Protein corona - from molecular adsorption to physiological complexity

Looking back, moving forward: protein corona of lipid nanoparticles

Lipid nanoparticles (LNPs) are commonly employed for drug delivery owing to their considerable drug-loading capacity, low toxicity, and excellent biocompatibility. Nevertheless, the formation of protein corona (PC) on their surfaces significantly influences the drug's in vivo fate (such as absorption, distribution, metabolism, and elimination) upon administration. PC denotes the phenomenon wherein one or multiple strata of proteins adhere to the external interface of nanoparticles (NPs) or microparticles within the biological milieu, encompassing ex vivo fluids (e.g., serum-containing culture media) and in vivo fluids (such as blood and tissue fluids). Hence, it is essential to claim the PC formation behaviors and mechanisms on the surface of LNPs. This overview provided a comprehensive examination of crucial aspects related to such issues, encompassing time evolution, controllability, and their subsequent impacts on LNPs. Classical studies of PC generation on the surface of LNPs were additionally integrated, and its decisive role in shaping the in vivo fate of LNPs was explored. The mechanisms underlying PC formation, including the adsorption theory and alteration theory, were introduced to delve into the formation process. Subsequently, the existing experimental outcomes were synthesized to offer insights into the research and application facets of PC, and it was concluded that the manipulation of PC held substantial promise in the realm of targeted delivery.

Protein corona formation on lipidic nanocapsules: Influence of the interfacial PEG repartition

The parameters currently used for characterization of nanoparticles, such as size and zeta potential, were not able to reflect the performance of a nanocarrier in the biological environment. Therefore, more thorough in vitro characterization is required to predict their behavior in vivo, where nanoparticles acquire a new biological identity due to interactions with biomolecules. In this present study, we performed in vitro characterization in biological fluids for lipid nanocapsules (LNCs) with varying means sizes (50 nm and 100 nm), different electrical surface charges and different Poly Ethylene Glycol (PEG) compositions. Then, different methods were applied to show the impact of the protein corona formation on LNCs. Even if all formulations attached to plasmatic proteins, a higher thickness of corona and highest protein binding was observed for certain LNC50 formulations. A better knowledge of the phenomenon of protein adsorption over NPs in the plasmatic media is a cornerstone of clinical translation. In fact, after short blood circulation time, it is not the initially designed nanoparticle but the complex nanoparticle bearing its protein corona which circulates to reach its target.

Local Environments Created by the Ligand Coating of Nanoparticles and Their Implications for Sensing and Surface Reactions

ConspectusThe ligand shells of colloidal nanoparticles (NPs) can serve different purposes. In general, they provide colloidal stability by introducing steric repulsion between NPs. In the context of biological applications, the ligand shell plays a critical role in targeting, enabling NPs to achieve specific biodistributions. However, there is also another important feature of the ligand shell of NPs, namely, the creation of a local environment differing from the bulk of the solvent in which the NPs are dispersed. It is known that charged ligand shells can attract or repel ions and change the effective charge of a NP through Debye-Hückel screening. Positively charged ions, such as H+ (or H3O+) are attracted to negatively charged surfaces, whereas negatively charged ions, such as Cl- are repelled. The distribution of the ions around charged NP surfaces is a radial function of distance from the center of the NP, which is governed by a balance of electrostatic forces and entropy of ions and ligands. As a result, the ion concentration at the NP surface is different from its bulk equilibrium concentration, i.e., the charged ligand shell around the NPs has formed a distinct local environment. This not only applies to charged ligand shells but also follows a more general principle of induced condensation and depletion. Polar/apolar ligand shells, for example, result in a locally increased concentration of polar/apolar molecules. Similar effects can be seen for biocatalysts like enzymes immobilized in nanoporous host structures, which provide a special environment due to their surface chemistry and geometrical nanoconfinement. The formation of a local environment close to the ligand shell of NPs has profound implications for NP sensing applications. As a result, analyte concentrations close to the ligand shell, which are the ones that are measured, may be very different from the analyte concentrations in bulk. Based on previous work describing this effect, it will be discussed herein how such local environments, created by the choice of used ligands, may allow for tailoring the NPs' sensing properties. In general, the ligand shell around NPs can be attractive/repulsive for molecules with distinct properties and thus forms an environment that can modulate the specific response. Such local environments can also be optimized to modulate chemical reactions close to the NP surface (for example, by size filtering within pores) or to attract specific low abundance proteins. The importance hereby is that this is based on interaction with low selectivity between the ligands and the target molecules.

Physiological determinants and plausible '6R' roadmap for clinical success of nanomedicines

Despite the promising features and aggressive research, the success of nanoparticles in clinical trials is minimal. This manuscript discusses the complex biological barriers that impede the journey of nanoparticles to the target site and the approaches used to overcome them. The '6R' framework (right route, right target, right design, right patient, right combination and right technology) is proposed to improve the clinical translation of nanomedicines. Disease-driven approach contrary to the traditional formulation-driven approach is suggested. Data-driven methods can analyze the relationships between various diseases, patient pathophysiology and the physicochemical properties of different nanomedicines, aiding in the precise selection of the most appropriate treatment options. Further research is needed to evaluate and refine these approaches to develop nanomedicines for clinical success.

The role of protein corona on nanodrugs for organ-targeting and its prospects of application

Nowadays, nanodrugs become a hotspot in the high-end medical field. They have the ability to deliver drugs to reach their destination more effectively due to their unique properties and flexible functionalization. However, the fate of nanodrugs in vivo is not the same as those presented in vitro, which indeed influenced their therapeutic efficacy in vivo. When entering the biological organism, nanodrugs will first come into contact with biological fluids and then be covered by some biomacromolecules, especially proteins. The proteins adsorbed on the surface of nanodrugs are known as protein corona (PC), which causes the loss of prospective organ-targeting abilities. Fortunately, the reasonable utilization of PC may determine the organ-targeting efficiency of systemically administered nanodrugs based on the diverse expression of receptors on cells in different organs. In addition, the nanodrugs for local administration targeting diverse lesion sites will also form unique PC, which plays an important role in the therapeutic effect of nanodrugs. This article introduced the formation of PC on the surface of nanodrugs and summarized the recent studies about the roles of diversified proteins adsorbed on nanodrugs and relevant protein for organ-targeting receptor through different administration pathways, which may deepen our understanding of the role that PC played on organ-targeting and improve the therapeutic efficacy of nanodrugs to promote their clinical translation.

The Formation of Protein Corona by Nanoplastics and Horseradish Peroxidase

In theory, nanoplastics (NPs) can adsorb biological macromolecules, such as proteins, in the surrounding environment to form protein corona (PC). In this study, we focus on amino polystyrene (PS) NPs and horseradish peroxidase (HRP) to explore the dynamic process of the formation of PS-HRP PC and their influence on PS and HRP. This work used atomic force microscopy, laser particle size and Zeta potential analyzer, and UV-vis spectrophotometer. According to the adsorption behavior of HRP to NPs, the surface morphology characteristics of NPs can be observed to change at 60 min. Meanwhile, the increase in size and hydrodynamic diameter, the decrease in Zeta potential, surface roughness and HRP activity, and the change in HRP structure attest to the PC formation. The thickness of the PC was approximately 30 nm and there are differences in the dynamic and static variations in the size of the PC. The PC formation process progresses gradually from 0 min to 240 min. Overall, the formation of PS-HRP PC is identified, and the changes in its properties are confirmed from the perspective of nanoplastics and peroxidase, which help study the effects of nanoplastics on the environment and creatures.

Toxicity mitigation and biodistribution of albumin corona coated graphene oxide and carbon nanotubes in Caenorhabditis elegans

In this work, the toxicity and biodistribution of graphene oxide (GO) and oxidized multi-walled carbon nanotubes (MWCNT) were investigated in Caenorhabditis elegans. Bovine serum albumin (BSA) was selected as a model protein to evaluate the influence of protein corona formation on materials physicochemical properties, colloidal stability, and toxicity. Biological assays were performed to assess the effects of bare and albumin corona coated materials on survival, oxidative stress, intestinal barrier permeability, growth, reproduction, and fertility. Critical alterations in topography, surface roughness and chemistry of GO and MWCNT were observed due to albumin corona formation. These modifications were associated with changes in colloidal stability of materials and prevention of their aggregation and sedimentation in nematode testing medium. Both GO and MWCNT caused damage to nematode survival, growth, reproduction, and fertility, as well as enhanced oxidative stress and permeability of the intestinal barrier. But GO was more toxic than MWCNT to C. elegans, especially at long-term assays. Albumin corona mitigated 100% of acute and chronic effects of MWCNT. In contrast, the negative effects of GO were not completely mitigated; GO inhibited 16.2% of nematode growth, 86.5% of reproduction, and 32.0% of fertility at the highest concentration evaluated (10 mg L^-1), while corona coated GO mitigated 50% and 100% of fertility and growth, respectively. Confocal Raman spectroscopy imaging was crucial to point out that bare and albumin corona coated GO and MWCNT crossed the C. elegans intestinal barrier reaching its reproductive organs. However, BSA corona protected the nematodes targeted organs from negative effects from MWCNT and blocked its translocation to other tissues, while coated GO was translocated inside the nematode affecting the functionality of crucial organs. In addition, coated MWCNT was excreted after 2 h of food resumption, whereas coated GO still accumulated in the nematode intestine. Our results demonstrate that the materials different translocation and excretion patterns in C. elegans had a relation to the impaired physiological functions of primary and secondary organs. This work is a contribution towards a better understanding of the impacts of protein corona on the toxicity of graphene oxide and carbon nanotubes; essential information for biological applications and nanosafety.

The Relevance of Physico-Chemical Properties and Protein Corona for Evaluation of Nanoparticles Immunotoxicity-In Vitro Correlation Analysis on THP-1 Macrophages

Alongside physiochemical properties (PCP), it has been suggested that the protein corona of nanoparticles (NPs) plays a crucial role in the response of immune cells to NPs. However, due to the great variety of NPs, target cells, and exposure protocols, there is still no clear relationship between PCP, protein corona composition, and the immunotoxicity of NPs. In this study, we correlated PCP and the protein corona composition of NPs to the THP-1 macrophage response, focusing on selected toxicological endpoints: cell viability, reactive oxygen species (ROS), and cytokine secretion. We analyzed seven commonly used engineered NPs (SiO2, silver, and TiO2) and magnetic NPs. We show that with the exception of silver NPs, all of the tested TiO2 types and SiO2 exhibited moderate toxicities and a transient inflammatory response that was observed as an increase in ROS, IL-8, and/or IL-1β cytokine secretion. We observed a strong correlation between the size of the NPs in media and IL-1β secretion. The induction of IL-1β secretion was completely blunted in NLR family pyrin domain containing 3 (NLRP3) knockout THP-1 cells, indicating activation of the inflammasome. The correlations analysis also implicated the association of specific NP corona proteins with the induction of cytokine secretion. This study provides new insights toward a better understanding of the relationships between PCP, protein corona, and the inflammatory response of macrophages for different engineered NPs, to which we are exposed on a daily basis.

Performance of nanoparticles for biomedical applications: The in vitro/in vivo discrepancy

Nanomedicine has a great potential to revolutionize the therapeutic landscape. However, up-to-date results obtained from in vitro experiments predict the in vivo performance of nanoparticles weakly or not at all. There is a need for in vitro experiments that better resemble the in vivo reality. As a result, animal experiments can be reduced, and potent in vivo candidates will not be missed. It is important to gain a deeper knowledge about nanoparticle characteristics in physiological environment. In this context, the protein corona plays a crucial role. Its formation process including driving forces, kinetics, and influencing factors has to be explored in more detail. There exist different methods for the investigation of the protein corona and its impact on physico-chemical and biological properties of nanoparticles, which are compiled and critically reflected in this review article. The obtained information about the protein corona can be exploited to optimize nanoparticles for in vivo application. Still the translation from in vitro to in vivo remains challenging. Functional in vitro screening under physiological conditions such as in full serum, in 3D multicellular spheroids/organoids, or under flow conditions is recommended. Innovative in vivo screening using barcoded nanoparticles can simultaneously test more than hundred samples regarding biodistribution and functional delivery within a single mouse.

Albumin-mediated “Unlocking” of supramolecular prodrug-like nanozymes toward selective imaging-guided phototherapy

An adaptive nanozyme without producing off-target toxicity has been successfully applied in phototherapy.

Targeting the Inside of Cells with Biologicals: Chemicals as a Delivery Strategy

Delivering macromolecules into the cytosol or nucleus is possible in vitro for DNA, RNA and proteins, but translation for clinical use has been limited. Therapeutic delivery of macromolecules into cells requires overcoming substantially higher barriers compared to the use of small molecule drugs or proteins in the extracellular space. Breakthroughs like DNA delivery for approved gene therapies and RNA delivery for silencing of genes (patisiran, ONPATTRO^®, Alnylam Pharmaceuticals, Cambridge, MA, USA) or for vaccination such as the RNA-based coronavirus disease 2019 (COVID-19) vaccines demonstrated the feasibility of using macromolecules inside cells for therapy. Chemical carriers are part of the reason why these novel RNA-based therapeutics possess sufficient efficacy for their clinical application. A clear advantage of synthetic chemicals as carriers for macromolecule delivery is their favourable properties with respect to production and storage compared to more bioinspired vehicles like viral vectors or more complex drugs like cellular therapies. If biologicals can be applied to intracellular targets, the druggable space is substantially broadened by circumventing the limited utility of small molecules for blocking protein–protein interactions and the limitation of protein-based drugs to the extracellular space. An in depth understanding of the macromolecular cargo types, carrier types and the cell biology of delivery is crucial for optimal application and further development of biologicals inside cells. Basic mechanistic principles of the molecular and cell biological aspects of cytosolic/nuclear delivery of macromolecules, with particular consideration of protein delivery, are reviewed here. The efficiency of macromolecule delivery and applications in research and therapy are highlighted.

SERS liquid biopsy: An emerging tool for medical diagnosis

Surface-enhanced Raman scattering (SERS) is emerging as a novel strategy for biofluid analysis. In this review, we delineate four experimental SERS protocols that are frequently used for the profiling of biofluids: 1) liquid SERS for the detection of purine metabolites; 2) iodide-modified liquid SERS for the detection of proteins; 3) dried SERS for the detection of both purine metabolites and proteins; 4) resonant Raman for the detection of carotenoids. To explain the selectivity of each experimental SERS protocol, we introduce a heuristic model for the chemisorption of analytes mediated by adsorbed ions (adions) onto the SERS substrate. Next, we show that the promising results of SERS liquid biopsy stem from the fact that the concentration levels of purine metabolites, proteins and carotenoids are informative of the cellular turnover rate, inflammation, and oxidative stress, respectively. These processes are perturbed in virtually every disease, from cancer to autoimmune maladies. Finally, we review recent SERS liquid biopsy studies and discuss future steps that are required for translating SERS in the clinical setting.

In vivo Cell Tracking Using Non-invasive Imaging of Iron Oxide-Based Particles with Particular Relevance for Stem Cell-Based Treatments of Neurological and Cardiac Disease

Stem cell-based therapeutics is a rapidly developing field associated with a number of clinical challenges. One such challenge lies in the implementation of methods to track stem cells and stem cell-derived cells in experimental animal models and in the living patient. Here, we provide an overview of cell tracking in the context of cardiac and neurological disease, focusing on the use of iron oxide-based particles (IOPs) visualized in vivo using magnetic resonance imaging (MRI). We discuss the types of IOPs available for such tracking, their advantages and limitations, approaches for labeling cells with IOPs, biological interactions and effects of IOPs at the molecular and cellular levels, and MRI-based and associated approaches for in vivo and histological visualization. We conclude with reviews of the literature on IOP-based cell tracking in cardiac and neurological disease, covering both preclinical and clinical studies.

Cytotoxicity, Accumulation and Translocation of Silver and Silver Sulfide Nanoparticles in contact with Rainbow Trout Intestinal Cells

Silver nanoparticles (Ag NPs) are widely used in consumer products especially because of their antimicrobial properties. However, this wide usage of Ag NPs is accompanied by their release into the environment where they will be rapidly transformed to other silver species - especially silver sulfide (Ag₂S). In the present study, we synthesized Ag NPs and sulfidized them to obtain a core-shell system Ag@Ag₂S NPs. Both types of particles form stable dispersions with hydrodynamic diameters of less than 100 nm when diluted in water, but tend to form micrometer-sized agglomerates in biological exposure media. Application of Ag and Ag@Ag₂S NPs to rainbow trout intestinal cells (RTgutGC) resulted in a concentration-dependent cytotoxicity for both types of particles, as assessed by a three-endpoint assay for metabolic activity, membrane integrity and lysosomal integrity. The Ag NPs were shown to be slightly more toxic than the Ag@Ag₂S NPs. Adding Ag or Ag@Ag₂S NPs to RTgutGC cells, grown on a permeable membrane to mimic the intestinal barrier, revealed considerable accumulation of silver for both types of particles. Indeed, the cells significantly attenuated the NP translocation, allowing only a fraction of the metal to translocate across the intestinal epithelium. These findings support the notion that the intestine constitutes an important sink for Ag NPs and that, despite the reduced cytotoxicity of a sulfidized NP form, the particles can enter fish where they may constitute a long-term source for silver ion release and cytotoxicity.

Cross-Species Comparisons of Nanoparticle Interactions with Innate Immune Systems: A Methodological Review

Many components of the innate immune system are evolutionarily conserved and shared across many living organisms, from plants and invertebrates to humans. Therefore, these shared features can allow the comparative study of potentially dangerous substances, such as engineered nanoparticles (NPs). However, differences of methodology and procedure between diverse species and models make comparison of innate immune responses to NPs between organisms difficult in many cases. To this aim, this review provides an overview of suitable methods and assays that can be used to measure NP immune interactions across species in a multidisciplinary approach. The first part of this review describes the main innate immune defense characteristics of the selected models that can be associated to NPs exposure. In the second part, the different modes of exposure to NPs across models (considering isolated cells or whole organisms) and the main endpoints measured are discussed. In this synergistic perspective, we provide an overview of the current state of important cross-disciplinary immunological models to study NP-immune interactions and identify future research needs. As such, this paper could be used as a methodological reference point for future nano-immunosafety studies.

Nanoparticle-Mediated Angiotensin-(1-9) Drug Delivery for the Treatment of Cardiac Hypertrophy

Ang-(1-9) peptide is a bioactive vasodilator peptide that prevents cardiomyocyte hypertrophy in vitro and in vivo as well as lowers blood pressure and pathological cardiovascular remodeling; however, it has a reduced half-life in circulation, requiring a suitable carrier for its delivery. In this work, hybrid nanoparticles composed of polymeric nanoparticles (pNPs) based on Eudragit^® E/Alginate (EE/Alg), and gold nanospheres (AuNS), were developed to evaluate their encapsulation capacity and release of Ang-(1-9) under different experimental conditions. Hybrid pNPs were characterized by dynamic light scattering, zeta potential, transmission and scanning electron microscopy, size distribution, and concentration by nanoparticle tracking analysis. Nanometric pNPs, with good polydispersity index and colloidally stable, produced high association efficiency of Ang-(1-9) and controlled release. Finally, the treatment of neonatal cardiomyocytes in culture with EE/Alg/AuNS 2% + Ang-(1-9) 20% pNPs decreased the area and perimeter, demonstrating efficacy in preventing norepinephrine-induced cardiomyocyte hypertrophy. On the other hand, the incorporation of AuNS did not cause negative effects either on the cytotoxicity or on the association capacity of Ang-(1-9), suggesting that the hybrid carrier EE/Alg/AuNS pNPs could be used for the delivery of Ang-(1-9) in the treatment of cardiovascular hypertrophy.

Protein corona precoating on redox-responsive chitosan-based nano-carriers for improving the therapeutic effect of nucleic acid drugs

Spontaneous formation of protein corona on chitosan-based nano-carriers is inevitable once they enter the blood, which is considered to be an important factor that weakens the delivery efficiency and therapeutic effect of nucleic acid drugs. For this, cyclic RGDyK peptide (cRGD) modified bovine serum albumin (BSA) was designed as a corona to precoat on redox-responsive chitosan-based nano-carriers (TsR NPs) before administration. The effects of the precoating corona on the pharmaceutical properties and delivery efficiency of the nano-carriers and the therapeutic effect of model siRNA (siVEGF) were investigated. The results showed that BSA-cRGD formed steady corona around TsR NPs, which enhanced targeting ability to cancer cells and reduced serum proteins adsorption. The Bc corona improved the stability and biocompatibility of TsR NPs, increased the intracellular uptake, facilitated the lysosomal escape and maintained their redox-sensitive responsiveness, resulting in enhanced gene silencing efficiency and anti-tumor proliferation effects both in vitro and in vivo.

Research progress and application opportunities of nanoparticle-protein corona complexes

Nanoparticles (NPs) can be used to design for nanomedicines with different chemical surface properties owing to their size advantages and the capacity of specific delivery to targeted sites in organisms. The discovery of the presence of protein corona (PC) has changed our classical view of NPs, stimulating researchers to investigate the in vivo fate of NPs as they enter biological systems. Both NPs and PC have their specificity but complement each other, so they should be considered as a whole. The formation and characterization of NP-PC complexes provide new insights into the design, functionalization, and application of nanocarriers. Based on progress of recent researches, we reviewed the formation, characterization, and composition of the PC, and introduced those critical factors influencing PC, simultaneously expound the effect of PC on the biological function of NPs. Especially we put forward the opportunities and challenges when NP-PC as a novel nano-drug carrier for targeted applications. Furthermore, we discussed the pros versus cons of the PC, as well as how to make better PC in the future application of NPs.

In vivo protein corona on nanoparticles: does the control of all material parameters orient the biological behavior?

Nanomaterials have a huge potential in research fields from nanomedicine to medical devices. However, surface modifications of nanoparticles (NPs) and thus of their physicochemical properties failed to predict their biological behavior. This requires investigating the "missing link" at the nano-bio interface. The protein corona (PC), the set of proteins binding to the NPs surface, plays a critical role in particle recognition by the innate immune system. Still, in vitro incubation offers a limited understanding of biological interactions and fails to explain the in vivo fate. To date, several reports explained the impact of PC in vitro but its applications in the clinical field have been very limited. Furthermore, PC is often considered as a biological barrier reducing the targeting efficiency of nano vehicles. But the protein binding can actually be controlled by altering PC both in vitro and in vivo. Analyzing PC in vivo could accordingly provide a deep understanding of its biological effect and speed up the transfer to clinical applications. This review demonstrates the need for clarifications on the effect of PC in vivo and the control of its behavior by changing its physicochemical properties. It unfolds the recent in vivo developments to understand mechanisms and challenges at the nano-bio interface. Finally, it reports recent advances in the in vivo PC to overcome and control the limitations of the in vitro PC by employing PC as a boosting resource to prolong the NPs half-life, to improve their formulations and thereby to increase its use for biomedical applications.

Current understanding of biological identity at the nanoscale and future prospects

Nanoscale objects are processed by living organisms using highly evolved and sophisticated endogenous cellular networks, specifically designed to manage objects of this size. While these processes potentially allow nanostructures unique access to and control over key biological machineries, they are also highly protected by cell or host defence mechanisms at all levels. A thorough understanding of bionanoscale recognition events, including the molecules involved in the cell recognition machinery, the nature of information transferred during recognition processes and the coupled downstream cellular processing, would allow us to achieve a qualitatively novel form of biological control and advanced therapeutics. Here we discuss evolving fundamental microscopic and mechanistic understanding of biological nanoscale recognition. We consider the interface between a nanostructure and a target cell membrane, outlining the categories of nanostructure properties that are recognized, and the associated nanoscale signal transduction and cellular programming mechanisms that constitute biological recognition.

Optimizing pDNA Lipo-polyplexes: A Balancing Act between Stability and Cargo Release

When optimizing nanocarriers, structural motifs that are beneficial for the respective type of cargo need to be identified. Here, succinoyl tetraethylene pentamine (Stp)-based lipo-oligoaminoamides (OAAs) were optimized for the delivery of plasmid DNA (pDNA). Structural variations comprised saturated fatty acids with chain lengths between C2 and C18 and terminal cysteines as units promoting nanoparticle stabilization, histidines for endosomal buffering, and disulfide building blocks for redox-sensitive release. Biophysical and tumor cell culture screening established clear-cut relationships between lipo-OAAs and characteristics of the formed pDNA complexes. Based on the optimized alternating Stp-histidine backbones, lipo-OAAs containing fatty acids with chain lengths around C6 to C10 displayed maximum gene transfer with around 500-fold higher gene expression than that of C18 lipo-OAA analogues. Promising lipo-OAAs, however, showed only moderate in vivo efficiency. In vitro testing in 90% full serum, revealing considerable inhibition of lytic and gene-transfer activity, was found as a new screening model predictive for intravenous applications in vivo.

Brij-stabilized zein nanoparticles as potential drug carriers

The current study was designed to provide a preliminary physico-chemical characterization of zein nanosystems prepared with various Brij surfactants (for the first time to the best of our knowledge) as a function of various external stimuli such as temperature, pH, serum incubation and the freeze-drying process. The results demonstrate that when Brijs are characterized by unsaturation (C18), considerable stabilization of the colloidal structure is promoted while the length of the polyethylene glycol fraction does not significantly modulate the physico-chemical properties of the nanosystems. Specifically, dynamic light scattering and nanoparticle tracking analysis demonstrated that the use of 0.2 % w/v of Brij O10 promoted the formation of stable zein nanosystems with mean sizes of ∼150 nm and a narrow size distribution, preserving their structures at various pHs and temperatures. The use of mannitol as cryoprotectant resulted in a formulation that can easily be re-suspended in water after the freeze-drying process. This nanoformulation demonstrated that it efficiently retained different amounts of both hydrophilic and lipophilic compounds and showed a prolonged release of the entrapped molecules. In addition, the nanosystems showed a favorable degree of in vitro safety on various cell lines when a concentration <50 μg/mL of protein was used, demonstrating the potential application of Brij O10-stabilized zein nanoparticles as innovative nanocarriers of several active compounds.

Influence of oscillating main flow on separation efficiency in asymmetrical flow field-flow fractionation

The steadily rising interest in the investigation of interactions between nanomaterials and biological media has also led to an increasing interest in asymmetrical flow field-flow fractionation (AF-FFF). The biggest strength of AF-FFF is the possibility to alter the flow profiles to suit a specific separation problem. In this paper, the influence of an oscillating main flow on the separation efficiency of AF-FFF is investigated. Such oscillations can e.g. be caused by the main pump To investigate the influence of such flow conditions on the separation efficiency in AF-FFF systematically, different oscillation profiles were applied and their influence on the elution profile and the retention times was observed. It could be shown, that the separation mechanism is extremely robust and a fractionation is still possible even under unfavorable conditions.

Dynamics of Human Serum Albumin Corona Formation on Gold Nanorods with Different Surface Ligands In Silico

The interaction between human serum albumin (HSA) and nanoparticles (NPs) to form HSA corona has widely been studied since endogenous functions of albumin are highly attractive for drug delivery. However, a full understanding of the molecular dynamics and factors behind the formation of HSA corona, including interactions between HSA and different surface ligands and between neighboring HSA molecules, resulting in conformational change of HSA is presently lacking. Here, we assembled 14 HSA molecules around gold nanorods (AuNRs) with different surface chemistries (bare gold surface, cetyltrimethylammonium bromide (CTAB), polystyrene sulfonate (PSS), and polydiallyldimethylammonium chloride (PDADMAC)) in silico and examined the dynamics of HSA corona formation using coarse-grained molecular dynamics for 300 ns of simulation. We observed that PDADMAC, being more flexible than PSS, resulted in all HSA molecules moving toward AuNR-PDADMAC, while the instability of CTAB on AuNR resulted in fewer HSA molecules moving toward AuNR-CTAB compared to AuNR-PSS. HSA molecules around AuNR-PDADMAC also exhibited the largest conformational change in terms of their radius of gyration (R_g) and root mean square deviation (RMSD). In the absence of surface ligands, HSA molecules around the bare AuNR were susceptible to steric hindrance with conformational change observed in terms of their RMSD but not their R_g unlike that of HSA molecules around AuNR-PDADMAC. The insights gained from the inclusion of neighboring HSA molecules in the simulation of corona formation could be more representative than examining a single adsorbed HSA molecule on AuNRs with different surface passivations.

Biostimulation and toxicity: The magnitude of the impact of nanomaterials in microorganisms and plants

Background

Biostimulation and toxicity constitute the continuous response spectrum of a biological organism against physicochemical or biological factors. Among the environmental agents capable of inducing biostimulation or toxicity are nanomaterials. On the < 100 nm scale, nanomaterials impose both physical effects resulting from the core’s and corona’s surface properties, and chemical effects related to the core’s composition and the corona’s functional groups.

Aim of Review

The purpose of this review is to describe the impact of nanomaterials on microorganisms and plants, considering two of the most studied physical and chemical properties: size and concentration.

Key Scientific Concepts of Review

Using a graphical analysis, the presence of a continuous biostimulation-toxicity spectrum is shown considering different biological responses. In microorganisms, the results showed high susceptibility to nanomaterials. Simultaneously, in plants, a hormetic response was found related to nanomaterials concentration and, in a few cases, a positive response in the smaller nanomaterials when these were applied at a higher level. With the above, it is concluded that: (1) microorganisms are more susceptible to nanomaterials than plants, (2) practically all nanomaterials seem to induce responses from biostimulation to toxicity in plants, and (3) the kind of response observed will depend in a complex way on the nanomateriaĺs physical and chemical characteristics, of the biological species with which they interact, and of the form and route of application and on the nature of the medium -soil, soil pore water, and biological surfaces- where the interaction occurs.

Observation of interaction forces by investigation of the influence of eluent additives on the retention behavior of aqueous nanoparticle dispersions in asymmetrical flow field-flow fractionation

The investigation and subsequent understanding of the interactions of nanomaterials with components of their surrounding media is important to be able to evaluate both potential use cases as well as potential risks for human health and for the environment. To investigate such interactions, asymmetrical flow field-flow fractionation (AF4) is an interesting analytical tool. This statement grounds on the fact that interactions of the analyte with the membrane and with components of the eluent are crucial for the retention behavior of the analyte within the field-flow fractionation (FFF) channel. Therefore, the investigation of the retention behavior provides an insight in the nature of the interactions between analyte, membrane and eluent. Within this publication, the influence of the composition of the eluent on the retention behavior of aqueous dispersions of two model analytes is investigated. Eluents with different types of salts and surfactants and eluents with different salt concentrations were prepared and the influence of the composition of these eluents on the retention behavior of polystyrene and polyorganosiloxane particles was compared. Three main trends were observed: Elution times increase with increasing electrolyte concentration; when comparing different electrolyte anions, the retention time increases the more kosmotropic the anion is; when comparing different electrolyte cations, the retention order depends on the surfactant. Additional dynamic light scattering (DLS) measurements were conducted to verify that the differences in retention times are not caused by actual differences in particle size. Instead, the differences in elution time can be correlated with the concentration and with the chao-/kosmotropicity of the added electrolyte ions. Therefore, AF4 proves to be sensitive to subtile changes of interaction forces on the level of Coulomb and van der Waals forces. The experimentally gathered elution times were used to develop a model describing the retention behavior, based on an enhanced version of the standard AF4 model: By introducing particle-medium-membrane interactions in the standard AF4 model via the respective Hamaker constants, the calculation of retention times was possible. The congruence of the calculated with the experimental retention times confirmed the validity of the simulation.

Research on nanoparticles in human perfused placenta: State of the art and perspectives

Increasing human exposure to nanoparticles (NPs) from various sources raises concerns for public health, especially for vulnerable risk groups like pregnant women and their developing fetuses. However, nanomedicine and the prospect of creating safe and effective NP-based formulations of drugs hold great promise to revolutionize treatment during pregnancy. With maternal and fetal health at stake, risks and opportunities of NPs in pregnancy need to be carefully investigated. Importantly, a comprehensive understanding of NP transport and effects at the placenta is urgently needed considering the central position of the placenta at the maternal-fetal interface and its many essential functions to enable successful pregnancy. The perfusion of human placental tissue provides a great opportunity to achieve predictive human relevant insights, circumventing uncertainties due to considerable differences in placental structure and function across species. Here, we have reviewed the current literature on the ex vivo human placenta perfusion of NPs. From 16 available studies, it was evident that placental uptake and transfer of NPs are highly dependent on their characteristics like size and surface modifications, which is in line with previous observations from in vitro and animal transport studies. These studies further revealed that special considerations apply for the perfusion of NPs and we identified relevant controls that should be implemented in future perfusion studies. While current studies mostly focused on placental transfer of NPs to conclude on potential fetal exposure, the ex vivo placental perfusion model has considerable potential to reveal novel insights on NP effects on placental tissue functionality and signaling that could indirectly affect maternal-fetal health.

Protein corona, understanding the nanoparticle-protein interactions and future perspectives: A critical review

Proteins are biopolymers of highly varied structures taking part in almost all processes occurring in living cells. When nanoparticles (NPs) interact with proteins in biological environments, they are surrounded by a layer of biomolecules, mainly proteins adsorbing to the surfaces. This protein rich layer formed around NPs is called the "protein corona". Consequential interactions between NPs and proteins are governed due to the characteristics of the corona. The features of NPs such as the size, surface chemistry, charge are the critical factors influencing the behavior of protein corona. Molecular properties and protein corona composition affect the cellular uptake of NPs. Understanding and analyzing protein corona formation in relation to protein-NP properties, and elucidating its biological implications play an important role in bio-related nano-research studies. Protein-NP interactions have been studied extensively for the purpose of investigating the potential use of NPs as carriers in drug delivery systems. Further study should focus on exploring the effects of various characteristic parameters, such as the particle size, modifier type, temperature, pH on protein-NP interactions, providing toxicity information of novel NPs. In this contribution, important aspects related to protein corona forming, influential factors, novel findings and future perspectives on protein-NP interactions are overviewed.

Boosting nanotoxicity to combat multidrug-resistant bacteria in pathophysiological environments

Nanomaterials are promising novel antibiotics, but often ineffective. We found that nanomaterial-bacteria complex formation occurred with various nanomaterials. The bactericidal activity of NMs strongly depends on their physical binding to (multidrug-resistant) bacteria. Nanomaterials' binding and antibiotic effect was reduced by various pathophysiological biomolecule coronas strongly inhibiting their antibiotic effects. We show from analytical to in vitro to in vivo that nanomaterial-based killing could be restored by acidic pH treatments. Here, complex formation of negatively-charged, plasma corona-covered, nanomaterials with bacteria was electrostatically enhanced by reducing bacteria's negative surface charge. Employing in vivo skin infection models, acidic pH-induced complex formation was critical to counteract Staphylococcus aureus infections by silver nanomaterials. We explain why nano-antibiotics show reduced activity and provide a clinically practical solution.

A review of the current understanding of nanoparticles protein corona composition

Upon entering into the biological environments, the surface of the nanoparticles is immediately coated with proteins and form the so-called a protein corona due to which a nanoparticle changes its “synthetic” identity to a new “biological” identity. Different types of nanoparticles have different protein binding profiles, which is why they have different protein corona composition and therefore it cannot be said that there is a universal protein corona. The composition and amount of protein in the corona depends on the physical and chemical characteristics of the nanoparticles, the type of biological medium and the exposure time. Protein corona increases the diameter but also changes the composition of the surface of the nanoparticles and these changes affect biodistribution, efficacy, and toxicity of the nanoparticles.

Engineering Strategies for Lymph Node Targeted Immune Activation

Development of vaccine technology that induces long lasting and potent adaptive immune responses is of vital importance to combat emerging pathogens and to design the next generation of cancer immunotherapies. Advanced biomaterials such as nanoparticle carriers are intensively explored to increase the efficacy and safety of vaccines and immunotherapies, based on their intrinsic potential to focus the therapeutic payload onto the relevant immune cells and to limit systemic distribution. With adaptive immune responses being primarily initiated in lymph nodes, the potency of nanoparticle vaccines in turn is tightly linked to their capacity to reach and accumulate in the lymph nodes draining the immunization site. Here, we discuss the main strategies applied to increase nanoparticle delivery to lymph nodes: (1) direct lymph node injection, (2) active cell-mediated transport through targeting of peripheral dendritic cells, and (3) exploiting passive transport through the afferent lymphatics.The intralymph nodal injection is obviously the most direct way for nanoparticles to reach lymph nodes, and multiple studies have demonstrated its capability in enhancing immunostimulant drugs' immune activation and increasing the therapeutic window. However, the requirement of using ultrasound guidance for mapping lymph nodes in patients renders intranodal administration unsuited for mass vaccination campaigns. As lymph nodes are fine structured organs with lymphocytes and chemokine gradients arrayed in a highly ordered fashion, the breakdown of such formats by the intralymph nodal injection is another concern. The exploitation of dendritic cells as live vectors for transporting nanoparticles to lymph nodes has intensively been studied both ex vivo and in vivo. While ex vivo engineering of dendritic cells in theory can achieve 100% dendritic cell-specific selectivity, a scenario impossible to be achieved in vivo, this procedure is usually laborious and complicated and entails the participation of professional staff and equipment. In addition, the poor efficiency of dendritic cell migration to the draining lymph node is another significant limitation following the injection of ex vivo cultured dendritic cells. Thus, in vivo targeting of surface receptors, particularly C-type lectin receptors, on dendritic cells by conjugating nanoparticles with antibodies or ligands is intensively studied by both academia and industry. Although such nanoparticles in vivo still face nonspecific engulfment by various phagocytes, multiple studies have shown its feasibility in targeting dendritic cells with high selectivity. Moreover, through optimizing the physicochemical properties of nanoparticles, nanoparticles can passively drain to lymph nodes carried by the interstitial flow. Compared to dendritic cell-mediated transport, passive draining is much faster and of higher efficiency. Of all such properties, size is the most important parameter as large particles (>500 nm) can only reach lymph nodes by an active cell-mediated transport. Other surface properties, such as the charge and the balance of hydrophobicity-vs-hydrophilicity, strongly influence the mobility of nanoparticles in the extracellular space. In addition, albumin, a natural fatty acid transporter, has recently been demonstrated capable of binding the amphiphiles through their lipid moiety and subsequent transporting them to lymph nodes.

Gold nanoparticles-biomembrane interactions: From fundamental to simulation

Gold Nanoparticles (AuNPs) are a class of promising nanomaterial for biomedical applications ranging from bioimaging, drug delivery to phototherapy because of their biocompatibility, easily tunable size and shape, and versatile surface modifications. In recent years, the rapid development of AuNPs in nanomedicine has made it imperative to seek fundamental understanding on their nano-biointeractions to minimize adverse effects and improve targeting/imaging efficiency. In this review, we summarize the different pathways of NPs-biomembrane interactions with a focus on AuNPs, follow by an analysis on how the physiochemical properties (size, surface charge, shape, surface ligands, and hydrophobicity etc.) of AuNPs can be involved in the mechanisms of cellular uptake. Finally, some recent advances on simulation modelling of AuNPs-biomembrane interactions and a brief outlook in the field are discussed.

A Protein Corona Adsorbed to a Bacterial Magnetosome Affects Its Cellular Uptake

Purpose

It is well known that when exposed to human blood plasma, nanoparticles are predominantly coated by a layer of proteins, forming a corona that will mediate the subsequent cell interactions. Magnetosomes are protein-rich membrane nanoparticles which are synthesized by magnetic bacteria; these have gained a lot of attention owing to their unique magnetic and biochemical characteristics. Nevertheless, whether bacterial magnetosomes have a corona after interacting with the plasma, and how such a corona affects nanoparticle–cell interactions is yet to be elucidated. The aim of this study was to characterize corona formation around a bacterial magnetosome and to assess the functional consequences.

Methods

Magnetosomes were isolated from the magnetotactic bacteria, M. gryphiswaldense (MSR-1). Size, morphology, and zeta potential were measured by transmission electron microscopy and dynamic light scattering. A quantitative characterization of plasma corona proteins was performed using LC-MS/MS. Protein absorption was further examined by circular dichroism and the effect of the corona on cellular uptake was investigated by microscopy and spectroscopy.

Results

Various serum proteins were found to be selectively adsorbed on the surface of the bacterial magnetosomes following plasma exposure, forming a corona. Compared to the pristine magnetosomes, the acquired corona promoted efficient cellular uptake by human vascular endothelial cells. Using a protein-interaction prediction method, we identified cell surface receptors that could potentially associate with abundant corona components. Of these, one abundant corona protein, ApoE, may be responsible for internalization of the magnetosome-corona complex through LDL receptor-mediated internalization.

Conclusion

Our findings provide clues as to the physiological response to magnetosomes and also reveal the corona composition of this membrane-coated nanomaterial after exposure to blood plasma.

Nano Meets Micro-Translational Nanotechnology in Medicine: Nano-Based Applications for Early Tumor Detection and Therapy

Nanomaterials have great potential for the prevention and treatment of cancer. Circulating tumor cells (CTCs) are cancer cells of solid tumor origin entering the peripheral blood after detachment from a primary tumor. The occurrence and circulation of CTCs are accepted as a prerequisite for the formation of metastases, which is the major cause of cancer-associated deaths. Due to their clinical significance CTCs are intensively discussed to be used as liquid biopsy for early diagnosis and prognosis of cancer. However, there are substantial challenges for the clinical use of CTCs based on their extreme rarity and heterogeneous biology. Therefore, methods for effective isolation and detection of CTCs are urgently needed. With the rapid development of nanotechnology and its wide applications in the biomedical field, researchers have designed various nano-sized systems with the capability of CTCs detection, isolation, and CTCs-targeted cancer therapy. In the present review, we summarize the underlying mechanisms of CTC-associated tumor metastasis, and give detailed information about the unique properties of CTCs that can be harnessed for their effective analytical detection and enrichment. Furthermore, we want to give an overview of representative nano-systems for CTC isolation, and highlight recent achievements in microfluidics and lab-on-a-chip technologies. We also emphasize the recent advances in nano-based CTCs-targeted cancer therapy. We conclude by critically discussing recent CTC-based nano-systems with high therapeutic and diagnostic potential as well as their biocompatibility as a practical example of applied nanotechnology.

Toxicity mechanisms of selected engineered nanoparticles on human neural cells in vitro

Environmental exposure to nanoparticles (NPs) has significantly increased in the last decades, mostly due to increased environmental pollution and frequent use of NP containing consumer products. Such NPs may enter our body and cause various health-related problems. The brain is a particularly problematic accumulation site due to its physiological and anatomical restrictions. Several mechanisms of NP neurotoxicity have already been identified, however not enough is known especially regarding toxicity of engineered/industrial NPs. The focus of this in vitro study was on analysis of neurotoxicity of different engineered NPs, with which we come into contact in our daily lives; SiO₂ NPs, food grade (FG) TiO₂ NPs, TiO₂ P25 and silver NPs as examples of industrial NPs, and polyacrylic acid (PAA) coated cobalt ferrite NPs as an example of biomedical NPs. All short term exposure experiments (24-72 h) were performed on SH-SY5Y human neuroblastoma cell line in vitro using higher (25-50 μg/ml) as well as lower (2-10 μg/ml), concentrations that are more relevant for in vivo NPs exposure. We show that NPs can cause neurotoxicity through different mechanisms, such as membrane damage, cell cycle interference, ROS formation and accumulation of autophagosomes, depending on their physico-chemical properties and stability in physiological media. Low, in vivo achievable concentrations of NPs induced only minor or no changes in vitro, however prolonged exposure and accumulation in vivo could negatively affect the cells. This was also shown in case of autophagy dysfunction for TiO₂ P25 NPs and decrease of cell viability for TiO₂ FG NPs, which were only evident after 72 h of incubation.

Understanding the relevance of protein corona in nanoparticle-based therapeutics and diagnostics

Over the past few decades, nanoparticle-based therapeutic and diagnostic systems have gained immense recognition. A relative improvement in the status of the global cancer burden has been successful due to the advent of nanoparticle-based formulations. However, exposure of nanoparticles (NPs) to a real-time biological media alters its native identity due to the formation of the biomolecular corona. Such biological interactions hinder the efficiency of the NPs system. The parameters that govern such intricate interaction are generally overlooked while designing nano drugs and delivery systems (nano-DDS). Fabricating nano-DDS with prolonged circulation time, enhanced drug-loading, and release capacity along with efficient clearance, remain the primary concerns associated with cancer therapeutics. This present review firstly aims to summarize the critical aspects that influence protein coronation on therapeutic nanoparticles designed for anti-cancer therapy. The role of protein corona in modifying the overall pharmacodynamics of the nanoparticle-based DDS has been discussed. Further, the studies and patents that extend the concept of protein corona into diagnostics have been elaborated. An understanding of the pros and cons associated with protein coronation would not only help us gain better insights into the fabrication of effective anti-cancer drug-delivery systems but also improve the shortcomings related to the clinical translation of these nanotherapeutics.

Protein corona and its applications.

Proteomic investigation on bio-corona of Au, Ag and Fe nanoparticles for the discovery of triple negative breast cancer serum protein biomarkers

Nowadays, there are no targeted therapeutic modalities for triple negative breast cancer (TNBC). This disease is associated with poor prognosis and worst clinical outcome because of the aggressive nature of the tumor, delayed diagnosis, and non-specific symptoms in the early stages. Therefore, identification of novel specific TNBC serum biomarkers for screening and therapeutic purposes remains an urgent clinical requirement. New user-friendly and cheap methods for biomarker identification are needed, and nanotechnology offers new opportunities. When dispersed in blood, nanoparticles (NPs) are covered by a protein shell termed "protein corona" (PC). While alterations in protein patterns are challeging to detect by conventional blood analyses, PC acts as a "nano-concentrator" of serum proteins with affinity for NPs' surface. So, the characterization of PC could allow the detection of otherwise undetectable changes in protein concentration at an early stage of the disease or after chemotherapy or surgery. To explore this research idea, serum samples from 8 triple negative breast cancer (TNBC) patients and 8 patients without malignancy were allowed to interact with gold nanoparticles (AuNPs: 10.02 ± 0.91 nm), silver nanoparticles (AgNPs: 9.73 ± 1.70 nm) and magnetic nanoparticles (MNPs: (9.30 ± 0.67 nm). Here, in order to identify biomarker candidates in serum of TNBC patients, these nanomaterials were combined with electrophoretic separation (SDS-PAGE) to performed qualitative and quantitative comparisons of the serum proteomes of TNBC patients (n = 8) and healthy controls (n = 8) by liquid chromatography tandem-mass spectrometry (LC-MS/MS) analysis. The results were validated through a sequential window acquisition of all theoretical mass spectra (SWATH) analysis, performed in total serum samples (patients and controls) using this approach as a multiple reaction monitoring (MRM) analysis. SIGNIFICANCE: It is well known that several proteins presented in human serum are important biomarkers for the diagnosis or prognosis of different diseases, as triple negative breast cancer (TNBC). Determining how nanomaterials as gold nanoparticles (AuNPs: 10.02 ± 0.91 nm), silver nanoparticles (AgNPs: 9.73 ± 1.70 nm) and magnetic nanoparticles (MNPs: (9.30 ± 0.67 nm) interact with human serum will assist not only in understanding their effects on the biological system (biocompability and toxicity), but also to obtain information for developing novel nanomaterials with high specificity and selectivity towards proteins with an important biological function (prognostic and diagnostic protein biomarkers).

Comprehensive In Vitro Testing of Calcium Phosphate-Based Bioceramics with Orthopedic and Dentistry Applications

Recently, a large spectrum of biomaterials emerged, with emphasis on various pure, blended, or doped calcium phosphates (CaPs). Although basic cytocompatibility testing protocols are referred by International Organization for Standardization (ISO) 10993 (parts 1-22), rigorous in vitro testing using cutting-edge technologies should be carried out in order to fully understand the behavior of various biomaterials (whether in bulk or low-dimensional object form) and to better gauge their outcome when implanted. In this review, current molecular techniques are assessed for the in-depth characterization of angiogenic potential, osteogenic capability, and the modulation of oxidative stress and inflammation properties of CaPs and their cation- and/or anion-substituted derivatives. Using such techniques, mechanisms of action of these compounds can be deciphered, highlighting the signaling pathway activation, cross-talk, and modulation by microRNA expression, which in turn can safely pave the road toward a better filtering of the truly functional, application-ready innovative therapeutic bioceramic-based solutions.

Analyzing the Interaction between Two Different Types of Nanoparticles and Serum Albumin

Two different types of nanoparticles (silicon dioxide and titanium dioxide) were selected within this study in order to analyze the interaction with bovine and human serum albumin. These particles were characterized by transmission and scanning electron microscopy (TEM and SEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDXS). In addition, the hydrodynamic size and the zeta potential were measured for all these nanoparticles. The serum proteins were incubated with the nanoparticles for up to one hour, and the albumin adsorption on the particle surface was investigated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The effect induced on the secondary structure of proteins was analyzed by Fourier transform infrared spectroscopy (FTIR). The results showed that albumin adsorbed on the surface of both types of nanoparticles, but in different quantities. In addition, we noticed different changes in the structure of albumin depending on the physicochemical properties of each type of particle tested. In conclusion, our study provides a comparative analysis between the different characteristics of nanoparticles and the protein corona formed on the particle surface and effects induced on protein structure in order to direct the development of “safe-by-design” nanoparticles, as their demands for research and applications continue to increase.

A dialysis-based in vitro drug release assay to study dynamics of the drug-protein transfer of temoporfin liposomes

Today, a growing number of nanotherapeutics is utilized to deliver poorly soluble compounds using the intravenous route of administration. The drug release and the direct transfer of the active pharmaceutical ingredient to serum proteins plays an important role in bioavailability and accumulation of the drug at the target site. It is closely related to the formation of a protein corona as well as the plasma protein binding of the compound. In the present study, two in vitro drug release methods, the flow-through cell and the dispersion releaser technology, were evaluated with regards to their capability to measure a time-resolved profile of the serum protein binding. In this context, the photosensitizer temoporfin and temoporfin-loaded liposomes were tested. While in the fine capillaries of the flow-through cell a rapid agglomeration of proteins occurred, the dispersion releaser technology in combination with the four-step model enabled the measurement of the transfer of drugs from liposomes to proteins. In presence of 10% of fetal calf serum approximately 20% of the model compound temoporfin were bound to serum proteins within the first 3 h. At higher serum concentration this binding remained stable for approximately 10 h.

Quantitative biokinetics over a 28 day period of freshly generated, pristine, 20 nm titanium dioxide nanoparticle aerosols in healthy adult rats after a single two-hour inhalation exposure

Background

Industrially produced quantities of TiO₂ nanoparticles are steadily rising, leading to an increasing risk of inhalation exposure for both professionals and consumers. Particle inhalation can result in inflammatory and allergic responses, and there are concerns about other negative health effects from either acute or chronic low-dose exposure.

Results

To study the fate of inhaled TiO₂-NP, adult rats were exposed to 2-h intra-tracheal inhalations of ⁴⁸V-radiolabeled, 20 nm TiO₂-NP aerosols (deposited NP-mass 1.4 ± 0.5 μg). At five time points (1 h, 4 h, 24 h, 7d, 28d) post-exposure, a complete balance of the [⁴⁸V]TiO₂-NP fate was quantified in organs, tissues, carcass, lavage and body fluids, including excretions.

After fast mucociliary airway clearance (fractional range 0.16–0.31), long-term macrophage-mediated clearance (LT-MC) from the alveolar region is 2.6-fold higher after 28d (integral fraction 0.40 ± 0.04) than translocation across the air-blood-barrier (integral fraction 0.15 ± 0.01). A high NP fraction remains in the alveoli (0.44 ± 0.05 after 28d), half of these on the alveolar epithelium and half in interstitial spaces. There is clearance from both retention sites at fractional rates (0.02–0.03 d^− 1) by LT-MC. Prior to LT-MC, [⁴⁸V]TiO₂-NP are re-entrained to the epithelium as reported earlier for 20 nm inhaled gold-NP (AuNP) and iridium-NP (IrNP).

Conclusion

Comparing the 28-day biokinetics patterns of three different inhaled NP materials TiO₂-NP, AuNP and IrNP, the long-term kinetics of interstitial relocation and subsequent re-entrainment onto the lung-epithelium is similar for AuNP and Ir-NP but slower than for TiO₂-NP. We discuss mechanisms and pathways of NP relocation and re-entrainment versus translocation. Additionally, after 28 days the integral translocated fractions of TiO₂-NP and IrNP across the air-blood-barrier (ABB) are similar and become 0.15 while the translocated AuNP fraction is only 0.04. While NP dissolution proved negligible, translocated TiO₂-NP and IrNP are predominantly excreted in urine (~ 0.1) while the urinary AuNP excretion amounts to a fraction of only 0.01. Urinary AuNP excretion is below 0.0001 during the first week but rises tenfold thereafter suggesting delayed disagglomeration. Of note, all three NP dissolve minimally, since no ionic radio-label release was detectable. These biokinetics data of inhaled, same-sized NP suggest significant time-dependent differences of the ABB translocation and subsequent fate in the organism.

Electronic supplementary material

The online version of this article (10.1186/s12989-019-0303-7) contains supplementary material, which is available to authorized users.

Elucidating the Inability of Functionalized Nanoparticles to Cross the Blood-Brain Barrier and Target Specific Cells in Vivo

The adsorption of serum proteins on the surface of nanoparticles (NPs) delivered into a biological environment has been known to alter NP surface properties and consequently their targeting efficiency. In this paper, we use random copolymer (p(HEMA- ran-GMA))-based NPs synthesized using 2-hydroxyethyl methacrylate (HEMA) and glycidyl methacrylate (GMA). We show that serum proteins bind to the NP and that functionalization with antibodies and peptides designed to facilitate NP passage across the blood-brain barrier (BBB) to bind specific cell types is ineffective. In particular, we use systematic in vitro and in vivo analyses to demonstrate that p(HEMA- ran-GMA) NPs functionalized with HIV-1 trans-activating transcriptor peptide (known to cross the BBB) and α neural/glial antigen 2 (NG2) (known for targeting oligodendrocyte precursor cells (OPCs)), individually and in combination, do not specifically target OPCs and are unable to cross the BBB, likely due to the serum protein binding to the NPs.

Is small smarter? Nanomaterial-based detection and elimination of circulating tumor cells: current knowledge and perspectives

Circulating tumor cells (CTCs) are disseminated cancer cells. The occurrence and circulation of CTCs seem key for metastasis, still the major cause of cancer-associated deaths. As such, CTCs are investigated as predictive biomarkers. However, due to their rarity and heterogeneous biology, CTCs’ practical use has not made it into the clinical routine. Clearly, methods for the effective isolation and reliable detection of CTCs are urgently needed. With the development of nanotechnology, various nanosystems for CTC isolation and enrichment and CTC-targeted cancer therapy have been designed. Here, we summarize the relationship between CTCs and tumor metastasis, and describe CTCs’ unique properties hampering their effective enrichment. We comment on nanotechnology-based systems for CTC isolation and recent achievements in microfluidics and lab-on-a-chip technologies. We discuss recent advances in CTC-targeted cancer therapy exploiting the unique properties of nanomaterials. We conclude by introducing developments in CTC-directed nanosystems and other advanced technologies currently in (pre)clinical research.

Target Site Delivery and Residence of Nanomedicines: Application of Quantitative Systems Pharmacology

Quantitative systems pharmacology (QSP), an emerging field that entails using modeling and computation to interpret, interrogate, and integrate drug effects spanning from the molecule to the whole organism to forecast treatment outcomes, is expected to enhance the efficiency of drug development. Since late 2017, the U.S. Food and Drug Administration has advocated the use of an analogous approach of model-informed drug development. This review focuses on issues pertaining to nanosized medicines (NP) and the potential utility of QSP to determine NP delivery and residence at extracellular or intracellular targets in vivo. The kinetic processes governing NP disposition and transport, interactions with biologic matrix components, binding and internalization in cells, and intracellular trafficking are determined, sometimes jointly, by NP properties (e.g., dimension, materials, surface charge and modifications, shape, and geometry) and target tissue properties (e.g., perfusion status, vessel pore size and wall thickness, vessel and cell density, composition of extracellular matrix, and void volume fraction). These various determinants, together with the heterogeneous tissue structures and microenvironment factors in solid tumors, lead to environment-, spatial-, and time-dependent changes in NP concentrations that are difficult to predict. Adding to the complexity is the recent discovery that NP surface-coating protein corona, whose composition depends on NP properties and which undergoes continuous evolution with time and local protein environments, is yet another unpredictable variable. Examples are provided to demonstrate the potential utility of QSP-based multiscale modeling to capture the physicochemical and biologic processes in equations to enable computational studies of the key kinetic processes in cancer treatments.

Protein corona variation in nanoparticles revisited: A dynamic grouping strategy

Bio-nano interface investigation models are mainly based on the type of proteins present on corona, bio-nano interaction responses and the evaluation of final outcomes. Due to the extensive diversity in correlative models for investigation of nanoparticles biological responses, a comprehensive model considering different aspects of bio-nano interface from nanoparticles properties to protein corona fingerprints appeared to be essential and cannot be ignored. In order to minimize divergence in studies in the era of bio-nano interface and protein corona with following therapeutic implications, a useful investigation model on the basis of RADAR concept is suggested. The contents of RADAR concept consist of five modules: 1- Reshape of our strategy for synthesis of nanoparticles (NPs), 2- Application of NPs selected based on human fluid, 3- Delivery strategy of NPs selected based on target tissue, 4- Analysis of proteins present on corona using correct procedures and 5- Risk assessment and risk reduction upon the collection and analysis of results to increase drug delivery efficiency and drug efficacy. RADAR grouping strategy for revisiting protein corona phenomenon as a key of success will be discussed with respect to the current state of knowledge.

Mechanistic insights into the pH-dependent membrane peptide ATRAM

pH-responsive peptides are promising therapeutic molecules that can specifically target the plasma membrane in the acidified extracellular medium that bathes cells in tumors. We designed the acidity-triggered rational membrane (ATRAM) peptide to have a pH-responsive membrane interaction. At physiological pH, ATRAM binds to the membrane surface in a largely unstructured conformation, while in acidic conditions it inserts into lipid bilayers forming a transmembrane helix. However, the molecular mechanism ATRAM uses to target and insert into tumor cells remains poorly understood. Here, we determined that ATRAM inserts into cancer cells with a preferential membrane orientation, where the C-terminus of the peptide traverses the plasma membrane and explores the cytoplasm. Using biophysical techniques, we determined that the membrane interaction of ATRAM is contingent on the concentration of the peptide. Kinetic studies showed that membrane insertion occurs in at least three steps, where only the first step was affected by the membrane density of ATRAM. These observations, combined with membrane binding and leakage data, indicate that the interaction of ATRAM with lipid membranes is dependent on its oligomerization state. SPECT/CT imaging in mice revealed that ATRAM accumulates in the blood pool, where it has a prolonged circulation time (> 4 h). Since fast peptide clearance and degradation in circulation are major problems for clinical development, we studied the mechanism ATRAM uses to remain in the blood stream. Using binding and transfer assays, we determined that ATRAM binds reversibly to human serum albumin. We propose that ATRAM uses albumin as a carrier in the blood stream to evade clearance and proteolysis before interacting with the plasma membrane of cancer cells. We also show that ATRAM is able to be deliver liposomes to cells in a pH dependent way. Our data highlight the potential of ATRAM as a specific therapeutic agent for diseases that lead to acidic tissues, including cancer.

MWCNT interactions with protein: surface-induced changes in protein adsorption and the impact of protein corona on cellular uptake and cytotoxicity

PURPOSE

Protein adsorption onto nanoparticles in the form of protein corona, affects properties of nanomaterials and their behavior in the biological milieu. This study aims at exploring the effects of multiwalled carbon nanotubes (MWCNTs) surface chemistry on bovine serum albumin (BSA) and immunoglobulin G (IgG), including their adsorption behavior and spatial configurations, as well as the impact on cellular uptake, cytotoxicity, and cellular responses.

METHODS

Three types of MWCNTs (pristine MWCNTs, MWCNTs-COOH, and MWCNTs-PEG) were synthesized by classical chemical reduction. The size, morphology, hydrodynamic size, and zeta potential were characterized using transmission electron microscopy and dynamic light scattering. MWCNTs were exposed to BSA and IgG solutions, then the amount of MWCNT absorption was performed by bicinchoninic acid assay, and the effects were assessed by utilizing fluorescence spectroscopy, circular dichroism (CD) spectroscopy. Quantitative measurement of MWCNTs uptake with or without protein corona was performed as turbidity method. CCK assay and a microdilution method were performed to evaluate the effects of protein corona on cytotoxicity and pro-inflammatory cytokines release.

RESULTS

The BSA and IgG adsorption capacities of MWCNTs followed the order pristine MWCNTs>MWCNTs-COOH and MWCNTs-PEG. MWCNT binding can cause fluorescence quenching and conformational changes in BSA and IgG, indicating that both the physicochemical properties of MWCNTs and protein properties play critical roles in determining their adsorption behavior. Further study showed time-dependent increases in MWCNT cellular uptake and internalization. Hydrophobicity is the major factor increasing cellular uptake of pristine MWCNTs, but a protein corona enriched with dysoposnins is the main factor reducing uptake of MWCNT-COOH by RAW264.7 cells. The cytotoxicity and pro-inflammatory response related to physicochemical properties of MWCNTs, and frustrated phagocytosis is a key initiating event in the pro-inflammatory response of MWCNT-exposed macrophages.

CONCLUSION

These findings shed light on how functionalized MWCNTs interact with protein coronas and provide useful insight into the dramatic effect of protein coronas on different functionalized MWCNTs. These events affect cellular uptake and cytotoxicity, which could inform how to enhance MWCNT biocompatibility and develop approaches for managing MWCNT hazards.

Current status and future perspectives of gold nanoparticle vectors for siRNA delivery

Discovering the vast therapeutic potential of siRNA opened up new clinical research areas focussing on a number of diseases and applications; however significant problems with siRNA stability and delivery have hindered its clinical applicability. As a result, interest in the development of practical siRNA delivery systems has grown in recent years. Of the numerous siRNA delivery strategies currently on offer, gold nanoparticles (AuNPs) stand out thanks to their biocompatibility and capacity to protect siRNA against degradation; not to mention the versatility offered by their tuneable shape, size and optical properties. Herein this review provides a complete summary of the methodologies for functionalizing AuNPs with siRNA, paying singular attention to the AuNP shape, size and surface coating, since these key factors heavily influence cellular interaction, internalization and, ultimately, the efficacy of the hybrid particle. The most noteworthy hybridization strategies have been highlighted along with the most innovative and outstanding in vivo studies with a view to increasing clinical interest in the use of AuNPs as siRNA nanocarriers.