Oligonucleotide loading determines cellular uptake of DNA-modified gold nanoparticles

Fluorescent-Raman Binary Star Ratio Probe for MicroRNA Detection and Imaging in Living Cells

The expression of microRNAs (miRNAs) is critical in gene regulation and has been counted into disease diagnosis marks. Precise imaging and quantification of miRNAs could afford the important information for clinical diagnosis. Here, two smart binary star ratio (BSR) probes were designed and constructed, and miRNA triggered the connection of the binary star probes and the reciprocal changes of dual signals in living cells. This multifunctional probe integrates fluorescence and surface enhanced Raman scattering (SERS) imaging, with enzyme-free numerator signal amplification for dual-mode imaging and dual-signal quantitative analysis of miRNA. First, compared with the single-mode ratio imaging method, using fluorescence-SERS complementary ratio imaging, this probe enables more accurate imaging contrast for direct visualization signal changes in living cells. Multiscale information about the dynamic behavior of miRNA and the probe is acquired. Next, via SERS reverse signal ratio response and a novel enzyme-free numerator signal amplification, the amplified signal and reduced black value were achieved in the quantification of miRNA. More importantly, BSR probes showed good stability in cells and were successfully used for accurate tracing and quantification of miR-203 from MCF-7 cells. Therefore, the reported BSR probe is a potential tool for the reliable monitoring of biomolecule dynamics in living cells.

Target-Induced Core-Satellite Nanostructure Assembly Strategy for Dual-Signal-On Fluorescence Imaging and Raman Quantification of Intracellular MicroRNA Guided Photothermal Therapy

Integrating biological detection and treatment into one system is a smart therapeutic maneuver for efficient cancer treatment. Herein, a target-activated core-satellite nanostructure (CS nanostructure) assembly built on gold nanobipyramids motor (AuNBPs motor)/gold nanoparticle probe (AuNP probe) exhibiting simultaneous dual signal-on imaging, quantification of intracellular microRNA-21 (miR-21), and photothermal therapy (PTT) for cancer is designed. Of note, when the AuNBPs motor/AuNP probe enters into cells, miR-21 triggers the reaction between AuNBPs motor and AuNP probe, resulting in the formation of CS nanostructure assembly. The process of assembling the CS nanostructure is accompanied with strong fluorescent signals from TAMRA and surface-enhanced Raman scattering (SERS) signals from adenine. The fluorescent signal is leveraged to image the intracellular miR-21 level, whereas the SERS signal is utilized for absolute quantification of intracellular miR-21, and the CS nanostructure acts as the photosensitizer for PTT. This strategy can successfully image and quantify miR-21 in a single cell, and also distinguish normal cells from tumor cells. Moreover, under the guidance of fluorescence signal, the assembly kills tumor cells and inhibits tumor growth via PTT. In vitro and in vivo results prove that the proposed strategy possesses enormous potential for application in the diagnosis and treatment of cancer.

Gene Regulation Using Spherical Nucleic Acids to Treat Skin Disorders

Spherical nucleic acids (SNAs) are nanostructures consisting of nucleic acids in a spherical configuration, often around a nanoparticle core. SNAs are advantageous as gene-regulating agents compared to conventional gene therapy owing to their low toxicity, enhanced stability, uptake by virtually any cell, and ability to penetrate the epidermal barrier. In this review we: (i) describe the production, structure and properties of SNAs; (ii) detail the mechanism of SNA uptake in keratinocytes, regulated by scavenger receptors; and (iii) report how SNAs have been topically applied and intralesionally injected for skin disorders. Specialized SNAs called nanoflares can be topically applied for gene-based diagnosis (scar vs. normal tissue). Topical SNAs directed against TNFα and interleukin-17A receptor reversed psoriasis-like disease in mouse models and have been tested in Phase 1 human trials. Furthermore, SNAs targeting ganglioside GM3 synthase accelerate wound healing in diabetic mouse models. Most recently, SNAs targeting toll-like receptor 9 are being used in Phase 2 human trials via intratumoral injection to induce immune responses in Merkel cell and cutaneous squamous cell carcinoma. Overall, SNAs are a valuable tool in bench-top and clinical research, and their advantageous properties, including penetration into the epidermis after topical delivery, provide new opportunities for targeted therapies.

Small interfering RNA for cancer treatment: overcoming hurdles in delivery

In many ways, cancer cells are different from healthy cells. A lot of tactical nano-based drug delivery systems are based on the difference between cancer and healthy cells. Currently, nanotechnology-based delivery systems are the most promising tool to deliver DNA-based products to cancer cells. This review aims to highlight the latest development in the lipids and polymeric nanocarrier for siRNA delivery to the cancer cells. It also provides the necessary information about siRNA development and its mechanism of action. Overall, this review gives us a clear picture of lipid and polymer-based drug delivery systems, which in the future could form the base to translate the basic siRNA biology into siRNA-based cancer therapies.

Biocomputing label-free security system based on homogenous ligation chain reaction-induced dramatic change in melting temperature for screening single nucleotide polymorphisms

The development of smart platform with accurate, inexpensive and reliable detection of single-nucleotide polymorphisms (SNPs) has long been concerned in the fields of medical diagnosis and basic research. Here, we present a ligation chain reaction (LCR)-based sensing system for the cost-effective screening of SNPs by simply conducting DNA melting analysis. No chemical modification is required and the signaling operation is accomplished in homogeneous solution, circumventing the complex modification process and possibly compromised enzymatic activity associated with heterogeneous materials, such as quantum dot (QD) and gold nanoparticle (GNP). Due to the enzymatic catalysis and high fidelity of ligase, the system is capable of executing signal amplification, providing a high sensitivity and selectivity. KRAS gene is easily recognized and the site-specific mutation of guanine (G) to adenine (A), thymine (T) or cytosine (C) is accurately screened. Moreover, the excellent reliability was demonstrated by blind test and recovery test. LCR-based signaling mechanism was further used to develop the biocomputing security system, and two logic gates consisting of four single-stranded DNAs (ssDNAs) offer a double insurance to protect the information against illegal invasion, guaranteeing the reliability of output information. Once in the absence of one essential factor, the security system was always locked regardless of target key, serving as a novel strategy to ensure the safety of output information at molecular level. As a proof-of-concept scheme, this contribution introduces new insight into the development of DNA security systems and the exploitation of powerful signal transduction strategy suitable for rapid and convenient disease diagnosis.

A framework for designing delivery systems

The delivery of medical agents to a specific diseased tissue or cell is critical for diagnosing and treating patients. Nanomaterials are promising vehicles to transport agents that include drugs, contrast agents, immunotherapies and gene editors. They can be engineered to have different physical and chemical properties that influence their interactions with their biological environments and delivery destinations. In this Review Article, we discuss nanoparticle delivery systems and how the biology of disease should inform their design. We propose developing a framework for building optimal delivery systems that uses nanoparticle-biological interaction data and computational analyses to guide future nanomaterial designs and delivery strategies.

DNA-nanoparticle interactions: Formation of a DNA corona and its effects on a protein corona

There has been much recent interest in the protein "corona," the nonspecific adsorption of proteins on the surface of nanoparticles used in biological applications. This research investigates an analogous DNA corona. We find that particles (200 nm and 1 μm) incubated with DNA form a DNA corona, with a higher concentration of DNA adsorbed on the surface of cationic nanoparticles. With protein present, a combined DNA and protein corona is formed although DNA in solution displaces protein from the nanoparticle surface. Displacement of protein from the nanoparticle surface is dependent on the concentration of DNA in solution and was also observed for planar surfaces. Overall, we expect this investigation of the DNA corona to be important for nanomedicine applications, as well as disease states, especially systemic lupus erythematosus, in which biological particles with bound DNA are important mediators of inflammation and thrombosis.

Role of Free Thiol on Protein Adsorption to Gold Nanoparticles

Protein-gold nanoparticle (AuNP) bioconjugates have many potential applications in nanomedicine. A thorough understanding of the interaction between the protein and the AuNP is critical to engineering these functional bioconjugates with desirable properties. In this work, we investigate the role of free thiols presented by the protein on the stability of the protein-AuNP conjugate. Human serum albumin (HSA) was modified with 2-iminothiolane (Traut's reagent) to introduce additional thiols onto the protein surface, and three variants of HSA were synthesized to present 1, 5, and 20 free thiols by controlling the molar excess of the chemical modifier. Protein exchange studies on AuNPs were conducted using these HSA species and an IgG antibody which exhibited 10 free thiols. Antibody-AuNP conjugates were synthesized, purified, and dispersed in solutions containing each of the HSA species. No protein exchange was detected with the HSA or modified HSA containing 5 thiols; however, 85% of the antibody was displaced on the AuNP surface by the extensively thiolated HSA presenting 20 free thiols. Furthermore, the impact of the protein adsorption sequence was probed in which each of the HSA species were preadsorbed onto the AuNP and dispersed in a solution of antibody. The antibody fully displaced the HSA with a single thiol from the AuNP within 3 h, required 24 h to completely displace the modified HSA containing 5 thiols, and was unable to displace the modified HSA containing 20 thiols. These results indicate that the number of Au-S interactions governs the binding interaction between the protein and the AuNP. This work provides further insight into the protein-AuNP binding mechanism and identifies important design principles for engineered proteins to optimize bioconjugates.

Development of Spherical Nucleic Acids for Prostate Cancer Immunotherapy

Although the strategy of therapeutic vaccination for the treatment of prostate cancer has advanced to and is available in the clinic (Sipuleucel-T), the efficacy of such therapy remains limited. Here, we develop Immunostimulatory Spherical Nucleic Acid (IS-SNA) nanostructures comprised of CpG oligonucleotides as adjuvant and prostate cancer peptide antigens, and evaluate their antitumor efficacy in syngeneic mouse models of prostate cancer. IS-SNAs with the specific structural feature of presenting both antigen and adjuvant CpG on the surface (hybridized model (HM) SNAs) induce stronger cytotoxic T lymphocyte (CTL) mediated antigen-specific killing of target cells than that for IS-SNAs with CpG on the surface and antigen encapsulated within the core (encapsulated model (EM) SNAs). Mechanistically, HM SNAs increase the co-delivery of CpG and antigen to dendritic cells over that for EM SNAs or admixtures of linear CpG and peptide, thereby improving cross-priming of antitumor CD8⁺ T cells. As a result, vaccination with HM SNAs leads to more effective antitumor immune responses in two prostate cancer models. These data demonstrate the importance of the structural positioning of peptide antigens together with adjuvants within IS-SNAs to the efficacy of IS-SNA-based cancer immunotherapy.

Delivery of drugs, proteins, and nucleic acids using inorganic nanoparticles

Inorganic nanoparticles provide multipurpose platforms for a broad range of delivery applications. Intrinsic nanoscopic properties provide access to unique magnetic and optical properties. Equally importantly, the structural and functional diversity of gold, silica, iron oxide, and lanthanide-based nanocarriers provide unrivalled control of nanostructural properties for effective transport of therapeutic cargos, overcoming biobarriers on the cellular and organismal level. Taken together, inorganic nanoparticles provide a key addition to the arsenal of delivery vectors for fighting disease and improving human health.

Influence of the Spatial Distribution of Cationic Functional Groups at Nanoparticle Surfaces on Bacterial Viability and Membrane Interactions

While positively charged nanomaterials induce cytotoxicity in many organisms, much less is known about how the spatial distribution and presentation of molecular surface charge impact nanoparticle-biological interactions. We systematically functionalized diamond nanoparticle surfaces with five different cationic surface molecules having different molecular structures and conformations, including four small ligands and one polymer, and we then probed the molecular-level interaction between these nanoparticles and bacterial cells. Shewanella oneidensis MR-1 was used as a model bacterial cell system to investigate how the molecular length and conformation of cationic surface charges influence their interactions with the Gram-negative bacterial membranes. Nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) demonstrate the covalent modification of the nanoparticle surface with the desired cationic organic monolayers. Surprisingly, bacterial growth-based viability (GBV) and membrane damage assays both show only minimal biological impact by the NPs functionalized with short cationic ligands within the concentration range tested, yet NPs covalently linked to a cationic polymer induce strong cytotoxicity, including reduced cellular viability and significant membrane damage at the same concentration of cationic groups. Transmission electron microscopy (TEM) images of these NP-exposed bacterial cells show that NPs functionalized with cationic polymers induce significant membrane distortion and the production of outer membrane vesicle-like features, while NPs bearing short cationic ligands only exhibit weak membrane association. Our results demonstrate that the spatial distribution of molecular charge plays a key role in controlling the interaction of cationic nanoparticles with bacterial cell membranes and the subsequent biological impact. Nanoparticles functionalized with ligands having different lengths and conformations can have large differences in interactions even while having nearly identical zeta potentials. While the zeta potential is a convenient and commonly used measure of nanoparticle charge, it does not capture essential differences in molecular-level nanoparticle properties that control their biological impact.

Defining the Design Parameters for in Vivo Enzyme Delivery Through Protein Spherical Nucleic Acids

The translation of proteins as effective intracellular drug candidates is limited by the challenge of cellular entry and their vulnerability to degradation. To advance their therapeutic potential, cell-impermeable proteins can be readily transformed into protein spherical nucleic acids (ProSNAs) by densely functionalizing their surfaces with DNA, yielding structures that are efficiently taken up by cells. Because small structural changes in the chemical makeup of a conjugated ligand can affect the bioactivity of the associated protein, structure-activity relationships of the linker bridging the DNA and the protein surface and the DNA sequence itself are investigated on the ProSNA system. In terms of attachment chemistry, DNA-based linkers promote a sevenfold increase in cellular uptake while maintaining enzymatic activity in vitro as opposed to hexaethylene glycol (HEG, Spacer18) linkers. Additionally, the employment of G-quadruplex-forming sequences increases cellular uptake in vitro up to fourfold. When translating to murine models, the ProSNA with a DNA-only shell exhibits increased blood circulation times and higher accumulation in major organs, including lung, kidney, and spleen, regardless of sequence. Importantly, ProSNAs with an all-oligonucleotide shell retain their enzymatic activity in tissue, whereas the native protein loses all function. Taken together, these results highlight the value of structural design in guiding ProSNA biological fate and activity and represent a significant step forward in the development of intracellular protein-based therapeutics.

Complementary Oligonucleotide Conjugated Multicolor Carbon Dots for Intracellular Recognition of Biological Events

By using complementary DNA sequences as surface ligands, we selectively allow two individual diffusing "dual-color" carbon dots to interact in situ and in vitro. Spontaneous nanoscale oxidation of surface-abundant nitroso-/nitro-functionalities leads to two distinctly colored carbon dots (CD) which are isolated by polarity driven chromatographic separation. Green- and red-emitting carbon dots (gCD and rCD) were decorated by complementary single-stranded DNAs which produce a marked increase in the fluorescence emission of the respective carbon dots. Mutual colloidal interactions are achieved through hybridization of complementary DNA base pairs attached to the respective particles, resulting in quenching of their photoluminescence. The observed post-hybridization quenching is presumably due to a combined effect from an aggregation of CDs post duplex DNA formation and close proximity of multicolored CDs, having overlapped spectral regions leading to a nonradiative energy transfer process possibly released as heat. This strategy may contribute to the rational design of mutually interacting carbon dots for a better control over the resulting assembly structure for studying different biological phenomenon including molecular cytogenetics. One of the newly synthesized CDs was successfully used to image intracellular location of GAPDH mRNA using an event of change in fluorescence intensity (FI) of CDs. This selectivity was introduced by conjugating an oligonucleotide harboring complementary sequence to GAPDH mRNA. FI of this conjugated carbon dot, rCD-GAPDH, was also found to decrease in the presence of Ca2+, varied in relation to H+ concentrations, and could serve as a tool to quantify the intracellular concentrations of Ca2+ and pH value (H+) which can give important information about cell survival. Therefore, CD-oligonucleotide conjugates could serve as efficient probes for cellular events and interventions.

Acid-Switchable DNAzyme Nanodevice for Imaging Multiple Metal Ions in Living Cells

Metal-assisted deoxyribozyme catalysis (DNAzyme) has been a general platform for constructing highly sensitive and selective detection sensors of metal ions. However, the "always on" mode of the traditional DNAzyme sensors greatly limits their application in the visual analysis of endogenous metal ions in a complex physiological microenvironment. To overcome this obstacle, a smart acid-switchable DNAzyme nanodevice is designed to control the DNAzyme activity in living cells and achieve simultaneous visualization of metal ions (Zn²⁺ and Pb²⁺) in situ. This nanodevice is built on DNAzyme precursors (DPs) and acid-switchable DNA (SW-DNA), precisely responding to pH variations in the range of 4.5-7.0, and the state of the three-strand hybridization of DPs successfully renders the DNAzymes inactive before being transported into cells. Once the nanodevice is taken up into living cells, the SW-DNA will change the configuration from linear to triplex in the acidic intracellular compartments (lysosomes, pH ∼4.5 to 5.0) and then the strands hybridized with the SW-DNA are liberated and subsequently react with DPs to form the active DNAzyme, which can further realize multi-imaging of intracellular metal ions. Moreover, this strategy has broad prospects as a powerful platform for constructing various acid-switchable nanodevices for visual analysis of multiple biomolecules in living cells.

Development of Dual Functional Nucleic Acid Delivery Nanosystem for DNA Induced Silencing of Bcl-2 Oncogene

Introduction

Cancer treatment using functionalized vehicles in order to block involved genes has attracted a remarkable interest. In this study, we investigated the cellular uptake and cytotoxic effects of three sizes of anti Bcl-2 DNAi-conjugated gold nanoparticles by MCF-7 cells.

Methods

Three different sizes of gold nanoparticles were synthesized by citrate reduction method and after characterization, the nanoparticles were functionalized by Bcl-2 targeted DNAi. Cell internalization of the nanoparticles was analyzed by atomic absorption spectroscopy and light microscopy. The cytotoxic effects of the nanoparticles were investigated by MTT assay, flow cytometry and RT-PCR of the target gene.

Results

While poor cell internalization of bare gold nanoparticles was observed, the results demonstrated that cellular uptake of DNAi-conjugated gold nanoparticles is completely size-dependent, and the largest nanoparticle (~42 nm) revealed the highest internalization rate compared to other sizes (~14 and ~26 nm). Experimental findings showed that the DNAi-conjugated gold nanoparticles induced apoptotic pathway by silencing of the targeted Bcl-2 gene. In addition, supplementary theoretical studies demonstrated that the 42 nm DNAi-conjugated gold nanoparticles have great photothermal conversion efficiency for treatment under external illumination and these nanoparticles can be induced further cytotoxic effect by approximately 10°C temperature elevations.

Conclusion

Remarkable photothermal properties of DNAi-conjugated 42 nm Au-NPs in parallel with their high cell internalization and cytotoxic effects introduce them as potential dual functional anticancer nanosystems.

Gold Nanobones Enhanced Ultrasensitive Surface-Enhanced Raman Scattering Aptasensor for Detecting Escherichia coli O157:H7

Sensitive, robust, and highly specific detection of Escherichia coli O157:H7, one of the most hazardous foodborne pathogens and the cause of numerous diseases, is needed to ensure public health. Herein, a one-pot step method is reported for the preparation of multifunctional gold nanobones (NBs) (GNR_Apt-1+RhB) from gold nanorods (GNRs) comediated by an aptamer (Apt-1) and the signal molecule rhodamine B (RhB) for surface-enhanced Raman scattering detection of E. coli O157:H7. The characterized result showed that Apt-1 and RhB were embedded in the gold NBs, and then, this combination exhibited good recognition, excellent stability, and significant Raman signal intensity enhancement. The Raman enhancement derived from a strong electromagnetic field distribution with the locations at the apex of both ends of the GNR_Apt-1+RhB and the signal stability was because of the firm embedment of Apt-1 (poly A20 + E. coli O157:H7 aptamers) and RhB on the surface of the GNR_Apt-1+RhB. Optimization experiments established that surface-enhanced Raman-scattered RhB absorption at 1350 cm^-1 had a strong linear relationship (y = 180.30x - 61.49; R² = 0.9982) with E. coli O157:H7 concentration over the range of 10-10,000 cfu/mL with a limit of detection of 3 cfu/mL. This novel aptasensor sensitively detects E. coli O157:H7 and has great promise for food pathogenic bacteria detection.

Attaching DNA to Gold Nanoparticles With a Protein Corona

DNA-functionalized gold nanoparticles (AuNPs) have been widely used in directed assembly of materials, biosensors, and drug delivery. This conjugate may encounter proteins in these applications and proteins may affect not only DNA adsorption but also the function of the attached DNA. Bovine serum albumin (BSA) with many cysteine residues can strongly adsorb on AuNPs and this conjugate showed high colloidal stability against salt, acid and base. Similar protection effects were also observed with a few other common proteins including catalase, hemoglobin, glucose oxidase, and horseradish peroxidase. DNA oligonucleotides without a thiol label can hardly displace adsorbed BSA, and BSA cannot displace pre-adsorbed DNA either, indicating a strongly kinetically controlled system. Thiolated DNA can be attached at a low density on the AuNPs with a BSA corona. The BSA corona did not facilitate the hybridization of the conjugated DNA, while a smaller peptide, glutathione allowed faster hybridization. Overall, proteins increase the colloidal stability of AuNPs, and they do not perturb the gold-thiol bond in the DNA conjugate, although a large protein corona may inhibit the hybridization function of DNA.

Gold Nanoparticles in Conjunction with Nucleic Acids as a Modern Molecular System for Cellular Delivery

Development of nanotechnology has become prominent in many fields, such as medicine, electronics, production of materials, and modern drugs. Nanomaterials and nanoparticles have gained recognition owing to the unique biochemical and physical properties. Considering cellular application, it is speculated that nanoparticles can transfer through cell membranes following different routes exclusively owing to their size (up to 100 nm) and surface functionalities. Nanoparticles have capacity to enter cells by themselves but also to carry other molecules through the lipid bilayer. This quality has been utilized in cellular delivery of substances like small chemical drugs or nucleic acids. Different nanoparticles including lipids, silica, and metal nanoparticles have been exploited in conjugation with nucleic acids. However, the noble metal nanoparticles create an alternative, out of which gold nanoparticles (AuNP) are the most common. The hybrids of DNA or RNA and metal nanoparticles can be employed for functional assemblies for variety of applications in medicine, diagnostics or nano-electronics by means of biomarkers, specific imaging probes, or gene expression regulatory function. In this review, we focus on the conjugates of gold nanoparticles and nucleic acids in the view of their potential application for cellular delivery and biomedicine. This review covers the current advances in the nanotechnology of DNA and RNA-AuNP conjugates and their potential applications. We emphasize the crucial role of metal nanoparticles in the nanotechnology of nucleic acids and explore the role of such conjugates in the biological systems. Finally, mechanisms guiding the process of cellular intake, essential for delivery of modern therapeutics, will be discussed.

The effector mechanism of siRNA spherical nucleic acids

Spherical nucleic acids (SNAs) are nanostructures formed by chemically conjugating short linear strands of oligonucleotides to a nanoparticle template. When made with modified small interfering RNA (siRNA) duplexes, SNAs act as single-entity transfection and gene silencing agents and have been used as lead therapeutic constructs in several disease models. However, the manner in which modified siRNA duplex strands that comprise the SNA lead to gene silencing is not understood. Herein, a systematic analysis of siRNA biochemistry involving SNAs shows that Dicer cleaves the modified siRNA duplex from the surface of the nanoparticle, and the liberated siRNA subsequently functions in a way that is dependent on the canonical RNA interference mechanism. By leveraging this understanding, a class of SNAs was chemically designed which increases the siRNA content by an order of magnitude through covalent attachment of each strand of the duplex. As a consequence of increased nucleic acid content, this nanostructure architecture exhibits less cell cytotoxicity than conventional SNAs without a decrease in siRNA activity.

Design strategies for programmable oligonucleotide nanotherapeutics

A systematic review on how to design different programmable nanotherapeutics using oligonucleotides as building blocks or as surface and matrix modifiers for controlled and targeted delivery of various therapeutic agents in presented.

A Dual Wavelength Polymerization and Bioconjugation Strategy for High Throughput Synthesis of Multivalent Ligands

Structure-function relationships for multivalent polymer scaffolds are highly complex due to the wide diversity of architectures offered by such macromolecules. Evaluation of this landscape has traditionally been accomplished case-by-case due to the experimental difficulty associated with making these complex conjugates. Here, we introduce a simple dual-wavelength, two-step polymerize and click approach for making combinatorial conjugate libraries. It proceeds by incorporation of a polymerization friendly cyclopropenone-masked dibenzocyclooctyne into the side chain of linear polymers or the α-chain end of star polymers. Polymerizations are performed under visible light using an oxygen tolerant porphyrin-catalyzed photoinduced electron/energy transfer-reversible addition-fragmentation chain-transfer (PET-RAFT) process, after which the deprotection and click reaction is triggered by UV light. Using this approach, we are able to precisely control the valency and position of ligands on a polymer scaffold in a manner conducive to high throughput synthesis.

Polymer stiffness governs template mediated self-assembly of liposome-like nanoparticles: simulation, theory and experiment

This study suggests that the self-assembly of a template-mediated liposome (TML) can be utilized as a general method to produce liposomes with controlled sizes. A polymer tethered core is used here as a starting configuration of a TML. Lipids anchored to the free ends of the tethered polymers direct the self-assembly of surrounding free lipid molecules to form liposome-like nanoparticles. Characterizing the flexibility of polymers by their persistence lengths, we performed large scale molecular simulations to investigate the self-assembly process of TMLs with tethered polymers of different stiffness values. The stiffness of tethered polymer is found to play a crucial role in the self-assembly process of TMLs. The flexible and rigid-like polymers can accelerate and delay the self-assembly of TMLs, respectively. In addition, the critical grafting of tethered polymers and required lipid concentrations to from perfectly encapsulated TMLs are found to increase with the flexibility of tethered polymers. To scrutinize these simulation-based findings, we synthesized DNA-polyethylene glycol (PEG) TMLs and performed corresponding experiments. To this end we incorporate increasing concentrations of DNA as a proxy for increasing the rigidity of the tethered polymers. We find that the resulting structures are indeed consistent with the simulated ones. Finally, a theory is developed that allows one to estimate the required free lipid number (or lipid concentration) and grafting density analytically for polymers of a given persistence length. Through these combined computational, experimental, and theoretical studies, we present a predictive model for determining the effect of polymer stiffness on the self-assembly of TMLs, which can be used as a general approach for obtaining perfectly encapsulated TMLs as potential drug delivery vehicles.

Silencing Breast Cancer Genes Using Morpholino Embedded DNA-Tile-AuNPs Nanostructures

There is an ongoing effort to increase the efficiency of gene delivery for the regulation of diseases-related genes. In this report, we demonstrate the efficiency of a DNA-based nanostructure to deliver morpholino antisense oligonucleotides for the upregulated genes in breast cancer as an alternative to the currently used delivery systems. A DNA-tile structure is constructed by embedding antisense oligonucleotides targeting the HER2 and ERα genes. Then, the sticky ends of the DNA-tile nanostructures are hybridized to gold nanoparticles (AuNPs) coated with the complementary oligonucleotides to enhance their cellular uptake. It is found that the morpholino antisense oligonucleotide embedded DNA-tile-AuNPs structure is 30% more effective than the liposome-based system to deliver morpholinos and induce gene silencing in breast cancer cells. The results of the study suggest that the prepared novel nanostructure is an effective and biocompatible carrier that can be used in in vitro gene silencing studies and can be further pursued in in vivo studies.

Rational Design of Nanocarriers for Intracellular Protein Delivery

Protein/antibody therapeutics have exhibited the advantages of high specificity and activity even at an extremely low concentration compared to small molecule drugs. However, they are accompanied by unfavorable physicochemical properties such as fragile tertiary structure, large molecular size, and poor penetration of the membrane, and thus the clinical use of protein drugs is hindered by inefficient delivery of proteins into the host cells. To overcome the challenges associated with protein therapeutics and enhance their biopharmaceutical applications, various protein-loaded nanocarriers with desired functions, such as lipid nanocapsules, polymeric nanoparticles, inorganic nanoparticles, and peptides, are developed. In this review, the different strategies for intracellular delivery of proteins are comprehensively summarized. Their designed routes, mechanisms of action, and potential therapeutics in live cells or in vivo are discussed in detail. Furthermore, the perspective on the new generation of delivery systems toward the emerging area of protein-based therapeutics is presented as well.

Construction of Bio/Nanointerfaces: Stable Gold Nanoparticle Bioconjugates in Complex Systems

The real application of DNA-functionalized gold nanoparticles (DNA-Au NPs) was limited by decreased stability and irreversible aggregation in high-ionic strength solutions and complex systems. Therefore, exploring a kind of DNA-Au NPs with excellent stability in high-ionic strength solutions and complex systems is challenging and significant. Herein, a novel universal bioconjugate strategy for constructing ultrastable DNA-Au NPs was designed based on the combination of polydopamine (PDA) shell and DNA linker. The obtained DNA-linked Au@polydopamine nanoparticles (DNA-Au@PDA NPs) showed colloidal stability in high-ionic strength solution and complex systems (such as human serum and cell culture supernatant). Moreover, the nanoparticles still maintained good dispersion after multiple freeze-thaw cycles. The high stability of DNA-Au@PDA NPs may be attributed to increasing the electrostatic and steric repulsions among nanoparticles through the effect of both PDA shell and DNA linker on Au@PDA NPs. For investigating the application of such nanoparticles, a highly sensitive assay for miRNA 141 detection was developed using DNA-Au@PDA NPs coupled with dynamic light scattering (DLS). Comparing with the regular DNA-Au NPs, DNA-Au@PDA NPs could detect as low as 50 pM miRNA 141 even in human whole serum. Taken together, the features of Bio/Nanointerface make the nanoparticle suitable for various applications in harsh biological and environmental conditions due to the stability. This work may provide a universal modification method for obtaining stable nanoparticles.

Non-viral transfection vectors: are hybrid materials the way forward?

Transfection is a process by which oligonucleotides (DNA or RNA) are delivered into living cells. This allows the synthesis of target proteins as well as their inhibition (gene silencing). However, oligonucleotides cannot cross the plasma membrane by themselves; therefore, efficient carriers are needed for successful gene delivery. Recombinant viruses are among the earliest described vectors. Unfortunately, they have severe drawbacks such as toxicity and immunogenicity. In this regard, the development of non-viral transfection vectors has attracted increasing interests, and has become an important field of research. In the first part of this review we start with a tutorial introduction into the biological backgrounds of gene transfection followed by the classical non-viral vectors (cationic organic carriers and inorganic nanoparticles). In the second part we highlight selected recent reports, which demonstrate that hybrid vectors that combine key features of classical carriers are a remarkable strategy to address the current challenges in gene delivery.

Impact of Sequence Specificity of Spherical Nucleic Acids on Macrophage Activation in Vitro and in Vivo

The effects of spherical nucleic acid (SNA) gold nanoparticle conjugates on the activation of macrophages in vitro and release of cytokines in vivo were explored. Herein, we show that G-quadruplexes, the formation of which is enhanced on gold nanoparticle surfaces, elicit an increase in cytokine release from mouse and human macrophages and induce the upregulation of activation receptors as well as NO₂ production in vitro. Moreover, these G-rich SNAs can induce cytokine release when injected intravenously, though there were no severe, long-term effects observed. These results further reinforce the notion that nucleic acid sequence and structure play an important role in how SNAs interact in biological milieu and highlight a key design parameter.

Impact of Protein Corona in Nanoflare-Based Biomolecular Detection and Quantification

Selective detection and precise quantification of biomolecules in intracellular settings play a pivotal role in the diagnostics and therapeutics of diseases, including various cancers and infectious epidemics. Because of this clinical relevance, nanoprobes with high sensitivity, wide tunability, and excellent biological stability have become of high demand. In particular, nanoflares based on gold nanoparticles have emerged as an attractive candidate for intracellular detection due to their efficient cellular uptake, enhanced binding affinity with complementary targets, and improved biological compatibility. However, nanoprobes, including these nanoflares, are known to be susceptible to the adsorption of proteins present in the biological environment, which leads to the formation of a so-called protein corona layer on their surface, leading to an altered targeting efficiency and cellular uptake. In this work, we leverage the nanoflares platform to demonstrate the effect of protein corona on biomolecular detection, quantification, as well as biological stability against enzymatic degradation. Nanoflares incubated in a biologically relevant concentration of serum albumin proteins (0.50 wt %) were shown to result in more than 20% signal reduction in target detection, with a decrease varying proportionally with the protein concentrations. In addition, similar signal reduction was observed for different serum proteins, and PEG backfilling was found to be ineffective in mitigating the negative impact induced by the corona formation. Furthermore, nuclease resistance in nanoflares was also severely compromised by the presence of the corona shell (∼2-fold increase in hydrolysis activity). This work demonstrates the consequences of an in situ formed protein corona layer on molecular detection/quantification and biological stability of nanoflares in the presence of nuclease enzymes, highlighting the importance of calibrating similar nanoprobes in proper biological media to improve the accuracy of molecular detection and quantification.

Riboflavin-Terminated, Multivalent Quantum Dot as Fluorescent Cell Imaging Probe

Bioconjugated nanoparticles are commonly used for targeting cellular/subcellular components, and labeling performance is known to depend on multivalency, i.e., the number of attached biomolecule per particle. However, these multivalency effects are largely unexplored. Here, we show that multivalency of nanoparticle-bound riboflavin controls the cellular interaction, cellular entry/exit mechanism, and subcellular trafficking property. We have synthesized riboflavin-functionalized quantum dot (QD) of 15-25 nm hydrodynamic size with average riboflavin multivalencies of 15, 30, and 70 [designated as QD(RF)₁₅, QD(RF)₃₀, and QD(RF)₇₀, respectively] and investigated their uptake mechanism in riboflavin receptor overexpressed KB cells. We found that increased multivalency from 15 to 70 increases the cellular interaction with QD, shifts the cell uptake mechanism from caveolae-clathrin to exclusive clathrin-mediated endocytosis, and enhances lysosomal trafficking. This work demonstrates the importance of multivalency of bioconjugated molecule at the nanoparticle surface toward biolabeling performance and should be optimized for best performance of designed nanobioconjugate.

Valency-Controlled Molecular Spherical Nucleic Acids with Tunable Biosensing Performances

Spherical nucleic acids (SNAs) play critical roles in many fields, such as molecular diagnostics, disease therapeutics, and materials application. Due to the important role of DNA density on the properties of SNAs, the controlled synthesis of monodisperse SNAs with precise DNA density is an important approach for the structure-function relationship study and finite functions regulation of SNAs. In particular, the construction of monodisperse SNAs in a valency-tunable and site-specific manner is highly important; however, it is still challenging. Herein, on the basis of the high controllability, nanometer precision, and addressable modification ability of framework nucleic acid (FNA), we develop the concept of valency-controlled framework nucleic acid core-based molecular spherical nucleic acids (FNA-mSNAs) with tunable biosensing performances. The FNA-mSNAs consist of a valency-tunable FNA-based DNA nanocube as the core and a controlled, precise number of DNA strands per core. By simply alternating the binding site number for shell DNA strands on the DNA nanocube, homogeneous FNA-mSNAs with different valencies were easily designed, which enabled the molecular level study of the effect of valency on their properties, such as nuclease stability and cellular uptake. Furthermore, taking advantage of the addressable modification ability of FNA, the first heterogeneous molecular SNAs with tunable valency were demonstrated. Importantly, the valency of heterogeneous FNA-mSNAs was able to tune their biosensing performance, such as response dynamics, detection sensitivity, and response range. With these remarkable features, FNA-mSNAs provide new research methods for the development of functional SNAs at the molecular level for a wide range of biological applications.

Antibodies Irreversibly Adsorb to Gold Nanoparticles and Resist Displacement by Common Blood Proteins

Gold nanoparticles (AuNPs) functionalized with proteins to impart desirable surface properties have been developed for many nanobiotechnology applications. A strong interaction between the protein and nanoparticle is critical to the formation of a stable conjugate to realize the potential of these emerging technologies. In this work, we examine the robustness of a protein layer adsorbed onto gold nanoparticles while under the stress of a physiological environment that could potentially lead to protein exchange on the nanoparticle surface. The adsorption interaction of common blood plasma proteins (transferrin, human serum albumin, and fibrinogen) and anti-horseradish peroxidase antibody onto AuNPs is investigated by nanoparticle tracking analysis. Our data show that a monolayer of protein is formed at saturation for each protein, and the maximum size increase for the conjugate, relative to the AuNP core, correlates with the protein size. The binding affinity of each protein to the AuNP is extracted from a best fit of the adsorption isotherm to the Hill equation. The antibody displays the greatest affinity (K_d = 15.2 ± 0.8 nM) that is ∼20-65 times stronger than the affinity of the other plasma proteins. Antibody-AuNP conjugates were prepared, purified, and suspended in solutions of blood plasma proteins to evaluate the stability of the antibody layer. An enzyme-mediated assay confirms that the antibody-AuNP interaction is irreversible, and the adsorbed antibody resists displacement by the plasma proteins. This work provides insight into the capabilities and potential limitations of antibody-AuNP-enabled technologies in biological systems.

Manipulating Immune Activation of Macrophages by Tuning the Oligonucleotide Composition of Gold Nanoparticles

This paper describes how the ligand shell containing immunostimulatory oligonucleotides surrounding gold nanoparticles affects the in vitro activation of macrophages. Nanoconstructs with similar ligand densities but different oligonucleotide compositions (from 0% to 100% immune-active cytosine-phosphate-guanine, CpG) were compared. Maximum immunostimulation was achieved with CpG content as low as 5% (with total oligonucleotide surface coverage remaining constant), correlating to high levels of antitumor cytokine release and low levels of cancer-promoting ones. Independent of CpG content, gold nanoparticles with low oligonucleotide densities exhibit poor cellular uptake, leading to insignificant immunostimulation and cytokine release. By identifying effects of ligand shell composition on macrophage activation, we can inform the design rules of therapeutic nanoconstructs to achieve specific immune responses.

Simultaneous recognition of cysteine and cytosine using thiophene-based organic nanoparticles decorated with Au NPs and bio-imaging of cells

Biomolecules like cysteine and cytosine play a significant role in many physiological processes, and their unusual level in biological systems can lead to many diseases including cancer. Indeed, the need for selective detection of these moieties by a fluorescence probe is imperative. Thus, thiophene based Schiff N,N'-bis(thiophene-2-ylmethylene)thiophenemethane (BMTM) was synthesized and then characterized using several analytical techniques before converting it into organic nanoparticles (ONPs). Then, fluorescent organic inorganic nanohybrids (FONs) were obtained after decorating ONPs with AuNPs to yield BMTM-Au-ONPs (FONPs). The morphology of the particles, analyzed using a Transmission Electron Microscope (TEM), shows that AuNPs were embedded with low density organic matter (ONPs). FONPs were employed to recognize cysteine and cytosine simultaneously. No interference was observed from other moieties such as guanine, uracyl, NADH, NAD, ATP, and adenine during the detection. It means that the intensity of the fluorescence signal was significantly changed (enhanced for cytosine and quenched for cysteine). So, FONPs were used to detect cysteine and cytosine in real samples, like Saccharomyces cerevisiae cells. As expected, no considerable fluorescence signal for cysteine was observed, while for cytosine, strong fluorescence signals were detected in the cells. DFT was used to explain the interaction of FONPs with cysteine or cytosine.

mRNA Guided Intracellular Self-Assembly of DNA-Gold Nanoparticle Conjugates as a Precise Trigger to Up-Regulate Cell Apoptosis and Activate Photothermal Therapy

The size of nanoparticles was generally accepted to have a close relationship with the penetration and retention properties among tumor sites, which is one of the most significant issues during nanomedicine delivery. Despite the outstanding stealth property when circulating and the penetration ability in tumor tissue, small nanoparticles still have the problem of inadequate retention time. Taking advantage of the precise self-assembly of DNA-nanoparticle conjugates, we developed an intracellular assembly system to realize the change of nanoparticle size from small to large as well as activation of therapeutic function inside cancer cells. A duplex sequence of cancer-cell-specific mRNA, survivin, was selected to hybridize with complementary sequence of gold nanoparticle-DNA (AuNP-DNA) conjugates in cancer cell cytoplasm, resulting in the specific and precise formation of intracellular assemblies. Enhanced retention behavior of AuNPs inside cancer cells was shown to be achieved because of the increased nanoparticle size. Meanwhile, an up-regulation effect of cell apoptosis and an activated photothermal therapy function were also created by the formation of AuNP aggregations, and eventually contributed to a high rate of cancer cells death up to 93.33%. In contrast, it exhibited almost no toxicity toward normal cells because of the absence of survivin-induced assembly. Therefore, this mRNA guided intracellular assembly system exhibited its potential as a new precise cancer therapy strategy, and also broadened the application field of DNA-conjugated nanoparticle assembly.

Discovery of and Insights into DNA "Codes" for Tunable Morphologies of Metal Nanoparticles

The discovery and elucidation of genetic codes has profoundly changed not only biology but also many fields of science and engineering. The fundamental building blocks of life comprises of four simple deoxyribonucleotides and yet their combinations serve as the carrier of genetic information that encodes for proteins that can carry out many biological functions due to their unique functionalities. Inspired by nature, the functionalities of DNA molecules have been used as a capping ligand for controlling morphology of nanomaterials, and such a control is sequence dependent, which translates into distinct physical and chemical properties of resulting nanoparticles. Herein, an overview on the use of DNA as engineered codes for controlling the morphology of metal nanoparticles, such as gold, silver, and Pd-Au bimetallic nanoparticles is provided. Fundamental insights into rules governing DNA controlled growth mechanisms are also summarized, based on understanding of the affinity of the DNA nucleobases to various metals, the effect of combination of nucleobases, functional modification of DNA, the secondary structures of DNA, and the properties of the seed employed. The resulting physical and chemical properties of these DNA encoded nanomaterials are also reviewed, while perspectives into the future directions of DNA-mediated nanoparticle synthesis are provided.

Progress toward Understanding the Interactions between DNA Nanostructures and the Cell

Advances in DNA nanotechnology empower the programmable assembly of DNA building blocks (oligonucleotides and plasmids) into DNA nanostructures with precise architectural control. As DNA nanostructures are biocompatible and can naturally enter mammalian cells without the aid of transfection agents, they have found numerous biological or biomedical applications as delivery carriers of therapeutic and imaging cargoes into mammalian cells for at least a decade. Nevertheless, mechanistic studies on how DNA nanostructures interact with cells have remained limited and incomprehensive until 2-3 years ago. This Review presents the recent progress in elucidating the "cell-nano" interactions of DNA nanostructures, with an emphasis on three key classes of structures commonly utilized in intracellular applications: tile-based structures, origami-based structures, and nanoparticle-templated structures. Structural parameters of DNA nanostructures and strategies of biochemical modification for promoting intracellular delivery are discussed. Biological mechanisms for cellular uptake, including specific pathways and receptors involved, are outlined. Routes of intracellular trafficking and degradation, together with strategies for re-directing their trafficking, are delineated. This Review concludes with several aspects of the "bio-nano" interactions of DNA nanostructures that warrant future investigations.

Programmable Atom Equivalents: Atomic Crystallization as a Framework for Synthesizing Nanoparticle Superlattices

Decades of research efforts into atomic crystallization phenomenon have led to a comprehensive understanding of the pathways through which atoms form different crystal structures. With the onset of nanotechnology, methods that use colloidal nanoparticles (NPs) as nanoscale "artificial atoms" to generate hierarchically ordered materials are being developed as an alternative strategy for materials synthesis. However, the assembly mechanisms of NP-based crystals are not always as well-understood as their atomic counterparts. The creation of a tunable nanoscale synthon whose assembly can be explained using the context of extensively examined atomic crystallization will therefore provide significant advancement in nanomaterials synthesis. DNA-grafted NPs have emerged as a strong candidate for such a "programmable atom equivalent" (PAE), because the predictable nature of DNA base-pairing allows for complex yet easily controlled assembly. This Review highlights the characteristics of these PAEs that enable controlled assembly behaviors analogous to atomic phenomena, which allows for rational material design well beyond what can be achieved with other crystallization techniques.

Au nanoparticle-decorated aragonite microdumbbells for enhanced antibacterial and anticancer activities

The present work reports the very first hydrothermal synthesis of 100% triclinic phase pure aragonite (A1) with microdumbbell microstructural architecture and Au Nanoparticle-decorated (AuNP-decorated) aragonites (A2, A3 and A4) with spherical, pentagonal/hexagonal and agglomerated AuNP-decorated microdumbbells having triclinic aragonite phase as the major and cubic AuNPs as the minor phase. Even in dark the AuNP-decorated aragonites (especially A2) show efficacies as high 90% against gram-negative e.g., Pseudomonas putida (P. putida) bacteria. Further the AuNP-decorated aragonites (A3) show anti-biofilm capability of as high as about 20% against P. putida. Most importantly the AuNP-decorated aragonites (A3) offer anti-cancer efficacy of as high as 53% while those of A1, A2, and A4 are e.g., 26%, 46% and 37%, respectively. For the very first time, based on detailed investigations, the mechanisms behind such advance antibiofilm and anticancer activities are linked to the generation of excess labile toxic reactive oxygen species (ROS). Thus, these materials show enormous potential as futuristic, multi-functional biomaterials for anti-bacterial, anti-biofilm and anti-cancer applications.

Label Free Particle-by-Particle Quantification of DNA Loading on Sorted Gold Nanostars

This paper describes a label free technique for determining ligand loading on metal nanoparticles using a variant of secondary ion mass spectrometry. Au4004+ clusters bombard DNA-functionalized anisotropic gold nanostars and isotropic nanospheres with similar surface areas to determine ligand density. For each projectile impact, co-localized molecules within the emission area of a single impact (diameter of 10-15 nm) were examined for each particle. Individual nanoparticle analysis allows for determination of the relationship between particle geometry and DNA loading. We found that branched particles exhibited increased ligand density versus nanospheres and determined that positive and neutral curvature could facilitate additional loading. This methodology can be applied to optimize loading for any ligand-core interaction independent of nanoparticle core, ligand, or attachment chemistry.

The Growing Development of DNA Nanostructures for Potential Healthcare-Related Applications

DNA self-assembly has proven to be a highly versatile tool for engineering complex and dynamic biocompatible nanostructures from the bottom up with a wide range of potential bioapplications currently being pursued. Primary among these is healthcare, with the goal of developing diagnostic, imaging, and drug delivery devices along with combinatorial theranostic devices. The path to understanding a role for DNA nanotechnology in biomedical sciences is being approached carefully and systematically, starting from analyzing the stability and immune-stimulatory properties of DNA nanostructures in physiological conditions, to estimating their accessibility and application inside cellular and model animal systems. Much remains to be uncovered but the field continues to show promising results toward developing useful biomedical devices. This review discusses some aspects of DNA nanotechnology that makes it a favorable ingredient for creating nanoscale research and biomedical devices and looks at experiments undertaken to determine its stability in vivo. This is presented in conjugation with examples of state-of-the-art developments in biomolecular sensing, imaging, and drug delivery. Finally, some of the major challenges that warrant the attention of the scientific community are highlighted, in order to advance the field into clinically relevant applications.

Terminal Deoxynucleotidyl Transferase-Catalyzed Preparation of pH-Responsive DNA Nanocarriers for Tumor-Targeted Drug Delivery and Therapy

Developing a highly efficient carrier for tumor-targeted delivery and site-specific release of anticancer drugs is a good way to overcome the side effects of traditional cancer chemotherapy. Benefiting from the nontoxic and biocompatible characteristics, DNA-based drug carriers have attracted increasing attention. Herein, we reported a novel and readily manipulated strategy to construct spherical DNA nanocarriers. In this strategy, terminal deoxynucleotidyl transferase (TdT)-catalyzed DNA extension reaction is used to prepare a thick DNA layer on a gold nanoparticle (AuNP) surface by extending long poly(C) sequences from DNA primers immobilized on AuNPs. The poly(C) extension products can then hybridize with G-rich oligonucleotides to give CG-rich DNA duplexes (for loading anticancer drug doxorubicin, Dox) and multiple AS1411 aptamers. Via synergic recognition of multiple aptamer units to nucleolin proteins, biomarker of malignant tumors, Dox-loaded DNA carrier can be efficiently internalized in cancer cells and achieve burst release of drugs in acidic organelles because of i-motif formation-induced DNA duplex destruction. An as-prepared pH-responsive drug carrier was demonstrated to be promising for highly efficient delivery of Dox and selective killing of cancer cells in both in vitro and in vivo experiments, thus showing a huge potential in anticancer therapy.

Promoting the Delivery of Nanoparticles to Atherosclerotic Plaques by DNA Coating

Many nanoparticle-based carriers to atherosclerotic plaques contain peptides, lipoproteins, and sugars, yet the application of DNA-based nanostructures for targeting plaques remains infrequent. In this work, we demonstrate that DNA-coated superparamagnetic iron oxide nanoparticles (DNA-SPIONs), prepared by attaching DNA oligonucleotides to poly(ethylene glycol)-coated SPIONs (PEG-SPIONs), effectively accumulate in the macrophages of atherosclerotic plaques following an intravenous injection into apolipoprotein E knockout (ApoE^-/-) mice. DNA-SPIONs enter RAW 264.7 macrophages faster and more abundantly than PEG-SPIONs. DNA-SPIONs mostly enter RAW 264.7 cells by engaging Class A scavenger receptors (SR-A) and lipid rafts and traffic inside the cell along the endolysosomal pathway. ABS-SPIONs, nanoparticles with a similarly polyanionic surface charge as DNA-SPIONs but bearing abasic oligonucleotides also effectively bind to SR-A and enter RAW 264.7 cells. Near-infrared fluorescence imaging reveals evident localization of DNA-SPIONs in the heart and aorta 30 min post-injection. Aortic iron content for DNA-SPIONs climbs to the peak (∼60% ID/g) 2 h post-injection (accompanied by profuse accumulation in the aortic root), but it takes 8 h for PEG-SPIONs to reach the peak aortic amount (∼44% ID/g). ABS-SPIONs do not appreciably accumulate in the aorta or aortic root, suggesting that the DNA coating (not the surface charge) dictates in vivo plaque accumulation. Flow cytometry analysis reveals more pronounced uptake of DNA-SPIONs by hepatic endothelial cells, splenic macrophages and dendritic cells, and aortic M2 macrophages (the cell type with the highest uptake in the aorta) than PEG-SPIONs. In summary, coating nanoparticles with DNA is an effective strategy of promoting their systemic delivery to atherosclerotic plaques.