Oral and Intra-nasal Administration of Nanoparticles in the Cerebral Ischemia Treatment in Animal Experiments: Considering its Advantages and Disadvantages

BACKGROUND

Over the past few decades, nanotechnology has dramatically advanced; from the precise strategies of synthesizing modern nanostructures to methods of entry into the body. Using nanotechnology in diagnosis, drug delivery, determining signaling pathways, and tissue engineering is great hope for the treatment of stroke. The drug-carrying nanoparticles are a way to increase drug absorption through the mouth or nose in treating the stroke.

OBJECTIVE

In this article, in addition to explaining pros and cons of oral and intra-nasal administration of nanoparticles in the brain ischemia treatment of animal models, the researchers introduce some articles in this field and briefly mentioned their work outcomes.

METHODS

A number of relevant published articles 183 were initially collected from three popular databases including PubMed, Google Scholar, and Scopus. The articles not closely related to the main purpose of the present work were removed from the study process. The present data set finally included 125 published articles.

RESULTS

Direct delivery of the drug to the animal brain through the mouth and nose has more therapeutic effects than systemic delivery of drugs. The strategy of adding drugs to the nanoparticles complex can potentially improve the direct delivery of drugs to the CNS.

CONCLUSION

Despite the limitations of oral and intra-nasal routes, the therapeutic potential of oral and intra-nasal administration of nano-medicines is high in cerebral ischemia treatment.

A Novel Approach towards Synthesis and Characterization of Non-Cytotoxic Gold Nanoparticles Using Taurine as Capping Agent

Metal gold nanoparticles are of great interest due to their unique physico-chemical properties and their potential to be used as nano-probes in biosensors, drug delivery, and therapeutic applications. Currently, many capping agents are used for metal gold nanoparticles, such as cetyltrimethylammonium bromide (CTAB) and tri-sodium citrate that have been reported to be toxic and hinders biological applications. To address this issue, we report, for the first time, the use of taurine as a stable non-cytotoxic capping agent for synthesizing gold nanoparticles by using an in situ wet-chemical method. This facile method resulted in monodisperse gold nanospheres with a high yield and stability. Monodisperse gold nanospheres with average diameters of 6.9 nm and 46 nm were synthesized at a high yield with controlled morphology. Temperature played a critical role in determining the size of the taurine-capped gold nanoparticles. The subtle changes in the reaction parameters had a tremendous effect on the final size of nanoparticles and their stability. The synthesized nanoparticles were characterized by using optical spectroscopy, a ZetaSizer, a NanoSight, Fourier Transform Infrared (FTIR) spectroscopy, X-ray Diffraction (XRD), X-ray Photon Spectroscopy (XPS) and Electron Microscopy to understand their physico-chemical properties. Taurine was explored as a capping and stabilizing agent for gold nanospheres, which were evaluated for their toxicity responses towards human liver carcinoma cells (HepG2) via MTT assay.

Unexpected intracellular biodegradation and recrystallization of gold nanoparticles

Gold nanoparticles are used in an expanding spectrum of biomedical applications. However, little is known about their long-term fate in the organism as it is generally admitted that the inertness of gold nanoparticles prevents their biodegradation. In this work, the biotransformations of gold nanoparticles captured by primary fibroblasts were monitored during up to 6 mo. The combination of electron microscopy imaging and transcriptomics study reveals an unexpected 2-step process of biotransformation. First, there is the degradation of gold nanoparticles, with faster disappearance of the smallest size. This degradation is mediated by NADPH oxidase that produces highly oxidizing reactive oxygen species in the lysosome combined with a cell-protective expression of the nuclear factor, erythroid 2. Second, a gold recrystallization process generates biomineralized nanostructures consisting of 2.5-nm crystalline particles self-assembled into nanoleaves. Metallothioneins are strongly suspected to participate in buildings blocks biomineralization that self-assembles in a process that could be affected by a chelating agent. These degradation products are similar to aurosomes structures revealed 50 y ago in vivo after gold salt therapy. Overall, we bring to light steps in the lifecycle of gold nanoparticles in which cellular pathways are partially shared with ionic gold, revealing a common gold metabolism.

Indocyanine Green J Aggregates in Polymersomes for Near-Infrared Photoacoustic Imaging

Clinical translation of photoacoustic imaging (PAI) has been limited by the lack of near-infrared (NIR) contrast agents with low toxicity required for regulatory approval. Herein, J aggregates of indocyanine green (ICG) with strong NIR absorbance were encapsulated at high loadings within small 77 nm polymersomes (nanocapsules) composed of poly(lactide-co-glycolide-b-poly(ethylene glycol)) (PLGA-b-PEG) bilayers, thus enabling PAI of of breast and ovarian cancer cells with high specificity and a sensitivity at the level of ∼100 total cells. All of the major components of the polymersomes are FDA approved and used in the clinic. During formation of polymersomes with a water-in-oil-in-water double emulsion process, loss of ICG from the ICG J aggregates was minimized by coating them with a layer of branched polyethylenimine and by providing excess "sacrificial" ICG to adsorb at the oil-water interfaces. The encapsulated J aggregates were protected against dissociation by the polymersome shell for 24 h in 100% fetal bovine serum, after which the polymersomes biodegraded and the J aggregates dissociated to ICG monomers.

The Effect of Stabilisation Agents on the Immunomodulatory Properties of Gold Nanoparticles Obtained by Ultrasonic Spray Pyrolysis

Gold nanoparticles (GNPs) have been investigated extensively as drug carriers in tumour immunotherapy in combination with photothermal therapy. For this purpose, GNPs should be stabilised in biological fluids. The goal of this study was to examine how stabilisation agents influence cytotoxicity and immune response in vitro. Spherical GNPs, 20 nm in size, were prepared by ultrasonic spray pyrolysis (USP). Three types of stabilising agents were used: sodium citrate (SC), polyvinyl-pyrrolidone (PVP), and poly-ethylene glycol (PEG). Pristine, non-stabilised GNPs were used as a control. The culture models were mouse L929 cells, B16F10 melanoma cells and human peripheral blood mononuclear cells (PBMNCs), obtained from healthy donors. Control SC- and PEG-GNPs were non-cytotoxic at concentrations (range 1–100 µg/mL), in contrast to PVP-GNPs, which were cytotoxic at higher concentrations. Control GNPs inhibited the production of IFN-ϒ slightly, and augmented the production of IL-10 by PHA-stimulated PBMNC cultures. PEG-GNPs inhibited the production of pro-inflammatory cytokines (IL-1, IL-6, IL-8, TNF-α) and Th1-related cytokines (IFN-ϒ and IL-12p70), and increased the production of Th2 cytokines (IL-4 and IL-5). SC-PEG inhibited the production of IL-8 and IL-17A. In contrast, PVP-GNPs stimulated the production of pro-inflammatory cytokines, Th1 cytokines, and IL-17A, but also IL-10. When uptake of GNPs by monocytes/macrophages in PBMNC cultures was analysed, the ingestion of PEG- GNPs was significantly lower compared to SC- and PVP-GNPs. In conclusion, stabilisation agents modulate biocompatibility and immune response significantly, so their adequate choice for preparation of GNPs is an important factor when considering the use of GNPs for application in vivo.

Probing the Self-Assembly and Nonlinear Friction Behavior of Confined Gold Nano-Particles

For the wide application of nanoparticles (NPs) (e.g., in nanotribology), it is of fundamental and practical importance to understand the self-assembly and lubrication behavior of confined NPs. In this work, a systematic study was conducted to probe the assembly and associated surface forces of spherical gold nanoparticles (Au NPs, diameter ∼5 nm) confined between pairs of mica (negatively charged) and (3-aminopropyl)triethoxysilane modified mica (APTES-mica, positively charged) surfaces using a surface forces apparatus (SFA) under aqueous conditions. It is observed that Au NPs were squeezed out of the confined gap between two mica surfaces during the loading process, resulting from the repulsive electric-double layer force. In contrast, multilayers of Au NPs were confined between two APTES-mica surfaces because of the attractive double-layer force between oppositely charged Au NPs and APTES-mica. Interestingly, the interaction between Au NPs and APTES-mica is stronger than the interactions between Au NPs, resulting in the rearrangement of the confined Au NPs under shearing. Importantly, a large friction coefficient (μ > 0.7) with unexpected nonlinear stick-slip friction was observed when sliding two APTES-mica surfaces with thin layers of Au NPs (∼20 nm) confined in between. The observed stick-slip motion could be explained by the velocity-dependent friction model where a critical shear velocity was required for transiting from stick-slip to smooth sliding. Our study provides useful information on the assembly and interaction forces of confined nanoparticles on charged surfaces, with implications for predicting the behaviors of NPs under confinement in various engineering applications.

X-Ray Fluorescence Computed Tomography Induced by Photon, Electron, and Proton Beams

X-ray fluorescence CT (XFCT) has shown promise for molecular imaging of gold nanoparticles. To date, XFCT has been induced by kilovoltage photon beams due to the high photoelectric interaction probability. We compare K-shell and L-shell XFCT induced by photon, electron, and proton beams for two phantom sizes. A 2.5 and 5.0-cm diameter phantom with four 5 mm and 10 mm vials, respectively, with gold-solutions of 0.1%-2% by weight were built in TOPAS, a GEANT4-based Monte Carlo simulation tool. The 2.5-cm phantom was imaged with XFCT induced by beams of 7.45×10⁴ 81 keV- and 5 MeV-photons, 220 kVp- and 6 MV-photons, 10 MeV- and 100 MeV-electrons, and 100 MeV- and 250 MeV-protons. The doses between each phantom size were equal. First-generation CT geometry with 0.5 mm × 0.5 mm pencil beams with 0.5 mm-translation and 2°-rotation steps over each phantom was modeled. The scattered x-rays were detected on an idealized spherical detector from which the K-shell and L-shell fluorescent x-rays were extracted in 0.5 keV and 0.2 keV bins. XFCT images were generated using iterative reconstruction algorithms. The highest gold sensitivity was seen in the 81 keV-photon K-shell and L-shell images (0.004% and 0.007%) of the 5.0 cm-phantom at 30 mGy. For the 2.5 cm-phantom, the detection limits were 0.006%, 0.62%, and 0.28% for 81 keV-photon K-shell, 100 MeV-electron K-shell, and 100 MeV-proton L-shell images, respectively. The mean imaging dose was approximately 2-3 orders of magnitude higher in electron- and proton-XFCT compared to 81keV-photon XFCT. Our MC study demonstrates that the small-object XFCT imaging achieves the best performance when induced with kilovoltage-photon beams. Due to high imaging doses, electron- and proton-induced XFCT might be feasible for guiding nanoparticle-enhanced charged-particle radiotherapy.

Endocytosis mechanism in physiologically-based pharmacokinetic modeling of nanoparticles

BACKGROUND

The physiologically based pharmacokinetic (PBPK) model is a useful tool to predict the pharmacokinetics of various types of nanoparticles (NPs). The endocytosis mechanism plays a key role in pharmacokinetics of NPs. However, the effect of endocytosis mechanism both in the blood and tissue are seldom considered in PBPK model.

OBJECTIVES

To investigate the biodistribution of intravenously injected pegylated AuNPs in mice and human using PBPK model considering the endocytosis mechanism both in the blood and tissue.

METHODS

Taking polyethylene glycol-coated gold nanoparticles (AuNPs) as an example, we developed a PBPK model to explore biodistribution of different size AuNPs. In the model, we considered the role of endocytosis mechanism both in the blood and tissue. In addition, the size-dependent permeability coefficient, excretion rate constant, phagocytic capacity, uptake rate, and release rate were derived from literatures. The mice PBPK model was extrapolated to the human by changing physiology parameters and the number of phagocytic cell (PCs).

RESULTS

AuNPs were primarily distributed in the blood, liver, and spleen regardless of particle size, and almost all captured by the PCs in the liver and spleen, while few was captured in the blood. There are more organ distribution and longer circulation for smaller NPs. The 24-h accumulation of AuNPs decreased with increasing size in the most organ, while the accumulation of AuNPs showed an inverted U-shaped curve in the liver and slight U-shaped curve in the blood. The human results of model-predicted displayed a similar tendency with those in mice. Size, partition coefficients, and body weight were the key factors influencing the organ distribution of AuNPs.

CONCLUSIONS

The size played an important role on the distribution and accumulation of AuNPs in various tissues. Our PBPK model was well predicted the NPs distribution in mice and human. A better understanding of these mechanisms could provide effective guides for nanomedine delivery.

A Three-Dimensional Cell Culture Platform for Long Time-Scale Observations of Bio-Nano Interactions

We know surprisingly little about the long-term outcomes for nanomaterials interacting with organisms. To date, most of what we know is derived from in vivo studies that limit the range of materials studied and the scope of advanced molecular biology tools applied. Long-term in vitro nanoparticle studies are hampered by a lack of suitable models, as standard cell culture techniques present several drawbacks, while technical limitations render current three-dimensional (3D) cellular spheroid models less suited. Now, by controlling the kinetic processes of cell assembly and division in a non-Newtonian culture medium, we engineer reproducible cell clusters of controlled size and phenotype, leading to a convenient and flexible long-term 3D culture that allows nanoparticle studies over many weeks in an in vitro setting. We present applications of this model for the assessment of intracellular polymeric and silica nanoparticle persistence and found that hydrocarbon-based polymeric nanoparticles undergo no apparent degradation over long time periods with no obvious biological impact, while amorphous silica nanoparticles degrade at different rates over several weeks, depending on their synthesis method.

One-pot synthesis and characterization of ovalbumin-conjugated gold nanoparticles: A comparative study of adjuvanticity against the physical mixture of ovalbumin and gold nanoparticles

Only few adjuvants are licensed for use in humans and there is a need to develop safe and improved vaccine adjuvants. In this study, we report the one-pot synthesis of antigen ovalbumin (OVA)-conjugated gold nanoparticles (OVA@GNPs). A systematical study was performed by comparing OVA@GNPs with the simple mixture of OVA and gold nanoparticles (OVA+GNPs), including their physiochemical properties through spectrometric and electrophoretic analysis, in vitro stability, cytotoxicity and cellular uptake, and in vivo humoral immune responses following subcutaneous and transcutaneous immunization in mice. The results demonstrate a much stronger interaction between protein and GNPs in OVA@GNPs than OVA+GNPs, which makes OVA@GNPs more stable under in vitro conditions than OVA+GNPs with the ability to induce 4 times higher OVA-specific serum IgG titers following subcutaneous immunization. We also show the dose sparing of OVA@GNPs, as the dosage for aluminum adjuvant required to reach to an equivalent OVA-specific antibody titer was almost five times higher than OVA@GNPs. However, we found that the co-administration of small-sized GNPs had a limited ability for the transcutaneous delivery of OVA. These results demonstrate the potential application of one-pot synthesis approach for producing antigen protein-conjugated gold nanoparticles for vaccine delivery.

Carbohydrate-Coated Gold-Silver Nanoparticles for Efficient Elimination of Multidrug Resistant Bacteria and in Vivo Wound Healing

Multidrug resistant (MDR) bacteria have emerged as a major clinical challenge. The unavailability of effective antibiotics has necessitated the use of emerging nanoparticles as alternatives. In this work, we have developed carbohydrate-coated bimetallic nanoparticles (Au-AgNP, 30-40 nm diameter) that are nontoxic toward mammalian cells yet highly effective against MDR strains as compared to their monometallic counterparts (Ag-NP, Au-NP). The Au-AgNP is much more effective against Gram-negative MDR Escherichia coli and Enterobacter cloacae when compared to most of the potent antibiotics. We demonstrate that in vivo, Au-AgNP is at least 11000 times more effective than Gentamicin in eliminating MDR Methicillin Resistant Staphylococcus aureus (MRSA) infecting mice skin wounds. Au-AgNP is able to heal and regenerate infected wounds faster and in scar-free manner. In vivo results show that this Au-AgNP is very effective antibacterial agent against MDR strains and does not produce adverse toxicity. We conclude that this bimetallic nanoparticle can be safe in complete skin regeneration in bacteria infected wounds.

Warfarin-Capped Gold Nanoparticles: Synthesis, Cytotoxicity, and Cellular Uptake

Currently, research studies on nanoparticle cytotoxicity, uptake or internalization into the body’s cells are of great interest for the improvement of diagnostic and therapeutic applications. We report here the synthesis and characterization of very stable novel warfarin-capped gold nanoparticles with an average diameter of 54 ± 10 nm which were prepared using sodium warfarin as a reducing agent. The nanoparticles were tested in terms of cytotoxicity and cellular internalization in vitro on two cell lines: normal lung fibroblast HFL-1 and human retinal pigment epithelial D407 cells. Our results showed that the normal lung fibroblast HFL-1 cells were more sensitive to the nanoparticle treatment compared to the human retinal pigment epithelial D407 cells. Moreover, any signs of potential cytotoxicity occurred during the first 24 h of treatment, the cellular viability remaining largely unchanged for longer exposure times. Transmission electron microscopy and dark field hyperspectral imaging revealed that the nanoparticles were effectively delivered and released to the HFL-1 and D407 cells’ cytoplasm. Our results provide valuable information to further investigate sodium warfarin-capped gold nanoparticles for possible biological applications.

Smart H2S-Triggered/Therapeutic System (SHTS)-Based Nanomedicine

Hydrogen sulfide (H2S) is of vital importance in several biological and physical processes. The significance of H2S-specific detection and monitoring is emphasized by its elevated levels in various diseases such as cancer. Nanotechnology enhances the performance of chemical sensing nanoprobes due to the enhanced efficiency and sensitivity. Recently, extensive research efforts have been dedicated to developing novel smart H2S-triggered/therapeutic system (SHTS) nanoplatforms for H2S-activated sensing, imaging, and therapy. Herein, the latest SHTS-based nanomaterials are summarized and discussed in detail. In addition, therapeutic strategies mediated by endogenous H2S as a trigger or exogenous H2S delivery are also included. A comprehensive understanding of the current status of SHTS-based strategies will greatly facilitate innovation in this field. Lastly, the challenges and key issues related to the design and development of SHTS-based nanomaterials (e.g., morphology, surface modification, therapeutic strategies, appropriate application, and selection of nanomaterials) are outlined.

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.

Theranostic small interfering RNA nanoparticles in cancer precision nanomedicine

Due to their ability to effectively downregulate the expression of target genes, small interfering RNA (siRNA) have emerged as promising candidates for precision medicine in cancer. Although some siRNA-based treatments have advanced to clinical trials, challenges such as poor stability during circulation, and less than optimal pharmacokinetics and biodistribution of siRNA in vivo present barriers to the systemic delivery of siRNA. In recent years, theranostic nanomedicine integrating siRNA delivery has attracted significant attention for precision medicine. Theranostic nanomedicine takes advantage of the high capacity of nanoplatforms to ferry cargo with imaging and therapeutic capabilities. These theranostic nanoplatforms have the potential to play a major role in gene specific treatments. Here we have reviewed recent advances in the use of theranostic nanoplatforms to deliver siRNA, and discussed the opportunities as well as challenges associated with this exciting technology. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Implantable Materials and Surgical Technologies > Nanomaterials and Implants.

Recent Advances in Nanomaterials-Based Chemo-Photothermal Combination Therapy for Improving Cancer Treatment

Conventional chemotherapy for cancer treatment is usually compromised by shortcomings such as insufficient therapeutic outcome and undesired side effects. The past decade has witnessed the rapid development of combination therapy by integrating chemotherapy with hyperthermia for enhanced therapeutic efficacy. Near-infrared (NIR) light-mediated photothermal therapy, which has advantages such as great capacity of heat ablation and minimally invasive manner, has emerged as a powerful approach for cancer treatment. A variety of nanomaterials absorbing NIR light to generate heat have been developed to simultaneously act as carriers for chemotherapeutic drugs, contributing as heat trigger for drug release and/or inducing hyperthermia for synergistic effects. This review aims to summarize the recent development of advanced nanomaterials in chemo-photothermal combination therapy, including metal-, carbon-based nanomaterials and particularly organic nanomaterials. The potential challenges and perspectives for the future development of nanomaterials-based chemo-photothermal therapy were also discussed.

Control of Arms of Au Stars Size and its Dependent Cytotoxicity and Photosensitizer Effects in Photothermal Anticancer Therapy

Gold nanostars (AuS NPs) are a very attractive nanomaterial, which is characterized by high effective transduction of the electromagnetic radiation into heat energy. Therefore, AuS NPs can be used as photosensitizers in photothermal therapy (PTT). However, understanding the photothermal conversion efficiency in nanostars is very important to select the most appropriate shape and size of AuS NPs. Therefore, in this article, the synthesis of AuS NPs with different lengths of star arms for potential application in PTT was investigated. Moreover, the formation mechanism of these AuS NPs depending on the reducer concentration is proposed. Transmission electron microscopy (TEM) with selected area diffraction (SEAD) and X-ray diffraction (X-Ray) showed that all the obtained AuS NPs are crystalline and have cores with similar values of the diagonal (parameter d), from 140 nm to 146 nm. However, the widths of the star arm edges (parameter c) and the lengths of the arms (parameter a) vary between 3.75 nm and 193 nm for AuS1 NPs to 6.25 nm and 356 nm for AuS4 NPs. Ultraviolet-visible (UV-Vis) spectra revealed that, with increasing edge widths and lengths of the star arms, the surface plasmon resonance (SPR) peak is shifted to the higher wavelengths, from 640 nm for AuS1 NPs to 770 nm for AuS4 NPs. Moreover, the increase of temperature in the AuS NPs solutions as well as the values of calculated photothermal efficiency grew with the elongation of the star arms. The potential application of AuS NPs in the PTT showed that the highest decrease of viability, around 75%, of cells cultured with AuS NPs and irradiated by lasers was noticed for AuS4 NPs with the longest arms, while the smallest changes were visible for gold nanostars with the shortest arms. The present study shows that photothermal properties of AuS NPs depend on edge widths and lengths of the star arms and the values of photothermal efficiency are higher with the increase of the arm lengths, which is correlated with the reducer concentration.

Refractive-Index-Insensitive Nanolaminated SERS Substrates for Label-Free Raman Profiling and Classification of Living Cancer Cells

Surface-enhanced Raman spectroscopy (SERS) has emerged as an ultrasensitive molecular-fingerprint-based technique for label-free biochemical analysis of biological systems. However, for conventional SERS substrates, SERS enhancement factors (EFs) strongly depend on background refractive index (RI), which prevents reliable spatiotemporal SERS analysis of living cells consisting of different extra-/intracellular organelles with a heterogeneous distribution of local RI values between 1.30 and 1.60. Here, we demonstrate that nanolaminated SERS substrates can support uniform arrays of vertically oriented nanogap hot spots with large SERS EFs (>10⁷) insensitive to background RI variations. Experimental and numerical studies reveal that the observed RI-insensitive SERS response is due to the broadband multiresonant optical properties of nanolaminated plasmonic nanostructures. As a proof-of-concept demonstration, we use RI-insensitive nanolaminated SERS substrates to achieve label-free Raman profiling and classification of living cancer cells with a high prediction accuracy of 96%. We envision that RI-insensitive high-performance nanolaminated SERS substrates can potentially enable label-free spatiotemporal biochemical analysis of living biological systems.

Facile in situ synthesis of ultrasmall near-infrared-emitting gold glyconanoparticles with enhanced cellular uptake and tumor targeting

The simultaneous possession of high tumor-targeting efficiency, long blood circulation, and low normal-tissue retention is critical for future clinically translatable nanomedicines. Herein, we reported a facile in situ glycoconjugation strategy for the synthesis of near-infrared (NIR)-emitting gold glyconanoparticles (AuGNPs, ∼2.4 nm) using 1-thio-β-d-glucose as both the surface ligand and the reducing agent in the presence of a gold precursor. The ultrasmall AuGNPs showed similar low healthy organ retention to that of the renal-clearable ultrasmall nonglyconanoparticles, but ∼10 and 2.5 times higher in vitro and in vivo tumor-targeting efficiencies, respectively, were observed. This facile glycoconjugation strategy of ultrasmall AuGNPs was found to show activity towards glucose transporters in the cancer cells and prolonged blood circulation with both renal and hepatobiliary clearance pathways, which synergistically enhanced the tumor targeting of the ultrasmall AuGNPs. This discovery provides a smart strategy for the improvement in tumor targeting by ultrasmall NPs and further strengthens our understanding of glycoconjugation in designing future clinically translatable nanomedicines.

Development of Gold-PAGE: towards the electrophoretic analysis of sulphurous biopolymers

The prevalence, distinctive reactivity and biological significance of sulphur-based groups in proteins and nucleic acids means that analysis of sulphur is of prime importance in biochemistry, biotechnology, and medicine. We report steps in the development of a method to aid in the detection of these moieties using gold nanoparticles as adjuncts in polyacrylamide gel electrophoresis (Gold-PAGE).

In vivo evaluation of safety, biodistribution and pharmacokinetics of laser-synthesized gold nanoparticles

Capable of generating plasmonic and other effects, gold nanostructures can offer a variety of diagnostic and therapy functionalities for biomedical applications, but conventional chemically-synthesized Au nanomaterials cannot always match stringent requirements for toxicity levels and surface conditioning. Laser-synthesized Au nanoparticles (AuNP) present a viable alternative to chemical counterparts and can offer exceptional purity (no trace of contaminants) and unusual surface chemistry making possible direct conjugation with biocompatible polymers (dextran, polyethylene glycol). This work presents the first pharmacokinetics, biodistribution and safety study of laser-ablated dextran-coated AuNP (AuNPd) under intravenous administration in small animal model. Our data show that AuNPd are rapidly eliminated from the blood circulation and accumulated preferentially in liver and spleen, without inducing liver or kidney toxicity, as confirmed by the plasmatic ALAT and ASAT activities, and creatininemia values. Despite certain residual accumulation in tissues, we did not detect any sign of histological damage or inflammation in tissues, while IL-6 level confirmed the absence of any chronic inflammation. The safety of AuNPd was confirmed by healthy behavior of animals and the absence of acute and chronic toxicities in liver, spleen and kidneys. Our results demonstrate that laser-synthesized AuNP are safe for biological systems, which promises their successful biomedical applications.

Gold and silver nanoparticles in resonance Rayleigh scattering techniques for chemical sensing and biosensing: a review

This review (with 116 refs.) summarizes the state of the art in resonance Rayleigh scattering (RRS)-based analytical methods. Following an introduction into the fundamentals of RRS and on the preparation of metal nanoparticles, a first large section covers RRS detection methods based on the use of gold nanoparticles, with subsections on proteins (albumin, bovine serum albumin and ovalbumin, glycoproteins, folate receptors, iron binding-proteins, G-proteins-coupled receptors, transmembrane proteins, epidermal growth factor receptors), on pesticides, saccharides, vitamins, heavy metal ions (such as mercury, silver, chromium), and on cationic dyes. This is followed by a section on RRS methods based on the use of silver nanoparticles, with subsections on the detection of nucleic acids and insecticides. Several Tables are presented where an RRS method is compared to the performance of other methods. A concluding section summarizes the current status, addresses current challenges, and gives an outlook on potential future trends. Graphical Abstract Change in the resonance Rayleigh scattering (RRS) intensity when mixing the nanoparticles with the specific analyte.

Thermocouple-tip-exposing temperature assessment technique for evaluating photothermal conversion efficiency of plasmonic nanoparticles at low laser power density

A new thermocouple (TC) tip-exposing temperature assessment technique that combines experimental temperature measurements with a numerical model of the photothermal conversion efficiency η is presented. The proposed technique is designed to evaluate η for a gold-coated superparamagnetic iron oxide nanoparticle (SPIO-Au NP) solution (26 nm, 12-70 ppm) at low continuous wave laser power (103 mW, 532 nm) irradiation in a convenient manner under ambient conditions. The TC tip temperature is measured during the first 30 s of the laser exposure, and the results are combined with a finite element model to simulate the temperature rise of the NP solution for a given concentration. The value of η is adjusted in the model until the model agrees with the measured transient TC temperature rise. Values of η = 1.00 were observed for all concentrations. Theoretical predictions of η derived by Mie theory confirmed the near unity conversion efficiency of the as-synthesized SPIO-Au NPs. Advantages of the current technique include co-locating the TC tip in the geometric center of the laser-heated region, rather than outside of this region. In addition, the technique can be done under ambient room conditions using unmodified commercially available hardware.

Biodistribution and toxickinetic variances of chemical and green Copper oxide nanoparticles in vitro and in vivo

In this study, chemical (S1) and green (S2) Copper Oxide nanoparticles (NPs) were synthesized to determine their biodistribution and toxicokinetic variances in vitro and in vivo. Both NPs significantly released Copper ions (Cu) in lymphocytes and were primarily deposited in the mononuclear phagocyte system (MPS) such as the liver and spleen in mice. In particular, S2NPs seemed to be prominently stored in the spleen, whereas the S1NPs were widely stored in more organs including the liver, heart, lungs, kidney and intestine. The circulation in the blood and fecal excretions both showed higher S2NPs contents respectively. Measurements of cell viability, Hemolysis assay, Reactive Oxygen Species (ROS) generation, biochemical estimation and apoptotic or necrotic study in lymphocytes after 24 h and measurements of body and organ weight, serum chemistry evaluation, cytokines level, protein expressions and histopathology of Balb/C mice after 15 days indicated significant toxicity difference between the S1NPs and S2NPs. Our observations proved that the NPs physiochemical properties influence toxicity and Biodistribution profiles in vitro and in vivo.

Toxicological Behavior of Gold Nanoparticles on Various Models: Influence of Physicochemical Properties and Other Factors

Potential applications of gold nanoparticles in biomedicine have increasingly been reported on account of the ease of synthesis, bioinert characteristics, optical properties, chemical stability, high biocompatibility, and specificity. The safety of these particles remains a great concern, as there are differences among toxicity study protocols used. This article focuses on integrating results of research on the toxicological behavior of gold nanoparticles. This can be influenced by the physicochemical properties, including size, shape, surface charge, and other factors, such as methods used in the synthesis of gold nanoparticles, models used, dose, in vivo route of administration, and interference of gold nanoparticles with in vitro toxicity assay systems. Several researchers have reported toxicological studies with regard to gold nanoparticles, using various in vitro, in vivo, and in ovo models. The conflicting results concerning the toxicity of gold nanoparticles should thus be addressed to justify the safe use of gold nanoparticles in biomedicine.

Synthesis, characterization, and mechanistic studies of a gold nanoparticle-amphotericin B covalent conjugate with enhanced antileishmanial efficacy and reduced cytotoxicity

Background

Amphotericin B (AmB) as a liposomal formulation of AmBisome is the first line of treatment for the disease, visceral leishmaniasis, caused by the parasite Leishmania donovani. However, nephrotoxicity is very common due to poor water solubility and aggregation of AmB. This study aimed to develop a water-soluble covalent conjugate of gold nanoparticle (GNP) with AmB for improved antileishmanial efficacy and reduced cytotoxicity.

Methods

Citrate-reduced GNPs (~39 nm) were functionalized with lipoic acid (LA), and the product GNP-LA (GL ~46 nm) was covalently conjugated with AmB using carboxyl-to-amine coupling chemistry to produce GNP-LA-AmB (GL-AmB ~48 nm). The nanoparticles were characterized by dynamic light scattering, transmission electron microscopy (TEM), and spectroscopic (ultraviolet–visible and infrared) methods. Experiments on AmB uptake of macrophages, ergosterol depletion of drug-treated parasites, cytokine ELISA, fluorescence anisotropy, flow cytometry, and gene expression studies established efficacy of GL-AmB over standard AmB.

Results

Infrared spectroscopy confirmed the presence of a covalent amide bond in the conjugate. TEM images showed uniform size with smooth surfaces of GL-AmB nanoparticles. Efficiency of AmB conjugation was ~78%. Incubation in serum for 72 h showed <7% AmB release, indicating high stability of conjugate GL-AmB. GL-AmB with AmB equivalents showed ~5-fold enhanced antileishmanial activity compared with AmB against parasite-infected macrophages ex vivo. Macrophages treated with GL-AmB showed increased immunostimulatory T_h1 (IL-12 and interferon-γ) response compared with standard AmB. In parallel, AmB uptake was ~5.5 and ~3.7-fold higher for GL-AmB-treated (P<0.001) macrophages within 1 and 2 h of treatment, respectively. The ergosterol content in GL-AmB-treated parasites was ~2-fold reduced compared with AmB-treated parasites. Moreover, GL-AmB was significantly less cytotoxic and hemolytic than AmB (P<0.01).

Conclusion

GNP-based delivery of AmB can be a better, cheaper, and safer alternative than available AmB formulations.

Targeted Gold Nanocluster-Enhanced Radiotherapy of Prostate Cancer

For over a hundred years, X-rays have been a main component of the radiotherapeutic approaches to treat cancer. Yet, to date, no radiosensitizer has been developed to selectively target prostate cancer. Gold has excellent X-ray absorptivity and is used as a radiotherapy enhancing material. In this work, ultrasmall Au25 nanoclusters (NCs) are developed for selective prostate cancer targeting, radiotherapy enhancement, and rapid clearance from the body. Targeted-Au25 NCs are rapidly and selectively taken up by prostate cancer in vitro and in vivo and also have fast renal clearance. When combined with X-ray irradiation of the targeted cancer tissues, radiotherapy is significantly enhanced. The selective targeting and rapid clearance of the nanoclusters may allow reductions in radiation dose, decreasing exposure to healthy tissue and making them highly attractive for clinical translation.

Designing inorganic nanomaterials for vaccines and immunotherapies

Vaccines and immunotherapies have changed the face of health care. Biomaterials offer the ability to improve upon these medical technologies through increased control of the types and concentrations of immune signals delivered. Further, these carriers enable targeting, stability, and delivery of poorly soluble cargos. Inorganic nanomaterials possess unique optical, electric, and magnetic properties, as well as defined chemistry, high surface-to-volume- ratio, and high avidity display that make this class of materials particularly advantageous for vaccine design, cancer immunotherapy, and autoimmune treatments. In this review we focus on this understudied area by highlighting recent work with inorganic materials - including gold nanoparticles, carbon nanotubes, and quantum dots. We discuss the intrinsic features of these materials that impact the interactions with immune cells and tissue, as well as recent reports using inorganic materials across a range of emerging immunological applications.

Depth-Resolved Enhanced Spectral-Domain OCT Imaging of Live Mammalian Embryos Using Gold Nanoparticles as Contrast Agent

High-resolution and real-time visualization of the morphological changes during embryonic development are critical for studying congenital anomalies. Optical coherence tomography (OCT) has been used to investigate the process of embryogenesis. However, the structural visibility of the embryo is decreased with the depth due to signal roll-off and high light scattering. To overcome these obstacles, in this study, combined is a spectral-domain OCT (SD-OCT) with gold nanorods (GNRs) for 2D/3D imaging of live mouse embryos. Inductively coupled plasma mass spectrometry is used to confirm that GNRs can be effectively delivered to the embryos during ex vivo culture. OCT signal, image contrast, and penetration depth are all enhanced on the embryos with GNRs. These results show that after GNR treatment, more accurate spatial localization and better contrasting of the borders among organs can be observed on E9.5 and E10.5 mouse embryos. Furthermore, the strong optical absorbance of GNRs results in much clearer 3D images of the embryos, which can be used for calculating the heart areas and volumes of E9.5 and E10.5 embryos. These findings provide a promising strategy for monitoring organ development and detecting congenital structural abnormalities in mice.

Therapeutic effect of gold nanoparticles on DSS-induced ulcerative colitis in mice with reference to interleukin-17 expression

Ulcerative colitis (UC) is among the most challenging human diseases. Nanotechnology has incontestable promising outcomes in inflammatory bowel diseases. This study aimed to investigate the therapeutic effect of naked gold nanoparticles (AuNPs) on dextran sodium sulphate (DSS) induced ulcerative colitis in mice. We also examined the expression of interleukin-17 (IL-17) following AuNPs treatment. Mice were randomly divided into control, DSS and DSS+ AuNPs groups. Severity of colitis was assessed by disease activity index (DAI) measurement. At the end of the experiment, the final body weights were recorded. The colon was dissected and processed for histopathological examinations by light and electron microscopes. Colon homogenates were prepared for assay of tissue malondialdehyde (MDA) and real-time PCR analysis of IL-17A. Immunohistochemical localization of IL-17A was carried out. Scanning electron microscopy (SEM) and Energy Dispersive X-ray (EDX) detector were used to detect the presence of AuNPs in the colonic tissue of DSS+ AuNPs groups. Our results showed that AuNPs effectively targeted the colonic tissue, and reduced changes induced by DSS. The underlying mechanisms could be related to anti-oxidant effect (as evident by decreasing tissue MDA) and anti-inflammatory potential of AuNPs. Our study draws attention to as a novel therapeutic strategy for treating UC.

Single-Cell Detection and Photostimulation on a Microfluidic Chip Aided with Gold Nanorods

Gold nanorods (GNRs) can be easily designed and synthesized to respond to photons in the near infrared (NIR) band. The photostimulation by laser irradiation can be mediated and enhanced by GNRs to introduce localized damage to cells for photodynamic/photothermal therapy (PDT or PTT). In this study, we show that cells stained with GNRs can be detected and stimulated simultaneously by short flashes of femtosecond-laser irradiation on a microfluidic system effectively. In the relatively high-throughput cell flow, the two-photon luminescence from GNRs can be excited and detected. The GNRs also mediate and enhance the transient photostimulation of the cells. After photostimulation, cells can remain alive, go to apoptosis, or necrosis, respectively. The stimulation effect is strongly dependent on the photon density and stimulation duration. We found the cells remain alive, go to apoptosis or necrosis, dependent on the GNR staining, the laser illumination pattern and duration. Hence, our system provides a simple and effective method for high-throughput cell stimulation and analysis on chip. © 2019 International Society for Advancement of Cytometry.

The role of olfactory transport in the penetration of manganese oxide nanoparticles from blood into the brain

There is no doubt that various nanoparticles (NPs) can enter the brain from the nasal cavity. It is assumed that NPs can penetrate from blood into the central nervous system (CNS) only by breaking the blood–brain barrier (BBB). The accumulation of NPs in CNS can provoke many neurological diseases; therefore, the understanding of its mechanisms is of both academic and practical interest. Although hitting from the surface of the lungs into the bloodstream, NPs can accumulate in various mucous membranes, including the nasal mucosa. Thus, we cannot rule out the ability of NPs to be transported from the bloodstream to the brain through the olfactory uptake. To test this hypothesis, we used paramagnetic NPs of manganese oxide (Mn3O4-NPs), whose accumulation patterns in the mouse brain were recorded using T1-weighted magnetic resonance imaging. The effect of intranasal application of endocytosis and axonal transport inhibitors on the brain accumulation patterns of intranasally or intravenously injected Mn3O4-NPs was evaluated. A comparative analysis of the results showed that the transport of Mn3O4-NPs from the nasal cavity to the brain is more efficient than their local permeation through BBB into CNS from the bloodstream, for example with the accumulation of Mn3O4NPs in the dentate gyrus of the hippocampus, and through the capture and transport of NPs from the blood by olfactory epithelium cells. Also, experiments with the administration of chlorpromazine, a specific inhibitor of clathrin-dependent endocytosis, and methyl-β-cyclodextrin, inhibitor of the lipid rafts involved in the capture of substances by endothelium cells, showed differences in the mechanisms of NP uptake from the nasal cavity and from the bloodstream. In this study, we show a significant contribution of axonal transport to NP accumulation patterns in the brain, both from the nasal cavity and from the vascular bed. This explains the accumulation of different sorts of submicron particles (neurotropic viruses, insoluble xenobiotics, etc.), unable to pass BBB, in the brain. The results will add to the understanding of the pathogenesis of various neurodegenerative diseases and help studying the side effects of therapeutics administered intravenously.

Small-Molecule Porphyrin-Based Organic Nanoparticles with Remarkable Photothermal Conversion Efficiency for in Vivo Photoacoustic Imaging and Photothermal Therapy

Near-infrared (NIR)-absorbing organic nanoparticles (ONPs) are emerging candidates for "one-for-all" theranostic nanomaterials with considerations of safety and formulation in mind. However, facile fabrication methods and improvements in the photothermal conversion efficiency (PCE) and photostability are likely needed before a clinically viable set of candidates emerges. Herein, a new organic compound, [porphyrin-diketopyrrolopyrrole (Por-DPP)] with the donor-acceptor structure was synthesized, where porphyrin was used as a donor unit while diketopyrrolopyrrole was used as an acceptor unit. Por-DPP exhibited efficient absorption extending from visible to NIR regions. After self-assembling into nanoparticles (NPs) (∼120 nm), the absorption spectrum of Por-DPP NPs broadened and red-shifted to some extent, relative to that of organic molecules. Furthermore, the architecture of NPs enhanced the acceptor-donor structure, leading to emission quenching and facilitating nonradiative thermal generation. The PCE of Por-DPP NPs was measured and calculated to be 62.5%, higher than most of ONPs. Under 808 nm laser irradiation, the Por-DPP NPs possessed a distinct photothermal therapy (PTT) effect in vitro and can damage cancer cells efficiently in vivo without significant side effects after phototherapy. Thus, the small-molecule porphyrin-based ONPs with high PCE demonstrated promising application in photoacoustic imaging-guided PTT.

Engineered Gold-Based Nanomaterials: Morphologies and Functionalities in Biomedical Applications. A Mini Review

In the last decade, several engineered gold-based nanomaterials, such as spheres, rods, stars, cubes, hollow particles, and nanocapsules have been widely explored in biomedical fields, in particular in therapy and diagnostics. As well as different shapes and dimensions, these materials may, on their surfaces, have specific functionalizations to improve their capability as sensors or in drug loading and controlled release, and/or particular cell receptors ligands, in order to get a definite targeting. In this review, the up-to-date progress will be illustrated regarding morphologies, sizes and functionalizations, mostly used to obtain an improved performance of nanomaterials in biomedicine. Many suggestions are presented to organize and compare the numerous and heterogeneous experimental data, such as the most important chemical-physical parameters, which guide and control the interaction between the gold surface and biological environment. The purpose of all this is to offer the readers an overview of the most noteworthy progress and challenges in this research field.

Suitability of 3D human brain spheroid models to distinguish toxic effects of gold and poly-lactic acid nanoparticles to assess biocompatibility for brain drug delivery

Background

The blood brain barrier (BBB) is the bottleneck of brain-targeted drug development. Due to their physico-chemical properties, nanoparticles (NP) can cross the BBB and accumulate in different areas of the central nervous system (CNS), thus are potential tools to carry drugs and treat brain disorders. In vitro systems and animal models have demonstrated that some NP types promote neurotoxic effects such as neuroinflammation and neurodegeneration in the CNS. Thus, risk assessment of the NP is required, but current 2D cell cultures fail to mimic complex in vivo cellular interactions, while animal models do not necessarily reflect human effects due to physiological and species differences.

Results

We evaluated the suitability of in vitro models that mimic the human CNS physiology, studying the effects of metallic gold NP (AuNP) functionalized with sodium citrate (Au-SC), or polyethylene glycol (Au-PEG), and polymeric polylactic acid NP (PLA-NP). Two different 3D neural models were used (i) human dopaminergic neurons differentiated from the LUHMES cell line (3D LUHMES) and (ii) human iPSC-derived brain spheroids (BrainSpheres). We evaluated NP uptake, mitochondrial membrane potential, viability, morphology, secretion of cytokines, chemokines and growth factors, and expression of genes related to ROS regulation after 24 and 72 h exposures. NP were efficiently taken up by spheroids, especially when PEGylated and in presence of glia. AuNP, especially PEGylated AuNP, effected mitochondria and anti-oxidative defense. PLA-NP were slightly cytotoxic to 3D LUHMES with no effects to BrainSpheres.

Conclusions

3D brain models, both monocellular and multicellular are useful in studying NP neurotoxicity and can help identify how specific cell types of CNS are affected by NP.

Electronic supplementary material

The online version of this article (10.1186/s12989-019-0307-3) contains supplementary material, which is available to authorized users.

The Role of Temperature and Lipid Charge on Intake/Uptake of Cationic Gold Nanoparticles into Lipid Bilayers

Understanding the molecular mechanisms governing nanoparticle-membrane interactions is of prime importance for drug delivery and biomedical applications. Neutron reflectometry (NR) experiments are combined with atomistic and coarse-grained molecular dynamics (MD) simulations to study the interaction between cationic gold nanoparticles (AuNPs) and model lipid membranes composed of a mixture of zwitterionic di-stearoyl-phosphatidylcholine (DSPC) and anionic di-stearoyl-phosphatidylglycerol (DSPG). MD simulations show that the interaction between AuNPs and a pure DSPC lipid bilayer is modulated by a free energy barrier. This can be overcome by increasing temperature, which promotes an irreversible AuNP incorporation into the lipid bilayer. NR experiments confirm the encapsulation of the AuNPs within the lipid bilayer at temperatures around 55 °C. In contrast, the AuNP adsorption is weak and impaired by heating for a DSPC-DSPG (3:1) lipid bilayer. These results demonstrate that both the lipid charge and the temperature play pivotal roles in AuNP-membrane interactions. Furthermore, NR experiments indicate that the (negative) DSPG lipids are associated with lipid extraction upon AuNP adsorption, which is confirmed by coarse-grained MD simulations as a lipid-crawling effect driving further AuNP aggregation. Overall, the obtained detailed molecular view of the interaction mechanisms sheds light on AuNP incorporation and membrane destabilization.

Potential of contrast agents to enhance in vivo confocal microscopy and optical coherence tomography in dermatology: A review

Distinction between normal skin and pathology can be a diagnostic challenge. This systematic review summarizes how various contrast agents, either topically delivered or injected into the skin, affect distinction between skin disease and normal skin when imaged by optical coherence tomography (OCT) and confocal microscopy (CM). A systematic review of in vivo OCT and CM studies using exogenous contrast agents on healthy human skin or skin disease was performed. In total, nine CM studies and one OCT study were eligible. Four contrast agents aluminum chloride (AlCl) n = 2, indocyanine green (ICG) n = 3, sodium fluorescein n = 3 and acetic acid n = 1 applied to CM in variety of skin diseases. ICG, acetic acid and AlCl showed promise to increase contrast of tumor nests in keratinocyte carcinomas. Fluorescein and ICG enhanced contrast of keratinocytes and adnexal structures. In OCT of healthy skin gold nanoshells, increased contrast of natural skin openings. Contrast agents may improve delineation and diagnosis of skin cancers; ICG, acetic acid and AlCl have potential in CM and gold nanoshells facilitate visualization of adnexal skin structures in OCT. However, as utility of bedside optical imaging increases, further studies with robust methodological quality are necessary to implement contrast agents into routine dermatological practice.

Plasmonic Heating of Nanostructures

The absorption of light by plasmonic nanostructures and their associated temperature increase are exquisitely sensitive to the shape and composition of the structure and to the wavelength of light. Therefore, much effort is put into synthesizing novel nanostructures for optimized interaction with the incident light. The successful synthesis and characterization of high quality and biocompatible plasmonic colloidal nanoparticles has fostered numerous and expanding applications, especially in biomedical contexts, where such particles are highly promising for general drug delivery and for tomorrow's cancer treatment. We review the thermoplasmonic properties of the most commonly used plasmonic nanoparticles, including solid or composite metallic nanoparticles of various dimensions and geometries. Common methods for synthesizing plasmonic particles are presented with the overall goal of providing the reader with a guide for designing or choosing nanostructures with optimal thermoplasmonic properties for a given application. Finally, the biocompatibility and biological tolerance of structures are critically discussed along with novel applications of plasmonic nanoparticles in the life sciences.

A pH-Sensitive Zwitterionic Iron Complex Probe with High Biocompatibility for Tumor-Specific Magnetic Resonance Imaging

Accurate diagnosis of tumor characteristics, including its location and boundary, is of immense value to subsequent therapy. Activatable magnetic resonance imaging (MRI) contrast agents that respond to tumor-specific microenvironments, such as the redox state, pH, and enzyme activity, enable better mapping of tumor tissue. However, the practical application of most reported activatable agents is hampered by problems including potential toxicity, inefficient elimination, and slow activation. In this study, we developed a zwitterionic iron complex (Fe-ZDS) as a positive MRI contrast agent for tumor-specific imaging. Fe-ZDS could dissociate in weakly acidic solution rapidly, accompanied by clear longitudinal relaxivity (r₁ ) enhancement, which enabled the complex to act as a pH-sensitive contrast agent for tumor-specific MR imaging. In vivo experiments showed that Fe-ZDS rapidly enhanced the tumor-to-normal contrast ratio by >40 %, which assisted in distinguishing the tumor boundary. Furthermore, Fe-ZDS circulated freely in the bloodstream and was excreted relatively safely via kidneys owing to its zwitterionic nature. Therefore, Fe-ZDS is an ideal candidate for a tumor-specific MRI contrast agent and holds considerable potential for clinical translation.

Rational Design of Microfabricated Electroconductive Hydrogels for Biomedical Applications

Electroconductive hydrogels (ECHs) are highly hydrated 3D networks generated through the incorporation of conductive polymers, nanoparticles, and other conductive materials into polymeric hydrogels. ECHs combine several advantageous properties of inherently conductive materials with the highly tunable physical and biochemical properties of hydrogels. Recently, the development of biocompatible ECHs has been investigated for various biomedical applications, such as tissue engineering, drug delivery, biosensors, flexible electronics, and other implantable medical devices. Several methods for the synthesis of ECHs have been reported, which include the incorporation of electrically conductive materials such as gold and silver nanoparticles, graphene, and carbon nanotubes, as well as various conductive polymers (CPs), such as polyaniline, polypyrrole, and poly(3,4-ethylenedioxyythiophene) into hydrogel networks. Theses electroconductive composite hydrogels can be used as scaffolds with high swellability, tunable mechanical properties, and the capability to support cell growth both in vitro and in vivo. Furthermore, recent advancements in microfabrication techniques such as three dimensional (3D) bioprinting, micropatterning, and electrospinning have led to the development of ECHs with biomimetic microarchitectures that reproduce the characteristics of the native extracellular matrix (ECM). In addition, smart ECHs with controlled structures and healing properties have also been engineered into devices with prolonged half-lives and increased durability. The combination of sophisticated synthesis chemistries and modern microfabrication techniques have led to engineer smart ECHs with advanced architectures, geometries, and functionalities that are being increasingly used in drug delivery systems, biosensors, tissue engineering, and soft electronics. In this review, we will summarize different strategies to synthesize conductive biomaterials. We will also discuss the advanced microfabrication techniques used to fabricate ECHs with complex 3D architectures, as well as various biomedical applications of microfabricated ECHs.

Probing the biological obstacles of nanomedicine with gold nanoparticles

Despite massive growth in nanomedicine research to date, the field still lacks fundamental understanding of how certain physical and chemical features of a nanoparticle affect its ability to overcome biological obstacles in vivo and reach its intended target. To gain fundamental understanding of how physical and chemical parameters affect the biological outcomes of administered nanoparticles, model systems that can systematically manipulate a single parameter with minimal influence on others are needed. Gold nanoparticles are particularly good model systems in this case as one can synthetically control the physical dimensions and surface chemistry of the particles independently and with great precision. Additionally, the chemical and physical properties of gold allow particles to be detected and quantified in tissues and cells with high sensitivity. Through systematic biological studies using gold nanoparticles, insights toward rationally designed nanomedicine for in vivo imaging and therapy can be obtained. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.