Enhancing cell recognition by scrutinizing cell surfaces with a nanoparticle array

Converting Nanotoxicity Data to Information Using Artificial Intelligence and Simulation

Decades of nanotoxicology research have generated extensive and diverse data sets. However, data is not equal to information. The question is how to extract critical information buried in vast data streams. Here we show that artificial intelligence (AI) and molecular simulation play key roles in transforming nanotoxicity data into critical information, i.e., constructing the quantitative nanostructure (physicochemical properties)-toxicity relationships, and elucidating the toxicity-related molecular mechanisms. For AI and molecular simulation to realize their full impacts in this mission, several obstacles must be overcome. These include the paucity of high-quality nanomaterials (NMs) and standardized nanotoxicity data, the lack of model-friendly databases, the scarcity of specific and universal nanodescriptors, and the inability to simulate NMs at realistic spatial and temporal scales. This review provides a comprehensive and representative, but not exhaustive, summary of the current capability gaps and tools required to fill these formidable gaps. Specifically, we discuss the applications of AI and molecular simulation, which can address the large-scale data challenge for nanotoxicology research. The need for model-friendly nanotoxicity databases, powerful nanodescriptors, new modeling approaches, molecular mechanism analysis, and design of the next-generation NMs are also critically discussed. Finally, we provide a perspective on future trends and challenges.

Nucleic acid nanoassembly-enhanced RNA therapeutics and diagnosis

RNAs are involved in the crucial processes of disease progression and have emerged as powerful therapeutic targets and diagnostic biomarkers. However, efficient delivery of therapeutic RNA to the targeted location and precise detection of RNA markers remains challenging. Recently, more and more attention has been paid to applying nucleic acid nanoassemblies in diagnosing and treating. Due to the flexibility and deformability of nucleic acids, the nanoassemblies could be fabricated with different shapes and structures. With hybridization, nucleic acid nanoassemblies, including DNA and RNA nanostructures, can be applied to enhance RNA therapeutics and diagnosis. This review briefly introduces the construction and properties of different nucleic acid nanoassemblies and their applications for RNA therapy and diagnosis and makes further prospects for their development.

Design of high-avidity multivalent ligand structures that target cells with high ligand economy

Novel cell-targeting ligand structures are constructed with a spikey core scaffold, where multiple copies of coiled-coil peptide nanorods are conjugated on the surface of a peptide nanosheet. Clustering of carbohydrate and aptamer ligands at the end of the coiled coils optimizes ligand accessibility to cell-surface receptors. Display of the ligand-coil conjugates on the nanosheet generates a patchy ligand pattern bearing two levels of multivalency. With the ligand-scaffold system, high-avidity cell targeting is realized using fewer ligands than ever, which facilitates future applications in cell detection and drug delivery.

Multiple-Aptamer-Integrated DNA-Origami-Based Chemical Nose Sensors for Accurate Identification of Cancer Cells

Developing simple, rapid, and accurate methods for cancer cell identification could facilitate early cancer diagnosis and tumor metastasis research. Herein, we develop a novel chemical nose sensor that employs the collective recognition abilities of a set of multiple-aptamer-integrated DNA origami (MADO) probes for discriminative identification of cancer cells. By controlling the types and/or copies of aptamers assembled on the DNA origami nanostructure, we constructed five MADO probes with differential binding affinities (ranging from 3.08 to 78.92 nM) to five types of cells (HeLa, MDA-MB-468, MCF-7, HepG2, and MCF-10A). We demonstrate the utility of the MADO-based chemical nose sensor in the identification of blinded unknown cell samples with a 95% accuracy. This sensing platform holds great potential for applications in medical diagnostics.

Metal/metal oxide nanoparticles: Toxicity concerns associated with their physical state and remediation for biomedical applications

Metal/metal oxide nanoparticles show promise for various applications, including diagnosis, treatment, theranostics, sensors, cosmetics, etc. Their altered chemical, optical, magnetic, and structural properties have differential toxicity profiles. Depending upon their physical state, these NPs can also change their properties due to alteration in pH, interaction with proteins, lipids, blood cells, and genetic material. Metallic nanomaterials (comprised of a single metal element) tend to be relatively stable and do not readily undergo dissolution. Contrarily, metal oxide and metal alloy-based nanomaterials tend to exhibit a lower degree of stability and are more susceptible to dissolution and ion release when introduced to a biological milieu, leading to reactive oxygen species production and oxidative stress to cells. Since NPs have considerable mobility in various biological tissues, the investigation related to their adverse effects is a critical issue and required to be appropriately addressed before their biomedical applications. Short and long-term toxicity assessment of metal/metal oxide nanoparticles or their nano-formulations is of paramount importance to ensure the global biome's safety; otherwise, to face a fiasco. This article provides a comprehensive introspection regarding the effects of metal/metal oxides' physical state, their surface properties, the possible mechanism of actions along with the potential future strategy for remediation of their toxic effects.

Cytotoxicity Induction by the Oxidative Reactivity of Nanoparticles Revealed by a Combinatorial GNP Library with Diverse Redox Properties

It is crucial to establish relationship between nanoparticle structures (or properties) and nanotoxicity. Previous investigations have shown that a nanoparticle's size, shape, surface and core materials all impact its toxicity. However, the relationship between the redox property of nanoparticles and their toxicity has not been established when all other nanoparticle properties are identical. Here, by synthesizing an 80-membered combinatorial gold nanoparticle (GNP) library with diverse redox properties, we systematically explored this causal relationship. The compelling results revealed that the oxidative reactivity of GNPs, rather than their other physicochemical properties, directly caused cytotoxicity via induction of cellular oxidative stress. Our results show that the redox diversity of nanoparticles is regulated by GNPs modified with redox reactive ligands.

Logic Gates Based on DNA Aptamers

DNA bio-computing is an emerging trend in modern science that is based on interactions among biomolecules. Special types of DNAs are aptamers that are capable of selectively forming complexes with target compounds. This review is devoted to a discussion of logic gates based on aptamers for the purposes of medicine and analytical chemistry. The review considers different approaches to the creation of logic gates and identifies the general algorithms of their creation, as well as describes the methods of obtaining an output signal which can be divided into optical and electrochemical. Aptameric logic gates based on DNA origami and DNA nanorobots are also shown. The information presented in this article can be useful when creating new logic gates using existing aptamers and aptamers that will be selected in the future.

Virtual Molecular Projections and Convolutional Neural Networks for the End-to-End Modeling of Nanoparticle Activities and Properties

Digitalizing complex nanostructures into data structures suitable for machine learning modeling without losing nanostructure information has been a major challenge. Deep learning frameworks, particularly convolutional neural networks (CNNs), are especially adept at handling multidimensional and complex inputs. In this study, CNNs were applied for the modeling of nanoparticle activities exclusively from nanostructures. The nanostructures were represented by virtual molecular projections, a multidimensional digitalization of nanostructures, and used as input data to train CNNs. To this end, 77 nanoparticles with various activities and/or physicochemical property results were used for modeling. The resulting CNN model predictions show high correlations with the experimental results. An analysis of a trained CNN quantitatively showed that neurons were able to recognize distinct nanostructure features critical to activities and physicochemical properties. This "end-to-end" deep learning approach is well suited to digitalize complex nanostructures for data-driven machine learning modeling and can be broadly applied to rationally design nanoparticles with desired activities.

Highly Specific, Single-step Cancer Cell Isolation with Multi-Aptamer-Mediated Proximity Ligation on Live Cell Membranes

A single-step method for isolation of specific cells based on multiple surface markers will have unique advantages because of its scalability, efficacy, and mildness. Herein, we developed multi-aptamer-mediated proximity ligation method on live cell membranes that leverages a multi-receptor co-recognition design for enhanced specificity, as well as a robust in situ signal amplification design for improved sensitivity of cell isolation. We demonstrated the promising efficacy of our method on differentiating tumor cell subtypes in both cell mixtures and clinical samples. Owing to its simple and fast operation with excellent cell isolation sensitivity and accuracy, this approach will have broad applications in biological science, biomedical engineering, and personalized medicine.

Amplified AND logic platform for cell identification

Herein, we developed an amplified AND logic platform (AALP) on a cell membrane, which integrated two DNA aptamers for cell recognition and localized catalytic hairpin assembly (LCHA) for signal amplification. The AALP could perform "AND" logic computing via a double-checked strategy of two biomarkers on similar cell surfaces and precisely label the target cells with an amplified fluorescence signal.

Applications of Photoinduced Phenomena in Supramolecularly Arranged Phthalocyanine Derivatives: A Perspective

This review focuses on the description of several examples of supramolecular assemblies of phthalocyanine derivatives differently functionalized and interfaced with diverse kinds of chemical species for photo-induced phenomena applications. In fact, the role of different substituents was investigated in order to tune peculiar aggregates formation as well as, with the same aim, the possibility to interface these derivatives with other molecular species, as electron donor and acceptor, carbon allotropes, cyclodextrins, protein cages, drugs. Phthalocyanine photo-physical features are indeed really interesting and appealing but need to be preserved and optimized. Here, we highlight that the supramolecular approach is a versatile method to build up very complex and functional architectures. Further, the possibility to minimize the organization energy and to facilitate the spontaneous assembly of the molecules, in numerous examples, has been demonstrated to be more useful and performing than the covalent approach.

Regulation of Cell Uptake and Cytotoxicity by Nanoparticle Core under the Controlled Shape, Size, and Surface Chemistries

Nanoparticle structural parameters, such as size, surface chemistry, and shape, are well-recognized parameters that affect biological activities of nanoparticles. However, whether the core material of a nanoparticle also plays a role remains unknown. To answer this long-standing question, we synthesized and investigated a comprehensive library of 36 nanoparticles with all combinations of three types of core materials (Au, Pt, and Pd), two sizes (6 and 26 nm), and each conjugated with one of six surface ligands of different hydrophobicity. Using this systematic approach, we were able to identify cellular perturbation specifically attributed to core, size, or surface ligand. We discovered that core materials exhibited a comparable regulatory ability as surface ligand on cellular ROS generation and cytotoxicity. Pt nanoparticles were much more hydrophilic and showed much less cell uptake compared to Au and Pd nanoparticles with identical size, shape, and surface ligands. Furthermore, diverse core materials also regulated levels of cellular redox activities, resulting in different cytotoxicity. Specifically, Pd nanoparticles significantly reduced cellular H₂O₂ and promoted cell survival, while Au nanoparticles with identical size, shape, and surface ligand induced higher cellular oxidative stress and cytotoxicity. Our results demonstrate that nanoparticle core material is as important as other structural parameters in nanoparticle-cell interactions, making it also a necessary consideration when designing nanomedicines.

Precision-Guided Missile-Like DNA Nanostructure Containing Warhead and Guidance Control for Aptamer-Based Targeted Drug Delivery into Cancer Cells in Vitro and in Vivo

It is crucial to deliver anticancer drugs to target cells with high precision and efficiency. While nanomaterials have been shown to enhance the delivery efficiency once they reach the target, it remains challenging for precise drug delivery to overcome the nonspecific adsorption and off-target effect. To meet this challenge, we report herein the design of a novel DNA nanostructure to act as a DNA nanoscale precision-guided missile (D-PGM) for highly efficient loading and precise delivery of chemotherapeutic agents to specific target cells. The D-PGM consists of two parts: a warhead (WH) and a guidance/control (GC). The WH is a rod-like DNA nanostructure as a drug carrier, whose trunk is a three-dimensionally self-assembled DNA nanoscale architecture from the programmed hybridization among two palindromic DNA sequences in the x-y dimension and two common DNA oligonucleotides in the z direction, making the WH possess a high payload capacity of drugs. The GC is an aptamer-based logic gate assembled in a highly organized fashion capable of performing cell-subtype-specific recognition via the sequential disassembly, mediated by cell-anchored aptamers. Because of the cooperative effects between the WH and the GC, the GC logic gates operate like the guidance and control system in a precision-guided missile to steer the doxorubicin (DOX)-loaded DNA WH toward target cancer cells, leading to selective and enhanced therapeutic efficacy. Moreover, fluorophores attached to different locations of D-PGM and DOX fluorescence dequenching upon release enable intracellular tracing of the DNA nanostructures and drugs. The results demonstrate that by mimicking the functionalities of a military precision-guided missile to design the sequential disassembly of the GC system in multistimuli-responsive fashion, our intrinsically biocompatible and degradable D-PGM can accurately identify target cancer cells in complex biological milieu and achieve active targeted drug delivery. The success of this strategy paves the way for specific cell identity and targeted cancer therapy.

Cytotoxicity-Related Bioeffects Induced by Nanoparticles: The Role of Surface Chemistry

Nanoparticles (NPs) are widely used in a variety of fields, including those related to consumer products, architecture, energy, and biomedicine. Once they enter the human body, NPs contact proteins in the blood and interact with cells in organs, which may induce cytotoxicity. Among the various factors of NP surface chemistry, surface charges, hydrophobicity levels and combinatorial decorations are found to play key roles inregulating typical cytotoxicity-related bioeffects, including protein binding, cellular uptake, oxidative stress, autophagy, inflammation, and apoptosis. In this review, we summarize the recent progress made in directing the levels and molecular pathways of these cytotoxicity-related effects by the purposeful design of NP surface charge, hydrophobicity, and combinatorial decorations.

Bispecific Aptamer Induced Artificial Protein-Pairing: A Strategy for Selective Inhibition of Receptor Function

Cell surface receptors play a critical role in modulating intracellular signal transduction, making them important drug targets. However, it remains challenging to develop a selective and efficient strategy for regulating receptor function. Herein, we develop a strategy, called bispecific aptamer induced artificial protein-pairing, to selectively regulate receptor function. In this strategy, bispecific aptamer probes act as molecular mediators to bind to both a target receptor protein and a paired protein, which brings the two proteins into close proximity on the living cell membrane. Importantly, the paired proteins work not only as a cancer biomarker for enhancing cell selectivity but also as a blocking assistant to inhibit target receptor function via strong steric hindrance effect. Compared with single-aptamer-mediated regulation, the proposed bispecific aptamer probes afford substantial improvement in selective and efficient regulation of receptor function and downstream signaling pathways. This work offers a versatile methodology to design molecular mediators that can modulate receptor function, thereby providing a new way for developing novel therapeutic drugs.

Design of Small Nanoparticles Decorated with Amphiphilic Ligands: Self-Preservation Effect and Translocation into a Plasma Membrane

Design of nanoparticles (NPs) for biomedical applications requires a thorough understanding of cascades of nano-bio interactions at different interfaces. Here, we take into account the cascading effect of NP functionalization on interactions with target cell membranes by determining coatings of biomolecules in biological media. Cell culture experiments show that NPs with more hydrophobic surfaces are heavily ingested by cells in both the A549 and HEK293 cell lines. However, before reaching the target cell, both the identity and amount of recruited biomolecules can be influenced by the pristine NPs' hydrophobicity. Dissipative particle dynamics (DPD) simulations show that hydrophobic NPs acquire coatings of more biomolecules, which may conceal the properties of the as-engineered NPs and impact the targeting specificity. Based on these results, we propose an amphiphilic ligand coating on NPs. DPD simulations reveal the design principle, following which the amphiphilic ligands first curl in solvent to reduce the surface hydrophobicity, thus suppressing the assemblage of biomolecules. Upon attaching to the membrane, the curled ligands extend and rearrange to gain contacts with lipid tails, thus dragging NPs into the membrane for translocation. Three NP-membrane interaction states are identified that are found to depend on the NP size and membrane surface tension. These results can provide useful guidelines to fabricate ligand-coated NPs for practical use in targeted drug delivery, and motivate further studies of nano-bio-interactions with more consideration of cascading effects.

In silico profiling nanoparticles: predictive nanomodeling using universal nanodescriptors and various machine learning approaches

Rational nanomaterial design is urgently demanded for new nanomaterial development with desired properties. However, computational nanomaterial modeling and virtual nanomaterial screening are not applicable for this purpose due to the complexity of nanomaterial structures. To address this challenge, a new computational workflow is established in this study to virtually profile nanoparticles by (1) constructing a structurally diverse virtual gold nanoparticle (GNP) library and (2) developing novel universal nanodescriptors. The emphasis of this study is the second task by developing geometrical nanodescriptors that are suitable for the quantitative modeling of GNPs and virtual screening purposes. The feasibility, rigor and applicability of this novel computational method are validated by testing seven GNP datasets consisting of 191 unique GNPs of various nano-bioactivities and physicochemical properties. The high predictability of the developed GNP models suggests that this workflow can be used as a universal tool for nanomaterial profiling and rational nanomaterial design.

Why are nanoparticles trapped at cell junctions when the cell density is high?

Research on nanoparticle (NP)-cell interactions has been extensively carried out in dilute cell cultures, where NPs are heavily internalized by cells. However, it is not known whether the findings from cell culture studies are still true in tissues where cells are tightly packed. Here, we show experimentally and theoretically that when cells are tightly packed, cellular uptake is strongly hindered. When simultaneously encountering two adjacent cells as is often the case in tissues, adhesion, bending and protrusion of at least two membranes from these cells generate complicated energy contributions that cause trapping of NPs at cell junctions with impeded uptake.

Measuring the Adhesion Forces for the Multivalent Binding of Vancomycin-Conjugated Dendrimer to Bacterial Cell-Wall Peptide

Multivalent ligand-receptor interaction provides the fundamental basis for the hypothetical notion that high binding avidity relates to the strong force of adhesion. Despite its increasing importance in the design of targeted nanoconjugates, an understanding of the physical forces underlying the multivalent interaction remains a subject of urgent investigation. In this study, we designed three vancomycin (Van)-conjugated dendrimers G5(Van) _n ( n = mean valency = 0, 1, 4) for bacterial targeting with generation 5 (G5) poly(amidoamine) dendrimer as a multivalent scaffold and evaluated both their binding avidity and physical force of adhesion to a bacterial model surface by employing surface plasmon resonance (SPR) spectroscopy and atomic force microscopy. The SPR experiment for these conjugates was performed in a biosensor chip surface immobilized with a bacterial cell-wall peptide Lys-d-Ala-d-Ala. Of these, G5(Van)₄ bound most tightly with a K_D of 0.34 nM, which represents an increase in avidity by 2 or 3 orders of magnitude relative to a monovalent conjugate G5(Van)₁ or free vancomycin, respectively. By single-molecule force spectroscopy, we measured the adhesion force between G5(Van) _n and the same cell-wall peptide immobilized on the surface. The distribution of adhesion forces increased in proportion to vancomycin valency with the mean force of 134 pN at n = 4 greater than 96 pN at n = 1 at a loading rate of 5200 pN/s. In summary, our results are strongly supportive of the positive correlation between the avidity and adhesion force in the multivalent interaction of vancomycin nanoconjugates.

Bio-distribution and bio-availability of silver and gold in rat tissues with silver/gold nanorod administration

Along with the increasing applications of nanomaterials in medical fields, to know the systemic distribution of nanomaterials in the body through a precise method is required for the biosafety assessment of nanomaterials. In this study, we firstly have established a reliable inductively coupled plasma mass spectrometry (ICP-MS) method for concentration measurement of silver (Ag) and gold (Au) in biological tissues. Then, based on this method, the Ag or Au distribution in rat blood and almost all of the organs were analyzed after an i.v. or s.c. administration of Au@Ag NRs. Both the time-dependent contents of Ag and Au in blood and two pharmacokinetic models confirmed the rapid clearance of Ag from blood. At 24 h after i.v. injection, there was the highest level of Ag in liver, followed by portal nodes, spleen, lung, bone marrow and pancreas. In addition, we also found there were gender-related distributions of Ag and Au in some organs, especially after s.c. injection. Therefore, these more comprehensive and important results would give fundamental information for the biological risk assessment of nanomaterials.

Gold Nanoparticle-Induced Cell Death and Potential Applications in Nanomedicine

Cell death is crucial to human health and is related to various serious diseases. Therefore, generation of new cell death regulators is urgently needed for disease treatment. Nanoparticles (NPs) are now routinely used in a variety of fields, including consumer products and medicine. Exhibiting stability and ease of decoration, gold nanoparticles (GNPs) could be used in diagnosis and disease treatment. Upon entering the human body, GNPs contact human cells in the blood, targeting organs and the immune system. This property results in the disturbance of cell function and even cell death. Therefore, GNPs may act as powerful cell death regulators. However, at present, we are far from establishing a structure–activity relationship between the physicochemical properties of GNPs and cell death, and predicting GNP-induced cell death. In this review, GNPs’ size, shape, and surface properties are observed to play key roles in regulating various cell death modalities and related signaling pathways. These results could guide the design of GNPs for nanomedicine.

Induction of oxidative stress and sensitization of cancer cells to paclitaxel by gold nanoparticles with different charge densities and hydrophobicities

An elevated reactive oxygen species (ROS) level leads to cellular oxidative stress, which has long been associated with diseases, such as cancer. Thus, the understanding and appropriate manipulation of cellular oxidative stress are needed for disease treatment. It has been reported that nanoparticles induce oxidative stress in human cells through different pathways. However, how the physicochemical properties of nanoparticles perturb cellular oxidative stress remains unclear. In this paper, we explored the effects of the positive/negative charge density and hydrophobicity of gold nanoparticles (GNPs) on the induction of oxidative stress and related mechanisms. In multiple human cell lines, we found that only the positive charge density and hydrophobicity of nanoparticles were correlated with the induction of cellular oxidative stress. Hydrophobic nanoparticles generated oxidative stress mainly through NADPH oxidase activation while positively charged nanoparticles generated it through perturbations of the mitochondria and modulation of intracellular Ca²⁺ concentration. Furthermore, nanoparticle-induced oxidative stress sensitized paclitaxel-induced cancer cell killing by 200%. These findings provided unequivocal structural parameters for the design of future nanomedicine and biocompatible nanocarriers.

Inhibition of thrombin by functionalized C60 nanoparticles revealed via in vitro assays and in silico studies

The studies on the human toxicity of nanoparticles (NPs) are far behind the rapid development of engineered functionalized NPs. Fullerene has been widely used as drug carrier skeleton due to its reported low risk. However, different from other kinds of NPs, fullerene-based NPs (C₆₀ NPs) have been found to have an anticoagulation effect, although the potential target is still unknown. In the study, both experimental and computational methods were adopted to gain mechanistic insight into the modulation of thrombin activity by nine kinds of C₆₀ NPs with diverse surface chemistry properties. In vitro enzyme activity assays showed that all tested surface-modified C₆₀ NPs exhibited thrombin inhibition ability. Kinetic studies coupled with competitive testing using 3 known inhibitors indicated that six of the C₆₀ NPs, of greater hydrophobicity and hydrogen bond (HB) donor acidity or acceptor basicity, acted as competitive inhibitors of thrombin by directly interacting with the active site of thrombin. A simple quantitative nanostructure-activity relationship model relating the surface substituent properties to the inhibition potential was then established for the six competitive inhibitors. Molecular docking analysis revealed that the intermolecular HB interactions were important for the specific binding of C₆₀ NPs to the active site canyon, while the additional stability provided by the surface groups through van der Waals interaction also play a key role in the thrombin binding affinity of the NPs. Our results suggest that thrombin is a possible target of the surface-functionalized C₆₀ NPs relevant to their anticoagulation effect.

Predicting Nano-Bio Interactions by Integrating Nanoparticle Libraries and Quantitative Nanostructure Activity Relationship Modeling

The discovery of biocompatible or bioactive nanoparticles for medicinal applications is an expensive and time-consuming process that may be significantly facilitated by incorporating more rational approaches combining both experimental and computational methods. However, it is currently hindered by two limitations: (1) the lack of high-quality comprehensive data for computational modeling and (2) the lack of an effective modeling method for the complex nanomaterial structures. In this study, we tackled both issues by first synthesizing a large library of nanoparticles and obtained comprehensive data on their characterizations and bioactivities. Meanwhile, we virtually simulated each individual nanoparticle in this library by calculating their nanostructural characteristics and built models that correlate their nanostructure diversity to the corresponding biological activities. The resulting models were then used to predict and design nanoparticles with desired bioactivities. The experimental testing results of the designed nanoparticles were consistent with the model predictions. These findings demonstrate that rational design approaches combining high-quality nanoparticle libraries, big experimental data sets, and intelligent computational models can significantly reduce the efforts and costs of nanomaterial discovery.

Photocontrolled Release of Doxorubicin Conjugated through a Thioacetal Photocage in Folate-Targeted Nanodelivery Systems

Despite their proven ability for precise and targeted release, nanoplatform systems for photocontrolled delivery often face formidable synthetic challenges, in part due to the paucity of advanced linker strategies. Here, we report on a novel linker strategy using a thioacetal ortho-nitrobenzaldehyde (TNB) cage, demonstrating its application for delivery of doxorubicin (Dox) in two nanoscale systems. This photocleavable linker, TNB(OH), which presents two identical arms, each terminated with a hydroxyl functionality, was prepared in a single step from 6-nitroveratraldehyde. TNB(OH) was used to cross-link Dox to a folate receptor (FAR)-targeting poly(amidoamine) dendrimer conjugate G5(FA)_n=5.4(Dox)_m=5.1, and also used to prepare an upconversion nanocrystal (UCN) conjugate, UCN-PPIX@(Dox)(G5FA), a larger core/shell nanostructure. In this core/shell nanostructure, the UCN core emits UV and visible light luminescence upon near-infrared (NIR) excitation, allowing for the photocleavage of the TNB linker as well as the photostimulation of protoporphyrin IX (PPIX) coupled as a cytotoxic photosensitizer. Drug-release experiments performed in aqueous solutions with long-wavelength ultraviolet A (UVA) light showed that Dox release occurred rapidly from its TNB linked form or from its dendrimer conjugated form with comparable decay kinetics. Cellular toxicity studies in FAR-overexpressing KB carcinoma cells demonstrated that each nanoconjugate lacked intrinsic cytotoxicity until exposed to UVA or NIR (980 nm) (for the UCN nanoconjugate), which resulted in induction of potent cytotoxicity. In summary, this new TNB strategy offers synthetic convenience in drug conjugation chemistry with the ability for the temporal control of drug activation at the delivery site.

Elucidation of the Molecular Determinants for Optimal Perfluorooctanesulfonate Adsorption Using a Combinatorial Nanoparticle Library Approach

Perfluorooctanesulfonate (PFOS) persistently accumulates in the environment and in humans, causing various toxicities. To determine the key molecular determinants for optimal PFOS specificity and efficiency, we designed and synthesized a combinatorial gold nanoparticle (GNP) library consisting of 18 members with rationally diversified hydrophobic, electrostatic, and fluorine-fluorine interaction components for PFOS bindings. According to our findings, the electrostatic and F-F interactions between PFOS and nanoparticles are complementary. When F-F attractions are relatively weak, the electrostatic interactions are dominant. As F-F interactions increase, the electrostatic contributions are reduced to as low as 20%, demonstrating that F-F binding may overpower even electrostatic interactions. Furthermore, F-F interactions (28-79% binding efficiency) are 2-fold stronger than regular hydrophobic interactions (15-39% binding efficiency) for PFOS adsorption, explaining why these novel PFOS-binding nanoparticles are superior to other conventional materials based on either hydrophobic or electrostatic binding. The PFOS adsorption by the optimized nanoparticles performs well in the presence of ionic interferences and in environmental wastewater. This library mapping approach can potentially be applied to recognition mechanism investigation of other pollutants and facilitate the discovery of effective monitoring probes and matrices for their removal.

Toward a systematic exploration of nano-bio interactions

Many studies of nanomaterials make non-systematic alterations of nanoparticle physicochemical properties. Given the immense size of the property space for nanomaterials, such approaches are not very useful in elucidating fundamental relationships between inherent physicochemical properties of these materials and their interactions with, and effects on, biological systems. Data driven artificial intelligence methods such as machine learning algorithms have proven highly effective in generating models with good predictivity and some degree of interpretability. They can provide a viable method of reducing or eliminating animal testing. However, careful experimental design with the modelling of the results in mind is a proven and efficient way of exploring large materials spaces. This approach, coupled with high speed automated experimental synthesis and characterization technologies now appearing, is the fastest route to developing models that regulatory bodies may find useful. We advocate greatly increased focus on systematic modification of physicochemical properties of nanoparticles combined with comprehensive biological evaluation and computational analysis. This is essential to obtain better mechanistic understanding of nano-bio interactions, and to derive quantitatively predictive and robust models for the properties of nanomaterials that have useful domains of applicability.

Differential array sensing for cancer cell classification and novelty detection

A series of semi-specific peptides reported in the literature to bind various epitopes on cell surfaces were used in a differential sensing array to pattern cell line identity.

A DNA dual lock-and-key strategy for cell-subtype-specific siRNA delivery

The efficient and precise delivery of siRNA to target cells is critical to successful gene therapy. While novel nanomaterials enhance delivery efficiency, it still remains challenging for precise gene delivery to overcome nonspecific adsorption and off-target effect. Here we design a dual lock-and-key system to perform cell-subtype-specific recognition and siRNA delivery. The siRNA is self-assembled in an oligonucleotide nano vehicle that is modified with a hairpin structure to act as both the ‘smart key’ and the delivery carrier. The auto-cleavable hairpin structure can be activated on site at target cell membrane by reacting with two aptamers as ‘dual locks’ sequentially, which leads to cell-subtype discrimination and precise siRNA delivery for high efficient gene silencing. The success of this strategy demonstrates the precise delivery of siRNA to specific target cells by controlling multiple parameters, thus paving the way for application of RNAi in accurate diagnosis and intervention.

Delivery of siRNA to target cells is essential for in vivo gene therapy. Here the authors demonstrate an oligonucleotide aptamer that targets therapeutic siRNA to a specific cell type.

A supramolecular nanovehicle toward systematic, targeted cancer and tumor therapy

A supramolecular nanovehicle (denoted as SNV) was fabricated by encapsulating zinc phthalocyanine (ZnPc) and doxorubicin (DOX) into a copolymer (PVP-b-PAA-g-FA), so as to achieve systematic and synergistic chemotherapy-photodynamic therapy (PDT), targeted tumor imaging and therapy. The sophisticated copolymer designed in this work can load the PDT photosensitizer (ZnPc) and chemotherapy drug (DOX) simultaneously, which exhibits an excellent performance in chemotherapy-PDT targeted cancer and tumor therapy for both in vitro studies performed with HepG2 cells and in vivo tests with mice. This work provides a new drug formulation with a chemotherapy-PDT synergistic effect by virtue of the supramolecular material design, which possesses the advantages of an ultra-low drug dosage and highly-efficient in vivo targeted tumor imaging/therapy.

Experimental modulation and computational model of nano-hydrophobicity

We demonstrate that nano-hydrophobicity, which governs the biological aggressiveness of nanoparticles, is determined by the outermost regions of surface ligands. We have also successfully modulated nano-hydrophobicity using systematic surface ligand modifications and built the first computational model of nano-hydrophobicity.

A lipopolysaccharide binding heteromultivalent dendrimer nanoplatform for Gram negative cell targeting

Heteromultivalent design of PAMAM dendrimer by conjugation with polymyxin B (PMB) ligand and excess auxiliary ethanolamine (EA) branches led to lipopolysaccharide (LPS) avidity two orders of magnitude greater than free PMB.

DNA "nano-claw": logic-based autonomous cancer targeting and therapy

Cell types, both healthy and diseased, can be classified by inventories of their cell-surface markers. Programmable analysis of multiple markers would enable clinicians to develop a comprehensive disease profile, leading to more accurate diagnosis and intervention. As a first step to accomplish this, we have designed a DNA-based device, called "Nano-Claw". Combining the special structure-switching properties of DNA aptamers with toehold-mediated strand displacement reactions, this claw is capable of performing autonomous logic-based analysis of multiple cancer cell-surface markers and, in response, producing a diagnostic signal and/or targeted photodynamic therapy. We anticipate that this design can be widely applied in facilitating basic biomedical research, accurate disease diagnosis, and effective therapy.

A monomeric photosensitizer for targeted cancer therapy

A targeted photosensitizer used in photodynamic therapy (PDT) was fabricated by incorporation of zinc phthalocyanine (ZnPc) and folic acid (FA) into polyvinylpyrrolidone (PVP) micelles, which exhibits excellent anticancer performance revealed by both in vitro studies and in vivo tests.

Size-dependent cell uptake of protein-coated graphene oxide nanosheets

As an emerging applied material, graphene has shown tremendous application potential in many fields, including biomedicine. However, the biological behavior of these nanosheets, especially their interactions with cells, is not well understood. Here, we report our findings about the cell surface adhesion, subcellular locations, and size-dependent uptake mechanisms of protein-coated graphene oxide nanosheets (PCGO). Small nanosheets enter cells mainly through clathrin-mediated endocytosis, and the increase of graphene size enhances phagocytotic uptake of the nanosheets. These findings will facilitate biomedical and toxicologic studies of graphenes and provide fundamental understanding of interactions at the interface of two-dimensional nanostructures and biological systems.