Particle Targeting in Complex Biological Media

Bridging the gap between in vitro and in vivo models: a way forward to clinical translation of mitochondrial transplantation in acute disease states

Mitochondrial transplantation and transfer are being explored as therapeutic options in acute and chronic diseases to restore cellular function in injured tissues. To limit potential immune responses and rejection of donor mitochondria, current clinical applications have focused on delivery of autologous mitochondria. We recently convened a Mitochondrial Transplant Convergent Working Group (CWG), to explore three key issues that limit clinical translation: (1) storage of mitochondria, (2) biomaterials to enhance mitochondrial uptake, and (3) dynamic models to mimic the complex recipient tissue environment. In this review, we present a summary of CWG conclusions related to these three issues and provide an overview of pre-clinical studies aimed at building a more robust toolkit for translational trials.

Stealth and Biocompatible Gold Nanoparticles through Surface Coating with a Zwitterionic Derivative of Glutathione

Gold nanoparticles (AuNPs) hold promise in biomedicine, but challenges like aggregation, protein corona formation, and insufficient biocompatibility must be thoroughly addressed before advancing their clinical applications. Designing AuNPs with specific protein corona compositions is challenging, and strategies for corona elimination, such as coating with polyethylene glycol (PEG), have limitations. In this study, we introduce a commercially available zwitterionic derivative of glutathione, glutathione monoethyl ester (GSHzwt), for the surface coating of colloidal AuNPs. Particles coated with GSHzwt were investigated alongside four other AuNPs coated with various ligands, including citrate ions, tiopronin, glutathione, cysteine, and PEG. We then undertook a head-to-head comparison of these AuNPs to assess their behavior in biological fluid. GSHzwt-coated AuNPs exhibited exceptional resistance to aggregation and protein adsorption. The particles could also be readily functionalized with biotin and interact with streptavidin receptors in human plasma. Additionally, they exhibited significant blood compatibility and noncytotoxicity. In conclusion, GSHzwt provides a practical and easy method for the surface passivation of AuNPs, creating "stealth" particles for potential clinical applications.

The interaction between particles and vascular endothelium in blood flow

Particle-based drug delivery systems have shown promising application potential to treat human diseases; however, an incomplete understanding of their interactions with vascular endothelium in blood flow prevents their inclusion into mainstream clinical applications. The flow performance of nano/micro-sized particles in the blood are disturbed by many external/internal factors, including blood constituents, particle properties, and endothelium bioactivities, affecting the fate of particles in vivo and therapeutic effects for diseases. This review highlights how the blood constituents, hemodynamic environment and particle properties influence the interactions and particle activities in vivo. Moreover, we briefly summarized the structure and functions of endothelium and simulated devices for studying particle performance under blood flow conditions. Finally, based on particle-endothelium interactions, we propose future opportunities for novel therapeutic strategies and provide solutions to challenges in particle delivery systems for accelerating their clinical translation. This review helps provoke an increasing in-depth understanding of particle-endothelium interactions and inspires more strategies that may benefit the development of particle medicine.

Impact of Targeting Moiety Type and Protein Corona Formation on the Uptake of Fn14-Targeted Nanoparticles by Cancer Cells

The TWEAK receptor, Fn14, is a promising candidate for active targeting of cancer nanotherapeutics to many solid tumor types, including metastatic breast and primary brain cancers. Targeting of therapeutic nanoparticles (NPs) has been accomplished using a range of targeting moieties including monoclonal antibodies and related fragments, peptides, and small molecules. Here, we investigated a full-length Fn14-specific monoclonal antibody, ITEM4, or an ITEM4-Fab fragment as a targeting moiety to guide the development of a clinical formulation. We formulated NPs with varying densities of the targeting moieties while maintaining the decreased nonspecific adhesivity with receptor targeting (DART) characteristics. To model the conditions that NPs experience following intravenous infusion, we investigated the impact of serum exposure in relation to the targeting moiety type and surface density. To further evaluate performance at the cancer cell level, we performed experiments to assess differences in cellular uptake and trafficking in several cancer cell lines using confocal microscopy, imaging flow cytometry, and total internal reflection fluorescence microscopy. We observed that Fn14-targeted NPs exhibit enhanced cellular uptake in Fn14-high compared to Fn14-low cancer cells and that in both cell lines uptake levels were greater than observed with control, nontargeted NPs. We found that serum exposure increased Fn14-targeted NP specificity while simultaneously reducing the total NP uptake. Importantly, serum exposure caused a larger reduction in cancer cell uptake over time when the targeting moiety was an antibody fragment (Fab region of the monoclonal antibody) compared with the full-length monoclonal antibody targeting moiety. Lastly, we uncovered that full monoclonal antibody-targeted NPs enter cancer cells via clathrin-mediated endocytosis and traffic through the endolysosomal pathway. Taken together, these results support a pathway for developing a clinical formulation using a full-length Fn14 monoclonal antibody as the targeting moiety for a DART cancer nanotherapeutic agent.

Steric-Deficient Oligoglycine Surrogates Facilitate Multivalent and Bifunctional Nanobody Synthesis via Combined Sortase A Transpeptidation and Click Chemistry

Conferring multifunctional properties to proteins via enzymatic approaches has greatly facilitated recent progress in protein nanotechnology. In this regard, sortase (Srt) A transpeptidation has facilitated many of these developments due to its exceptional specificity, mild reaction conditions, and complementation with other bioorthogonal techniques, such as click chemistry. In most of these developments, Srt A is used to seamlessly tether oligoglycine-containing molecules to a protein of interest that is equipped with the enzyme's recognition sequence, LPXTG. However, the dependence on oligoglycine attacking nucleophiles and the associated cost of certain derivatives (e.g., cyclooctyne) limit the utility of this approach to lab-scale applications only. Thus, the quest to identify appropriate alternatives and understand their effectiveness remains an important area of research. This study identifies that steric and nucleophilicity-associated effects influence Srt A transpeptidation when two oligoglycine surrogates were examined. The approach was further used in complementation with click chemistry to synthesize bivalent and bifunctional nanobody conjugates for application in epithelial growth factor receptor targeting. The overall technique and tools developed here may facilitate the advancement of future nanotechnologies.

Targeted Anticancer Agent with Original Mode of Action Prepared by Supramolecular Assembly of Antibody Oligonucleotide Conjugates and Cationic Nanoparticles

Despite their clinical success, Antibody-Drug Conjugates (ADCs) are still limited to the delivery of a handful of cytotoxic small-molecule payloads. Adaptation of this successful format to the delivery of alternative types of cytotoxic payloads is of high interest in the search for novel anticancer treatments. Herein, we considered that the inherent toxicity of cationic nanoparticles (cNP), which limits their use as oligonucleotide delivery systems, could be turned into an opportunity to access a new family of toxic payloads. We complexed anti-HER2 antibody-oligonucleotide conjugates (AOC) with cytotoxic cationic polydiacetylenic micelles to obtain Antibody-Toxic-Nanoparticles Conjugates (ATNPs) and studied their physicochemical properties, as well as their bioactivity in both in vitro and in vivo HER2 models. After optimising their AOC/cNP ratio, the small (73 nm) HER2-targeting ATNPs were found to selectively kill antigen-positive SKBR-2 cells over antigen-negative MDA-MB-231 cells in serum-containing medium. Further in vivo anti-cancer activity was demonstrated in an SKBR-3 tumour xenograft model in BALB/c mice in which stable 60% tumour regression could be observed just after two injections of 45 pmol of ATNP. These results open interesting prospects in the use of such cationic nanoparticles as payloads for ADC-like strategies.

Functionalized zein nanoparticles targeting neonatal Fc receptor to enhance lung absorption of peptides

Peptides have a distinguished therapeutic potential for several chronic conditions, and more than 80 peptides exist in the global market. However, most of these marketed peptide drugs are currently delivered intravenously or subcutaneously due to their fast degradation and limited absorption through non-invasive routes. The pulmonary route is favored as a non-invasive route. Neonatal Fc receptor (FcRn) is expressed in adult human lungs and has a role in enhancing the pulmonary absorption of monoclonal antibodies. In this work, we developed and characterized candidate protein delivery systems for the pulmonary administration of peptides. The prepared bare and loaded zein nanoparticles (ZNPs), targeted, physically, and covalently PEGylated ZNPs showed hydrodynamic diameters between 137 and 155 nm and a narrow distribution index. Insulin, which was used as a protein model, showed an association efficiency of 72%, while the FcRn-targeted peptide conjugation efficiency was approximately 68%. The physically adsorbed poloxamer 407 on insulin-loaded ZNPs showed slower and controlled insulin release. The in vitro cell culture model consists of the NCI-H441 epithelial cell line, which confirmed its expression of the targeted receptor, FcRn. The safety of ZNPs was verified after incubation with both cell lines of the in vitro pulmonary model, namely NCI-H441 and HPMEC-ST1.6R, for 24 h. It was observed that targeted ZNPs enhanced insulin permeability by showing a higher apparent permeation coefficient than non-targeted ZNPs. Overall, both targeted PEGylated ZNPs showed to be suitable peptide carriers and adequately fit the demands of delivery systems designed for pulmonary administration.

Size-Controlled DNA Tile Self-Assembly Nanostructures Through Caveolae-Mediated Endocytosis for Signal-Amplified Imaging of MicroRNAs in Living Cells

Signal-amplified imaging of microRNAs (miRNAs) is a promising strategy at the single-cell level because liquid biopsy fails to reflect real-time dynamic miRNA levels. However, the internalization pathways for available conventional vectors predominantly involve endo-lysosomes, showing nonideal cytoplasmic delivery efficiency. In this study, size-controlled 9-tile nanoarrays are designed and constructed by integrating catalytic hairpin assembly (CHA) with DNA tile self-assembly technology to achieve caveolae-mediated endocytosis for the amplified imaging of miRNAs in a complex intracellular environment. Compared with classical CHA, the 9-tile nanoarrays possess high sensitivity and specificity for miRNAs, achieve excellent internalization efficiency by caveolar endocytosis, bypassing lysosomal traps, and exhibit more powerful signal-amplified imaging of intracellular miRNAs. Because of their excellent safety, physiological stability, and highly efficient cytoplasmic delivery, the 9-tile nanoarrays can realize real-time amplified monitoring of miRNAs in various tumor and identical cells of different periods, and imaging effects are consistent with the actual expression levels of miRNAs, ultimately demonstrating their feasibility and capacity. This strategy provides a high-potential delivery pathway for cell imaging and targeted delivery, simultaneously offering a meaningful reference for the application of DNA tile self-assembly technology in relevant fundamental research and medical diagnostics.

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.

Nanoparticle Targeting with Antibodies in the Central Nervous System

Treatments for disease in the central nervous system (CNS) are limited because of difficulties in agent penetration through the blood-brain barrier, achieving optimal dosing, and mitigating off-target effects. The prospect of precision medicine in CNS treatment suggests an opportunity for therapeutic nanotechnology, which offers tunability and adaptability to address specific diseases as well as targetability when combined with antibodies (Abs). Here, we review the strategies to attach Abs to nanoparticles (NPs), including conventional approaches of chemisorption and physisorption as well as attempts to combine irreversible Ab immobilization with controlled orientation. We also summarize trends that have been observed through studies of systemically delivered Ab-NP conjugates in animals. Finally, we discuss the future outlook for Ab-NPs to deliver therapeutics into the CNS.

Reagents for Mass Cytometry

Mass cytometry (cytometry by time-of-flight detection [CyTOF]) is a bioanalytical technique that enables the identification and quantification of diverse features of cellular systems with single-cell resolution. In suspension mass cytometry, cells are stained with stable heavy-atom isotope-tagged reagents, and then the cells are nebulized into an inductively coupled plasma time-of-flight mass spectrometry (ICP-TOF-MS) instrument. In imaging mass cytometry, a pulsed laser is used to ablate ca. 1 μm² spots of a tissue section. The plume is then transferred to the CyTOF, generating an image of biomarker expression. Similar measurements are possible with multiplexed ion bean imaging (MIBI). The unit mass resolution of the ICP-TOF-MS detector allows for multiparametric analysis of (in principle) up to 130 different parameters. Currently available reagents, however, allow simultaneous measurement of up to 50 biomarkers. As new reagents are developed, the scope of information that can be obtained by mass cytometry continues to increase, particularly due to the development of new small molecule reagents which enable monitoring of active biochemistry at the cellular level. This review summarizes the history and current state of mass cytometry reagent development and elaborates on areas where there is a need for new reagents. Additionally, this review provides guidelines on how new reagents should be tested and how the data should be presented to make them most meaningful to the mass cytometry user community.

Recent Progress of Gold-Based Nanostructures towards Future Emblem of Photo-Triggered Cancer Theranostics: A Special Focus on Combinatorial Phototherapies

Cancer is one of the most dangerous health problems in the millennium and it is the third foremost human cause of death in the universe. Traditional cancer treatments face several disadvantages and cannot often afford adequate outcomes. It has been exhibited that the outcome of several therapies can be improved when associated with nanostructures. In addition, a modern tendency is being developed in cancer therapy to convert single-modal into multi-modal therapies with the help of existing various nanostructures. Among them, gold is the most successful nanostructure for biomedical applications due to its flexibility in preparation, stabilization, surface modifications, less cytotoxicity, and ease of bio-detection. In the past few decades, gold-based nanomaterials rule cancer treatment applications, currently, gold nanostructures were the leading nanomaterials for synergetic cancer therapies. In this review article, the synthesis, stabilization, and optical properties of gold nanostructures have been discussed. Then, the surface modifications and targeting mechanisms of gold nanomaterials will be described. Recent signs of progress in the application of gold nanomaterials for synergetic cancer therapies such as photodynamic and photo-thermal therapies in combination with other common interventions such as radiotherapy, chemotherapy, and will be reviewed. Also, a summary of the pharmacokinetics of gold nanostructures will be delivered. Finally, the challenges and outlooks of the gold nanostructures in the clinics for applications in cancer treatments are debated.

Virus-like particles for drug delivery: a review of methods and applications

Virus-like particles (VLPs) are self-assembling protein nanoparticles that have great promise as vectors for drug delivery. VLPs are derived from viruses but retain none of their infection or replication capabilities. These protein particles have defined surface chemistries, uniform sizes, and stability properties that make them attractive starting points for drug-delivery scaffolds. Here, we review recent advances in tailoring VLPs for drug-delivery applications, including VLP platform engineering approaches as well as methods for cargo loading, activation, and release. Finally, we highlight several successes using VLPs for drug delivery in model systems.

Tailor-Made Protein Corona Formation on Polystyrene Microparticles and its Effect on Epithelial Cell Uptake

Microplastic particles are pollutants in the environment with a potential impact on ecology and human health. As soon as microplastic particles get in contact with complex (biological) environments, they will be covered by an eco- and/or protein corona. In this contribution, protein corona formation was conducted under defined laboratory conditions on polystyrene (PS) microparticles to investigate the influence on surface properties, protein corona evolution, particle-cell interactions, and uptake in two murine epithelial cells. To direct protein corona formation, PS particles were preincubated with five model proteins, namely, bovine serum albumin (BSA), myoglobin, β-lactoglobulin, lysozyme, and fibrinogen. Subsequently, the single-protein-coated particles were incubated in a cell culture medium containing a cocktail of serum proteins to analyze changes in the protein corona profile as well as in the binding kinetics of the model proteins. Therein, we could show that the precoating step has a critical impact on the final composition of the protein corona. Yet, since proteins building the primary corona were still detectable after additional incubations in a protein-containing medium, backtracking of the particle's history is possible. Interestingly, whereas the precoating history significantly disturbs particle-cell interactions (PCIs), the cellular response (i.e., metabolic activity, MTT assay) stays unaffected. Of note, lysozyme precoating revealed one of the highest rates in PCI for both epithelial cell lines. Taken together, we could show that particle history has a significant impact on protein corona formation and subsequently on the interaction of particles with murine intestinal epithelial-like cells. However, as this study was limited to one cell type, further work is needed to assess if these observations can be generalized to other cell types.

Navigations of the targeting pathway of nanomedicines towards tumor

INTRODUCTION

Nanomedicines (NMs) have emerged as a promising approach for revolutionizing cancer treatment outcomes, mainly due to their benefits in the tumor targeted delivery of therapeutics. The preferential accumulation of NMs in tumor has been widely verified by macroscopical technologies. Accordingly, several classic and emerging targeting mechanisms have been proposed to support the tumor-specific delivery of NMs. The targeting mechanism has been a topic of intensive interest and controversy in the field of NMs development. Especially, the mechanisms by which NMs target tumor remain elusive.

AREA COVERED

This topical review mainly discussed the evolution of the targeting mechanisms, crucial issues associated with each mechanism, and confused debates among the mechanisms. The targeting mechanisms of tumor-specific NMs discussed here include the enhanced permeability and retention (EPR) effect, protein corona-mediated targeting delivery, circulating cell mediated transportation, and transcytosis.

EXPERT OPINION

It is of great significance for ultimate clinical translation to have more comprehensive considerations on the mechanism driving the pathway of NMs toward tumors. Our thoughts in this review are expected to provide comprehensive understanding on the mechanisms and elicit thorough explorations on new mechanism to renovate the knowledge framework of NMs delivery.

Structure-function relationships in polymeric multilayer capsules designed for cancer drug delivery

The targeted delivery of cancer drugs to tumor-specific molecular targets represents a major challenge in modern personalized cancer medicine. Engineering of micron and submicron polymeric multilayer capsules allows the obtaining of multifunctional theranostic systems serving as controllable stimulus-responsive tools with a high clinical potential to be used in cancer therapy and detection. The functionalities of such theranostic systems are determined by the design and structural properties of the capsules. This review (1) describes the current issues in designing cancer cell-targeting polymeric multilayer capsules, (2) analyzes the effects of the interactions of the capsules with the cellular and molecular constituents of biological fluids, and (3) presents the key structural parameters determining the effectiveness of capsule targeting. The influence of the morphological and physicochemical parameters and the origin of the structural components and surface ligands on the functional activity of polymeric multilayer capsules at the molecular, cellular, and whole-body levels are summarized. The basic structural and functional principles determining the future trends of theranostic capsule development are established and discussed.

Nanoparticulates reduce tumor cell migration through affinity interactions with extracellular migrasomes and retraction fibers

Nano-tumor interactions are fundamental for cancer nanotherapy, and the cross-talk of nanomedicines with the extracellular matrix (ECM) is increasingly considered essential. Here, we specifically investigate the nano-ECM interactivity using drug-free nanoparticulates (NPs) and highly metastatic cancer cells as models. We discover with surprise that NPs closely bind to specific types of ECM components, namely, retraction fibers (RFs) and migrasomes, which are located at the rear of tumor cells during their migration. This interaction is observed to alter cell morphology, limit cell motion range and change cell adhesion. Importantly, NPs are demonstrated to inhibit tumor cell removal in vitro, and their anti-metastasis potential is preliminarily confirmed in vivo. Mechanically, the NPs are found to coat and form a rigid shell on the surface of migrasomes and retraction fibers via interaction with lipid raft/caveolae substructures. In this way, NPs block the recognition, endocytosis and elimination of migrasomes by their surrounding tumor cells. Thereby, NPs interfere with the cell-ECM interaction and reduce the promotion effect of migrasomes on cell movement. Additionally, NPs trigger alteration of the expression of proteins related to cell-cell adhesion and cytoskeleton organization, which also restricts cell migration. In summary, all the findings here provide a potential target for anti-tumor metastasis nanomedicines.

Micro/Nanosystems for Magnetic Targeted Delivery of Bioagents

Targeted delivery of pharmaceuticals is promising for efficient disease treatment and reduction in adverse effects. Nano or microstructured magnetic materials with strong magnetic momentum can be noninvasively controlled via magnetic forces within living beings. These magnetic carriers open perspectives in controlling the delivery of different types of bioagents in humans, including small molecules, nucleic acids, and cells. In the present review, we describe different types of magnetic carriers that can serve as drug delivery platforms, and we show different ways to apply them to magnetic targeted delivery of bioagents. We discuss the magnetic guidance of nano/microsystems or labeled cells upon injection into the systemic circulation or in the tissue; we then highlight emergent applications in tissue engineering, and finally, we show how magnetic targeting can integrate with imaging technologies that serve to assist drug delivery.

Toxicity Assessment of Mesoporous Silica Nanoparticles upon Intravenous Injection in Mice: Implications for Drug Delivery

Nanoparticles are popular tools utilized to selectively deliver drugs and contrast agents for identification and treatment of disease. To determine the usefulness and translational potential of mesoporous silica nanoparticles (MSNs), further evaluations of toxicity are required. MSNs are among the most utilized nano-delivery systems due to ease of synthesis, pore structure, and functionalization. This study aims to elucidate toxicity as a result of intravenous injection of 25 nm MSNs coated with chitosan (C) or polyethylene glycol (PEG) in mice. Following acute and chronic injections, blood was evaluated for standard blood chemistry and complete blood count analyses. Blood chemistry results primarily indicated that no abnormalities were present following acute or chronic injections of MSNs, or C/PEG-coated MSNs. After four weekly administered treatments, vital organs showed minor exacerbation of pre-existing lesions in the 35KPEG-MSN and moderate exacerbation of pre-existing lesions in uncoated MSN and 2KPEG-MSN treatment groups. In contrast, C-MSN treatment groups had minimal changes compared to controls. This study suggests 25 nm MSNs coated with chitosan should elicit minimal toxicity when administered as either single or multiple intravenous injections, but MSNs coated with PEG, especially 2KPEG may exacerbate pre-existing vascular conditions. Further studies should evaluate varying sizes and types of nanoparticles to provide a better overall understanding on the relation between nanoparticles and in vivo toxicity.

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.

Designing Functional Bionanoconstructs for Effective In Vivo Targeting

The progress achieved over the last three decades in the field of bioconjugation has enabled the preparation of sophisticated nanomaterial–biomolecule conjugates, referred to herein as bionanoconstructs, for a multitude of applications including biosensing, diagnostics, and therapeutics. However, the development of bionanoconstructs for the active targeting of cells and cellular compartments, both in vitro and in vivo, is challenged by the lack of understanding of the mechanisms governing nanoscale recognition. In this review, we highlight fundamental obstacles in designing a successful bionanoconstruct, considering findings in the field of bionanointeractions. We argue that the biological recognition of bionanoconstructs is modulated not only by their molecular composition but also by the collective architecture presented upon their surface, and we discuss fundamental aspects of this surface architecture that are central to successful recognition, such as the mode of biomolecule conjugation and nanomaterial passivation. We also emphasize the need for thorough characterization of engineered bionanoconstructs and highlight the significance of population heterogeneity, which too presents a significant challenge in the interpretation of in vitro and in vivo results. Consideration of such issues together will better define the arena in which bioconjugation, in the future, will deliver functional and clinically relevant bionanoconstructs.

Nanoparticle protein corona evolution: from biological impact to biomarker discovery

Nanoparticles exposed to biological fluids such as blood, quickly interact with their surrounding milieu resulting in a biological coating that results in large part as a function of the physicochemical properties of the nanomaterial. The large nanoparticle surface area-to-volume ratio further augments binding of biological molecules and the resulting biomolecular or protein corona, once thought of as problematic biofouling, is now viewed as a rich source of biological information that can guide the development of nanomedicines. This review gives an overview of the utility of the protein corona in proteomic profiling and discusses how a better understanding of nano-bio interactions can accelerate the clinical translation of nanomedicines and facilitate the identification of disease-specific biomarkers. With the FDA requirement of the protein corona analysis of nanoparticles in place, it is envisaged that analyzing the protein corona of nanoparticles on a case-by-case basis can provide highly valuable nano-bio interface information that can aid and improve their clinical translation.

Nano-Bio Interface-Guided Nanoparticle Protein Corona Antigen for Immunoassays and Immunoimaging in a Complex Matrix

Engineered nanoparticles are widely used in biological imaging and drug delivery because of their excellent physical and chemical properties, but almost all the original functions of engineered nanoparticles suffer from a complex matrix. Herein, we proposed a strategy of preparing nanoparticle protein corona antigens (NPCAgs) through exposing a magnetic core silicon shell (Fe₃O₄@SiO₂) fluorescent probe to an antigen protein solution, which could reduce the adsorption of nanoparticles (NPs) with other proteins in serum. In the presence of target anti-BSA IgG, a competitive-type displacement reaction was implemented between NPs@BSA and other proteins by target anti-BSA IgG through the specific antigen-antibody reaction. In addition, secondary structure analysis showed that almost all of the NPCAgs retained their natural conformation, which ensured the function of the NPCAgs, specifically capturing an antibody. Therefore, the NPCAgs showed good performance in immunoassays and immunoimaging, which should shed light on the application in imaging and identification of other nanomaterials.

Supervised learning model predicts protein adsorption to carbon nanotubes

Engineered nanoparticles are advantageous for biotechnology applications including biomolecular sensing and delivery. However, testing compatibility and function of nanotechnologies in biological systems requires a heuristic approach, where unpredictable protein corona formation prevents their effective implementation. We develop a random forest classifier trained with mass spectrometry data to identify proteins that adsorb to nanoparticles based solely on the protein sequence (78% accuracy, 70% precision). We model proteins that populate the corona of a single-walled carbon nanotube (SWCNT)–based nanosensor and study the relationship between the protein’s amino acid–based properties and binding capacity. Protein features associated with increased likelihood of SWCNT binding include high content of solvent-exposed glycines and nonsecondary structure–associated amino acids. To evaluate its predictive power, we apply the classifier to identify proteins with high binding affinity to SWCNTs, with experimental validation. The developed classifier provides a step toward undertaking the otherwise intractable problem of predicting protein-nanoparticle interactions.

Antibody-Functionalized Carnauba Wax Nanoparticles to Target Breast Cancer Cells

Development of safer nanomedicines for drug delivery applications requires immense efforts to improve clinical outcomes. Targeting a specific cell, biocompatibility and biodegradability are vital properties of a nanoparticle to fulfill the safety criteria in medical applications. Herein, we fabricate antibody-functionalized carnauba wax nanoparticles encapsulated a hydrophobic drug mimetic, which is potentially interesting for clinical use due to the inert and nontoxic properties of natural waxes. The nanoparticles are synthesized applying miniemulsion methods by solidifying molten wax droplets and further evaporating the solvent from the dispersion. The pH-selective adsorption of antibodies (IgG1, immunoglobulin G1, and CD340, an antihuman HER2 antibody) onto the nanoparticle surface is performed for practical and effective functionalization, which assists to overcome the complexity in chemical modification of carnauba wax. The adsorption behavior of the antibodies is studied using isothermal titration calorimetry (ITC), which gives thermodynamic parameters including the enthalpy, association constant, and stoichiometry of the functionalization process. Both antibodies exhibit strong binding at pH 2.7. The CD340-decorated wax nanoparticles show specific cell interaction toward BT474 breast cancer cells and retain the targeting function even after 6 months of storage period.

Scratching the Surface (Modification): Developing a Quantitative Liquid Chromatography-Tandem Mass Spectrometry Method for the Investigation of PEGylated and Non-PEGylated Lipid Mixtures on Lipid-Coated Lanthanide Nanoparticles

We are interested in developing lanthanide nanoparticles (LnNPs) of the general formula NaLnF₄ as high-sensitivity reagents for mass cytometry. These LnNPs must be coated to provide colloidal stability in aqueous buffer and functionality for detecting cellular biomarkers. Lipid bilayer coatings are a promising approach, but one requires an analytical technique to enable characterization of the NP coating composition as opposed to the composition of the lipid formulation used in the coating process. However, quantification of the lipid composition of lipid coatings on polymer and inorganic NPs is not common practice in the field. Here we describe a method based on high-performance liquid chromatography (LC) for separations and triple quadrupole tandem mass spectrometry (MS/MS) instrumentation for detection and show that it can quantify complex lipid mixtures using small (<1 μg) amounts of sample. Our lipid formulation consisted of a mixture of egg sphingomyelin, 1,2-dioleoyl-sn-glycero-3-phosphocholine, 1,2-dioleoyl-3-trimethylammonium-propane, cholesterol-PEG600, and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[biotinyl(polyethylene glycol)-2000]. We were able to extract the coating from lipid-coated 35 nm diameter LnNPs, quantify the lipid/NP ratio, and show that the coating composition differed from the composition of the lipid formulation for several of the species. Knowledge of the actual composition of the lipid coating for lipid-coated NPs is critical for designing and optimizing application of these materials. Our results establish the value of LC-MS/MS characterization of lipid-coated NPs, thus providing an important new addition to the toolbox available for characterizing these types of nanomaterials.

Application of Gold Nanoparticle-Based Materials in Cancer Therapy and Diagnostics

Several metal nanoparticles have been developed for medical application. While all have their benefits, gold nanoparticles (AuNPs) are ideal in cancer therapy and diagnosis as they are chemically inert and minimally toxic. Several studies have shown the potential of AuNPs in the therapeutic field, as photosensitizing agents in sonochemical and photothermal therapy and as drug delivery, as well as in diagnostics and theranostics. Although there is a significant number of reviews on the application of AuNPs in cancer medicine, there is no comprehensive review on their application both in therapy and diagnostics. Therefore, considering the high number of studies on AuNPs’ applications, this review summarizes data on the application of AuNPs in cancer therapy and diagnostics. In addition, we looked at the influence of AuNPs’ shape and size on their biological properties. We also present the potential use of hybrid materials based on AuNPs in sonochemical and photothermal therapy and the possibility of their use in diagnostics. Despite their potential, the use of AuNPs and derivatives in cancer medicine still has some limitations. In this review, we provide an overview of the biological, physicochemical, and legal constraints on using AuNPs in cancer medicine.

Biofabrication of functional protein nanoparticles through simple His-tag engineering

We have developed a simple, robust, and fully transversal approach for the a-la-carte fabrication of functional multimeric nanoparticles with potential biomedical applications, validated here by a set of diverse and unrelated polypeptides. The proposed concept is based on the controlled coordination between Zn2+ ions and His residues in His-tagged proteins. This approach results in a spontaneous and reproducible protein assembly as nanoscale oligomers that keep the original functionalities of the protein building blocks. The assembly of these materials is not linked to particular polypeptide features, and it is based on an environmentally friendly and sustainable approach. The resulting nanoparticles, with dimensions ranging between 10 and 15 nm, are regular in size, are architecturally stable, are fully functional, and serve as intermediates in a more complex assembly process, resulting in the formation of microscale protein materials. Since most of the recombinant proteins produced by biochemical and biotechnological industries and intended for biomedical research are His-tagged, the green biofabrication procedure proposed here can be straightforwardly applied to a huge spectrum of protein species for their conversion into their respective nanostructured formats.

Preparation of Magnetic-Luminescent Bifunctional Rapeseed Pod-Like Drug Delivery System for Sequential Release of Dual Drugs

Drug delivery systems (DDSs) limited to a single function or single-drug loading are struggling to meet the requirements of clinical medical applications. It is of great significance to fabricate DDSs with multiple functions such as magnetic targeting or fluorescent labeling, as well as with multiple-drug loading for enhancing drug efficacy and accelerating actions. In this study, inspired by the dual-chamber structure of rapeseed pods, biomimetic magnetic–luminescent bifunctional drug delivery carriers (DDCs) of 1.9 ± 0.3 μm diameter and 19.6 ± 4.4 μm length for dual drug release were fabricated via double-needle electrospraying. Morphological images showed that the rapeseed pod-like DDCs had a rod-like morphology and Janus dual-chamber structure. Magnetic nanoparticles and luminescent materials were elaborately designed to be dispersed in two different chambers to endow the DDCs with excellent magnetic and luminescent properties. Synchronously, the Janus structure of DDCs promoted the luminescent intensity by at least threefold compared to single-chamber DDCs. The results of the hemolysis experiment and cytotoxicity assay suggested the great blood and cell compatibilities of DDCs. Further inspired by the core–shell structure of rapeseeds containing oil wrapped in rapeseed pods, DDCs were fabricated to carry benzimidazole molecules and doxorubicin@chitosan nanoparticles in different chambers, realizing the sequential release of benzimidazole within 12 h and of doxorubicin from day 3 to day 18. These rapeseed pod-like DDSs with excellent magnetic and luminescent properties and sequential release of dual drugs have potential for biomedical applications such as targeted drug delivery, bioimaging, and sustained treatment of diseases.

Magnetothermal regulation of in vivo protein corona formation on magnetic nanoparticles for improved cancer nanotherapy

Engineering the protein corona (PC) on nanodrugs is emerging as an effective approach to improve their pharmacokinetics and therapeutic efficacy, but conventional in vitro pre-programmed methods have shown great limitation for regulation of the PC in the complex and dynamic in vivo physiological environment. Here, we demonstrate an magnetothermal regulation approach that allows us to in situ modulate the in vivo PC composition on iron oxide nanoparticles for improved cancer nanotherapy. Experimental results revealed that the relative levels of major opsonins and dysopsonins in the PC can be tuned quantitatively by means of heat induction mediated by the nanoparticles under an alternating magnetic field. When the PC was magnetically optimized in vivo, the nanoparticles exhibited prolonged circulation and enhanced tumor delivery efficiency in mice, 2.53-fold and 2.02-fold higher respectively than the control. This led to a superior thermotherapeutic efficacy of systemically delivered nanoparticles. In vivo magnetothermal regulation of the PC on nanodrugs will find wide applications in biomedicine.

In Vivo T Cell-Targeting Nanoparticle Drug Delivery Systems: Considerations for Rational Design

T cells play an important role in immunity and repair and are implicated in diseases, including blood cancers, viral infections, and inflammation, making them attractive targets for the treatment and prevention of diseases. Over recent years, the advent of nanomedicine has shown an increase in studies that use nanoparticles as carriers to deliver therapeutic cargo to T cells for ex vivo and in vivo applications. Nanoparticle-based delivery has several advantages, including the ability to load and protect a variety of drugs, control drug release, improve drug pharmacokinetics and biodistribution, and site- or cell-specific targeting. However, the delivery of nanoparticles to T cells remains a major technological challenge, which is primarily due to the nonphagocytic nature of T cells. In this review, we discuss the physiological barriers to effective T cell targeting and describe the different approaches used to deliver cargo-loaded nanoparticles to T cells for the treatment of disease such as T cell lymphoma and human immunodeficiency virus (HIV). In particular, engineering strategies that aim to improve nanoparticle internalization by T cells, including ligand-based targeting, will be highlighted. These nanoparticle engineering approaches are expected to inspire the development of effective nanomaterials that can target or manipulate the function of T cells for the treatment of T cell-related diseases.

Unraveling the In Vivo Protein Corona

Understanding the behavior of nanoparticles upon contact with a physiological environment is of urgent need in order to improve their properties for a successful therapeutic application. Most commonly, the interaction of nanoparticles with plasma proteins are studied under in vitro conditions. However, this has been shown to not reflect the complex situation after in vivo administration. Therefore, here we focused on the investigation of magnetic nanoparticles with blood proteins under in vivo conditions. Importantly, we observed a radically different proteome in vivo in comparison to the in vitro situation underlining the significance of in vivo protein corona studies. Next to this, we found that the in vivo corona profile does not significantly change over time. To mimic the in vivo situation, we established an approach, which we termed “ex vivo” as it uses whole blood freshly prepared from an animal. Overall, we present a comprehensive analysis focusing on the interaction between nanoparticles and blood proteins under in vivo conditions and how to mimic this situation with our ex vivo approach. This knowledge is needed to characterize the true biological identity of nanoparticles.

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.

Fabrication of tumor-targeting composites based on the triple helical β-glucan through conjugation of aptamer

Herein the nucleic acid aptamers were attached to the polydeoxyadenylic acid (poly(dA)) tail for improving the tumor-targetability and cellular internalization of s-LNT/poly(dA) composite composed of two single chains of triple helical β-glucan lentinan (s-LNT) and one poly(dA) chain. The in vitro results demonstrate that the cellular uptake of s-LNT/poly(dA) composites in MCF-7 cancer cells was enhanced effectively after attaching the aptamer. The as-prepared fluorescin isothiocyanate (FITC)-labelled LNT (LNT-FITC) through grafting was used for tracing the enhanced tumor-targetability of the composites. As a result, the cellular internalization of the LNT-FITC into MCF-7 and 4T1 cancer cells was further increased by the aptamer conjugated to poly(dA). Meanwhile, the in vivo experiments further demonstrate more s-LNT/poly(dA)-aptamer composites were effectively accumulated at the tumor site compared with s-LNT alone. This work provides a novel strategy for fabricating triplex β-glucan as delivery vectors with active tumor-targetability.

Hybrid nanomaterials of biomolecule corona coated magnetic nanoparticles and their interaction with biological systems

Magnetic nanoparticles (MNPs) are interesting for various applications in medicine. If administered to a biological system like the human body, a so-called biomolecule corona is formed on the surface of the particles, which highly determines the biological fate of the particles. To elucidate whether a preconditioning of the MNPs by incubation with biomolecules influences biocompatibility and bioavailability, the formation of such a corona was investigated in more detail. For this, the influence of particle characteristics, e.g., surface charge, as well as various incubation parameters on the resulting corona was investigated. It was found that the biomolecule corona is formed immediately after bringing together the particles with the biomolecule source. By variation of the biomolecule content of the incubation medium, the size of the corona can be modulated. Regarding the interaction of the nanoparticles with cells, it was shown that the presence of a biomolecule corona reduces the interaction and that a more pronounced biomolecule corona leads to a reduced uptake of the magnetic nanohybrids into the cells. Cell viability tests confirmed biocompatibility of the biomolecule-coated particles. A more pronounced corona promotes a higher cell viability. By using a shell-less hen’s egg model, no or reduced adverse effects of all biomolecule-coated MNP for this in vivo test were found. Resulting from these investigations, we were able to demonstrate that our newly developed nanohybrids significantly reduce in vivo toxicity compared to uncoated MNPs.

On the importance of the linking chemistry for the PEGylation of mesoporous silica nanoparticles

The typical method for minimizing serum protein adsorption in biological settings and prolonging blood circulation time of nanoparticles, is to anchor hydrophilic polymers (e.g., poly(ethylene glycol), PEG) on the particle surface, which is most often done by covalent attachment (PEGylation). Herein, different PEGylation methods were realised and compared to functionalize mesoporous silica nanoparticles (MSNs). First, reactive groups were installed using post-grafting procedures with different functional silanes. Further, PEGs carrying a functional group and having different chain lengths and termini, were used. The grafting efficacy as well as the structural and physicochemical characteristics of the resulting particles were determined. Finally, the serum protein adsorption behaviour of these functionalized particles was investigated using thermogravimetric analysis. The type of selected coupling method was shown to strongly influence the grafting efficiency as well as the resulting protein adsorption. The results highlight the importance of the right choice of the linking chemistry when aiming at surface functionalization of nanoparticles.

Person-Specific Biomolecular Coronas Modulate Nanoparticle Interactions with Immune Cells in Human Blood

When nanoparticles interact with human blood, a multitude of plasma components adsorb onto the surface of the nanoparticles, forming a biomolecular corona. Corona composition is known to be influenced by the chemical composition of nanoparticles. In contrast, the possible effects of variations in the human blood proteome between healthy individuals on the formation of the corona and its subsequent interactions with immune cells in blood are unknown. Herein, we prepared and examined a matrix of 11 particles (including organic and inorganic particles of three sizes and five surface chemistries) and plasma samples from 23 healthy donors to form donor-specific biomolecular coronas (personalized coronas) and investigated the impact of the personalized coronas on particle interactions with immune cells in human blood. Among the particles examined, poly(ethylene glycol) (PEG)-coated mesoporous silica (MS) particles, irrespective of particle size (800, 450, or 100 nm in diameter), displayed the widest range (up to 60-fold difference) of donor-dependent variance in immune cell association. In contrast, PEG particles (after MS core removal) of 860, 518, or 133 nm in diameter displayed consistent stealth behavior (negligible cell association), irrespective of plasma donor. For comparison, clinically relevant PEGylated doxorubicin-encapsulated liposomes (Doxil) (74 nm in diameter) showed significant variance in association with monocytes and B cells across all plasma donors studied. An in-depth proteomic analysis of each biomolecular corona studied was performed, and the results were compared against the nanoparticle-blood cell association results, with individual variance in the proteome driving differential association with specific immune cell types. We identified key immunoglobulin and complement proteins that explicitly enriched or depleted within the corona and which strongly correlated with the cell association pattern observed across the 23 donors. This study demonstrates how plasma variance in healthy individuals significantly influences the blood immune cell interactions of nanoparticles.

Construction of a tumor microenvironment pH-responsive cleavable PEGylated hyaluronic acid nano-drug delivery system for colorectal cancer treatment

In order to improve active tumor targeting, tumor cell uptake efficiency and circulation time of doxorubicin (DOX) in vivo, we constructed a cleavable PEGylated hyaluronic acid nano-drug delivery system (HA-mPEG2k-DOX) based on a tumor microenvironment pH-responsive imine bond. In this study, HA-mPEG2k-DOX can self-assemble into stable nanoparticles (HA-mPEG2k-DOX NPs) with a particle size of 50 nm. And the NPs can efficiently target CD44 positive CT26 cells and the pH-responsive cleavable PEG shell can be detached under weakly acidic environments and effectively promote the cellular uptake of HA-DOX NPs. Compared with DOX·HCl, the HA-mPEG2k-DOX NPs can significantly increase the DOX circulation time by 12.5 times, efficiently target the tumor tissues of CT26 tumor-bearing mice and remain for 72 hours. Therefore, the antitumor results in vivo indicated that the HA-mPEG2k-DOX NPs have the best anti-tumor effect while reducing the toxicity of the DOX. Overall, the cleavable PEGylated HA-mPEG2k-DOX NPs responding to pH-sensitive imine bonds, while actively targeting CD44-positive tumor cells, improve the dilemma of cellular uptake and delivery by the PEGylated nano delivery system.

The biomolecule corona of lipid nanoparticles contains circulating cell-free DNA

The spontaneous adsorption of biomolecules onto the surface of nanoparticles (NPs) in complex physiological biofluids has been widely investigated over the last decade. Characterisation of the protein composition of the 'biomolecule corona' has dominated research efforts, whereas other classes of biomolecules, such as nucleic acids, have received no interest. Scarce, speculative statements exist in the literature about the presence of nucleic acids in the biomolecule corona, with no previous studies attempting to describe the contribution of genomic content to the blood-derived NP corona. Herein, we provide the first experimental evidence of the interaction of circulating cell-free DNA (cfDNA) with lipid-based NPs upon their incubation with human plasma samples, obtained from healthy volunteers and ovarian carcinoma patients. Our results also demonstrate an increased amount of detectable cfDNA in patients with cancer. Proteomic analysis of the same biomolecule coronas revealed the presence of histone proteins, suggesting an indirect, nucleosome-mediated NP-cfDNA interaction. The finding of cfDNA as part of the NP corona, offers a previously unreported new scope regarding the chemical composition of the 'biomolecule corona' and opens up new possibilities for the potential exploitation of the biomolecule corona for the enrichment and analysis of blood-circulating nucleic acids.

Effect of surface morphology change of polystyrene microspheres through etching on protein corona and phagocytic uptake

Surface physicochemistry properties of polymer particles are crucial for protein corona formation and macrophage phagocytosis when they contact with living body. In this work, polystyrene microspheres (PS-MSs) were selected as a model of polymer microparticles and fabricated by chromic acid etching through controlling conditions to obtain different surface morphology structures and to investigate their effect on the protein adsorption and phagocytic uptake of PS-MSs. The adsorption of bovine serum albumin (BSA) and fibrinogen (FIB) on PS-MSs showed almost the same tendency, i.e. the etched PS-MSs presented lower protein adsorption compared with original microspheres. The adsorption of BSA and FIB was the lowest when the protuberances on the etched surfaces were maximum and the size of the protuberances was minimum. Furthermore, the surface morphologies of PS-MSs were influenced in return not only by the amounts of proteins but also by protein types. Meanwhile, the macrophages phagocytosis of PS-MSs depended on the amounts and kinds of adsorbed proteins, especially the albumin content. In a word, phagocytosis and protein adsorption can be regulated by microsphere morphologies through etching, which provides a promising strategy to avoid invalid uptake for polymer particles such as drug delivery carriers.

A custom-made functionalization method to control the biological identity of nanomaterials

Here we propose a one-step strategy to endow nanomaterials with a custom-designed bio-identity. This study designs a universal 'nanomaterial binding domain' that can be genetically attached to any protein ensuring precise and spontaneous protein orientation. We demonstrate how, despite the simplicity of the method, the bioconjugation achieved: (i) is highly efficient, even in the presence of competing proteins, (ii) is stable at extreme physiological conditions (pH ranges 5.2-9.0; NaCl concentrations 0-1 M); (iii) prevents unwanted protein biofouling days after incubation in biologically-relevant conditions; and finally, (iv) avoids nanoparticle interaction with promiscuous unspecific receptors. In summary, this protein biocoating technique, applicable to a wide array of nano-designs, integrates material science and molecular biology procedures to create hybrid nanodevices with well-defined surfaces and predictable biological behaviors, opening a chapter in precision nanodiagnostics, nanosensing or nanotherapeutic applications.

Gambogic acid: A shining natural compound to nanomedicine for cancer therapeutics

The United States Food and Drug Administration has permitted number of therapeutic agents for cancer treatment. Most of them are expensive and have some degree of systemic toxicity which makes overbearing in clinical settings. Although advanced research continuously applied in cancer therapeutics, but drug resistance, metastasis, and recurrence remain unanswerable. These accounts to an urgent clinical need to discover natural compounds with precisely safe and highly efficient for the cancer prevention and cancer therapy. Gambogic acid (GA) is the principle bioactive and caged xanthone component, a brownish gamboge resin secreted from the of Garcinia hanburyi tree. This molecule showed a spectrum of biological and clinical benefits against various cancers. In this review, we document distinct biological characteristics of GA as a novel anti-cancer agent. This review also delineates specific molecular mechanism(s) of GA that are involved in anti-cancer, anti-metastasis, anti-angiogenesis, and chemo-/radiation sensitizer activities. Furthermore, recent evidence, development, and implementation of various nanoformulations of gambogic acid (nanomedicine) have been described.

Ultrasmall Gold Nanoparticles Coated with Zwitterionic Glutathione Monoethyl Ester: A Model Platform for the Incorporation of Functional Peptides

Ultrasmall gold nanoparticles (AuNPs) are an emerging class of nanomaterials exhibiting distinctive physicochemical, molecular, and in vivo properties. Recently, we showed that ultrasmall AuNPs encompassing a zwitterionic glutathione monoethyl ester surface coating (AuGSHzwt) were highly resistant to aggregation and serum protein interactions. Herein, we performed a new set of biointeraction studies to gain a more fundamental understanding into the behavior of both pristine and peptide-functionalized AuGSHzwt in complex media. Using the model Strep-tag peptide (WSHPQFEK) as an integrated functional group, we established that AuGSHzwt could be conjugated with increasing numbers of Strep-tags by simple ligand exchange, which provides a generic approach for AuGSHzwt functionalization. It was found that the strep-tagged AuGSHzwt particles were highly resistant to nonspecific protein interactions and retained their targeting capability in biological fluid, displaying efficient binding to Streptactin receptors in nearly undiluted serum. However, AuGSHzwt functionalized with multiple Strep-tags displayed somewhat lower resistance to protein interactions and lower levels of binding to Streptactin than monofunctionalized AuGSHzwt under given conditions. These results underscore the need for optimizing ligand density onto the surface of ultrasmall AuNPs for improved performance. Collectively, our findings support ultrasmall AuGSHzwt as an attractive platform for engineering functional, protein-mimetic nanostructures capable of specific protein recognition within the complex biological milieu.

Protein coating composition targets nanoparticles to leaf stomata and trichomes

Plant nanobiotechnology has the potential to revolutionize agriculture. However, the lack of effective methods to deliver nanoparticles (NPs) to the precise locations in plants where they are needed impedes these technological innovations. Here, model gold nanoparticles (AuNP) were coated with citrate, bovine serum albumin (BSA) as a protein control, or LM6-M, an antibody with an affinity for functional groups unique to stomata on leaf surfaces to deliver the AuNPs to stomata. One-month-old Vicia faba leaves were exposed via drop deposition to aqueous suspensions of LM6-M-coated AuNPs and allowed to air dry. After rinsing, Au distribution on the leaf surface was investigated by enhanced dark-field microscopy and X-ray fluorescence mapping. While citrate-coated AuNPs randomly covered the plant leaves, LM6M-AuNPs strongly adhered to the stomata and remained on the leaf surface after rinsing, and BSA-AuNPs specifically targeted trichome hairs. To the authors' knowledge, this is the first report of active targeting of live leaf structures using NPs coated with molecular recognition molecules. This proof-of-concept study provides a strategy for future targeted nanopesticide delivery research.

Sub-10 nm Theranostic Unimolecular Micelles with High Tumor-Specific Accumulation, Retention, and Inhibitory Effect

Theranostic agents that integrate far-red/near-infrared fluorescence and anticancer drugs are useful for biomedical applications such as imaging-guided therapy of cancers. However, the clinical translation of previously reported theranostic agents is still limited by factors such as weak fluorescence of the imaging probe, premature and off-target release of fluorophores and drugs during blood circulation, the long-term retention in the reticuloendothelial system, and side effects of toxicity. Here, we report a new type of ultrasmall theranostic unimolecular micelles with an average diameter below 10 nm, and dual functionalities of bright fluorescence in the spectral window of 600-800 nm toward noninvasive in vivo bioimaging and covalently bound anticancer drugs for specific cancer treatment. Each unimolecular micelle is formed by an amphiphilic bottlebrush copolymer containing a fluorescent conjugated backbone of poly(fluorene-alt-(4,7-bis(hexylthien)-2,1,3-benzothiadiazole)), from which hydrophobic disulfide-linked camptothecin as an anticancer drug and hydrophilic oligo(ethylene glycol) are grafted. These ultrasmall unimolecular micelles exhibit remarkably high efficiency of accumulation and retention in tumor tissues with a tumor inhibitory rate of 50%, but little distribution in other healthy organs and tissues. Such a feature of enhanced tumor targeting and reduced toxic side effects against healthy cells and tissues is promising for future clinical translation of imaging-guided cancer therapy.

Engineered Polymeric Materials for Biological Applications: Overcoming Challenges of the Bio-Nano Interface

Nanomedicine has generated significant interest as an alternative to conventional cancertherapy due to the ability for nanoparticles to tune cargo release. However, while nanoparticletechnology has promised significant benefit, there are still limited examples of nanoparticles inclinical practice. The low translational success of nanoparticle research is due to the series ofbiological roadblocks that nanoparticles must migrate to be effective, including blood and plasmainteractions, clearance, extravasation, and tumor penetration, through to cellular targeting,internalization, and endosomal escape. It is important to consider these roadblocks holistically inorder to design more effective delivery systems. This perspective will discuss how nanoparticlescan be designed to migrate each of these biological challenges and thus improve nanoparticledelivery systems in the future. In this review, we have limited the literature discussed to studiesinvestigating the impact of polymer nanoparticle structure or composition on therapeutic deliveryand associated advancements. The focus of this review is to highlight the impact of nanoparticlecharacteristics on the interaction with different biological barriers. More specific studies/reviewshave been referenced where possible.