A Versatile Theranostic Delivery Platform Integrating Magnetic Resonance Imaging/Computed Tomography, pH/cis-Diol Controlled Release, and Targeted Therapy

Recent development of pH-responsive theranostic nanoplatforms for magnetic resonance imaging-guided cancer therapy

The acidic characteristic of the tumor site is one of the most well-known features and provides a series of opportunities for cancer-specific theranostic strategies. In this regard, pH-responsive theranostic nanoplatforms that integrate diagnostic and therapeutic capabilities are highly developed. The fluidity of the tumor microenvironment (TME), with its temporal and spatial heterogeneities, makes noninvasive molecular magnetic resonance imaging (MRI) technology very desirable for imaging TME constituents and developing MRI-guided theranostic nanoplatforms for tumor-specific treatments. Therefore, various MRI-based theranostic strategies which employ assorted therapeutic modes have been drawn up for more efficient cancer therapy through the raised local concentration of therapeutic agents in pathological tissues. In this review, we summarize the pH-responsive mechanisms of organic components (including polymers, biological molecules, and organosilicas) as well as inorganic components (including metal coordination compounds, metal oxides, and metal salts) of theranostic nanoplatforms. Furthermore, we review the designs and applications of pH-responsive theranostic nanoplatforms for the diagnosis and treatment of cancer. In addition, the challenges and prospects in developing theranostic nanoplatforms with pH-responsiveness for cancer diagnosis and therapy are discussed.

A pH/GSH dual responsive nanoparticle with relaxivity amplification for magnetic resonance imaging and suppression of tumors and metastases

Engineered magnetic nanoparticles combining diagnosis and therapy functions into one entity hold great potential to rejuvenate cancer treatment; however, they are still constrained by the "always on" signals and unsatisfactory therapeutic effect. Here, we report an intelligent theranostic probe based on Mn₃O₄ tetragonal bipyramids (MnTBs), which simultaneously respond to H⁺ and glutathione (GSH) with high sensitivity and quickly decompose to release Mn²⁺ in mild acidic and reductive intracellular environments. Mn²⁺ binds to the surrounding proteins to achieve a remarkable relaxivity amplification and selectively brighten the tumors. Particularly, this MR signal improvement is also effective in the detection of millimeter-sized liver metastases, with an ultrahigh contrast of 316%. Moreover, Mn²⁺ would trigger chemodynamic therapy (CDT) by exerting the Fenton-like activity to generate ˙OH from H₂O₂. Subsequently, a significant tumor suppression effect can be achieved by the GSH depletion-enhanced CDT. Besides, MnTBs manifest efficient urinary and hepatic excretions with biodegradability and minimal systemic toxicity. A pH/GSH dual responsive nanoprobe that integrates tumor diagnostic and therapeutic activities was developed to provide a new paradigm for precise diagnosis and treatment of tumors and metastases.

Lifetime-Based Responsive Probes: Design and Applications in Biological Analysis

With the development of modern biomedicine, biological analysis and detection are very important in disease diagnosis, detection of curative effect, prognosis and prediction of tumor recurrence. Compared with the currently widely used optical probes based on intensity signals, the lifetime signal does not depend on the influence of conditions such as the concentration of luminophore, tissue penetration depth and measurement method. Therefore, biological detection methods based on lifetime-based responsive probes have attracted great attention from the scientific community. Here, we briefly review the key advances in lifetime-based responsive probes in recent years (2017-2022). The review focuses on the design strategies of lifetime-based responsive probes and the research progress of their applications in the field of bioanalysis, and discusses the challenges they face. We hope it will further promote the development of lifetime-based responsive probes in the field of bioanalysis. With the development of modern biomedicine, biological analysis and detection are very important in disease diagnosis, detection of curative effect, prognosis and prediction of tumor recurrence. Compared with the currently widely used optical probes based on intensity signals, the lifetime signal does not depend on the influence of conditions such as the concentration of luminophore, tissue penetration depth and measurement method. Therefore, biological detection methods based on lifetime-based responsive probes have attracted great attention from the scientific community. Here, we briefly review the key advances in lifetime-based responsive probes in recent years (2017-2022). The review focuses on the design strategies of lifetime-based responsive probes and the research progress of their applications in the field of bioanalysis, and discusses the challenges they face. We hope it will further promote the development of lifetime-based responsive probes in the field of bioanalysis.

MnCO3@BSA-ICG nanoparticles as a magnetic resonance/photoacoustic dual-modal contrast agent for functional imaging of acute ischemic stroke

Timely and accurate diagnosis of acute ischemic stroke (AIS) and simultaneous functional imaging of cerebral oxygen saturation (sO₂) are essential to improve the survival rate of stroke patients but remains challenging. Herein, we developed a pH-responsive manganese (Mn)-based nanoplatform as a magnetic resonance/photoacoustic (MR/PA) dual-modal contrast agent for AIS diagnosis. The Mn-based nanoplatform was prepared via a simple and green biomimetic method using bovine serum albumin (BSA) as a scaffold for fabrication of MnCO₃ NPs as the T₁ MR contrast agent and accommodation of indocyanine green (ICG) as the PA probe. The obtained MnCO₃@BSA-ICG NPs were biocompatible and exhibited a pH-responsive longitudinal relaxation rate and a concentration-dependent PA signal. In vivo MR/PA dual-modal imaging demonstrated that MnCO₃@BSA-ICG NPs quickly and efficiently led to the MR/PA contrast enhancements in the infarcted area while not in the normal region, allowing a timely and accurate diagnosis of AIS. Moreover, PA imaging could directly monitor the sO₂ level, enabling a functional imaging of AIS. Therefore, MnCO₃@BSA-ICG NPs could be applied as a potential MR/PA contrast agent for timely and functional imaging of AIS.

Tumor-penetrating iron oxide nanoclusters for T1/T2 dual mode MR imaging-guided combination therapy

A hyaluronic acid (HA)-stabilized iron oxide nanocluster (Fe2O3@PFDH NC) was developed as an intelligent tumor-penetrating theranostic nanoagent for dual-mode MRI guided chemo-photothermal therapy.

Improving the sensitivity of T 1 contrast-enhanced MRI and sensitive diagnosing tumors with ultralow doses of MnO octahedrons

Rationale: Sensitive and accurate imaging of cancer is essential for early diagnosis and appropriate treatment. For generally employed magnetic resonance imaging (MRI) in clinic, comprehending how to enhance the contrast effect of T₁ imaging is crucial for improving the sensitivity of cancer diagnosis. However, there is no study ever to reveal the clear mechanism of how to enhance the effect of T₁ imaging and accurate relationships of influencing factors. Herein, this study aims to figure out key factors that affect the sensitivity of T₁ contrast-enhanced MRI (CE-MRI), thereby to realize sensitive detection of tumors with low dose of CAs.

Methods: Manganese oxide (MnO) nanoparticles (NPs) with various sizes and shapes were prepared by thermal decomposition. Factors impacting T₁ CE-MRI were investigated from geometric volume, surface area, crystal face to r₂/r₁ ratio. T₁ CE-MR imaging of liver, hepatic and subcutaneous tumors were conducted with MnO NPs of different shapes.

Results: The surface area and occupancy rate of manganese ions have positive impacts on the sensitivity of T₁ CE-MRI, while volume and r₂/r₁ ratio have negative effects. MnO octahedrons have a high r₁ value of 20.07 mM^-1s^-1 and exhibit an excellent enhanced effect in liver T₁ imaging. ZDS coating facilitates tumor accumulation and cellular uptake, hepatic and subcutaneous tumors could be detected with MnO octahedrons at an ultralow dose of 0.4 mg [Mn]/kg, about 1/10 of clinical dose.

Conclusions: This work is the first quantitative study of key factors affecting the sensitivity of T₁ CE-MRI of MnO nanoparticles, which can serve as a guidance for rational design of high-performance positive MRI contrast agents. Moreover, these MnO octahedrons can detect hepatic and subcutaneous tumors with an ultralow dose, hold great potential for sensitive and accurate diagnosis of cancer with lower cost, less dosages and side effects in clinic.

A pH-Activatable MnCO3 Nanoparticle for Improved Magnetic Resonance Imaging of Tumor Malignancy and Metastasis

Engineered magnetic nanoparticles have been extensively explored for magnetic resonance imaging (MRI) diagnosis of a tumor to improve the visibility. However, most of these nanoparticles display "always-on" signals without tumor specificity, causing insufficient contrast and false positives. Here, we provide a new paradigm of MRI diagnosis using MnCO₃ nanorhombohedras (MnNRs) as an ultrasensitive T₁-weighted MRI contrast agent, which smartly enhances the MR signal in response to the tumor microenvironment. MnNRs would quickly decompose and release Mn²⁺ at mild acidity, one of the pathophysiological parameters associated with cancer malignancy, and then Mn²⁺ binds to surrounding proteins to achieve a remarkable amplification of T₁ relaxivity. In vivo MRI experiments demonstrate that MnNRs can selectively brighten subcutaneous tumors from the edge to the interior may be because of the upregulated vascular permeation at the tumor edge, where cancer cell proliferation and angiogenesis are more active. Specially, benefiting from the T₂ shortening effect in normal liver tissues, MnNRs can detect millimeter-sized liver metastases with an ultrahigh contrast of 294%. The results also indicate an effective hepatic excretion of MnNRs through the gallbladder. As such, this pH-activatable MRI strategy with facility, biocompatibility, and excellent efficiency may open new avenues for tumor malignancy and metastasis diagnosis and holds great promise for precision medicine.

Folic Acid Functionalized Chlorin e6-Superparamagnetic Iron Oxide Nanocarriers as a Theranostic Agent for MRI-Guided Photodynamic Therapy

Imaging-guided cancer theranostic is a promising strategy for cancer diagnostic and therapeutic. Photodynamic therapy (PDT), as an approved treatment modality, is limited by the poor solubility and dispersion of photosensitizers (PS) in biological fluids. Herein, it is demonstrated that superparamagnetic iron oxide (SPIO)-based nanoparticles (SCFs), prepared by conjugated with Chlorin e6 (Ce6) and modified with folic acid (FA) on the surface, can be used as versatile drug delivery vehicles for effective PDT. The nanoparticles are great carriers for photosensitizer Ce6 with an extremely high loading efficiency. In vitro fluorescence imaging and in vivo magnetic resonance imaging (MRI) results indicated that SCFs selectively accumulated in tumor cells. Under near-infrared laser irradiation, SCFs were confirmed to be capable of inducing low cell viability of RM-1 cells In vitro and displaying efficient tumor ablation with negligible side effects in tumor-bearing mice models.

Application of Magnetic Resonance Imaging Based on Fe₃O₄ Nanoparticles in the Treatment of Cerebrovascular Diseases

Due to its high stability and excellent performance, inorganic nanomaterials have attracted much attention in the research of disease diagnosis and treatment. Focusing on inorganic nanomaterials, high-temperature pyrolysis has been used to successfully prepare Fe₃O₄ nanoparticles with different particle sizes. The diagnosis and treatment of Alzheimer's disease have advanced, and many new diagnostic methods have been adopted clinically. In this paper, Fe₃O₄ nanoparticle magnetic resonance imaging technology is used to explore the application of magnetic Fe₃O₄ inorganic nanomaterials in cerebrovascular diseases in vivo. The results show that SWI has higher sensitivity and semi-quantitative advantages than traditional T2WI imaging technology. With different critical SWI concentrations, this article lays the experimental foundation for the clinical progress of inorganic nanomaterials and plays an important role in the treatment of cerebrovascular diseases.

T1-Positive Mn2+-Doped Multi-Stimuli Responsive poly(L-DOPA) Nanoparticles for Photothermal and Photodynamic Combination Cancer Therapy

In this study, we designed near-infrared (NIR)-responsive Mn2+-doped melanin-like poly(L-DOPA) nanoparticles (MNPs), which act as multifunctional nano-platforms for cancer therapy. MNPs, exhibited favorable π-π stacking, drug loading, dual stimuli (NIR and glutathione) responsive drug release, photothermal and photodynamic therapeutic activities, and T1-positive contrast for magnetic resonance imaging (MRI). First, MNPs were fabricated via KMnO4 oxidation, where the embedded Mn2+ acted as a T1-weighted contrast agent. MNPs were then modified using a photosensitizer, Pheophorbide A, via a reducible disulfide linker for glutathione-responsive intracellular release, and then loaded with doxorubicin through π-π stacking and hydrogen bonding. The therapeutic potential of MNPs was further explored via targeted design. MNPs were conjugated with folic acid (FA) and loaded with SN38, thereby demonstrating their ability to bind to different anti-cancer drugs and their potential as a versatile platform, integrating targeted cancer therapy and MRI-guided photothermal and chemotherapeutic therapy. The multimodal therapeutic functions of MNPs were investigated in terms of T1-MR contrast phantom study, photothermal and photodynamic activity, stimuli-responsive drug release, enhanced cellular uptake, and in vivo tumor ablation studies.

Mesoporous Silica Nanoparticles in Bioimaging

A biomedical contrast agent serves to enhance the visualisation of a specific (potentially targeted) physiological region. In recent years, mesoporous silica nanoparticles (MSNs) have developed as a flexible imaging platform of tuneable size/morphology, abundant surface chemistry, biocompatibility and otherwise useful physiochemical properties. This review discusses MSN structural types and synthetic strategies, as well as methods for surface functionalisation. Recent applications in biomedical imaging are then discussed, with a specific emphasis on magnetic resonance and optical modes together with utility in multimodal imaging.

A Combinative Assembly Strategy Inspired Reversibly Borate-Bridged Polymeric Micelles for Lesion-Specific Rapid Release of Anti-Coccidial Drugs

HIGHLIGHTS

A combined assembly strategy from hydrophobicity-driving and reversible borate bridges is proposed for high drug-loading efficiency and superior stability. Intestinal environment-triggered drug delivery system represents an effective treatment for local infection due to the site-specific targeting and shuttling of drugs. The reduced dosage brought by the drug-loading micelles could solve the problem of drug residue in breeding industry.

ABSTRACT

Stimuli-triggered drug delivery systems hold vast promise in local infection treatment for the site-specific targeting and shuttling of drugs. Herein, chitosan conjugates (SPCS) installed with sialic acid (SA) and phenylboronic acid (PBA) were synthesized, of which SA served as targeting ligand for coccidium and reversible-binding bridge for PBA. The enhanced drug-loading capacity of SPCS micelles was attributed to a combination assembly from hydrophobicity-driving and reversible borate bridges. The drug-loaded SPCS micelles shared superior biostability in upper gastrointestinal tract. After reaching the lesions, the borate bridges were snipped by carbohydrates under a higher pH followed by accelerated drug release, while SA exposure on micellar surface facilitated drug cellular internalization to eliminate parasites inside. The drug-micelles revealed an enhanced anti-coccidial capacity with a higher index of 185.72 compared with commercial preparation. The dual-responsive combination of physicochemical assembly could provide an efficient strategy for the exploitation of stable, safe and flexible anti-infectious drug delivery systems. [Image: see text]

ELECTRONIC SUPPLEMENTARY MATERIAL

The online version of this article (10.1007/s40820-020-00495-1) contains supplementary material, which is available to authorized users.

Dual-Mode Avocado-like All-Iron Nanoplatform for Enhanced T1/T2 MRI-Guided Cancer Theranostic Therapy

Development of T₁/T₂ dual-mode MRI contrast agents that can also treat cancer is an attractive prospect for personalized precision medicine. Unfortunately, conventional contrast agents can suffer from toxicity and lack any ability to treat cancer. An all-iron T₁/T₂ MR imaging agent with photothermal and drug delivery capability would overcome these issues. Here, an avocado-like Fe³⁺/Fe₂O₃ composed T₁-T₂ dual-mode contrast agent based on Fe-TA coordination network (CNMN) is developed. This material possesses suitable longitudinal and transverse relaxation coefficients. Moreover, the strong heat generation property of Fe-TA endows CNMN with the capability to act as a potent photothermal agent. Furthermore, CNMN can also act as an effective delivery platform for the chemotherapeutic drug doxorubicin (DOX) to achieve high effective chemo-photothermal combination therapy. The work demonstrates reliable T₁-T₂ MRI-guided chemo-photothermal therapy for safe and effective clinical application.

<p>Recent Advances of Magnetic Nanomaterials in the Field of Oncology</p>

Nanomagnetic devices, such as nano-field effect transistor biosensors and radio frequency magnetic induction therapies, came into being with the development of medical nanomaterials. The application of nanomagnetic materials in the treatment of cancers is rapidly becoming increasingly important because of its ability to target therapy and diagnose early. In this review, an untechnical overview of the fundamental of magnetism in nanomaterials and an illustration of how these materials are applied are presented. The applications of nano-field effect transistor biosensors for the detection of tumor biomarker nanomaterials in the therapy and diagnosis of cancers and nanomagnetic materials are summarized in this paper. A systemic summary of the use of nanomagnetic materials and nano-filed effect transistor biosensors for the treatment and diagnosis of tumors is also provided in the review.

Bismuth-Based Nanomaterials: Recent Advances in Tumor Targeting and Synergistic Cancer Therapy Techniques

Despite all of the efforts in the field of cancer therapy, the heterogeneous properties of tumor cells induce an insufficient therapeutic outcome when treated with conventional monotherapies, necessitating a shift in cancer treatment from monotherapy to combination therapy for complete cancer treatment. Multifunctional bismuth (Bi)-based nanomaterials (NMs) with therapeutic functions hold great promise for the fields of cancer diagnosis and therapy based on their low toxicity, X-ray sensitive capabilities, high atomic number, near-infrared driven semiconductor properties, and low cost. Herein, a comprehensive review of recent advances in various medicinal aspects of Bi-based NMs is presented including: evaluation of in-tumor site accumulation, tumor targeting, and therapeutic performance, as well as the characteristics, benefits, and shortcomings of Bi-based NM-mediated major monotherapies. In addition, the cooperative enhancement mechanisms between two or more of these monotherapies are described in detail to address common challenges in cancer therapy, such as multidrug resistance, hypoxia, and metastasis. Finally, this review opens new insights into the design of multimodal synergistic therapies for potential future clinical applications of Bi-based NMs.

Collaborative assembly of doxorubicin and galactosyl diblock glycopolymers for targeted drug delivery of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) patients suffer from severe pain due to the serious systemic side effects and low efficiency of chemotherapeutic drugs, and it is important to develop novel drug delivery systems to circumvent these issues. In this study, a series of galactose-based glycopolymers, poly(N-(prop-2-enoyl)-β-d-galactopyranosylamine)-b-poly(N-isopropyl acrylamide) (pGal(OH)-b-pNIPAA), were prepared through a sequential reversible addition-fragmentation chain transfer (RAFT) polymerization and tetrabutylammonium hydroxide (TBAOH)-mediated removal of acetyl groups. Hydrophilic doxorubicin hydrochloride was introduced to undergo collaborative assembly with poly(N-(prop-2-enoyl)-β-d-peracetylated galactosamine)-b-poly(N-isopropyl acrylamide) (pGal(Ac)-b-pNIPAA) via TBAOH treatment. pGal-b-pNIPAA/doxorubicin (DOX) delivery nanoparticles (GND NPs) formed by collaborative assembly were fully characterized by NMR, TEM and FT-IR, indicating the well-controlled formation of particles with uniform size and high efficiency in terms of drug loading and encapsulation compared with conventional adsorption methods. Meanwhile, the GND NPs were observed to be rapidly disintegrated under acidic conditions and resulted in an increased release of DOX. Cellular experiments showed that pGal-b-pNIPAA/DOX is apparently an asialoglycoprotein receptor (ASGPR)-mediated target of HCC, resulting in enhanced cellular uptake to HepG2 cells and anti-tumor efficacy in vitro. Furthermore, GND NPs III exerted more sustainable and effective anti-tumor effects compared to free DOX on a transgenic zebrafish TO(Kras^G12V) model in vivo. These results indicated that the biocompatible nanomaterials developed by collaborative assembly with galactosyl diblock glycopolymers and DOX may serve as a promising candidates for targeting therapy of HCC.

Conformation-Dependent Coordination of Carboxylic Acids with Fe3O4 Nanoparticles Studied by ATR-FTIR Spectral Deconvolution

The coordination of valeric acid (VA), glutaric acid (GA), and tricarballylic acid (TA) with Fe-OH on the Fe₃O₄ nanoparticle surface has been systematically studied to elucidate the effects of COOH, molecular configuration, and ligand concentration on the coordination by the combined use of attenuated total reflectance Fourier transform infrared (ATR-FTIR) and thermogravimetric analysis (TGA). The results show that the binding ability of the acids increases with the increase in the COOH number. Multiple conformations coexist for the dicarboxylic and tricarboxylic acid coordinated on the iron oxide NPs. Saturated coordination formed with only a one-, two-, or three-COOH conformation for VA, GA, and TA, respectively, occurs under ligand-scarce conditions, while unsaturated coordination formed with the mixture of uncoordinated, one-, and/or two-COOH conformations for VA, GA, and TA, respectively, exists under ligand-abundant conditions. The maximum coordination numbers for monolayer adsorption for VA, GA, and TA on Fe₃O₄ NPs are 9, 2.4, and 2.7 nm^-2, respectively. This study helps us to understand the fine coordination mechanism caused by the acid molecules with different configurations and elucidates, for the first time, the fine conformational variance incurred by the surrounding ligand with different concentrations and the way in which the ligand is added.

Polypseudorotaxane functionalized magnetic nanoparticles as a dual responsive carrier for roxithromycin delivery

A magnetic-pH dual responsive drug delivery system was prepared for antibacterial therapy to reduce the side effects on nonpathological cells or tissues. Iron oxide (Fe₃O₄) core was surface-functionalized with silane coupling agents to link β‑cyclodextrin (β-CD) (CDMNP), and a polypseudorotaxanes shell where polyethyleneglycol chains threaded much CD molecules was further prepared on the magnetic Fe₃O₄ core (CDMNP-PEG-CD) to enhance loading capacity of roxithromycin (ROX). CDMNP-PEG-CD with a hydrodynamic diameter of ~168 nm was cytocompatible, superparamagnetic, magnetic-responsive and stable for 180 min of storage. No significant interaction with serum albumin was shown for the nanocomposites. The in vitro release from ROX-loaded CDMNP-PEG-CD nanocomposites was about 76% of total drug within 30 min at pH 1.0, 1.6-fold of that at pH 7.4 and 2-fold of that at pH 8.0, presenting pH-responsive drug release behaviors. The nanocomposites showed positive antibacterial activity against both E. coli and S. aureus based on an agar diffusion method. The antibacterial activity of the nanocomposites was more sensitive against E. coli than S. aureus, and the inhibition halo against E. coli was 85% more than that of Fe₃O₄. CDMNP-PEG-CD nanocomposites allowed for the localization and fast concentration of hydrophobic drugs, providing a broad potential range of therapeutic applications.

Recent advances in nanomaterial-based synergistic combination cancer immunotherapy

This review aims to summarize various synergistic combination cancer immunotherapy strategies based on nanomaterials.

pH-Responsive polyelectrolyte coated gadolinium oxide-doped mesoporous silica nanoparticles (Gd2O3@MSNs) for synergistic drug delivery and magnetic resonance imaging enhancement

Theranostic platforms that combine therapeutic and imaging modalities have received increasing interest.

Modified core–shell magnetic mesoporous zirconia nanoparticles formed through a facile “outside-to-inside” way for CT/MRI dual-modal imaging and magnetic targeting cancer chemotherapy

Iron oxide based magnetic nanoparticles (MNPs) as typical theranostic nanoagents have been popularly used in various biomedical applications. Conventional core–shell MNPs are usually synthesized from inside to outside. This method has strict requirements on the interface properties of magnetic cores and the precursors of the coating shell. The shape and size of MNPs are significantly influenced by that of the pre-synthesized magnetic cores. Most core–shell MNPs have only single T2W MRI imaging ability. Herein, we propose a new synthetic strategy for core-mesoporous shell structural MNPs, where hollow mesoporous nanospheres which exhibit an intrinsic property for both CT imaging and drug loading were used as the shell and the magnetic cores were produced in the cavity of the shell. A new type of MNPs, Fe₃O₄@ZrO₂ nanoparticles (M-MZNs), were developed using this facile outside-to-inside way, where multiple Fe₃O₄ nanoparticles grew inside the cavity of the mesoporous hollow ZrO₂ nanospheres through chemical coprecipitation. The obtained MNPs not only exhibited superior magnetic properties and CT/MR imaging ability but also high drug loading capacity. In vitro experiment results revealed that M-MZNs-PEG loaded with doxorubicin (DOX) presented selective growth inhibition against cancer cells due to pH-sensitive DOX release and enhanced endocytosis by cancer cells under a magnetic field. Furthermore, the proposed MNPs exhibited CT/MRI dual modal imaging ability and effective physical targeting to tumor sites in vivo. More importantly, experiments of magnetic targeting chemotherapy on tumor bearing mice demonstrated that the nanocomposites significantly suppressed tumor growth without obvious pathological damage to major organs. Henceforth, this study provides a new strategy for CT/MRI dual-modal imaging guided and magnetic targeting cancer therapy.

Magnetic mesoporous zirconia nanoparticle was synthesized by producing multiple iron oxide cores inside the cavity of mesoporous ZrO₂ hollow nanospheres and was used for CT/MRI dual-modal imaging and magnetic targeting chemotherapy.

Zn2+ Ion Surface Enrichment in Doped Iron Oxide Nanoparticles Leads to Charge Carrier Density Enhancement

Here, we report the development of monodisperse Zn-doped iron oxide nanoparticles (NPs) with different amounts of Zn (Zn _x Fe_3-x O₄, 0 < x < 0.43) by thermal decomposition of a mixture of zinc and iron oleates. The as-synthesized NPs show a considerable fraction of wüstite (FeO) which is transformed to spinel upon 2 h oxidation of the NP reaction solutions. At any Zn doping amounts, we observed the enrichment of the NP surface with Zn²⁺ ions, which is enhanced at higher Zn loadings. Such a distribution of Zn²⁺ ions is attributed to the different thermal decomposition profiles of Zn and Fe oleates, with Fe oleate decomposing at much lower temperature than that of Zn oleate. The decomposition of Zn oleate is, in turn, catalyzed by a forming iron oxide phase. The magnetic properties were found to be strongly dependent on the Zn doping amounts, showing the saturation magnetization to decrease by 9 and 20% for x = 0.05 and 0.1, respectively. On the other hand, X-ray photoelectron spectroscopy near the Fermi level demonstrates that the Zn_0.05Fe_2.95O₄ sample displays a more metallic character (a higher charge carrier density) than undoped iron oxide NPs, supporting its use as a spintronic material.

Wetting transition in nanochannels for biomimetic free-blocking on-demand drug transport

Water wetting behavior in nanometer dimensions is of great importance to the signal transmission and substance transport of organisms, e.g., aquaporins on cell membranes. A biological channel can control the transport of water and ions by regulating channel wettability, which results from the transition between the intrinsic hydrophobic state and the stimulus-induced hydration state. Inspired by aquaporins in nature, herein, a biomimetic free-blocking on-demand delivery system is proposed, which is constructed by controlling the wettability of the inner surface of nanochannels of mesoporous silica nanoparticles (MSNs). Such a system is completely different from the traditional physically occluding pore controlled release system. It circumvents the use of other extra capping agents, thus overcoming the limitations of the traditional nano "gate" blockage system with inherent instability, poor plugging capability and low biocompatibility. Additionally, further applications in drug delivery have shown that this system can selectively release entrapped drugs in beta cells triggered by intracellular glucose in a controlled manner but not in normal cells. This hydrophobic gating drug delivery system with simple and effective performance provides a new opportunity for constructing a mass transport platform from the perspective of surface wettability.

Non-peptidic guanidinium-functionalized silica nanoparticles as selective mitochondria-targeting drug nanocarriers

We report on the design and fabrication of a Fe₃O₄ core-mesoporous silica nanoparticle shell (Fe₃O₄@MSNs)-based mitochondria-targeting drug nanocarrier. A guanidinium derivative (GA) was conjugated onto the Fe₃O₄@MSNs as the mitochondria-targeting ligand. The fabrication of the Fe₃O₄@MSNs and their functionalization with GA were carried out by the sol-gel polymerization of alkoxysilane groups. Doxorubicin (DOX), an anti-cancer drug, was loaded into the pores of a GA-attached Fe₃O₄@MSNs due to both its anti-cancer properties and to allow for the fluorescent visualization of the nanocarriers. The selective and efficient mitochondria-targeting ability of a DOX-loaded GA-Fe₃O₄@MSNs (DOX/GA-Fe₃O₄@MSNs) was demonstrated by a co-localization study, transmission electron microscopy, and a fluorometric analysis on isolated mitochondria. It was found that the DOX/GA-Fe₃O₄@MSNs selectively accumulated into mitochondria within only five minutes; to the best of our knowledge, this is the shortest accumulation time reported for mitochondria targeting systems. Moreover, 2.6 times higher amount of DOX was accumulated in mitochondria by DOX/GA-Fe₃O₄@MSNs than by DOX/TPP-Fe₃O₄@MSNs. A cell viability assay indicated that the DOX/GA-Fe₃O₄@MSNs have high cytotoxicity to cancer cells, whereas the GA-Fe₃O₄@MSNs without DOX are non-cytotoxic; this indicates that the DOX/GA-Fe₃O₄@MSNs have great potential for use as biocompatible and effective mitochondria-targeting nanocarriers for cancer therapy.

Tracking embryonic hematopoietic stem cells to the bone marrow: nanoparticle options to evaluate transplantation efficiency

BACKGROUND

As the prevalence of therapeutic approaches involving transplanted cells increases, so does the need to noninvasively track the cells to determine their homing patterns. Of particular interest is the fate of transplanted embryonic stem cell-derived hematopoietic progenitor cells (HPCs) used to restore the bone marrow pool following sublethal myeloablative irradiation. The early homing patterns of cell engraftment are not well understood at this time. Until now, longitudinal studies were hindered by the necessity to sacrifice several mice at various time points of study, with samples of the population of lymphoid compartments subsequently analyzed by flow cytometry or fluorescence microscopy. Thus, long-term study and serial analysis of the transplanted cells within the same animal was cumbersome, making difficult an accurate documentation of engraftment, functionality, and cell reconstitution patterns.

METHODS

Here, we devised a noninvasive, nontoxic modality for tracking early HPC homing patterns in the same mice longitudinally over a period of 9 days using mesoporous silica nanoparticles (MSNs) and magnetic resonance imaging.

RESULTS

This approach of potential translational importance helps to demonstrate efficient uptake of MSNs by the HPCs as well as retention of MSN labeling in vivo as the cells were traced through various organs, such as the spleen, bone marrow, and kidney. Altogether, early detection of the whereabouts and engraftment of transplanted stem cells may be important to the overall outcome. To accomplish this, there is a need for the development of new noninvasive tools.

CONCLUSIONS

Our data suggest that multifunctional MSNs can label viably blood-borne HPCs and may help document the distribution and homing in the host followed by successful reconstitution.

pH-responsive Drug Delivery Systems

Acidic microenvironments exist in selected organs, tissues, and subcellular compartments, as well as in many dysregulated pathological states. A continuous effort has been made to harness the unique acidic properties of biological tissues for site-specific delivery of drugs. Various pH-responsive drug delivery systems have been designed and developed with improved spatio-temporal control of payload delivery with enhanced efficacy. This chapter will focus on the recent advances in the development of pH-sensitive materials, mechanisms of payload release, and pH-triggered drug targeting in various biomedical applications.

An autonomous tumor-targeted nanoprodrug for reactive oxygen species-activatable dual-cytochrome c/doxorubicin antitumor therapy

The precise tumor cell-specific delivery of therapeutic proteins and the elimination of side effects associated with routine chemotherapeutic agents are two current critical considerations for tumor therapy. In this study, we report a reactive oxygen species (ROS)-activated yolk-shell nanoplatform for the tumor-specific co-delivery of cytochrome c (Cyt c) prodrug and doxorubicin, in which the bioactivity of Cyt c could be restored by the intracellular ROS-trigger and readily initiate the sequential doxorubicin release. The DOX-loaded lactobionic acid-modified yolk-shell mesoporous silica nanoparticles were first encapsulated with 4-nitrophenyl 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl carbonate (NBC)-modified Cyt c via boronic ester linkages, and functionalized again with lactobionic acid to further shield Cyt c and confer the selective tumor targeting against liver cancer cells. The key feature in this design is that by taking advantage of the boronic ester linkage, the cytotoxicity of Cyt c capped on the nanoparticle could be temporarily deactivated during blood transportation and rapidly restored upon exposure to the ROS-rich microenvironment within liver cancer cells, thereby simultaneously achieving the protein therapy and stimuli-responsive doxorubicin release. This study presents a novel strategy for the development of tumor-sensitive co-delivery nanoplatforms.

Mesoporous Silica and Organosilica Nanoparticles: Physical Chemistry, Biosafety, Delivery Strategies, and Biomedical Applications

Predetermining the physico-chemical properties, biosafety, and stimuli-responsiveness of nanomaterials in biological environments is essential for safe and effective biomedical applications. At the forefront of biomedical research, mesoporous silica nanoparticles and mesoporous organosilica nanoparticles are increasingly investigated to predict their biological outcome by materials design. In this review, it is first chronicled that how the nanomaterial design of pure silica, partially hybridized organosilica, and fully hybridized organosilica (periodic mesoporous organosilicas) governs not only the physico-chemical properties but also the biosafety of the nanoparticles. The impact of the hybridization on the biocompatibility, protein corona, biodistribution, biodegradability, and clearance of the silica-based particles is described. Then, the influence of the surface engineering, the framework hybridization, as well as the morphology of the particles, on the ability to load and controllably deliver drugs under internal biological stimuli (e.g., pH, redox, enzymes) and external noninvasive stimuli (e.g., light, magnetic, ultrasound) are presented. To conclude, trends in the biomedical applications of silica and organosilica nanovectors are delineated, such as unconventional bioimaging techniques, large cargo delivery, combination therapy, gaseous molecule delivery, antimicrobial protection, and Alzheimer's disease therapy.

One-Step Fast Synthesis of Nanoparticles for MRI: Coating Chemistry as the Key Variable Determining Positive or Negative Contrast

Iron oxide nanomaterial is a typical example of a magnetic resonance imaging probe for negative contrast. It has also been shown how this nanomaterial can be synthesized for positive contrast by modification of the composition and size of the core. However, the role of the organic coating in the relaxometric properties is largely unexplored. Here, maghemite nanoparticles with either excellent positive or very good negative contrast performance are obtained by modifying coating thickness while the core is kept unchanged. Different nanoparticles with tailored features as contrast agent according to the coating layer thickness have been obtained in a single-step microwave-driven synthesis by heating at different temperatures. A comprehensive analysis is conducted of how the composition and structure of the coating affects the final magnetic, relaxometric, and imaging performance. These results show how the organic coating plays a fundamental role in the intrinsic relaxometric parameters of iron oxide-based contrast media.

Free-Blockage Mesoporous Anticancer Nanoparticles Based on ROS-Responsive Wetting Behavior of Nanopores

To achieve an excellent delivery effect of drug, stimuli-responsive nano "gate" with physical blockage units is usually constructed on the surface of the mesoporous silica nanocarriers (MSNs). In nature, the aquaporins in cell membrane can control the transport of water molecules by regulating the channel wettability, which is resulted from the conformational change of amino acids in the channel. Inspired by this phonomenon, herein a new concept of free-blockage controlled release system is proposed, which is achieved by controlling the wettability of the internal surface of nanopores on MSNs. Such a new system is different from the physical-blockage controlled release system, which bypasses the use of nano "gate" and overcomes the limitations of traditional physical blockage system. Moreover, further studies have shown that the system can selectively release the entrapped doxorubicin in human breast adenocarcinoma (MCF-7) cells triggered by intracellular reactive oxygen species (ROS) but not in normalhuman umbilical vein endothelial cells (HUVECs) containing ROS with low levels. The wettability-determined free-blockage controlled release system is simple and effective, and it can also be triggered by intracellular biological stimuli, which provides a new approach for the future practical application of drug delivery and cancer therapy.

Polydopamine-Coated Manganese Carbonate Nanoparticles for Amplified Magnetic Resonance Imaging-Guided Photothermal Therapy

This study reports a multifunctional nanoparticle (NP) that can be used for amplified magnetic resonance image (MRI)-guided photothermal therapy (PTT) due to its surface coating with a polydopamine (PDA) shell. Importantly, by means of introducing the surface coating of PDA, large quantities of water can be trapped around the NPs allowing more efficient water exchange, leading to greatly improved MR contrast signals compared with those from NPs without the PDA coating. Further, a distinct photothermal effect can be obtained arising from the strong absorption of PDA in the near-infrared (NIR) region. By synthesizing multifunctional MnCO₃@PDA NPs, for example, we found that the longitudinal relaxivity (r₁) of MnCO₃ NPs can improve from 5.7 to 8.3 mM^-1 s^-1. Subsequently, in vitro MRI and PTT results verified that MnCO₃@PDA could serve as an excellent MRI/PTT theranostic agent. Furthermore, the MnCO₃@PDA NPs were applied as an MRI/PTT theranostic agent for in vivo MRI-guided photothermal ablation of tumors by intratumoral injection in 4T1 tumor-bearing mice. The MR imaging result shows a significantly bright MR image in the tumor site. The MnCO₃@PDA-mediated PTT result shows high therapeutic efficiency as a result of high photothermal conversion efficiency. The present strategy of amplified MRI-guided PTT based on PDA coating of NPs will be widely applicable to other multifunctional NPs.

Facilely synthesized pH-responsive fluorescent polymer dots entrapping doped and coupled doxorubicin for nucleus-targeted chemotherapy

The combination of physical doping and chemical coupling can significantly enhance the drug loading/release efficiency and improve the effect of cancer treatment. Based on this strategy, PEG-Dox doped and coupled PFBT polymer dots were optimized as a nucleus-targeted drug delivery platform for tumor therapy.