DNA-modified Prussian blue nanozymes for enhanced electrochemical biosensing

Prussian blue nanoparticles exhibit the potential to be employed in bioanalytical applications due to their robust stability, peroxidase-like catalytic functionality, straightforward synthesis, and biocompatibility. An efficient approach is presented for the synthesis of nucleic acid-modified Prussian blue nanoparticles (DNA-PBNPs), utilizing nanoparticle porosity to adsorb nucleic acids (polyT). This strategic adsorption leads to the exposure of nucleic acid sequences on the particle surface while retaining catalytic activity. DNA-PBNPs further couple with functional nucleic acid sequences and aptamers through complementary base pairing to act as transducers in biosensors and amplify signal acquisition. Subsequently, we integrated a copper ion-dependent DNAzyme (Cu2+-DNAzyme) and a vascular endothelial growth factor aptamer (VEGF aptamer) onto screen-printed electrodes to serve as recognition elements for analytes. Significantly, our approach leverages DNA-PBNPs as a superior alternative to traditional enzyme-linked antibodies in electrochemical biosensors, thereby enhancing both the efficiency and adaptability of these devices. Our study conclusively demonstrates the application of DNA-PBNPs in two different biosensing paradigms: the sensitive detection of copper ions and vascular endothelial growth factor (VEGF). These results indicate the promising potential of DNA-modified Prussian blue nanoparticles in advancing bioanalytical sensing technologies.

Homogeneous and Nanogranular Prussian Blue to Enable Long-Term-Stable Electrochromic Devices

The increasing demand for the state-of-the-art electrochromic devices has received great interest in synthesizing Prussian blue (PB) nanoparticles with a uniform diameter that exhibit excellent electrochromism, electrochemistry, and cyclability. Herein, we report the controllable synthesis of sub-100 nm PB nanoparticles via the coprecipitation method. The diameter of PB nanoparticles can be modulated by adjusting the reactant concentration, the selection of a chelator, and their purification. The self-assembled nanogranular thin films, homogeneously fabricated by using optimized PB nanoparticles with an average diameter of 50 nm as building blocks via the blade coating technique enable excellent performance with a large optical modulation of 80% and a high coloration efficiency of 417.79 cm2 C-1. It is also demonstrated by in situ and ex situ observations that the nanogranular PB thin films possess outstanding structural and electrochemical reversibility. Furthermore, such nanogranular PB thin films can enjoy the enhanced long-term cycling stability of the PB-WO3 complementary electrochromic devices having a 91.4% optical contrast retention after 16,000 consecutive cycles. This work provides a newly and industrially compatible approach to producing a complementary electrochromic device with extraordinary durability for various practical applications.

Nanosized Prussian blue and its analogs for bioimaging and cancer theranostics

Prussian blue (PB) nanoparticles (NPs) and Prussian blue analogs (PBAs) can form metal-organic frameworks through the programmable coordination of ferrous ions with cyanide. PB and PBAs represent a burgeoning class of hybrid functional nano-systems with a wide-ranging application spectrum encompassing biomedicine, cancer diagnosis, and therapy. A comprehensive overview of recent advancements is crucial for gaining insights for future research. In this context, we reviewed the synthesis techniques and surface modification strategies employed to tailor the dimensions, morphology, and attributes of PB NPs. Subsequently, we explored advanced biomedical utilities of PB NPs, encompassing photoacoustic imaging, magnetic resonance imaging, ultrasound (US) imaging, and multimodal imaging. In particular, the application of PB NPs-mediated photothermal therapy, photodynamic therapy, and chemodynamic therapy to cancer treatment was reviewed. Based on the literature, we envision an evolving trajectory wherein the future of Prussian blue-driven biological applications converge into an integrated theranostic platform, seamlessly amalgamating bioimaging and cancer therapy. STATEMENT OF SIGNIFICANCE: Prussian blue, an FDA-approved coordinative pigment with a centuries-long legacy, has paved the way for Prussian blue nanoparticles (PB NPs), renowned for their remarkable biocompatibility and biosafety. These PB NPs have found their niche in biomedicine, playing crucial roles in both diagnostics and therapeutic applications. The comprehensive review goes beyond PB NP-based cancer therapy. Alongside in-depth coverage of PB NP synthesis and surface modifications, the review delves into their cutting-edge applications in the realm of biomedical imaging, encompassing techniques such as photoacoustic imaging, magnetic resonance imaging, ultrasound imaging, and multimodal imaging.

Unidirectional Current in Layered Metal Hexacyanometallate Thin Films: Implication for Alternative Wet-Processed Electronic Materials

Rectifying behavior of alternative electronic materials is demonstrated with layered structures of a crystalline coordination network whose mixed ionic and electronic conductivity can be manipulated by switching the redox state of coordinated transition-metal ions. The coordinated transition-metal ions can convey additional functionality such as (redox)catalysis or electrochromism. In order to obtain rectifying behavior and charge trapping, layered films of such materials are explored. Specifically, layered films of iron hexacyanoruthenate (Fe-HCR) and nickel hexacyanoferrate (Ni-HCF) were formed by the combination of different deposition procedures. They comprise electrodeposition during voltammetric cycles for Fe-HCR and Ni-HCF, layer-by-layer deposition of Ni-HCF without redox chemistry, and drop casting of presynthesized Ni-HCF nanoparticles. The obtained materials were structurally characterized by X-ray diffraction analysis, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy for nanoparticles, and scanning force microscopy (SFM). Voltammetry in 1 mol L-1 KCl and current-voltage curves (I-V curves) recorded between a conductive SFM tip and the back electrode outside of an electrolyte solution demonstrated charge trapping and rectifying behavior based on the different formal potentials of the redox centers in the films.

Advances in macrophage-targeting nanoparticles for the diagnosis and treatment of inflammatory bowel disease

The pathogenesis of inflammatory bowel disease (IBD) is not fully elucidated. However, it has been considered that inflammatory macrophages may be involved in the imbalance of the intestinal mucosal immunity to regulate several signaling pathways, leading to IBD progression. The ratio of M1 to M2 subtypes of activated macrophages tends to increase in the inflamed intestinal section. There are challenges in the diagnosis and treatment of IBD, such as unsatisfactory specificity of imaging findings, low drug accumulation in the intestinal lesions, unstable therapeutic efficacy, and drug-related systemic toxicity. Recently developed nanoparticles may provide a new approach for the diagnosis and treatment of IBD. Nanoparticles targeted to macrophages can be used as contrast agents to improve the imaging quality or used as a drug delivery vector to increase the therapeutic efficiency of IBD. This article reviews the research progress on macrophage-targeting nanoparticles for the diagnosis and treatment of IBD to provide a reference for further research and clinical application.

Tracking intracellular nuclear targeted-chemotherapy of chidamide-loaded Prussian blue nanocarriers by SERS mapping

The novel histone deacetylase drug chidamide (CHI) has been proven to regulate gene expression associated with oncogenesis via epigenetic mechanisms. However, huge side effects such as non-targeting, poor intracellular accumulation and low nuclear entry efficiency severely restrict its therapeutic efficacy. Dual-targeted nanodrug delivery systems have been proposed as the solution. Herein, we developed a CHI-loaded drug delivery nanosystem based on Prussian blue (PB) nanocarrier, which combines surface-enhanced Raman scattering (SERS) tracking function with cancer cell/nuclear-targeted chemotherapy capability. With the property of background-free SERS mapping, PB nanocarriers can serve as tracking agents to localize intracellular CHI. The incorporation of targeted molecules specifically enhances the cancer cell/nuclear internalization and chemotherapeutic effects of CHI-loaded PB nanocarriers. In vitro cytotoxicity assay clearly shows that the constructed CHI-loaded PB nanocarriers have significant inhibitory on Jurkat cell proliferation. Furthermore, SERS spectral analysis of Jurkat cells incubated with the CHI-loaded PB nanocarriers reveals obvious features of cellular apoptosis: DNA skeleton fragmentation, chromatin depolymerization, histone acetylation, and nucleosome conformation change. Importantly, this CHI-loaded PB nanocarrier will provide a new insight for lymphoblastic leukemia targeted chemotherapy.

A Dormant Reagent Reaction-Diffusion Method for the Generation of Co-Fe Prussian Blue Analogue Periodic Precipitate Particle Libraries

Liesegang patterns that develop as a result of reaction-diffusion can simultaneously form products with slightly different sizes spatially separated in a single medium. We show here a reaction-diffusion method using a dormant reagent (citrate) for developing Liesegang patterns of cobalt hexacyanoferrate Prussian Blue analog (PBA) particle libraries. This method slows the precipitation reaction and produces different-sized particles in a gel medium at different locations. The gel-embedded particles are still catalytically active. Finally, the applicability of the new method to other PBAs and 2D systems is presented. The method proves promising for obtaining similar inorganic framework libraries with catalytic abilities.

Quercetin@Gd3+ doped Prussian blue nanocubes induce the pyroptotic death of MDA-MB-231 cells: combinational targeted multimodal therapy, dual modal MRI, intuitive modelling of r1-r2 relaxivities

Quercetin (Qu), a potential bioflavonoid has gained considerable interest as a promising chemotherapeutic drug which can inhibit the proliferation of triple-negative breast cancer (TNBC) cells due to its regulation of the expression of tumor-suppressor gene metastasis and antioxidant property. Notably, Qu exhibits a very negligible cytotoxic effect on normal cells, even with high-dose treatment, while it is shows high affinity to TNBC. However, the efficiency of Qu is limited clinically due to its poor bioavailability, caused by its low aqueous solubility (2.15 μg mL^-1 at 25 °C), rapid gastrointestinal digestion and chemical instability in alkaline and neutral media. Herein, polydopamine (PDA)-coated, NH₂-PEG-NH₂ and hyaluronic acid (HA)-functionalized Gd³⁺-doped Prussian blue nanocubes (GPBNC) are reported as a multifunctional platform for the codelivery of Qu as a chemotherapeutic agent and GPBNC as a photodynamic (PDT) and photothermal (PTT) agent with improved therapeutic efficiency to overcome theses barriers. PDA, NH₂-PEG-NH₂ and HA stabilize GPBNC@Qu and facilitate bioavailability and active-targeting, while absorption of near infrared (NIR) (808 nm; 1 W cm^-2) induces PDT and PTT activities and dual T₁-T₂-weighted magnetic resonance imaging (MRI) with high relaxometric parameters (r₁ 10.06 mM^-1 s^-1 and r₂ 24.96 mM^-1 s^-1 at a magnetic field of 3 T). The designed platform shows a pH-responsive Qu release profile and NIR-induced therapeutic efficiency of ∼79% in 20 minutes of irradiation, wherein N-terminal gardermin D (N-GSDMD) and a P2X7-receptor-mediated pyroptosis pathway induces cell death, corroborating the up-regulation of NLRP3, caspase-1, caspase-5, N-GSDMD, IL-1β, cleaved Pannexin-1 and P2X7 proteins. More interestingly, the increasing relaxivity values of Prussian blue nanocubes with Gd³⁺ doping have been explained on the basis of Solomon-Bloembergen-Morgan theory, considering inner- and outer-sphere relaxivity, wherein crystal defects, coordinated water molecules, tumbling rate, metal to water proton distance, correlation time, magnetisation value etc. play a significant role. In summary, our study suggests that GPBNC could be a beneficial nanocarrier for theranostic purposes against TNBC, while our conceptual study clearly demonstrates the role of various factors in increasing relaxometric parameters.

Prussian Blue nanoparticles: An FDA-approved substance that may quickly degrade at physiological pH

Prussian blue (PB) is a coordination polymer based on the Fe^2+…CN^…Fe³⁺ sequence. It is an FDA-approved drug, intended for oral use at the acidic pH of the stomach and of most of the intestine track. However, based on FDA approval, a huge number of papers proposed the use of PB nanoparticles (PBnp) under "physiological conditions", meaning pH buffered at 7.4 and high saline concentration. While most of these papers report that PBnp are stable at this pH, a small number of papers describes instead PBnp degradation at the same or similar pH values, i.e. in the 7-8 range. Here we give a definitively clear picture: PBnp are intrinsically unstable at pH ≥ 7, degrading with the fast disappearance of their 700 nm absorption band, due to the formation of OH^- complexes from the labile Fe³⁺ centers. However, we show also that the presence of a polymeric coating (PVP) can protect PBnp at pH 7.4 for over 24 h. Moreover, we demonstrate that when "physiological conditions" include serum, a protein corona is rapidly formed on PBnp, efficiently avoiding degradation. We also show that the viability of PBnp-treated EA.hy926, NCI-H1299, and A549 cells is not affected in a wide range of conditions that either prevent or promote PBnp degradation.

Microbial synthesis of Prussian blue for potentiating checkpoint blockade immunotherapy

Cancer immunotherapy is revolutionizing oncology. The marriage of nanotechnology and immunotherapy offers a great opportunity to amplify antitumor immune response in a safe and effective manner. Here, electrochemically active Shewanella oneidensis MR-1 can be applied to produce FDA-approved Prussian blue nanoparticles on a large-scale. We present a mitochondria-targeting nanoplatform, MiBaMc, which consists of Prussian blue decorated bacteria membrane fragments having further modifications with chlorin e6 and triphenylphosphine. We find that MiBaMc specifically targets mitochondria and induces amplified photo-damages and immunogenic cell death of tumor cells under light irradiation. The released tumor antigens subsequently promote the maturation of dendritic cells in tumor-draining lymph nodes, eliciting T cell-mediated immune response. In two tumor-bearing mouse models using female mice, MiBaMc triggered phototherapy synergizes with anti-PDL1 blocking antibody for enhanced tumor inhibition. Collectively, the present study demonstrates biological precipitation synthetic strategy of targeted nanoparticles holds great potential for the preparation of microbial membrane-based nanoplatforms to boost antitumor immunity.

A facile and sensitive magnetic relaxation sensing strategy based on the conversion of Fe3+ ions to Prussian blue precipitates for the detection of alkaline phosphatase and ascorbic acid oxidase

Herein, a novel magnetic relaxation sensing strategy based on the change in Fe³⁺ content has been proposed by utilizing the conversion of Fe³⁺ ions to Prussian blue (PB) precipitates. Compared with the common detection approach based on the valence state change of Fe³⁺ ions, our strategy can cause a larger change in the relaxation time of water protons and higher detection sensitivity since PB precipitate can induce a larger change in the Fe³⁺ ion concentration and has a weaker effect on the relaxation process of water protons relative to Fe²⁺ ions. Then, we employ alkaline phosphatase (ALP) as a model target to verify the feasibility and detection performance of the as-proposed strategy. Actually, ascorbic acid (AA) generated from the ALP-catalyzed L-ascorbyl-2-phosphate hydrolysis reaction can reduce potassium ferricyanide into potassium ferrocyanide, and potassium ferrocyanide reacts with Fe³⁺ to form PB precipitates, leading to a higher relaxation time. Under optimum conditions, the method for ALP detection has a wide linear range from 5 to 230 mU/mL, and the detection limit is 0.28 mU/mL, sufficiently demonstrating the feasibility and satisfactory analysis performance of this strategy, which opens up a new path for the construction of magnetic relaxation sensors. Furthermore, this strategy has also been successfully applied to ascorbic acid oxidase detection, suggesting its expansibility in magnetic relaxation detection.

Paper disc interfaced Prussian blue nanocube modified immunodevice for electrochemical detection of diverse biomarker at point of care

The detection of specific biomarkers is used in various phases of the diagnosis of plant and human diseases, from prognosis to monitoring. Herein, we report a Prussian blue nanocube-modified immunodevice interfaced with a paper disc for the detection of plant biomarkers via streptavidin-biotin recognition. The detection ability of the immunodevice was assessed using Potato virus X as a model biomarker and analyzed using cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. The immunodevice displayed excellent performance for Potato virus X detection with a detection limit of 0.92 nM (3S/N). The selectivity of the fabricated Potato virus X immunodevice was investigated using closely associated antigens, such as potato aucuba mosaic virus, Potato virus Y, and Potato virus A. The Potato virus X immunodevice exhibited ∼ 90 % recovery in spiked complex plant samples with a relative error of ∼ 9 %. Furthermore, the immunodevice was used to screen for Potato virus X in 10 samples from potato tubers and leaves. The paper-disc-interfaced immunodevice was also evaluated by detecting other biomarkers, such as potato aucuba mosaic virus in plant diseases and C-reactive protein in human ones. This immunodevice may allow the on-site monitoring of diverse biomarkers by simplifying the current point of care diagnostic tools.

Hybrid Au-star@Prussian blue for high-performance towards bimodal imaging and photothermal treatment

In recent years, branched or star-shaped Au nanostructures composed of core and protruding arms have attracted much attention due to their unique optical properties and morphology. As the clinically adapted nanoagent, prussian blue (PB) has recently gained widespread attention in cancer theranostics with potential applications in magnetic resonance (MR) imaging. In this article, we propose a hybrid star gold nanostructure（Au-star@PB）as a novel theranostic agent for T1-weighted magnetic resonance imaging (MRI)/ photoacoustic imaging（PAI） and photothermal therapy (PTT) of tumors. Importantly, the Au-star@PB nanoparticles function as effective MRI/PA contrast agents in vivo by increasing T1-weighted MR/PAI signal intensity and as effective PTT agents in vivo by decreasing the tumor volume in MCF-7 tumor bearing BALB / c mouse model as well as in vitro by lessening tumor cells growth rate. Interestingly, we found the main photothermal effect of Au-star@PB is derived from Au-star, but not PB. In summary, the hybrid structure of Au-star@PB NPs with good biological safety, significant photostability, dual imaging capability, and high therapeutic efficiency, might offer a novel avenue for the future diagnosis and treatment of cancer.

Progress in the preparation of Prussian blue-based nanomaterials for biomedical applications

Prussian blue (PB) is composed of the coordination network of Fe²⁺-CN-Fe³⁺ mixed valence state as a classic metal complex, which includes a C atom and Fe²⁺ (low spin), N atom and Fe³⁺ (high spin). PB and its analogues (PBA) have excellent biosafety, good magnetic properties, outstanding photothermal properties and the ability to mimic enzymatic behaviors due to their stable structure, tunable size, controllable morphology, abundant modification methods and excellent physicochemical properties. They have received increasing research interest and have shown promising applications in the biomedical field. Here, progress in the preparation of PB-based nanomaterials for biomedical applications is summarized and discussed. The preparation strategies, traditional synthesis and emerging preparation methods of PB are summarized systematically in this review. The design and preparation of PBA, PB(PBA)-based hollow structures and PB(PBA)-based composites are also included. While introducing the preparation status, some PB-based nanomaterials that have performed well in specific biomedical fields are emphasized. More importantly, the key factors and future development of PB for the clinical translation as multifunctional nanomaterials are also discussed. This review provides a reference for the design and biomedical application of PB-based nanomaterials.

Metal-organic framework-based nanoplatform enhance fibroblast activity to treat periodontitis

After periodontal tissue injury, reconstruct soft tissue sealing around the tooth surface is of fundamental importance to treat periodontitis. Among multiple cell types, fibroblast plays a central role in reestablishing functional periodontium. To enhance fibroblast activity, a novel metal-organic framework-based nanoplatform is fabricated using mesoporous Prussian blue (MPB) nanoparticles to load baicalein (BA), named MPB-BA. Drug release test displayed sustained BA release of MPB-BA. Cell proliferation, transwell migration and wound healing tests revealed accelerated fibroblast proliferation and migration for the established MPB-BA nanoplatform. Moreover, vinculin immunofluorescence staining, western blot and quantitative real-time PCR analysis showed up-regulated vinculin protein and integrin α5 and integrin β1 gene expressions for MPB-BA, suggesting improved cell adhesion. In addition, hematoxylin and eosin (H&E) and Masson trichromatic staining suggested superior anti-inflammatory and collagen fiber reconstruction effects for MPB-BA in a rat experimental periodontitis model in vivo. Our study may provide a promising strategy for the treatment of periodontitis.

Europium-151 and iron-57 nuclear resonant vibrational spectroscopy of naturally abundant KEu(III)Fe(II)(CN)6 and Eu(III)Fe(III)(CN)6 complexes

We have performed and analyzed the first combined 151Eu and 57Fe nuclear resonant vibrational spectroscopy (NRVS) for naturally abundant KEu(III)[Fe(II)(CN)6] and Eu(III)[Fe(III)(CN)6] complexes. Comparison of the observed 151Eu vs.57Fe NRVS spectroscopic features confirms that Eu(III) in both KEu(III)[Fe(II)(CN)6] and Eu(III)[Fe(III)(CN)6] occupies a position outside the [Fe(CN)6] core and coordinates to the N atoms of the CN- ions, whereas Fe(III) or Fe(II) occupies the site inside the [Fe(CN)6]4- core and coordinates to the C atoms of the CN- ions. In addition to the spectroscopic interest, the results from this study provide invaluable insights for the design and evaluation of the nanoparticles of such complexes as potential cellular contrast agents for their use in magnetic resonance imaging. The combined 151Eu and 57Fe NRVS measurements are also among the first few explorations of bi-isotopic NRVS experiments.

Tumor microenvironment targeting and regulating iron-based metal-organic framework for magnetic resonance imaging guided synergetic therapy of doxorubicin and hydroxyl radicals

Fe³⁺and 2-methylimidazole were selected to prepare tumor microenvironment targeted and regulated multifunctional drug carrier Fe-MOFs. The fact that Doxorubicin hydrochloride (DOX·HCl) release climbed 70% from 25% upon regulating the pH from 7.4 to 5.8 proved the pH responsive drug release of Fe-MOFs. Hydroxyl radicals (·OH) analysis proved that Fe-MOFs only generated hydroxyl radicals at pH 5.8, and dissolved oxygen performance showed the O₂was produced during the process, which was expected to regulate hypoxia in tumor cells to increase anticancer effect. Cell viability experiments proved the selectivity of Fe-MOFs and the excellent performance of synergy therapy of DOX·HCl and hydroxyl radicals.In vivomagnetic resonance imaging experiments demonstrated excellent performance of positive images. All experiments showed that Fe-MOFs can be used for image-guided collaborative treatment to improve treatment efficiency and reduce side effects.

Rapid vertical flow technique for the highly sensitive detection of Brucella antibodies with Prussian blue nanoparticle labeling and nanozyme-catalyzed signal amplification

Brucellosis is a chronic infectious disease caused by Brucella, which is characterized by inflammation of reproductive organs and fetal membranes, abortion, infertility, and local inflammatory lesions of various tissues. Due to the widespread prevalence and spread of brucellosis, it has not only caused huge losses to animal husbandry, but also brought serious impacts on human health and safety. Therefore, rapid and accurate diagnosis is of great significance for the effective control of brucellosis. Therefore, we have developed a rapid vertical flow technique (RVFT) using Prussian blue nanoparticles (PBNPs) as a marker material for the detection of brucellosis antibodies. Lipopolysaccharide (LPS) was purified and used to detect brucellosis antibodies to improve the sensitivity of this technique. To enhance the sensitivity of serum antibody detection, a single multifunctional compound buffer was created using whole blood as a biological sample while retaining the advantages of typical lateral flow immunoassays. After signal amplification, standard Brucella-positive serum (containing Brucella antibody at 4000 IU mL^-1) could be detected in this system even at a dilution factor of 1 × 10^-2. The detection limit was 40 IU mL^-1, which is ten times that before signal amplification. This RVFT displayed good specificity and no cross-reactivity. This RVFT effectively avoided the false negative phenomenon of lateral flow immunoassays, was easy to operate, had a short reaction time, has good repeatability, and could elicit results that were visible to the naked eye for 2 ~ 3 min without any equipment. Since this method is very important for controlling the prevalence of brucellosis, it holds great promise for application in primary medical units and veterinary brucellosis detection.

Separation and Removal of Radionuclide Cesium from Water by Biodegradable Magnetic Prussian Blue Nanospheres

As the main component of radioactive wastewater, the cesium ion has seriously endangered the environment and human health. Prussian blue nanoparticles (PB NPs) are used as adsorbents for the purification of cesium-containing wastewater because of their ability to selectively adsorb cesium ions. In this work, novel magnetic Prussian blue nanospheres (MPBNs) were developed from polylactic acid nanospheres as a carrier, loaded with Fe3O4 nanoparticles (Fe3O4 NPs) inside and PB NPs outside for the removal of cesium ions with the help of magnetic separation. Meanwhile, the effects on the adsorption efficiency of MPBNs, such as pH, time, temperature and initial concentration of cesium ion solution, were studied. The adsorption isotherms, kinetic models and adsorption thermodynamics were investigated to research the absorption mechanism. The results showed that MPBNs were spherical with a rough surface, and their particle size, iron content and saturation magnetization were 268.2 ± 1.4 nm, 40.01% and 41.71 emu/g, which can be recovered by magnetic separation. At 293 K, MPBNs could reduce the cesium ion solution from 40 mg/L to 4.8 mg/L, and its cesium ion removal rate and adsorption capacity were 82.46% and 16.49 mg/g, respectively. The optimum pH of MPBNs for cesium ion adsorption was 5~9, the adsorption equilibrium time was 60 min, and the maximum adsorption capacity was 17.03 mg/g. In addition, MPBNs were separated rapidly by an external magnetic field, and the adsorption process was an endothermic reaction. The adsorption isotherm and kinetics of MPBNs were in accordance with the Freundlich model and quasi-second-order fitting model, respectively, and the adsorption process of MPBNs was controlled by the diffusion step in particles. Notably, these MPBNs could be effectively separated from water by a magnetic field, facilitating engineering applications in cesium-containing wastewater.

Recent Advances in Metal-Organic Frameworks for Applications in Magnetic Resonance Imaging

Diagnostics is an important part of medical practice. The information required for diagnosis is typically collected by performing diagnostic tests, some of which include imaging. Magnetic resonance imaging (MRI) is one of the most widely used and effective imaging techniques. To improve the sensitivity and specificity of MRI, contrast agents are used. In this review, the usage of metal-organic frameworks (MOFs) and composite materials based on them as contrast agents for MRI is discussed. MOFs are crystalline porous coordination polymers. Due to their huge design variety and high density of metal ions, they have been studied as a highly promising class of materials for developing MRI contrast agents. This review highlights the most important studies and focuses on the progress of the field over the last five years. The materials are classified based on their design and structural properties into three groups: MRI-active MOFs, composite materials based on MOFs, and MRI-active compounds loaded in MOFs. Moreover, an overview of MOF-based materials for heteronuclear MRI including 129Xe and 19F MRI is given.

Smartphone-Integrated Photoacoustic Analytical Device for Point-of-Care Testing of Food Contaminant Azodicarbonamide

Azodicarbonamide (ADA) is widely used as a flour additive due to its oxidizing and bleaching properties, but it reacts with wet flour during heat processing and is easily decomposed into semicarbazide with genotoxicity and carcinogenicity. In order to improve the efficiency of food safety supervision and expand the scope of food safety control, it is of great significance to develop a facile method for point-of-care testing (POCT) of ADA. Herein, a field-portable and universal smartphone-based photoacoustic (PA) integration device is constructed for quantitative POCT of ADA in flour. The recognition probe Prussian blue with favorable stability is loaded on a flexible substrate for fabricating a portable test strip. In the presence of target ADA, the PA signal changes driven by a modulated 808 nm laser beam can be conveniently collected through the recording application (Audio Lab) of the smartphone. By combining the economic test strip and portable PA device with smartphone readout, it not only greatly simplifies the operation steps but also dramatically reduces the size and cost of the instrument. There is a favorable linear relationship between the PA signal and ADA concentration in the range of 10-200 μmol L^-1 (R² = 0.9928), and a detection limit of 5 μmol L^-1 obtained is much lower than the maximum allowable ADA level in the extract of flour (388 μmol L^-1). The present miniature PA device with strong POCT ability holds enormous public health significance and economic value in the field of food safety, especially in resource-limited settings.

Zinc-doped Prussian blue nanoparticles for mutp53-carrying tumor ion interference and photothermal therapy

Quite a great proportion of known tumor cells carry mutation in TP53 gene, expressing mutant p53 proteins (mutp53) missing not only original genome protective activities but also acquiring gain-of-functions that favor tumor progression and impede treatment of cancers. Zinc ions were reported as agents cytocidal to mutp53-carrying cells by recovering p53 normal functions and abrogating mutp53. Meanwhile in a hyperthermia scenario, the function of wild type p53 is required to ablate tumors upon heat treatment hence the effects might be hindered in a mutp53 background. We herein synthesized zinc-doped Prussian blue (ZP) nanoparticles (NPs) to combine Zn²⁺ based and photothermal therapeutic effects. An efficient release of Zn²⁺ in a glutathione-enriched tumor intracellular microenvironment and a prominent photothermal conversion manifested ZP NPs as zinc ion carriers and photothermal agents. Apoptotic death and autophagic mutp53 elimination were found to be induced by ZP NPs in R280K mutp53-containing MDA-MB-231 cells and hyperthermia was rendered to ameliorate the treatment in vitro through further mutp53 elimination and increased cell death. The combinatorial therapeutic effect was also confirmed in vivo in a mouse model. This study might expand zinc delivery carriers and shed a light on potential interplay of hyperthermia and mutp53 degradation in cancer treatment.

Manganese-Based Prussian Blue Nanocatalysts Suppress Non-Small Cell Lung Cancer Growth and Metastasis via Photothermal and Chemodynamic Therapy

Based on the safety of prussian blue (PB) in biomedical application, we prepared manganese-based prussian blue (MnPB) nanocatalysts to achieve enhanced photothermal therapy and chemodynamic therapy. And we conducted a series of experiments to explore the therapeutic effects of MnPB nanoparticles (NPs) on non-small cell lung cancer (NSCLC) in vivo and in vitro. For in vitro experiments, the MnPB NPs suppressed growth of A549 cells by reactive oxygen species upregulation and near-infrared irradiation. Moreover, the MnPB NPs could inhibit lung cancer metastasis through downregulating the matrix metalloproteinase (MMP)-2 and MMP-9 expression in A549 cells. And for in vivo experiments, the MnPB NPs inhibited the growth of xenografted tumor effectively and were biologically safe. Meanwhile, Mn²⁺ as a T1-weighted agent could realize magnetic resonance imaging-guided diagnosis and treatment. To sum up, the results in this study clearly demonstrated that the MnPB NPs had remarkable effects for inhibiting the growth and metastasis of NSCLC and might serve as a promising multifunctional nanoplatform for NSCLC treatment.

Nanotechnology-Based Diagnostic and Therapeutic Strategies for Neuroblastoma

Neuroblastoma (NB), as the most common extracranial solid tumor in childhood, is one of the critical culprits affecting children's health. Given the heterogeneity and invisibility of NB tumors, the existing diagnostic and therapeutic approaches are inadequate and ineffective in early screening and prognostic improvement. With the rapid innovation and development of nanotechnology, nanomedicines have attracted widespread attention in the field of oncology research for their excellent physiological and chemical properties. In this review, we first explored the current common obstacles in the diagnosis and treatment of NB. Then we comprehensively summarized the advancements in nanotechnology-based multimodal synergistic diagnosis and treatment of NB and elucidate the underlying mechanisms. In addition, a discussion of the pending challenges in biocompatibility and toxicity of nanomedicine was conducted. Finally, we described the development and application status of nanomaterials against some of the recognized targets in the field of NB research, and pointed out prospects for nanomedicine-based precision diagnosis and therapy of NB.

New Approach to Generate Ratiometric Signals on Immunochromatographic Strips for Small Molecules

The self-calibration capability of ratiometric signals has been widely considered to enhance the accuracy, sensitivity, and anti-interference ability of immunoassays. Exploring a new approach to generate ratiometric signals can provide more options for various requirements. Herein, we integrated the negative-readout competitive and positive-readout noncompetitive immunoassays into a single assay by employing different color tracers, labeled peptidomimetic and anti-immunocomplex peptides, to create a new unconstrained ratiometric signal approach. Using an immunochromatographic strip (ICS) and a fungicide benzothiostrobin as the analytical platform and analyte, respectively, we showed that this approach can be extensively applied to fluorescence and colorimetry readouts, which have also been proven for strong anti-interference ability to an external light environment. Moreover, the enormous intuitional color changes of ratiometric fluorescent and colorimetric ICSs (RFICS and RCICS) enabled the formation of the color reference cards (like the pH paper) for visual judgment. After adaptation with a portable smartphone, the quantitative detection limits for RFICS and RCICS were 0.17 and 0.44 ng mL^-1, respectively. In addition, the ICSs showed good accuracy for the detection of benzothiostrobin in spiked samples.

Prussian Blue Nanozymes with Enhanced Catalytic Activity: Size Tuning and Application in ELISA-like Immunoassay

Prussian blue nanozymes possessing peroxidase-like activity gather significant attention as alternatives to natural enzymes in therapy, biosensing, and environmental remediation. Recently, Prussian blue nanoparticles with enhanced catalytic activity prepared by reduction of FeCl₃/K₃[Fe(CN)₆] mixture have been reported. These nanoparticles were denoted as ‘artificial peroxidase’ nanozymes. Our study provides insights into the process of their synthesis. We studied how the size of nanozymes and synthesis yield can be controlled via adjustment of the synthesis conditions. Based on these results, we developed a reproducible and scalable method for the preparation of ‘artificial peroxidase’ with tunable sizes and enhanced catalytic activity. Nanozymes modified with gelatin shell and functionalized with affine molecules were applied as labels in colorimetric immunoassays of prostate-specific antigen and tetanus antibodies, enabling detection of these analytes in the range of clinically relevant concentrations. Protein coating provides excellent colloidal stability of nanozymes in physiological conditions and stability upon long-term storage.

Synthesis and Application of Albumin Nanoparticles Loaded with Prussian Blue Nanozymes

Prussian blue nanozymes exhibit peroxidase-like catalytic activity and are therefore considered a stable and inexpensive alternative to natural peroxidases in the enzyme-linked immunosorbent assay (ELISA). In this work, we propose a robust method of Prussian blue nanozyme functionalization, which relies on the entrapment of nanozymes into albumin nanoparticles. The principle of the method is the addition of ethanol to a solution that contains albumin and nanozymes. At a high ethanol concentration solubility of albumin decreases, resulting in the formation of albumin nanoparticles loaded with nanozymes. The hydrodynamic diameter of nanoparticles was between 120 and 230 nm and depended on the nanozyme-to-BSA ratio. Encapsulation efficiency of nanozymes reached 96–99% and up to 190 μg of nanozymes were loaded per 1 mg of nanoparticles. Nanoparticles were stable at pH 5.5–7.5 and upon long-term storage in deionized water. Excellent reproducibility of the synthesis procedure was confirmed by the preparation of three individual batches of Prussian-blue-loaded BSA nanoparticles with almost identical properties. Nanoparticles were functionalized with monoclonal antibodies using glutaraldehyde cross-linking. The resulting conjugates were applied as labels in an ELISA-like assay of tumor marker prostate-specific antigen (PSA). The lower limit of detection was below 1 ng/mL, which enables measurement of PSA in the range of clinically relevant concentrations.

Ultrasensitive CRISPR/Cas12a-Driven SERS Biosensor for On-Site Nucleic Acid Detection and Its Application to Milk Authenticity Testing

An ultrasensitive surface-enhanced Raman scattering (SERS) biosensor driven by CRISPR/Cas12a was proposed for on-site nucleic acid detection. We tactfully modified single-strand DNA (ssDNA) with a target-responsive Prussian blue (PB) nanolabel to form a probe and fastened it in the microplate. Attributed to the specific base pairing and highly efficient trans-cleavage ability of the CRISPR/Cas12a effector, precise target DNA recognition and signal amplification can be achieved, respectively. In the presence of target DNA, trans-cleavage towards the probe was activated, leading to the release of a certain number of PB nanoparticles (NPs). Then, these free PB NPs would be removed. Under alkali treatment, the breakdown of the remaining PB NPs in the microplate was triggered, producing massive ferricyanide anions (Fe(CN)₆^4-), which could exhibit a unique characteristic Raman peak that was located in the "biological Raman-silent region". By mixing the alkali-treated solution with the SERS substrate, Au@Ag core-shell NP, the concentration of the target DNA was finally exhibited as SERS signals with undisturbed background, which can be detected by a portable Raman spectrometer. Importantly, this strategy could display an ultralow detection limit of 224 aM for target DNA. Furthermore, by targeting cow milk as the adulterated ingredient in goat milk, the proposed biosensor was successfully applied to milk authenticity detection.

A Prussian blue nanoparticles-based fluorescent nanoprobe for monitoring microRNA-92a and microRNA-21

Since microRNA-92a (miR-92a) and microRNA-21 (miR-21) are crucial biomarkers for colorectal cancer (CRC), monitoring miR-92a and miR-21 in serum is very significant for the early diagnosis of CRC. In this work, we developed a simple and sensitive fluorescent biosensor for the detection of miR-92a and miR-21 based on the quenching ability of Prussian blue nanoparticles (PBNPs) to fluorophores. Carboxyl fluorescein (FAM)-modified ssDNA (P-92a) and Cyanine 5 (Cy5)-modified ssDNA (P-21) were completely complementary to miR-92a and miR-21 separately. They were adsorbed on PBNPs surface by the binding of PO43- in DNA and Fe3+ in PBNPs to fabricate the P-92a + P-21@PBNPs sensing system. The fluorescence responses from P-92a + P-21@PBNPs show good selection to miR-92a and a great linear process with the miR-92a concentration ranging from 1 to 30 nM (ΔF = 10.978 cmiR-92a + 71.457). Meanwhile, the fluorescence responses from P-92a + P-21@PBNPs is linearly relative to miR-21 from 3 to 30 nM; the linear equation is ΔF = 5.7560 cmiR-21 + 48.729. Furthermore, the detections of miR-92a and miR-21 added in serum samples were achieved. In summary, this method is sensitive, highly specific, time-saving, cost-effective and applicable for the detection of miR-92a and miR-21. Therefore, this present sensor was expected to be used in clinical applications, which lays a potential foundation for an early diagnosis of cancer.

Biomimetic Hybrid Membrane-Coated Xuetongsu Assisted with Laser Irradiation for Efficient Rheumatoid Arthritis Therapy

Rheumatoid arthritis (RA) is a systemic autoimmune disease underlying a cascade of chronic inflammatory processes. Over the past decades, the response rate of effective RA treatments has remained scarce despite numerous advancements in the current therapeutic interventions, owing largely to the associated off-target adverse events and poor accumulation in the inflamed joints. Recently, there is a high interest in the development of targeted drug delivery system by using nanotechnology, as it can provide a handle to improve the therapy efficacy of RA. Here, multifunctional HA@RFM@PB@SE nanoparticles (HRPS NPs) are developed by loading schisanlactone E (SE, also called with xuetongsu), an anti-RA compound isolated from Tujia ethnomedicine xuetong, into Prussian blue nanoparticles (PB NPs) and further camouflage of RBC-RAFLS hybrid membrane with HA modification onto PB@SE NPs (PS NPs). We demonstrated that the modification of RFM makes PB NPs ideal decoys for targeting inflammatory mediators of arthritis due to the homing effects of the parental cells. Moreover, the encapsulation of RFM on the PB@SE NPs extended the blood circulation time and improved its targeting ability, which accordingly achieved optimal accumulation of SE in arthritic rat paws. In vitro and in vivo assay demonstrated the outstanding performance of HRPS NPs for synergistic chemo-/photothermal therapy of RA without side effects to healthy tissues. Molecular mechanism exploration indicated that the ultrastrong inhibition of synovial hyperplasia and bone destruction was partly via suppressing NF-κB signaling pathway and the expression of matrix metalloproteinases. In summary, the nanodrug delivery system showed controllable release behavior, targeted accumulation at arthritic sites and systemic regulation of immunity, hence improved therapeutic efficacy and clinical outcomes of the disease without attenuating safety.

Post-synthetic modification of Prussian blue type nanoparticles: tailoring the chemical and physical properties

This review focuses on recent advances in the post-synthetic modification of nano-sized Prussian blue and its analogues and compares them with the current strategies used in metal–organic frameworks to give future outlooks in this field.

Fundamental understanding of the size and surface modification effects on r1, the relaxivity of Prussian blue nanocube@m-SiO2: a novel targeted chemo-photodynamic theranostic agent to treat colon cancer

A targeted multimodal strategy on a single nanoplatform is attractive in the field of nanotheranostics for the complete ablation of cancer. Herein, we have designed mesoporous silica (m-SiO₂)-coated Prussian blue nanocubes (PBNCs), functionalized with hyaluronic acid (HA) to construct a multifunctional PBNC@m-SiO₂@HA nanoplatform that exhibited good biocompatibility, excellent photodynamic activity, and in vitro T₁-weighted magnetic resonance imaging ability (r₁ ∼ 3.91 mM⁻¹ s⁻¹). After loading doxorubicin into the as-prepared PBNC@m-SiO₂@HA, the developed PBNC@m-SiO₂@HA@DOX displayed excellent pH-responsive drug release characteristics. Upon irradiation with 808 nm (1.0 W cm⁻²) laser light, PBNC@m-SiO₂@HA@DOX exhibited synergistic photodynamic and chemotherapeutic efficacy (∼78% in 20 minutes) for human colorectal carcinoma (HCT 116) cell line compared to solo photodynamic or chemotherapy. Herein, the chemo-photodynamic therapeutic process was found to follow the apoptotic pathway via ROS-mediated mitochondrion-dependent DNA damage with a very low cellular uptake of PBNC@m-SiO₂@HA@DOX for the human embryonic kidney (HEK 293) cell line, illustrating its safety. Hence, it may be stated that the developed nanoplatform can be a potential theranostic agent for future applications. Most interestingly, we have noted variation in r₁ at each step of the functionalization along with size variation that has been the first time modelled on the basis of the Solomon–Bloembergen–Morgan theory considering changes in the defect crystal structure, correlation time, water diffusion rate, etc., due to varied interactions between PBNC and water molecules.

A targeted multimodal strategy on a single nanoplatform is attractive in the field of nanotheranostics for the complete ablation of cancer.

Near-infrared light-triggered nano-prodrug for cancer gas therapy

Gas therapy (GT) has attracted increasing attention in recent years as a new cancer treatment method with favorable therapeutic efficacy and reduced side effects. Several gas molecules, such as nitric oxide (NO), carbon monoxide (CO), hydrogen (H2), hydrogen sulfide (H2S) and sulfur dioxide (SO2), have been employed to treat cancers by directly killing tumor cells, enhancing drug accumulation in tumors or sensitizing tumor cells to chemotherapy, photodynamic therapy or radiotherapy. Despite the great progress of gas therapy, most gas molecules are prone to nonspecific distribution when administered systemically, resulting in strong toxicity to normal tissues. Therefore, how to deliver and release gas molecules to targeted tissues on demand is the main issue to be considered before clinical applications of gas therapy. As a specific and noninvasive stimulus with deep penetration, near-infrared (NIR) light has been widely used to trigger the cleavage and release of gas from nano-prodrugs via photothermal or photodynamic effects, achieving the on-demand release of gas molecules with high controllability. In this review, we will summarize the recent progress in cancer gas therapy triggered by NIR light. Furthermore, the prospects and challenges in this field are presented, with the hope for ongoing development.

A rational study of the influence of Mn2+-insertion in Prussian blue nanoparticles on their photothermal properties

We investigated a series of Mn²⁺-Prussian blue (PB) nanoparticles Na_zMn_xFe_1-x[Fe(CN)₆]_1-y□y·nH₂O of similar size, surface state and cubic morphology with various amounts of Mn²⁺ synthesized through a one step self-assembly reaction. We demonstrated by a combined experimental-theoretical approach that during the synthesis, Mn²⁺ substituted Fe³⁺ up to a Mn/Na-Mn-Fe ratio of 32 at% in the PB structure, while for higher amounts, the Mn₂[Fe(CN)₆] analogue is obtained. For comparison, the post-synthetic insertion of Mn2+ in PB nanoparticles was also investigated and completed with Monte-Carlo simulations to probe the plausible adsorption sites. The photothermal conversion efficiency (η) of selected samples was determined and showed a clear dependence on the Mn²⁺amount with a maximum efficiency for a Mn/Na-Mn-Fe ratio of 10 at% associated with a dependence on the nanoparticle concentration. Evaluation of the in vitro photothermal properties of these nanoparticles performed on triple negative human breast adenocarcinoma (MDA-MB-231) cells by using continuous and pulsed laser irradiation confirm their excellent PTT efficiency permitting low dose use.

K2 Mn3 [FeII (CN)6 ]2 NPs with High T1 -Relaxivity Attributable to Water Coordination on the Mn(II) Center for Gastrointestinal Tract MR Imaging

The lack of acid stability in the stomach and of temporal stability when moving through the gastrointestinal (GI) tract has made the development of oral magnetic resonance imaging (MRI) contrast agents based on the platform of Gd³⁺ -complexes problematic.On the other hand, the negative contrast enhancement produced by the T₂ -weighted magnetic metal oxide nanoparticles (NPs) often renders the image readout difficult. Biocompatible NPs of the manganese Prussian blue analog K₂ Mn₃ [Fe^II (CN)₆ ]₂ exhibit extremely high stability under the acidic conditions of the gastric juice. Additionally, the high r₁ relaxivity, low toxicity, and high temporal stability of such NPs offer great potential for the development of a true T₁ -weighted oral contrast agent for MRI of the entire GI tract.

Multifunctional Biodegradable Prussian Blue Analogue for Synergetic Photothermal/Photodynamic/Chemodynamic Therapy and Intrinsic Tumor Metastasis Inhibition

To date, various Prussian blue analogues (PBAs) have been prepared for biomedical applications due to their unique structural advantages. However, the safety and effectiveness of tumor treatment still need further exploration. This contribution reports a facile synthesis of PBA with superior tumor synergetic therapeutic effects and a detailed mechanistic evaluation of their intrinsic tumor metastasis inhibition activity. The as-synthesized PBA has a uniform cube structure with a diameter of approximately 220 nm and shows high near-infrared light (NIR) photoreactivity, photothermal conversion efficiency (41.44%), and photodynamic effect. Additionally, PBA could lead to a chemodynamic effect, which is caused by the Fenton reaction and ferroptosis. The combined therapy strategy of PBA exhibits notable tumor ablation properties due to photothermal therapy (PTT)/photodynamic therapy (PDT)/chemodynamic therapy (CDT) effects without obvious toxicity in vivo. The PBA has also shown potential as a contrast agent for magnetic resonance imaging (MRI) and photoacoustic (PA) imaging. More importantly, careful investigations reveal that PBA displays excellent biodegradation and anti-metastasis properties. Further exploration of the PBA implies that its underlying mechanism of intrinsic tumor metastasis inhibition activity can be attributed to the modulation of epithelial-mesenchymal transition (EMT) expression. The considerable potential exhibited by the as-synthesized PBA makes it an ideal candidate as a synergetic therapeutic agent for tumor treatment.

Nanoparticles-mediated emerging approaches for effective treatment of ischemic stroke

Ischemic stroke leads to high disability and mortality. The limited delivery efficiency of most therapeutic substances is a major challenge for effective treatment of ischemic stroke. Inspired by the prominent merit of nanoscale particles in brain targeting and blood-brain barrier (BBB) penetration, various functional nanoparticles have been designed as promising drug delivery platforms that are expected to improve the therapeutic effect of ischemic stroke. Based on the complex pathological mechanisms of ischemic stroke, this review outline and summarize the rationally designed nanoparticles-mediated emerging approaches for effective treatment of ischemic stroke, including recanalization therapy, neuroprotection therapy, and combination therapy. On this bases, the potentials and challenges of nanoparticles in the treatment of ischemic stroke are revealed, and new thoughts and perspectives are proposed for the design of feasible nanoparticles for effective treatment of ischemic stroke.

Cancer Cytomembrane-Cloaked Prussian Blue Nanoparticles Enhance the Efficacy of Mild-Temperature Photothermal Therapy by Disrupting Mitochondrial Functions of Cancer Cells

Despite its success against cancer, photothermal therapy (PTT) (>50 °C) suffers from several limitations such as triggering inflammation and facilitating immune escape and metastasis and also damage to the surrounding normal cells. Mild-temperature PTT has been proposed to override these shortcomings. We developed a nanosystem using HepG2 cancer cell membrane-cloaked zinc glutamate-modified Prussian blue nanoparticles with triphenylphosphine-conjugated lonidamine (HmPGTL NPs). This innovative approach achieved an efficient mild-temperature PTT effect by downregulating the production of intracellular ATP. This disrupts a section of heat shock proteins that cushion cancer cells against heat. The physicochemical properties, anti-tumor efficacy, and mechanisms of HmPGTL NPs both in vitro and in vivo were investigated. Moreover, the nanoparticles cloaked with the HepG2 cell membrane substantially prolonged the circulation time in vivo. Overall, the designed nanocomposites enhance the efficacy of mild-temperature PTT by disrupting the production of ATP in cancer cells. Thus, we anticipate that the mild-temperature PTT nanosystem will certainly present its enormous potential in various biomedical applications.

Formation mechanisms of hollow manganese hexacyanoferrate particles and construction of a multiple-shell structure

Formation mechanisms of hollow manganese hexacyanoferrate (Mn-HCF) particles have been investigated. Mn-HCF particles, which were precipitated by mixing an aqueous solution of K3[Fe(CN)6] with MnCl2 in the presence of sodium citrate, could be converted into a hollow structure just by washing with distilled water. The powder X-ray diffractometry suggested that the as-prepared particle has a core/shell morphology with different crystal structures: cubic-core and monoclinic-shell. The time evolutions of the particle size and shell thickness indicated that the core was rapidly (but not instantaneously) formed at the initial stage of the precipitation process, followed by a slower shell growth. In addition, the solubility of the cubic core was estimated to be about 2.5 times higher than that of the monoclinic shell, resulting in the preferential dissolution of the interior of the particle by the washing process. The formation procedure has been used to construct multiple-shell hollow Mn-HCF particles containing up to quadruple separated nesting shells by associating an additional growth technique.

How to Build Prussian Blue Based Water Oxidation Catalytic Assemblies: Common Trends and Strategies

Prussian blue (PB) and its analogues (PBAs) have at least a three-century-long history in coordination chemistry. Recently, cobalt-based PBAs have been acknowledged as efficient and robust water oxidation catalysts. Given the flexibility in their synthesis, the structure and morphology of cobalt-based PBAs have been modified for enhanced catalytic activity under electrochemical (EC), photocatalytic (PC), and photoelectrochemical (PEC) conditions. Here, in this review, the work on cobalt-based PBAs is presented in four sections: i) electrocatalytic water oxidation with bare PBAs, ii) photocatalytic processes in the presence of a photosensitizer (PS), iii) photoelectrochemical water oxidation by coupling PBAs to proper semiconductors (SCs), and iv) the utilization of PBA-PS assemblies coated on SCs for the dye-sensitized photoelectrochemical water oxidation. This review will guide readers through the structure and catalytic activity relationship in cobalt-based PBAs by describing the role of each structural component. Furthermore, this review aims to provide insight into common strategies to enhance the catalytic activity of PBAs.

Dual Effect of Prussian Blue Nanoparticles on Aβ40 Aggregation: β-Sheet Fibril Reduction and Copper Dyshomeostasis Regulation

Alzheimer's disease (AD), affecting almost 50 million individuals worldwide, is currently the first cause of dementia. Despite the tremendous research efforts in the last decade, only four supportive or palliative drugs, namely, acetylcholinesterase (AChE) inhibitors donepezil, galantamine, and rivastigmine and the glutamate NMDA receptor antagonist memantine, are currently available. New therapeutic strategies are becoming prominent, such as the direct inhibition of amyloid formation or the regulation of metal homeostasis. In the present report, the potential use of Prussian blue (PB), a drug that is in the World Health Organization Model List of Essential Medicines, in AD treatment is demonstrated. Both in vitro and in cellulo studies indeed suggest that PB nanoparticles (PBNPs) are capable of reducing the formation of typical amyloid-β fibers (detected by thioflavin T fluorescence) and restoring the usual amyloid fibrillation pathway via chelation/sequestration of copper, which is found in high concentrations in senile plaques.

A portable device with low-power consumption for monitoring mouse vital signs during in vivo photoacoustic imaging and photothermal therapy

OBJECTIVE

The aim of this study was to monitor the physiological changes and cytotoxic effects of exogenous contrast agents during photoacoustic imaging (PAI) and photothermal therapy (PTT). In this paper, a low-power telemetric device for mouse vital signs monitoring was designed and demonstrated.

APPROACH

The power consumption was optimized through hardware and software co-design with a 17% increased operating time compared with typical operation. To demonstrate the feasibility of the monitoring device, PAI and PTT experiments with chitosan-polypyrrole nanocomposites (CS-PPy NCs) as exogenous contrast agents were conducted. Herein, the physiological variation in groups of mice with different CS-PPy NC concentrations was observed and analyzed.

MAIN RESULTS

The experimental results indicated the influence of CS-PPy NCs and anesthesia on mouse vital signs in PAI and PTT. Additionally, the association between core temperature, heart rate, and saturation of peripheral oxygen (SpO₂) during PAI and PTT was shown. The strong near-infrared absorbance of exogenous contrast agents could account for the increase in mouse core temperature and tumor temperature in this study. Furthermore, high cross-correlation values between core temperature, heart rate, and SpO₂ were demonstrated to explain the fluctuation of mouse vital signs during PAI and PTT.

SIGNIFICANCE

A design of a vital signs monitoring device, with low power consumption, was introduced in this study. A high cross correlation coefficient of mouse vital signs and the effects of CS-PPy NCs were observed, which explained the mouse physiological variation during the PAI and PTT experiments.

Achieving Ultrasmall Prussian Blue Nanoparticles as High-Performance Biomedical Agents with Multifunctions

Prussian blue nanoparticles (PBNPs), which belong to the iron-based metal-organic frameworks, are important biomedical agents. Reducing the size of PBNPs can bring improved functional properties, but unfortunately, has been a long-standing challenge. Herein, sub-5 nm ultrasmall PBNPs (USPBNPs) were successfully synthesized by using ethanol/water mixture as the solvent and polyvinyl pyrrolidone (PVP) as the surface capping agent. Adjusting the ethanol/water ratio is not only able to control the nucleation time and size of PBNPs but also tune the conformation of PVP molecules so as to prevent interparticle attachment and enlargement. At an ethanol/water ratio of 3:1, highly stable USPBNPs with a size of ∼3.4 nm were synthesized. Due to their large specific surface area, they demonstrated high peroxidase-like and catalase-like activities, which outperform PBNPs synthesized by a conventional method. In addition, they also showed a high longitudinal relaxation rate (r₁) of 1.3 mM^-1 S^-1, suggesting their potential to be used as T₁ MRI agent.

The Application of Prussian Blue Nanoparticles in Tumor Diagnosis and Treatment

Prussian blue nanoparticles (PBNPs) have attracted increasing research interest in immunosensors, bioimaging, drug delivery, and application as therapeutic agents due to their large internal pore volume, tunable size, easy synthesis and surface modification, good thermal stability, and favorable biocompatibility. This review first outlines the effect of tumor markers using PBNPs-based immunosensors which have a sandwich-type architecture and competitive-type structure. Metal ion doped PBNPs which were used as T1-weight magnetic resonance and photoacoustic imaging agents to improve image quality and surface modified PBNPs which were used as drug carriers to decrease side effects via passive or active targeting to tumor sites are also summarized. Moreover, the PBNPs with high photothermal efficiency and excellent catalase-like activity were promising for photothermal therapy and O2 self-supplied photodynamic therapy of tumors. Hence, PBNPs-based multimodal imaging-guided combinational tumor therapies (such as chemo, photothermal, and photodynamic therapies) were finally reviewed. This review aims to inspire broad interest in the rational design and application of PBNPs for detecting and treating tumors in clinical research.