial inhibition compared with free PNG and pristine LDHs. In specific, PNG/LDH with much higher cost-effectiveness showed a potent antimicrobial activity and maintained the activity for up to 10 days, significantly elongating the antibacterial effect compared with just 1 day for free PNG in the same conditions. Our results suggest suitable composition of nanoparticle carriers and antibiotics could significantly enhance antibacterial activity of antibiotics for a long period via the synergistic effect between carrier and antibiotics, a potential approach to overcome the bacterial resistance to antibiotics.

Induction of Au-methotrexate conjugates by sugar molecules: production, assembly mechanism, and bioassay studies

Au-methotrexate (Au-MTX) conjugates induced by sugar molecules were produced by a simple, one-pot, hydrothermal growth method. Herein, the Au(III)-MTX complexes were used as the precursors to form Au-MTX conjugates. Addition of different types of sugar molecules with abundant hydroxyl groups resulted in the formation of Au-MTX conjugates featuring distinct characteristics that could be explained by the diverse capping mechanisms of sugar molecules. That is, the instant-capping mechanism of glucose favored the generation of peanut-like Au-MTX conjugates with high colloidal stability while the post-capping mechanism of dextran and sucrose resulted in the production of Au-MTX conjugates featuring excellent near-infrared (NIR) optical properties with a long-wavelength plasmon resonance near 630-760 nm. Moreover, in vitro bioassays showed that cancer cell viabilities upon incubation with free MTX, Au-MTX conjugates doped with glucose, dextran and sucrose for 48 h were 74.6%, 55.0%, 62.0%, and 63.1%, respectively. Glucose-doped Au-MTX conjugates exhibited a higher anticancer activity than those doped with dextran and sucrose, therefore potentially presenting a promising treatment platform for anticancer therapy. Based on the present study, this work may provide the first example of using biocompatible sugars as regulating agents to effectively guide the shape and assembly behavior of Au-MTX conjugates. Potentially, the synergistic strategy of drug molecules and sugar molecules may offer the possibility to create more gold-based nanocarriers with new shapes and beneficial features for advanced anticancer therapy.

Impact of Anti-Biofouling Surface Coatings on the Properties of Nanomaterials and Their Biomedical Applications

Understanding and subsequently controlling non-specific interactions between engineered nanomaterials and biological environment have become increasingly important for further developing and advancing nanotechnology for biomedical applications. Such non-specific interactions, also known as the biofouling effect, mainly associate with the adsorption of biomolecules (such as proteins, DNAs, RNAs, and peptides) onto the surface of nanomaterials and the adhesion or uptake of nanomaterials by various cells. By altering the surface properties of nanomaterials the biofouling effect can lead to in situ changes of physicochemical properties, pharmacokinetics, functions, and toxicity of nanomaterials. This review provides discussions on the current understanding of the biofouling effect, the factors that affect the non-specific interactions associated with biofouling, and the impact of the biofouling effect on the performances and functions of nanomaterials. An overview of the development and applications of various anti-biofouling coating materials to preserve and improve the properties and functions of engineered nanomaterials for intended biomedical applications is also provided.

Controlling the Graphene-Bio Interface: Dispersions in Animal Sera for Enhanced Stability and Reduced Toxicity

Liquid phase exfoliation of graphite in six different animal sera and evaluation of its toxicity are reported here. Previously, we reported the exfoliation of graphene using proteins, and here we extend this approach to complex animal fluids. A kitchen blender with a high-turbulence flow gave high quality and maximum exfoliation efficiency in all sera tested, when compared to the values found with shear and ultrasonication methods. Raman spectra and electron microscopy confirmed the formation of three- or four-layer, submicrometer size graphene, independent of the serum used. Graphene prepared in serum was directly transferred to cell culture media without post-treatments. Contrary to many reports, a nanotoxicity study of this graphene fully dispersed to human embryonic kidney cells, human lung cancer cells, and nematodes (Caenorhabditis elegans) showed no acute toxicity for up to 7 days at various doses (50-500 μg/mL), but prolonged exposure at higher doses (300-500 μg/mL, 10-15 days) showed cytotoxicity to cells (∼95% death) and reproductive toxicity to C. elegans (5-10% reduction in brood size). The origin of toxicity was found to be due to the highly fragmented smaller graphene sheets (<200 nm), while the larger sheets were nontoxic (50-300 μg/mL dose). In contrast, graphene produced with sodium cholate as the mediator has been found to be cytotoxic to these cells at these dosages. We demonstrated the toxicity of liquid phase exfoliated graphene is attributed to highly fragmented fractions or nonbiocompatible exfoliating agents. Thus, low-toxicity graphene/serum suspensions are produced by a facile method in biological media, and this approach may accelerate the much-anticipated development of graphene for biological applications.

Effects of surface modification and size on oral drug delivery of mesoporous silica formulation

The surface chemistry and size of nanoparticles can greatly impact their interaction with biological pathways and alter efficacy. However, the interplay between surface modification and particle size has not been well investigated especially for oral delivery. It is necessary to maximize the bioavailability of loading therapeutics. Here, we prepared different sized mesoporous silica nanoparticles (100-500 nm) and conjugated them with polyethylenimine-coated carbondots (PCD) for effective transepithelial absorption. The nanoparticles were also coated with polyethylene glycol (PEG) polymers for improved mucus permeability. These mesoporous silica nanoparticles conjugated to PCD and coated in PEG (MSN@PCD@PEG) were used to study the influence of particle size and surface chemistry on transepithelial transport and bioavailability. Results demonstrated that the MSN@PCD@PEG with a diameter 250 nm had the highest transepithelial transport and oral bioavailability compared to other formulations. Drug release, endocytosis pathways, transepithelial transport and degradation of these different nanocarriers were systematically studied in order to investigate effects of size variety. The findings indicated that nanoparticle-based oral drug delivery can be potentially improved by adjusting physicochemical properties. We believe that understanding the importance of surface chemistry and particle size in the oral delivery will improve nanoparticle engineering and oral application.

Small size mesoporous organosilica nanorods with different aspect ratios: Synthesis and cellular uptake

In the work, small size thioether-bridged mesoporous organosilica nanorod (MONRs) are successfully synthesized using cetyltrimethylammonium bromide (CTAB) as structure-directing agent and bis[3-(triethoxysilyl)propyl]tetrasulfide (TETS) and tetraethoxysilane (TEOS) as co-precursors. The MONRs have tunable aspect ratios of 2, 3, and 4 (denoted as MONRs-2, MONRs-3, and MONRs-4), small and controllable lengths (75-310nm), high surface area (570-870cm²g^-1), uniform mesopores (2.4-2.6nm), large pore volume (0.34cm³g^-1), and excellent biocompatibility. The uptake of the MONRs by multidrug resistant human breast cancer MDR-MCF-7 cells is related to their aspect ratios. The MONRs-3 shows a faster and higher cellular internalization compared to the MONRs-4 and MONRs-2, respectively. Thanks to the high cellular uptake, doxorubicin (DOX) loaded MONRs-3 show obviously improved chemotherapeutic effect on MDR-MCF-7 cancer cells. It is expected that the MONRs provide a useful platform for drug delivery and therapeutics.

A Facile Way of Modifying Layered Double Hydroxide Nanoparticles with Targeting Ligand-Conjugated Albumin for Enhanced Delivery to Brain Tumour Cells

Active targeting of nanoparticles (NPs) for cancer treatment has attracted increasing interest in the past decades. Various ligand modification strategies have been used to enhance the targeting of NPs to the tumor site. However, how to reproducibly fabricate diverse targeting NPs with narrowly changeable biophysiochemical properties remains as a major challenge. In this study, layered double hydroxide (LDH) NPs were modified as a target delivery system. Two brain tumor targeting ligands, i.e., angiopep-2 and rabies virus glycoprotein, were conjugated to the LDH NPs via an intermatrix protein moiety, bovine serum albumin (BSA), simultaneously endowing the LDHs with excellent colloidal stability and targeting capability. The ligands were first covalently linked with BSA through the heterobifunctional cross-linker sulfosuccinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate. Then, the ligand-linked BSA and pristine BSA were together coated onto the surface of LDHs through electrostatic interaction, followed by cross-linking with the cross-linker glutaraldehyde to immobilize these BSAs on the LDH surface. In this way, we are able to readily prepare colloidally stabilized tumor-targeted LDH NPs. The targeting efficacy of the ligand-conjugated LDH delivery system has been evidenced in the uptake by two neutral cells (U87 and N2a) compared to unmodified LDHs. This new approach provides a promising strategy for rational design and preparation of target nanoparticles as a selective and effective therapeutic treatment for brain tumors.

Techniques for the experimental investigation of the protein corona

Due to its enormous relevance the corona formation of adsorbed proteins around nanoparticles is widely investigated. A comparison of different experimental techniques is given. Direct measurements of proteins, such as typically performed with mass spectrometry, will be compared with indirect analysis, in which instead information about the protein corona is gathered from changes in the properties of the nanoparticles. The type of measurement determines also whether before analysis purification from unbound excess proteins is necessary, which may change the equilibrium, or if measurements can be performed in situ without required purification. Pros and contras of the different methods will be discussed.

Layered double hydroxide bio-composites toward excellent systematic anticancer therapy

A supramolecular bio-composite with an excellent chemotherapy–PDT synergistic anticancer effect is fabricated and shows potential application in the field of cancer therapy.