The Nature of a Hard Protein Corona Forming on Quantum Dots Exposed to Human Blood Serum

Nano-bio convergence unveiled: Systematic review on quantum dots-protein interaction, their implications, and applications

Quantum dots (QDs) are semiconductor nanocrystals (2-10 nm) with unique optical and electronic properties due to quantum confinement effects. They offer high photostability, narrow emission spectra, broad absorption spectrum, and high quantum yields, making them versatile in various applications. Due to their highly reactive surfaces, QDs can conjugate with biomolecules while being used, produced, or unintentionally released into the environment. This systematic review delves into intricate relationship between QDs and proteins, examining their interactions that influence their physicochemical properties, enzymatic activity, ligand binding affinity, and stability. The research utilized electronic databases like PubMed, WOS, and Proquest, along with manual reviews from 2013 to 2023 using relevant keywords, to identify suitable literature. After screening titles and abstracts, only articles meeting inclusion criteria were selected for full text readings. This systematic review of 395 articles identifies 125 articles meeting the inclusion criteria, categorized into five overarching themes, encompassing various mechanisms of QDs and proteins interactions, including adsorption to covalent binding, contingent on physicochemical properties of QDs. Through a meticulous analysis of existing literature, it unravels intricate nature of interaction, significant influence on nanomaterials and biological entities, and potential for synergistic applications harnessing both specific and nonspecific interactions across various fields.

Perspectives on Protein-Nanoparticle Interactions at the In Vivo Level

The distinct features of nanoparticles have provided a vast opportunity of developing new diagnosis and therapy strategies for miscellaneous diseases. Although a few nanomedicines are available in the market or in the translation stage, many important issues are still unsolved. When entering the body, nanomaterials will be quickly coated by proteins from their surroundings, forming a corona on their surface, the so-called protein corona. Studies have shown that the protein corona has many important biological implications, particularly at the in vivo level. For example, they can promote the immune system to rapidly clear these outer materials and prevent nanoparticles from playing their designed role in therapy. In this Perspective, the available techniques for characterizing protein-nanoparticle interactions are critically summarized. Effects of nanoparticle properties and environmental factors on protein corona formation, which can further regulate the in vivo fate of nanoparticles, are highlighted and discussed. Moreover, recent progress on the biomedical application of protein corona-engineered nanoparticles is introduced, and future directions for this important yet challenging research area are also briefly discussed.

Current Advances in the Biomedical Applications of Quantum Dots: Promises and Challenges

Quantum dots (QDs) are a type of nanoparticle with exceptional photobleaching-resistant fluorescence. They are highly sought after for their potential use in various optical-based biomedical applications. However, there are still concerns regarding the use of quantum dots. As such, much effort has been invested into understanding the mechanisms behind the behaviors of QDs, so as to develop safer and more biocompatible quantum dots. In this mini-review, we provide an update on the recent advancements regarding the use of QDs in various biomedical applications. In addition, we also discuss# the current challenges and limitations in the use of QDs and propose a few areas of interest for future research.

A Comparative Study of Nanobio Interaction of Zn-Doped CdTe Quantum Dots with Lactoferrin Using Different Spectroscopic Methods

In this paper, glutathione (GSH)-coated Zn-doped CdTe quantum dots (QDs) with different particle sizes were synthesized using the "reflow method", and the interaction mechanism between the two QDs and lactoferrin (LF) was investigated systemically with different spectroscopic methods. The steady-state fluorescence spectra showed that the LF formed a tight complex with the two QDs through static bursting and that the electrostatic force was the main driving force between the two LF-QDs systems. The complex generation process was found to be spontaneous (ΔG < 0) and accompanied by exothermic and increasing degrees of freedom (ΔH < 0, ΔS > 0) by using the temperature-dependent fluorescence spectroscopy. The critical transfer distance (R₀) and donor-acceptor distance (r) of the two LF-QDs systems were obtained based on the fluorescence resonance energy transfer theory. In addition, it was observed that the QDs changed the secondary and tertiary structures of LF, leading to an increase in the hydrophobicity of LF. Further, the nano-effect of orange QDs on LF is much larger than that of green QDs. The above results provide a basis for metal-doped QDs with LF in safe nano-bio applications.

Mechanistic Understanding of Protein Corona Formation around Nanoparticles: Old Puzzles and New Insights

Although a wide variety of nanoparticles (NPs) have been engineered for use as disease markers or drug delivery agents, the number of nanomedicines in clinical use has hitherto remained small. A key obstacle in nanomedicine development is the lack of a deep mechanistic understanding of NP interactions in the bio-environment. Here, the focus is on the biomolecular adsorption layer (protein corona), which quickly enshrouds a pristine NP exposed to a biofluid and modifies the way the NP interacts with the bio-environment. After a brief introduction of NPs for nanomedicine, proteins, and their mutual interactions, research aimed at addressing fundamental properties of the protein corona, specifically its mono-/multilayer structure, reversibility and irreversibility, time dependence, as well as its role in NP agglomeration, is critically reviewed. It becomes quite evident that the knowledge of the protein corona is still fragmented, and conflicting results on fundamental issues call for further mechanistic studies. The article concludes with a discussion of future research directions that should be taken to advance the understanding of the protein corona around NPs. This knowledge will provide NP developers with the predictive power to account for these interactions in the design of efficacious nanomedicines.

The impact of Zn doping on CdTe quantum dots-protein corona formation and the subsequent toxicity at the molecular and cellular level

Understanding the formation of protein corona (PC) is of vital importance for exploring the toxicity of nanoparticles and promoting their safe applications. In this study, CdTe QDs doping with 0, 1%, 5% and 10% Zn were synthesized using one-pot hydrothermal methods. Afterwards, this study explored and compared the formation of pure and Zn doped-QDs PC as well as the subsequent molecular and cellular toxicity. Result found that Zn doping regulated the toxicity of Cd-QDs by controlling their ability to adsorb serum proteins. The adsorption to Cd-QDs induced the dispersion, unfolding, secondary structural changes and the activity loss of bovine serum albumin (BSA). Among the synthesized Cd-QDs, 10%Zn-QDs exhibited the highest fluorescence quantum yield and lowest molecular toxicity. The formations of pure QDs and 10%Zn-QDs with BSA corona are majorly driven by different forces with different patterns. The regulation of BSA on the cytotoxicity differences of pure QDs and 10%Zn-QDs was similar with fetal bovine serum, proving the significant contribution of BSA to the cytotoxicity of Cd-QDs PC. Compared with pure QDs PC, the higher cytotoxicity and oxidative stress level of 10%Zn-QDs PC were correlated with higher intracellular [Cd²⁺]. Both larger amount of BSA adsorption and higher level of intracellular reactive oxygen species could accelerate the dissolution rates of 10%Zn-QDs and thus result in higher intracellular [Cd²⁺].

Fast and Dynamic Mapping of the Protein Corona on Nanoparticle Surfaces by Photocatalytic Proximity Labeling

Protein corona broadly affects the delivery of nanomedicines in vivo. Although it has been widely studied by multiple strategies like centrifugal sedimentation, the rapidly forming mechanism and the dynamic structure of the protein corona at the seconds level remains challenging. Here, a photocatalytic proximity labeling technology in nanoparticles (nano-PPL) is developed. By fabricating a "core-shell" nanoparticle co-loaded with chlorin e6 catalyst and biotin-phenol probe, nano-PPL technology is validated for the rapid and precise labeling of corona proteins in situ. Nano-PPL significantly improves the temporal resolution of nano-protein interactions to 5 s duration compared with the classical centrifugation method (>30 s duration). Furthermore, nano-PPL achieves the fast and dynamic mapping of the protein corona on anionic and cationic nanoparticles, respectively. Finally, nano-PPL is deployed to verify the effect of the rapidly formed protein corona on the initial interaction of nanoparticles with cells. These findings highlight a significant methodological advance toward nano-protein interactions in the delivery of nanomedicines in vivo.

Interaction of Atomically Precise Thiolated Copper Nanoclusters with Proteins: A Comparative Study

A facile synthesis of glutathione-stabilized copper nanoclusters (CuNCs) is carried out in H₂O/ tetrahydrofuran medium. The photophysical and morphological studies performed with as-synthesized CuNCs revealed the formation of green-emissive, stable, and smaller nanoclusters. The precise composition of these as-synthesized CuNCs was predicted with the aid of electrospray ionization mass spectrometry analysis as Cu₁₂(SG)₉. Furthermore, the systematic studies of the interaction of synthesized CuNCs with three plasmatic proteins, namely, bovine serum albumin (BSA), lysozyme (Lys), and hemoglobin (Hb) have been performed by using a series of spectroscopic studies. The conformational changes in these proteins upon interacting with CuNCs and their binding stoichiometries have been investigated from the combination of UV-visible and steady-state fluorescence measurements. The changes in the microenvironment of proteins caused by CuNCs were investigated by circular dichroism spectroscopy. Among these three proteins, BSA and Lys had a minor effect on the luminescence of CuNCs, which makes them suitable candidates for biological applications. There are no drastic changes in the microenvironment of NCs as well as proteins because of the possibilities of weak electrostatic and H-bonding interactions of CuNCs with BSA and Lys. The feasibility of strong metallophic interaction between the Fe²⁺ present in the heme group of Hb and Cu(I) or -S atoms present in the CuNCs brings considerable changes in the photophysical activity of CuNCs and their interactions with Hb. The functional groups on NCs as well as active amino acid residues present in proteins play a crucial role in determining their interactions. This work shed a piece of knowledge on designing NCs for specific biological applications.

The Surface Charge of Polymer-Coated Upconversion Nanoparticles Determines Protein Corona Properties and Cell Recognition in Serum Solutions

Applications of nanoparticles (NPs) in the life sciences require control over their properties in protein-rich biological fluids, as an NP quickly acquires a layer of proteins on the surface, forming the so-called "protein corona" (PC). Understanding the composition and kinetics of the PC at the molecular level is of considerable importance for controlling NP interaction with cells. Here, we present a systematic study of hard PC formation on the surface of upconversion nanoparticles (UCNPs) coated with positively-charged polyethyleneimine (PEI) and negatively-charged poly (acrylic acid) (PAA) polymers in serum-supplemented cell culture medium. The rationale behind the choice of UCNP is two-fold: UCNP represents a convenient model of NP with a size ranging from 5 nm to >200 nm, while the unique photoluminescent properties of UCNP enable direct observation of the PC formation, which may provide new insight into this complex process. The non-linear optical properties of UCNP were utilised for direct observation of PC formation by means of fluorescence correlation spectroscopy. Our findings indicated that the charge of the surface polymer coating was the key factor for the formation of PC on UCNPs, with an ensuing effect on the NP-cell interactions.

Protein Desorption Kinetics Depends on the Timescale of Observation

The presence of so-called reversible and irreversible protein adsorption on solid surfaces is well documented in the literature and represents the basis for the development of nanoparticles and implant materials to control interactions in physiological environments. Here, using a series of complementary single-molecule tracking approaches appropriate for different timescales, we show that protein desorption kinetics is much more complex than the traditional reversible-irreversible binary picture. Instead, we find that the surface residence time distribution of adsorbed proteins transitions from power law to exponential behavior when measured over a large range of timescales (10^-2-10⁶ s). A comparison with macroscopic results obtained using a quartz crystal microbalance suggested that macroscopic measurements have generally failed to observe such nonequilibrium phenomena because they are obscured by ensemble-averaging effects. These findings provide new insights into the complex phenomena associated with protein adsorption and desorption.

Solution properties of spherical gold nanoparticles with grafted DNA chains from simulation and theory

There has been a rapidly growing interest in the use of functionalized Au nanoparticles (NPs) as platforms in multiple applications in medicine and manufacturing. The sensing and targeting characteristics of these NPs, and the realization of precisely organized structures in manufacturing applications using such NPs, depend on the control of their surface functionalization. NP functionalization typically takes the form of polymer grafted layers, and a detailed knowledge of the chemical and structural properties of these layers is required to molecularly engineer the particle characteristics for specific applications. However, the prediction and experimental determination of these properties to enable the rational engineering of these particles is a persistent problem in the development of this class of materials. To address this situation, molecular dynamic simulations were performed based on a previously established coarse-grained single-stranded DNA (ssDNA) model to determine basic solution properties of model ssDNA-grafted NP-layers under a wide range of conditions. In particular, we emphasize the calculation of the hydrodynamic radius for ssDNA-grafted Au NPs as a function of structural parameters such as ssDNA length, NP core size, and surface coverage. We also numerically estimate the radius of gyration and the intrinsic viscosity of these NPs, which in combination with hydrodynamic radius estimates, provide valuable information about the fluctuating structure of the grafted polymer layers. We may then understand the origin of the commonly reported variation in effective NP "size" by different measurement methods, and then exploit this information in connection to material design and characterization in connection with the ever-growing number of applications utilizing polymer-grafted NPs.

In situ analysis of nanoparticle soft corona and dynamic evolution

How soft corona, the protein corona’s outer layer, contributes to biological identity of nanomaterials is largely because capturing protein composition of the soft corona in situ remains challenging. We herein develop an in situ Fishing method that can monitor the dynamic formation of protein corona on ultra-small chiral Cu₂S nanoparticles (NPs) allowing us to directly separate and identify the corona protein composition. Our method detects spatiotemporal processes in the evolution of hard and soft coronas on chiral NPs, revealing subtle differences in NP − protein interactions even within several minutes. This study highlights the importance of in situ and dynamic analysis of soft/hard corona, provides insights into the role of soft corona in mediating biological responses of NPs, and offers a universal strategy to characterize soft corona to guide the rational design of biomedical nanomaterials.

Characterizing the soft protein corona on nanoparticles i.e. the outer layer of the corona, remains a longstanding challenge. Here, the authors develop an in situ method to monitor the dynamic processes of multilayered corona formation and evolution that offers a universal strategy to characterize the soft corona proteome.

In Situ Characterization of the Protein Corona of Nanoparticles In Vitro and In Vivo

A new theoretical framework that enables the use of differential dynamic microscopy (DDM) in fluorescence imaging mode to quantify in situ protein adsorption onto nanoparticles (NP) while simultaneously monitoring for NP aggregation is proposed. This methodology is used to elucidate the thermodynamic and kinetic properties of the protein corona (PC) in vitro and in vivo. The results show that protein adsorption triggers particle aggregation over a wide concentration range and that the formed aggregate structures can be quantified using the proposed methodology. Protein affinity for polystyrene (PS) NPs is observed to be dependent on particle concentration. For complex protein mixtures, this methodology identifies that the PC composition changes with the dilution of serum proteins, demonstrating a Vroman effect never quantitatively assessed in situ on NPs. Finally, DDM allows monitoring of the evolution of the PC in vivo. This results show that the PC composition evolves significantly over time in zebrafish larvae, confirming the inherently dynamic nature of the PC. The performance of the developed methodology allows to obtain quantitative insights into nano-bio interactions in a vast array of physiologically relevant conditions that will serve to further improve the design of nanomedicine.

X-Ray Photon Correlation Spectroscopy Towards Measuring Nanoparticle Diameters in Biological Environments Allowing for the In Situ Analysis of their Bio-Nano Interface

X-ray photon correlation spectroscopy (XPCS), a synchrotron source-based technique to measure sample dynamics, is used to determine hydrodynamic diameters of gold nanoparticles (Au NPs) of different sizes in biological environments. In situ determined hydrodynamic diameters are benchmarked with values obtained by dynamic light scattering. The technique is then applied to analyze the behavior of the Au NPs in a biological environment. First, a concentration-dependent agglomeration in the presence of NaCl is determined. Second, concentration-dependent increase in hydrodynamic diameter of the Au NPs upon the presence of proteins is determined. As X-rays in the used energy range are barely scattered by biological matter, dynamics of the Au NPs can be also detected in situ in complex biological environments, such as blood. These measurements demonstrate the possibility of XPCS for in situ analytics of nanoparticles (NPs) in biological environments where similar detection techniques based on visible light would severely suffer from scattering, absorption, and reflection effects.

Realization of a Model-Free Pathway for Quantum Dot-Protein Interaction Beyond Classical Protein Corona or Protein Complex

Although in recent times nanoparticles (NPs) are being used in various biological applications, their mechanism of binding interactions still remains hazy. Usually, the binding mechanism is perceived to be mediated through either the protein corona (PC) or protein complex (PCx). Herein, we report that the nanoparticle (NP)-protein interaction can also proceed via a different pathway without forming the commonly observed PC or PCx. In the present study, the NP-protein interaction between less-toxic zinc-silver-indium-sulfide (ZAIS) quantum dots (QDs) and bovine serum albumin (BSA) was investigated by employing spectroscopic and microscopic techniques. Although the analyses of data obtained from fluorescence and thermodynamic studies do indicate the binding between QDs and BSA, they do not provide clear experimental evidence in favor of PC or PCx. Quite interestingly, high-resolution transmission electron microscopy (HRTEM) studies have shown the formation of a new type of species where BSA protein molecules are adsorbed onto some portion of a QD surface rather than the entire surface. To the best of our knowledge, we believe that this is the first direct experimental evidence in favor of a model-free pathway for NP-protein interaction events. Thus, the outcome of the present study, through experimental evidence, clearly suggests that NP-protein interaction can proceed by following a pathway that is different from classical PC and PCx.

Aquatic organisms modulate the bioreactivity of engineered nanoparticles: focus on biomolecular corona

The increased use of nanoparticle (NP)-enabled materials in everyday-life products have raised concerns about their environmental implications and safety. This motivated the extensive research in nanoecotoxicology showing the possibility that NPs could cause harm to the aquatic organisms if present at high concentrations. By contrast, studies dealing with influence that organisms could exert on the fate and thus effects of NPs are still very rare. Drawing on the existing up-to-date knowledge we critically discuss the formation of biomolecular corona as one of the mechanisms by which organisms exerted control on the NPs fate in the aquatic and biotic environments. We focused the formation of corona by exogeneous and endogenous biomolecules and illustrated the discussion with the specific example of phytoplankton and aquatic invertebrate species. We highlighted the necessity to incorporate the concept of biomolecular corona within more general framework considering the feedback of aquatic organisms and the control they exert in shaping the fate and impact of NPs in the aquatic and biological environment. In our view such broader perspective will contribute to get novel insights into the drivers of environmental transformations of NPs and their mechanisms, which are important in environmental risk assessment.

Protein-based nanomaterials: a new tool for targeted drug delivery

Protein nanomaterials are well-defined, hollow protein nanoparticles comprised of virus capsids, virus-like particles, ferritin, heat shock proteins, chaperonins and many more. Protein-based nanomaterials are formed by the self-assembly of protein subunits and have numerous desired properties as drug-delivery vehicles, including being optimally sized for endocytosis, nontoxic, biocompatible, biodegradable and functionalized at three separate interfaces (external, internal and intersubunit). As a result, protein nanomaterials have been intensively investigated as functional entities in bionanotechnology, including drug delivery, nanoreactors and templates for organic and inorganic nanomaterials. Several variables influence efficient administration, particularly active targeting, cellular uptake, the kinetics of the release and systemic elimination. This review examines the wide range of medicines, loading/release processes, targeted therapies and treatment effectiveness.

Bovine serum albumin-gold nanoclusters protein corona stabilized polystyrene nanoparticles as dual-color fluorescent nanoprobes for breast cancer detection

Breast cancer is the most prevalent malignancy and the first leading cause of cancer-related mortality among the female population worldwide. Approaches for precise and reliable detection of breast cancer cells, particularly in the nascent state, are desperately needed for elevating the survival rate of patients bearing the breast tumor. In this work, we successfully performed the sensitive, precise, and reliable breast cancer cell detection using facilely fabricated bovine serum albumin-gold nanocluster (BSA-AuNCs) protein corona stabilized, epithelial cell adhesion molecule (EpCAM) aptamer linked fluorescent polystyrene nanoparticle (PS NP), termed as PS-BSA-AuNCs-Apt. The rapidly adsorbed BSA-AuNCs hard protein corona without complicated covalent conjugation not only imparted excellent colloidal stability to the PS nanoparticles, but also offered numerous active anchors for the targeted EpCAM aptamers to locate. With the remarkable aid of the aptamers specifically targeting the EpCAM-positive breast cancer cells, the PS-BSA-AuNCs-Apt emitted strong and photostable dual-color fluorescent signals for precise and reliable cancer cell detection by overcoming the false signals. The specific identification potency of the PS-BSA-AuNCs-Apt system was further verified by successfully detecting the xenografted breast tumor tissue. Notably, to the best of our knowledge, the protein corona formed nanoprobes was exploited for direct tumor cell and tissue detection with high efficacy for the first time, demonstrating their promising potential in clinical tumor detection.

Chiral NIR-II fluorescent Ag2S quantum dots with stereospecific biological interactions and tumor accumulation behaviors

Near-infrared II (NIR-II) fluorescent nanoprobes hold great potential for biomedical applications. Elucidating the relationship between surface properties of NIR-II nanoprobes and their biological behaviors is particularly important for future probe design and their performance optimization. Despite the rapid development of NIR-II nanoprobes, the distinct role of surface chirality on their biological fates has rarely been exploited. Herein, chiral NIR-II fluorescent Ag₂S quantum dots (QDs) are synthesized to investigate the relationship between their chirality and biological functions at both in vitro and in vivo levels. D-/L-Ag₂S QDs exhibit significant differences on their interactions with serum proteins, which further affect the cellular uptake. As a result, D-Ag₂S QDs can be internalized with higher efficiency (over 2-fold) than that of L-Ag₂S QDs. Moreover, in vivo studies reveal that the chirality determines the primary localization of these chiral QDs, where a more efficient renal elimination of D-Ag₂S QDs was observed than that of L-Ag₂S QDs. Importantly, D-Ag₂S QDs show preferential accumulation in tumor region than that of L-Ag₂S QDs in orthotopic kidney tumor model, which points out a new avenue of enhancing targeting capabilities of nanoprobes by engineering their surface chirality.

A Dense Layer of Polyethyleneglycol and Zwitterionic Bone Targeting Peptide on the Surface of Stereocomplex Polylactide-Polyethyleneglycol Nanoparticles Improves Shelf-Storage Stability and the Serum Compatibility

The surface properties of nanoparticles (NPs) affect their stability and formation of the protein corona, which influence their targeting abilities. We evaluated these properties using bone (hydroxyapatite; HAP) targeting peptide on tamoxifen (TAM)-loaded stereocomplexformed polylactide-polyethyleneglycol (SC-PLA-PEG) NPs. Octaaspartic acid-octaglycine-cysteine (D8G8C) anionic derivative (Ani. pep.) and octa-aspartic acid-octa lysine-cysteine (D8K8C), a zwitterionic derivative (Zwi. pep.) were conjugated with SC-PLA-PEG NPs as HAP-targeting peptides. The addition of hydrophobic PLA homopolymers increased the surface PEG density on the NPs. Denser PEG chains on NPs decreased their specific surface area, reducing protein adsorption on the NPs and TAM release from NPs. NPs with dense PEG chains and Zwi. pep. showed superior shelf stability and lower protein adsorption than NPs with dense PEG chains and Ani. pep. in murine serum. Furthermore, the HAP-binding ability of NPs with Zwi. pep. was significantly higher than that of NPs with Ani. pep. These results indicate that decreasing the specific surface area and zwitterionization of HAP-targeting peptides on NPs are promising approaches to improve the serum compatibility and stability of NPs.

Designing the Surface Chemistry of Inorganic Nanocrystals for Cancer Imaging and Therapy

Inorganic nanocrystals, such as gold, iron oxide and semiconductor quantum dots, offer promising prospects for cancer diagnostics, imaging and therapy, due to their specific plasmonic, magnetic or fluorescent properties. The organic coating, or surface ligands, of these nanoparticles ensures their colloidal stability in complex biological fluids and enables their functionalization with targeting functions. It also controls the interactions of the nanoparticle with biomolecules in their environment. It therefore plays a crucial role in determining nanoparticle biodistribution and, ultimately, the imaging or therapeutic efficiency. This review summarizes the various strategies used to develop optimal surface chemistries for the in vivo preclinical and clinical application of inorganic nanocrystals. It discusses the current understanding of the influence of the nanoparticle surface chemistry on its colloidal stability, interaction with proteins, biodistribution and tumor uptake, and the requirements to develop an optimal surface chemistry.

Protein adsorption onto nanomaterials engineered for theranostic applications

The key role of biomolecule adsorption onto engineered nanomaterials for therapeutic and diagnostic purposes has been well recognized by the nanobiotechnology community, and our mechanistic understanding of nano-bio interactions has greatly advanced over the past decades. Attention has recently shifted to gaining active control of nano-bio interactions, so as to enhance the efficacy of nanomaterials in biomedical applications. In this review, we summarize progress in this field and outline directions for future development. First, we briefly review fundamental knowledge about the intricate interactions between proteins and nanomaterials, as unraveled by a large number of mechanistic studies. Then, we give a systematic overview of the ways that protein-nanomaterial interactions have been exploited in biomedical applications, including the control of protein adsorption for enhancing the targeting efficiency of nanomedicines, the design of specific protein adsorption layers on the surfaces of nanomaterials for use as drug carriers, and the development of novel nanoparticle array-based sensors based on nano-bio interactions. We will focus on particularly relevant and recent examples within these areas. Finally, we conclude this topical review with an outlook on future developments in this fascinating research field.

Structural changes in selected human proteins induced by exposure to quantum dots, their biological relevance and possible biomedical applications

Quantum dots (QDs) are semi-conductor luminescent nanocrystals usually of 2-10 nm diameter, attracting the significant attention in biomedical studies since emerged. Due to their unique optical and electronic properties, i.e. wide absorption spectra, narrow tunable emission bands or stable, bright photoluminescence, QDs seem to be ideally suited for multi-colour, simultaneous bioimaging and cellular labeling at the molecular level as new-generation probes. A highly reactive surface of QDs allows for conjugating them to biomolecules, what enables their direct binding to areas of interest inside or outside the cell for biosensing or targeted delivery. Particularly protein-QDs conjugates are current subjects of research, as features of QDs can be combined with protein specific functionalities and therefore used as a complex in variety of biomedical applications. It is known that QDs are able to interact with cells, organelles and macromolecules of the human body after administration. QDs are reported to cause changes at proteins level, including unfolding and three-dimensional structure alterations which might hamper proteins from performing their physiological functions and thereby limit the use of QD-protein conjugates in vivo. Moreover, these changes may trigger unwanted cellular outcomes as the effect of different signaling pathways activation. In this review, characteristics of QDs interactions with certain human proteins are presented and discussed. Besides that, the following manuscript provides an overview on structural changes of specific proteins exposed to QDs and their biological and biomedical relevance.

Developing a Solution for Nasal and Olfactory Transport of Nanomaterials

With advances in nanotechnology, engineered nanomaterial applications are a rapidly growing sector of the economy. Some nanomaterials can reach the brain through nose-to-brain transport. This transport creates concern for potential neurotoxicity of insoluble nanomaterials and a need for toxicity screening tests that detect nose-to-brain transport. Such tests can involve intranasal instillation of aqueous suspensions of nanomaterials in dispersion media that limit particle agglomeration. Unfortunately, protein and some elements in existing dispersion media are suboptimal for potential nose-to-brain transport of nanomaterials because olfactory transport has size- and ion-composition requirements. Therefore, we designed a protein-free dispersion media containing phospholipids and amino acids in an isotonic balanced electrolyte solution, a solution for nasal and olfactory transport (SNOT). SNOT disperses hexagonal boron nitride nanomaterials with a peak particle diameter below 100 nm. In addition, multiwalled carbon nanotubes (MWCNTs) in an established dispersion medium, when diluted with SNOT, maintain dispersion with reduced albumin concentration. Using stereomicroscopy and microscopic examination of plastic sections, dextran dyes dispersed in SNOT are demonstrated in the neuroepithelium of the nose and olfactory bulb of B6;129P2-Omp^tm3Mom/MomJ mice after intranasal instillation in SNOT. These findings support the potential for SNOT to disperse nanomaterials in a manner permitting nose-to-brain transport for neurotoxicity studies.

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.

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.

Shining Light on Polymeric Drug Nanocarriers with Fluorescence Correlation Spectroscopy

The use of nanoparticles as carriers is an extremely promising way for administration of therapeutic agents, such as drug molecules, proteins and nucleic acids. Such nanocarriers (NCs) can increase the solubility of hydrophobic compounds, protect their cargo from the environment, and if properly functionalized, deliver it to specific target cells and tissues. Polymer-based NCs are especially promising, because they offer high degree of versatility and tunability. However, in order to get a full advantage of this therapeutic approach and develop efficient delivery systems, a careful characterization of the NCs is needed. This Feature Article highlights the fluorescence correlation spectroscopy (FCS) technique as a powerful and versatile tool for NCs characterization at all stages of the drug delivery process. In particular, FCS can monitor and quantify the size of the NCs and the drug loading efficiency after preparation, the NCs stability and possible interactions with, e.g., plasma proteins in the blood stream and the kinetic of drug release in the cytoplasm of the target cells. This article is protected by copyright. All rights reserved.

Fluorescence Correlation Spectroscopy Monitors the Fate of Degradable Nanocarriers in the Blood Stream

The use of nanoparticles as carriers to deliver pharmacologically active compounds to specific parts of the body via the bloodstream is a promising therapeutic approach for the effective treatment of various diseases. To reach their target sites, nanocarriers (NCs) need to circulate in the bloodstream for prolonged periods without aggregation, degradation, or cargo loss. However, it is very difficult to identify and monitor small-sized NCs and their cargo in the dense and highly complex blood environment. Here, we present a new fluorescence correlation spectroscopy-based method that allows the precise characterization of fluorescently labeled NCs in samples of less than 50 μL of whole blood. The NC size, concentration, and loading efficiency can be measured to evaluate circulation times, stability, or premature drug release. We apply the new method to follow the fate of pH-degradable fluorescent cargo-loaded nanogels in the blood of live mice for periods of up to 72 h.

The impact of protein corona on the biological behavior of targeting nanomedicines

For successful translation of targeting nanomedicines from bench to bedside, it is vital to address their most common drawbacks namely rapid clearance and off-target accumulation. These complications evidently originate from a phenomenon called "protein corona (PC) formation" around the surface of targeting nanoparticles (NPs) which happens once they encounter the bloodstream and interact with plasma proteins with high collision frequency. This phenomenon endows the targeting nanomedicines with a different biological behavior followed by an unexpected fate, which is usually very different from what we commonly observe in vitro. In addition to the inherent physiochemical properties of NPs, the targeting ligands could also remarkably dictate the amount and type of adsorbed PC. As very limited studies have focused their attention on this particular factor, the present review is tasked to discuss the best simulated environment and latest characterization techniques applied to PC analysis. The effect of PC on the biological behavior of targeting NPs engineered with different targeting moieties is further discussed. Ultimately, the recent progresses in manipulation of nano-bio interfaces to achieve the most favorite therapeutic outcome are highlighted.

Mapping the Time Dependent DNA Fragmentation caused by doxorubicin Loaded on PEGylated Carbogenic Nanodots using Fluorescence Lifetime Imaging and Super-resolution microscopy

Doxorubicin is an anthracycline drug most commonly used in cancer therapy. It intercalates with the nuclear DNA and induces toxicity by causing DNA breaks and histone evictions. However, the kinetics...

Protein nanoparticles in drug delivery: animal protein, plant proteins and protein cages, albumin nanoparticles

In this article, we will describe the properties of albumin and its biological functions, types of sources that can be used to produce albumin nanoparticles, methods of producing albumin nanoparticles, its therapeutic applications and the importance of albumin nanoparticles in the production of pharmaceutical formulations. In view of the increasing use of Abraxane and its approval for use in the treatment of several types of cancer and during the final stages of clinical trials for other cancers, to evaluate it and compare its effectiveness with conventional non formulations of chemotherapy Paclitaxel is paid. In this article, we will examine the role and importance of animal proteins in Nano medicine and the various benefits of these biomolecules for the preparation of drug delivery carriers and the characteristics of plant protein Nano carriers and protein Nano cages and their potentials in diagnosis and treatment. Finally, the advantages and disadvantages of protein nanoparticles are mentioned, as well as the methods of production of albumin nanoparticles, its therapeutic applications and the importance of albumin nanoparticles in the production of pharmaceutical formulations.

Hard and Soft Protein Corona of Nanomaterials: Analysis and Relevance

Upon contact with a biological milieu, nanomaterials tend to interact with biomolecules present in the media, especially proteins, leading to the formation of the so-called "protein corona". As a result of these nanomaterial-protein interactions, the bio-identity of the nanomaterial is altered, which is translated into modifications of its behavior, fate, and pharmacological profile. For biomedical applications, it is fundamental to understand the biological behavior of nanomaterials prior to any clinical translation. For these reasons, during the last decade, numerous publications have been focused on the investigation of the protein corona of many different types of nanomaterials. Interestingly, it has been demonstrated that the structure of the protein corona can be divided into hard and soft corona, depending on the affinity of the proteins for the nanoparticle surface. In the present document, we explore the differences between these two protein coronas, review the analysis techniques used for their assessment, and reflect on their relevance for medical purposes.

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.

Probing the Interaction of Bovine Serum Albumin with Copper Nanoclusters: Realization of Binding Pathway Different from Protein Corona

With an aim to understand the interaction mechanism of bovine serum albumin (BSA) with copper nanoclusters (CuNCs), three different types CuNCs having chemically different surface ligands, namely, tannic acid (TA), chitosan, and cysteine (Cys), have been fabricated, and investigations are carried out in the absence and presence of protein (BSA) at ensemble-averaged and single-molecule levels. The CuNCs, capped with different surface ligands, are consciously chosen so that the role of surface ligands in the overall protein-NCs interactions is clearly understood, but, more importantly, to find whether these CuNCs can interact with protein in a new pathway without forming the "protein corona", which otherwise has been observed in relatively larger nanoparticles when they are exposed to biological fluids. Analysis of the data obtained from fluorescence, ζ-potential, and ITC measurements has clearly indicated that the BSA protein in the presence of CuNCs does not attain the binding stoichiometry (BSA/CuNCs > 1) that is required for the formation of "protein corona". This conclusion is further substantiated by the outcome of the fluorescence correlation spectroscopy (FCS) study. Further analysis of data and thermodynamic calculations have revealed that the surface ligands of the CuNCs play an important role in the protein-NCs binding events, and they can alter the mode and thermodynamics of the process. Specifically, the data have demonstrated that the binding of BSA with TA-CuNCs and Chitosan-CuNCs follows two types of binding modes; however, the same with Cys-CuNCs goes through only one type of binding mode. Circular dichroism (CD) measurements have indicated that the basic structure of BSA remains almost unaltered in the presence of CuNCs. The outcome of the present study is expected to encourage and enable better application of NCs in biological applications.

Exploring the interactions between protein coronated CdSe quantum dots and nanoplastics

QDs after protein coronation can undergo sequential interaction with other pollutants which may alter the physiochemical property of the QDs and influence the stability of the corona proteins.

Brownian motion-based nanoparticle sizing-A powerful approach for in situ analysis of nanoparticle-protein interactions

A key hurdle toward effective application of nanoparticles (NPs) in biomedicine is still the incomplete understanding of the biomolecular adsorption layer, the so-called protein corona, which inevitably forms around NPs when they are immersed in a biofluid. NP sizing techniques via the analysis of Brownian motions offer a powerful way to measure the thickness of the protein corona in situ. Here, the fundamentals of three techniques, dynamic light scattering, fluorescence correlation spectroscopy, and nanoparticle tracking analysis are briefly summarized. Then, experimental procedures for the determination of binding curves are presented in a tutorial fashion. Nanoparticle sizing experiments are illustrated with a selection of recent results on the interactions of transferrin with hydrophilic and hydrophobic polystyrene nanoparticles, and key insights gained from this work are discussed.

Mapping and identification of soft corona proteins at nanoparticles and their impact on cellular association

The current understanding of the biological identity that nanoparticles may acquire in a given biological milieu is mostly inferred from the hard component of the protein corona (HC). The composition of soft corona (SC) proteins and their biological relevance have remained elusive due to the lack of analytical separation methods. Here, we identify a set of specific corona proteins with weak interactions at silica and polystyrene nanoparticles by using an in situ click-chemistry reaction. We show that these SC proteins are present also in the HC, but are specifically enriched after the capture, suggesting that the main distinction between HC and SC is the differential binding strength of the same proteins. Interestingly, the weakly interacting proteins are revealed as modulators of nanoparticle-cell association mainly through their dynamic nature. We therefore highlight that weak interactions of proteins at nanoparticles should be considered when evaluating nano-bio interfaces.

Toward Diffusion Measurements of Colloidal Nanoparticles in Biological Environments by Nuclear Magnetic Resonance

Protein corona formation on the surface of nanoparticles (NPs) is observed in situ by measuring diffusion coefficients of the NPs under the presence of proteins with a ¹⁹ F nuclear magnetic resonance (NMR) based methodology. Formation of a protein corona reduces the diffusion coefficient of the NPs, based on an increase in their effective hydrodynamic radii. With this methodology it is demonstrated that the apparent dissociation constant of protein-NP complexes may vary over at least nine orders of magnitude for different types of proteins, in line with the Vroman effect. Using this methodology, the interaction between one type of protein and one type of nanoparticle can be studied quantitatively. Due to the NMR-based detection, this methodology has no interference by absorption/scattering effects, by which optical detection schemes are affected. By using the potential of the NMR chemical shift, the detection of multiple ¹⁹ F signals simultaneously opens the possibility to study the diffusion of several NPs at the same time. The ¹⁹ F labeling of the NPs has negligible effect on their acute toxicity and moderate effect on NPs uptake by cells.

Analysing the nanoparticle-protein corona for potential molecular target identification

When nanoparticles are introduced into biological systems, host proteins tend to associate on the particle surface to form a protein layer termed the "protein corona" (PC). Identifying the proteins that constitute the PC can yield useful information about nanoparticle processing, bio-distribution, toxicity and clearance. Similarly, characterizing and identifying proteins within the PC from patient samples provides opportunities to probe disease proteomes and identify molecules that influence the disease process. Thus, nanoparticles represent unique probing tools for discovery of molecular targets for diseases. Here, we report a first review on target identification using nanoparticles in biological samples based on analysing physico chemical interactions. We also summarize the evolution of the PC surrounding various nano-systems, comment on PC signature, address PC complexity in fluids, and outline challenges associated with analysing the PC. In addition, the influence on PC formation of various nanoparticle parameters is summarized; nanoparticle characteristics considered include size, charge, temperature, and surface modifications for both organic and inorganic nanomaterials. We also discuss the advantages of nanotechnology, over other more invasive and laborious methods, for identifying potential diagnostic and therapeutic targets.

Recent advances in the analysis of nanoparticle-protein coronas

In spite of radical advances in nanobiotechnology, the clinical translation of nanoparticle (NP)-based agents is still a major challenge due to various physiological factors that influence their interactions with biological systems. Recent decade witnessed meticulous investigation on protein corona (PC) that is the first surrounds NPs once administered into the body. Formation of PC around NP surface exhibits resilient effects on their circulation, distribution, therapeutic activity, toxicity and other factors. Although enormous literature is available on the role of PC in altering pharmacokinetics and pharmacodynamics of NPs, understanding on its analytical characterization methods still remains shallow. Therefore, the current review summarizes the impact of PC on biological fate of NPs and stressing on analytical methods employed for studying the NP-PC.

Elucidating the Role of Surface Coating in the Promotion or Prevention of Protein Corona around Quantum Dots

Nonspecific interactions in biological media can lead to the formation of a protein corona around nanocolloids, which tends to alter their behavior and limit their effectiveness when used as probes for imaging or sensing applications. Yet, understanding the corona buildup has been challenging. We hereby investigate these interactions using luminescent quantum dots (QDs) as a model nanocolloid system, where we carefully vary the nature of the hydrophilic block in the surface coating, while maintaining the same dihydrolipoic acid (DHLA) bidentate coordinating motif. We first use agarose gel electrophoresis to track changes in the mobility shift upon exposure of the QDs to protein-rich media. We find that QDs capped with DHLA (which presents a hydrophobic alkyl chain terminated with a carboxyl group) promote corona formation, in a concentration-dependent manner. However, when a polyethylene glycol block or a zwitterion group is appended onto DHLA, it yields a coating that prevents corona buildup. Our results clearly confirm that nonspecific interactions with protein-rich media are strongly dependent on the nature of the hydrophilic motif used. Additional gel experiments using SDS-PAGE have allowed further characterization of the corona protein, and showed that mainly a soft corona forms around the DHLA-capped QDs. These findings will be highly informative when designing nanocolloids that can find potential use in biological applications.

Understanding the Chemical Nature of Nanoparticle-Protein Interactions

The formation of a protein corona has been considered a pitfall in the clinical translation of nanomedicines. Hence, interdisciplinary studies on corona characterization are critically essential. A deep understanding of the formation of hard and soft protein coronas upon in vivo administration of nanoparticles is vital. The protein corona gives the nanoplatform a new biological identity. Furthermore, the control of and mechanistic understanding of corona formation as it is regulated by the physicochemical properties of nanoparticles is crucial for developing safe nanomedicines. A growing number of analytical techniques have been developed in the past decade for examining NP-protein interactions, contributing to a better understanding of protein corona formation on the surface of nanoparticles. In this Review, we summarize the latest developments in the in vivo and in vitro study of dynamic protein corona formation. Insights derived from techniques used to visualize, quantify, and define protein coronas, as well as the methods for examining the kinetics and structural changes of coronal proteins, are discussed. The potential challenges and future perspectives in the study of protein corona formation and its effects on biological behavior and applications of therapeutic nanomaterials are also provided.