Facile Formation of Gold-Nanoparticle-Loaded γ-Polyglutamic Acid Nanogels for Tumor Computed Tomography Imaging

Dendrimer nanoclusters loaded with gold nanoparticles for enhanced tumor CT imaging and chemotherapy via an amplified EPR effect

The design of efficient multifunctional nanomedicines to overcome adverse side effects within biological systems and to achieve desirable computed tomography (CT) imaging and therapeutics of tumors remains challenging. Herein, we report the design of multifunctional nanoclusters (NCs) based on generation 3 (G3) poly(amidoamine) (PAMAM) dendrimers. In brief, G3 dendrimers were crosslinked with 4,4'-dithiodibutryic acid (DA) to generate disulfide-bond-containing dendrimer nanoclusters (DNCs), functionalized with 1,3-propane sultone (1,3-PS) to be zwitterionic, in situ loaded with gold nanoparticles (Au NPs), and finally encapsulated with the drug doxorubicin (DOX). The designed DOX/Au@DNCs-PS possess a favorable colloidal stability with a hydrodynamic size of 249.4 nm, a redox-responsive drug release profile, and enhanced cellular uptake in vitro. We show that DOX/Au@DNCs-PS have a greater DOX penetration and growth inhibition of three-dimensional (3D) tumor spheroids than the single dendrimer counterpart in vitro. Furthermore, the developed Au@DNCs-PS enable a better Au-mediated X-ray attenuation property than the single dendrimer counterpart material. Likely due to the amplified enhanced permeability and retention (EPR) effect, the created Au@DNCs-PS and DOX/Au@DNCs-PS enable better CT imaging and chemotherapeutic effect of a mouse breast tumor model, respectively, than the single dendrimer counterparts. With its proven biocompatibility, the constructed formulation may hold promising potential for development for different cancer nanomedicine applications.

Nanogels: Recent Advances in Synthesis and Biomedical Applications

In the context of advanced nanomaterials research, nanogels (NGs) have recently gained broad attention for their versatility and promising biomedical applications. To date, a significant number of NGs have been developed to meet the growing demands in various fields of biomedical research. Summarizing preparation methods, physicochemical and biological properties, and recent applications of NGs may be useful to help explore new directions for their development. This article presents a comprehensive overview of the latest NG synthesis methodologies, highlighting advances in formulation with different types of hydrophilic or amphiphilic polymers. It also underlines recent biomedical applications of NGs in drug delivery and imaging, with a short section dedicated to biosafety considerations of these innovative nanomaterials. In conclusion, this article summarizes recent innovations in NG synthesis and their numerous applications, highlighting their considerable potential in the biomedical field.

Biomimetic Dual-Target Theranostic Nanovaccine Enables Magnetic Resonance Imaging and Chemo/Chemodynamic/Immune Therapy of Glioma

Development of theranostic nanomedicines to tackle glioma remains to be challenging. Here, we present an advanced blood-brain barrier (BBB)-crossing nanovaccine based on cancer cell membrane-camouflaged poly(N-vinylcaprolactam) (PVCL) nanogels (NGs) incorporated with MnO2 and doxorubicin (DOX). We show that the disulfide bond-cross-linked redox-responsive PVCL NGs can be functionalized with dermorphin and imiquimod R837 through cell membrane functionalization. The formed functionalized PVCL NGs having a size of 220 nm are stable, can deplete glutathione, and responsively release both Mn2+ and DOX under the simulated tumor microenvironment to exert the chemo/chemodynamic therapy mediated by DOX and Mn2+, respectively. The combined therapy induces tumor immunogenic cell death to maturate dendritic cells (DCs) and activate tumor-killing T cells. Further, the nanovaccine composed of cancer cell membranes as tumor antigens, R837 as an adjuvant with abilities of DC maturation and macrophages M1 repolarization, and MnO2 with Mn2+-mediated stimulator of interferon gene activation of tumor cells can effectively act on both targets of tumor cells and immune cells. With the dermorphin-mediated BBB crossing, cell membrane-mediated homologous tumor targeting, and Mn2+-facilitated magnetic resonance (MR) imaging property, the designed NG-based theranostic nanovaccine enables MR imaging and combination chemo-, chemodynamic-, and imnune therapy of orthotopic glioma with a significantly decreased recurrence rate.

Multifunctional Low-Generation Dendrimer Nanogels as an Emerging Probe for Tumor-Specific CT/MR Dual-Modal Imaging

The development of nanoprobes that have amplified enhanced permeability and retention (EPR) effect is crucial for their precise cancer diagnosis performance. Here, we present the development of functional dendrimer-based nanogels (DNGs) with the generation three primary amine-terminated poly(amidoamine) (PAMAM) dendrimers (G3·NH₂) cross-linked by N,N'-bis(acryloyl) cystamine (BAC). The DNGs were prepared through a Michael addition reaction between G3·NH₂ dendrimers and BAC via an inverse microemulsion method and entrapped with gold nanoparticles (Au NPs) to form Au-DNGs. The Au-DNGs were sequentially modified with diethylenetriamine penta-acetic acid (DTPA)-gadolinium (Gd) complex, poly(ethylene glycol) (PEG)-linked arginine-glycine-aspartic (RGD) peptide, and 1,3-propanesultone (1,3-PS). The formed multifunctional RGD-Gd@Au-DNGs-PS (R-G@ADP) possessing an average diameter of 122 nm are colloidally stable and display a high X-ray attenuation coefficient, excellent r₁ relaxivity (9.13 mM^-1 s^-1), desired protein resistance rendered by the zwitterionic modification, and cytocompatibility. With the targeting specificity mediated by RGD and the much better tumor penetration capability than the counterpart material of single dendrimer-entrapped Au NPs, the developed multifunctional R-G@ADP enable targeted and enhanced computed tomography (CT)/magnetic resonance (MR) dual-modal imaging of a pancreatic tumor model in vivo. The current work demonstrates a unique design of targeted and zwitterionic DNGs with prolonged blood circulation time as an emerging nanoprobe for specific tumor CT/MR imaging through amplified passive EPR effect.

Polyethyleneimine-Based Drug Delivery Systems for Cancer Theranostics

With the development of nanotechnology, various types of polymer-based drug delivery systems have been designed for biomedical applications. Polymer-based drug delivery systems with desirable biocompatibility can be efficiently delivered to tumor sites with passive or targeted effects and combined with other therapeutic and imaging agents for cancer theranostics. As an effective vehicle for drug and gene delivery, polyethyleneimine (PEI) has been extensively studied due to its rich surface amines and excellent water solubility. In this work, we summarize the surface modifications of PEI to enhance biocompatibility and functionalization. Additionally, the synthesis of PEI-based nanoparticles is discussed. We further review the applications of PEI-based drug delivery systems in cancer treatment, cancer imaging, and cancer theranostics. Finally, we thoroughly consider the outlook and challenges relating to PEI-based drug delivery systems.

Multifunctional stimuli-responsive hybrid nanogels for cancer therapy: Current status and challenges

With cancer research shifting focus to achieving multifunctionality in cancer treatment strategies, hybrid nanogels are making a rapid rise to the spotlight as novel, multifunctional, stimuli-responsive, and biocompatible cancer therapeutic strategies. They can possess cancer cell-specific cytotoxic effects themselves, carry drugs or enzymes that can produce cytotoxic effects, improve imaging modalities, and target tumor cells over normal cells. Hybrid nanogels bring together a wide range of desirable properties for cancer treatment such as stimuli-responsiveness, efficient loading and protection of molecules such as drugs or enzymes, and effective crossing of cellular barriers among other properties. Despite their promising abilities, hybrid nanogels are still far from being used in the clinic, and their available data remains relatively limited. However, many studies can be done to facilitate this clinical transition. This review is critically summarizing and analyzing the recent information and progress on the use of hybrid nanogels particularly inorganic nanoparticle-based and organic nanoparticle-based hybrid nanogels in the field of oncology and future directions to aid in transferring those results to the clinic. This work concludes that the future of hybrid nanogels is greatly impacted by therapeutic and non-therapeutic factors. Therapeutic factors include the lack of hemocompatibility studies, acute and chronic toxicological studies, and information on agglomeration capability and extent, tumor heterogeneity, interaction with proteins in physiological fluids, endocytosis-exocytosis, and toxicity of the nanogels' breakdown products. Non-therapeutic factors include the lack of clear regulatory guidelines and standardized assays, limitations of animal models, and difficulties associated with good manufacture practices (GMP).

Construction of a double-responsive modified guar gum nanoparticles and its application in oral insulin administration

The use of intelligent insulin delivery systems has become more important for treating diabetes. In this study, a dual-responsive oral insulin delivery nanocarrier that responds to glucose and pH has been developed. First, the oleic acid hydrophobic modified guar gum (GG) was synthesized by the esterification reaction, and the γ-polyglutamic acid (γ-PGA) was coupled with GG by the amidation reaction. The obtained pH-responsive copolymer (γ-PGA-GG) was cross-linked by concanavalin A to obtain pH/glucose dual-responsive nanocarriers, and insulin was effectively loaded into the dual-responsive nanocarriers. The insulin-loaded nanoparticles can achieve effective pH and glucose responses, releasing insulin on demand. In vitro and in vivo studies demonstrated the dual-responsive nanoparticles can protect insulin against the pH changes in the digestive tract and deliver insulin into the body to exert a hypoglycemic effect. Moreover, the dual-responsive nanoparticles have significant potential to be employed for oral insulin delivery.

One stone, many birds: Recent advances in functional nanogels for cancer nanotheranostics

Inspired by the development of nanomedicine and nanotechnology, more and more possibilities in cancer theranostic have been provided in the last few years. Emerging therapeutic modalities like starvation therapy, chemodynamic therapy, and tumor oxygenation have been integrated with diagnosis, giving a plethora of theranostic nanoagents. Among all of them, nanogels (NGs) show superiority benefiting from their unique attributes: high stability, high water-absorption, large specific surface area, mechanical strength, controlled responsiveness, and high encapsulation capacity. There have been a vast number of investigations supporting various NGs combining drug delivery and multiple bioimaging techniques, encompassing photothermal imaging, photoacoustic imaging, fluorescent imaging, ultrasound imaging, magnetic resonance imaging, and computed tomography. This review summarizes recent advances in functional NGs for theranostic nanomedicine and discusses the challenges and future perspectives of this fast-growing field. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

Molecular Contrast Optical Coherence Tomography and Its Applications in Medicine

The growing need to understand the molecular mechanisms of diseases has prompted the revolution in molecular imaging techniques along with nanomedicine development. Conventional optical coherence tomography (OCT) is a low-cost in vivo imaging modality that provides unique high spatial and temporal resolution anatomic images but little molecular information. However, given the widespread adoption of OCT in research and clinical practice, its robust molecular imaging extensions are strongly desired to combine with anatomical images. A range of relevant approaches has been reported already. In this article, we review the recent advances of molecular contrast OCT imaging techniques, the corresponding contrast agents, especially the nanoparticle-based ones, and their applications. We also summarize the properties, design criteria, merit, and demerit of those contrast agents. In the end, the prospects and challenges for further research and development in this field are outlined.

Translating Therapeutic Microgels into Clinical Applications

Microgels are crosslinked, water-swollen networks with a 10 nm to 100 µm diameter and can be modified chemically or biologically to render them biocompatible for advanced clinical applications. Depending on their intended use, microgels require different mechanical and structural properties, which can be engineered on demand by altering the biochemical composition, crosslink density of the polymer network, and the fabrication method. Here, the fundamental aspects of microgel research and development, as well as their specific applications for theranostics and therapy in the clinic, are discussed. A detailed overview of microgel fabrication techniques with regards to their intended clinical application is presented, while focusing on how microgels can be employed as local drug delivery materials, scavengers, and contrast agents. Moreover, microgels can act as scaffolds for tissue engineering and regeneration application. Finally, an overview of microgels is given, which already made it into pre-clinical and clinical trials, while future challenges and chances are discussed. This review presents an instructive guideline for chemists, material scientists, and researchers in the biomedical field to introduce them to the fundamental physicochemical properties of microgels and guide them from fabrication methods via characterization techniques and functionalization of microgels toward specific applications in the clinic.

Macrophage Membrane-Camouflaged Responsive Polymer Nanogels Enable Magnetic Resonance Imaging-Guided Chemotherapy/Chemodynamic Therapy of Orthotopic Glioma

Development of innovative nanomedicine formulations to traverse the blood-brain barrier (BBB) for effective theranostics of glioma remains a great challenge. Herein, we report the creation of macrophage membrane-camouflaged multifunctional polymer nanogels coloaded with manganese dioxide (MnO₂) and cisplatin for magnetic resonance (MR) imaging-guided chemotherapy/chemodynamic therapy (CDT) of orthotopic glioma. Redox-responsive poly(N-vinylcaprolactam) (PVCL) nanogels (NGs) formed via precipitation polymerization were in situ loaded with MnO₂ and physically encapsulated with cisplatin to have a mean size of 106.3 nm and coated with macrophage membranes to have a good colloidal stability. The generated hybrid NGs display dual pH- and redox-responsive cisplatin and Mn(II) release profiles and can deplete glutathione (GSH) rich in tumor microenvironment through reaction with disulfide-containing cross-linkers within the NGs and MnO₂. The thus created Mn(II) enables enhanced CDT through a Fenton-like reaction and T₁-weighted MR imaging, while the loaded cisplatin not only exerts its chemotherapy effect but also promotes the reactive oxygen species generation to enhance the CDT efficacy. Importantly, the macrophage membrane coating rendered the hybrid NGs with prolonged blood circulation time and ability to traverse BBB for specific targeted chemotherapy/CDT of orthotopic glioma. Our study demonstrates a promising self-adaptive and cooperative NG-based nanomedicine platform for highly efficient theranostics of glioma, which may be extended to tackle other difficult cancer types.

Core-Shell Tecto Dendrimers Enable Enhanced Tumor MR Imaging through an Amplified EPR Effect

Development of nanoplatforms that can amplify the passive tumor targeting effect based on enhanced permeability and retention (EPR) effect is crucial for precision cancer nanomedicine applications. Herein, we present the development of core-shell tecto dendrimers (CSTDs) as a platform for enhanced tumor magnetic resonance (MR) imaging through an amplified EPR effect. In this work, poly(amidoamine) (PAMAM) dendrimers of generation 5 (G5) were decorated with β-cyclodextrin (CD) and then assembled with G3 PAMAM dendrimers premodified with adamantane (Ad) via supramolecular recognition of CD and Ad. The formed G5-CD/Ad-G3 CSTDs were conjugated with tetraazacyclododecane tetraacetic acid (DOTA)-Gd(III) chelators and further acetylated to neutralize the remaining CSTD periphery amines. We reveal that the formed CSTD.NHAc-DOTA(Gd) (CSTD-D-Gd) complexes have a narrow size distribution and satisfactory colloidal stability, and are cytocompatible within the concentration range studied. Compared to the single dendrimer counterpart of G5.NHAc-DOTA(Gd) (G5-D-Gd) complexes, the CSTD-D-Gd complexes with a higher molecular weight and volume possess a longer rotation correlation time, hence having a longitudinal relaxivity (r₁) of 7.34 mM^-1 s^-1, which is 1.5 times larger than that of G5-D-Gd complexes (4.92 mM^-1 s^-1). More importantly, the CSTD-D-Gd complexes display better permeability in the three-dimensional (3D) cell spheroids in vitro through fluorescence imaging and a more significant EPR effect for improved tumor MR imaging in vivo than the G5-DOTA-Gd complexes. The generated CSTD-D-Gd complexes may be adopted for enhanced tumor MR imaging through an amplified passive EPR effect and also be further extended for different cancer theranostic applications.

A novel multimodal nanoplatform for targeting tumor necrosis

Peri-necrotic tumor regions have been found to be a source of cancer stem cells (CSC), important in tumor recurrence. Necrotic and peri-necrotic tumor zones have poor vascular supply, limiting effective exposure to systemically administered therapeutics. Therefore, there is a critical need to develop agents that can effectively target these relatively protected tumor areas. We have developed a multi-property nanoplatform with necrosis avidity, fluorescence imaging and X-ray tracking capabilities to evaluate its feasibility for therapeutic drug delivery. The developed nanoparticle consists of three elements: poly(ethylene glycol)-block-poly(ε-caprolactone) as the biodegradable carrier; hypericin as a natural compound with fluorescence and necrosis avidity; and gold nanoparticles for X-ray tracking. This reproducible nanoparticle has a hydrodynamic size of 103.9 ± 1.7 nm with a uniform spherical morphology (polydispersity index = 0.12). The nanoparticle shows safety with systemic administration and a stable 30 day profile. Intravenous nanoparticle injection into a subcutaneous tumor-bearing mouse and intra-arterial nanoparticle injection into rabbits bearing VX2 orthotopic liver tumors resulted in fluorescence and X-ray attenuation within the tumors. In addition, ex vivo and histological analysis confirmed the accumulation of hypericin and gold in areas of necrosis and peri-necrosis. This nanoplatform, therefore, has the potential to enhance putative therapeutic drug delivery to necrotic and peri-necrotic areas, and may also have an application for monitoring early response to anti-tumor therapies.

Au-Hyp-NP developed by encapsulation of gold and hypericin into PEG-PCL nanoplatform for fluorescence and X-ray tracking with tumor necrosis targeting.

Recent Advances in Crosslinked Nanogel for Multimodal Imaging and Cancer Therapy

Nanomaterials have been widely applied in the field of cancer imaging and therapy. However, conventional nanoparticles including micelles and liposomes may suffer the issue of dissociation in the circulation. In contrast, crosslinked nanogels the structures of which are covalently crosslinked have better physiological stability than micelles and liposomes, making them more suitable for cancer theranostics. In this review, we summarize recent advances in crosslinked nanogels for cancer imaging and therapy. The applications of nanogels in drug and gene delivery as well as development of novel cancer therapeutic methods are first introduced, followed by the introduction of applications in optical and multimodal imaging, and imaging-guided cancer therapy. The conclusion and future direction in this field are discussed at the end of this review.

Colorimetric detection of Cr3+ ions in aqueous solution using poly(γ-glutamic acid)-stabilized gold nanoparticles

Detection of heavy metal ions in water is of paramount significance for environmental pollution control. Here, we report the use of γ-polyglutamic acid (γ-PGA)-stabilized gold nanoparticles (γ-PGA-Au NPs) as a probe to sense trivalent chromium (Cr3+) in aqueous solution. In our study, γ-PGA-Au NPs were first formed through one-step sodium borohydride reduction of Au salt in the presence of γ-PGA. The formed γ-PGA-Au NPs with a mean particle size of 4.6 nm show desirable colloidal stability and a significant color change from wine red to gray after exposure to Cr3+ ions, which is visible to the naked eye and easily detected by colorimetric assay using UV-vis spectrometry. The limit of detection of Cr3+ ions is 100 ppb by the naked eye and 0.2 ppb by UV-vis spectroscopy, respectively. We further show that the detection of Cr3+ using γ-PGA-Au NPs has excellent selectivity, and the recovery percentage is higher than 82% for different water samples such as lake water, river water, tap water or mineral water. Our study demonstrates that γ-PGA-Au NPs can be utilized as an efficient probe for colorimetric sensing of Cr3+ ions in a water environment.

Polyethylenimine Nanogels Incorporated with Ultrasmall Iron Oxide Nanoparticles and Doxorubicin for MR Imaging-Guided Chemotherapy of Tumors

Development of versatile nanoplatforms for cancer theranostics remains a hot topic in the area of nanomedicine. We report here a general approach to create polyethylenimine (PEI)-based hybrid nanogels (NGs) incorporated with ultrasmall iron oxide (Fe₃O₄) nanoparticles (NPs) and doxorubicin for T₁-weighted MR imaging-guided chemotherapy of tumors. In this study, PEI NGs were first prepared using an inverse emulsion approach along with Michael addition reaction to cross-link the NGs, modified with citric acid-stabilized ultrasmall Fe₃O₄ NPs through 1-ethyl-3-(3-(dimethylamino)propyl) carbodiimide hydrochloride (EDC) coupling, and physically loaded with anticancer drug doxorubicin (DOX). The formed hybrid NGs possess good water dispersibility and colloidal stability, excellent DOX loading efficiency (51.4%), pH-dependent release profile of DOX with an accelerated release rate under acidic pH, and much higher r₁ relaxivity (2.29 mM^-1 s^-1) than free ultrasmall Fe₃O₄ NPs (1.15 mM^-1 s^-1). In addition, in contrast to the drug-free NGs that possess good cytocompatibility, the DOX-loaded hybrid NGs display appreciable therapeutic activity and can be taken up by cancer cells in vitro. With these properties, the developed hybrid NGs enabled effective inhibition of tumor growth under the guidance of T₁-weighted MR imaging. The developed hybrid NGs may be applied as a versatile nanoplatform for MR imaging-guided chemotherapy of tumors.

Multifunctional PVCL nanogels with redox-responsiveness enable enhanced MR imaging and ultrasound-promoted tumor chemotherapy

Development of versatile nanoplatforms that simultaneously integrate therapeutic and diagnostic features for stimuli-responsive delivery to tumors remains a great challenge. In this work, we report a novel intelligent redox-responsive hybrid nanosystem composed of MnO₂ nanoparticles (NPs) and doxorubicin (DOX) co-loaded within poly(N-vinylcaprolactam) nanogels (PVCL NGs) for magnetic resonance (MR) imaging-guided and ultrasound-targeted microbubble destruction (UTMD)-promoted tumor chemotherapy. Methods: PVCL NGs were first synthesized via a precipitation polymerization method, decorated with amines using ethylenediamine, and loaded with MnO₂ NPs through oxidation with permanganate and DOX via physical encapsulation and Mn-N coordination bonding. The as-prepared DOX/MnO₂@PVCL NGs were well characterized. UTMD-promoted cellular uptake and therapeutic efficacy of the hybrid NGs were assessed in vitro, and a xenografted tumor model was used to test the NGs for MR imaging and UTMD-promoted tumor therapy in vivo. Results: The as-prepared DOX/MnO₂@PVCL NGs with a size of 106.8 nm display excellent colloidal stability, favorable biocompatibility, and redox-responsiveness to the reductive intracellular environment and tumor tissues having a relatively high glutathione (GSH) concentration that can trigger the synchronous release of Mn²⁺ for enhanced T₁-weighted MR imaging and DOX for enhanced cancer chemotherapy. Moreover, the DOX/MnO₂@PVCL NGs upon the UTMD-promotion exhibit a significantly enhanced tumor growth inhibition effect toward subcutaneous B16 melanoma owing to the UTMD-improved cellular internalization and tumor penetration. Conclusion: Our work thereby proposes a promising theranostic nanoplatform for stimuli-responsive T₁-weighted MR imaging-guided tumor chemotherapy.

Polyethylenimine-Based Nanogels for Biomedical Applications

Nanogels (NGs) are 3-dimensional (3D) networks composed of hydrophilic or amphiphilic polymer chains, allowing for effective and homogeneous encapsulation of drugs, genes, or imaging agents for biomedical applications. Polyethylenimine (PEI), possessing abundant positively charged amine groups, is an ideal platform for the development of NGs. A variety of effective PEI-based NGs have been designed and much effort has been devoted to study the relationship between the structure and function of the NGs. In particular, PEI-based NGs can be prepared either using PEI as the major NG component or using PEI as a crosslinker. This review reports the recent progresses in the design of PEI-based NGs for gene and drug delivery and for bioimaging applications with a target focus to tackle the diagnosis and therapy of cancer.

131I-labeled polyethylenimine-entrapped gold nanoparticles for targeted tumor SPECT/CT imaging and radionuclide therapy

Purpose: Polyethylenimine (PEI) has been widely used as a versatile template to develop multifunctional nanosystems for disease diagnosis and treatment. In this study, we manufactured iodine-131 (131I)-labeled PEI-entrapped gold nanoparticles (Au PENPs) as a novel nanoprobe for single-photon emission computed tomography/computed tomography (SPECT/CT) imaging and radionuclide therapy. Materials and methods: PEI was PEGylated and sequentially conjugated with Buthus martensii Karsch chlorotoxin (BmK CT, a tumor-specific ligand which can selectively bind to MMP2), 3-(4'-hydroxyphenyl)propionic acid-OSu (HPAO), and fluorescein isothiocyanate to form the multifunctional PEI template for entrapment of Au NPs. Then, the PEI surface was radiolabeled with 131I via HPAO to produce the novel nanoprobe (BmK CT-Au PENPs-131I). Results: The synthesized multifunctional Au PENPs before and after 131I radiolabeling were well-characterized as follows: structure, X-ray attenuation coefficient, colloid stability, cytocompatibility, and radiochemical stability in vitro. Furthermore, BmK CT-Au PENPs-131I were suitable for targeted SPECT/CT imaging and radionuclide therapy of tumor cells in vitro and in a xenograft tumor model in vivo. Conclusion: The developed multifunctional Au PENPs are a promising theranostic platform for targeted imaging and treatment of different MMP2-overexpressing tumors.

Manganese(iii)-chelated porphyrin microbubbles for enhanced ultrasound/MR bimodal tumor imaging through ultrasound-mediated micro-to-nano conversion

Manganese(iii)-chelated porphyrin microbubbles (MnP-MBs) were fabricated by self-assembly from a Mn-chelated porphyrin lipid followed by encapsulating perfluoropropane-an inert gas. The obtained MnP-MBs exhibited enhanced ultrasound imaging ability after intravenous injection. Under the guidance of ultrasound imaging, MnP-MBs could be converted into nanoparticles in situ with local tumor ultrasound disruption, achieving rapid tumor MRI contrast enhancement within 30 min at a very low Mn injection dose of 0.09 mg (1.65 μmol) per kg.

Evaluation of X-ray tomography contrast agents: A review of production, protocols, and biological applications

X-ray computed tomography is a strong tool that finds many applications both in medical applications and in the investigation of biological and nonbiological samples. In the clinics, X-ray tomography is widely used for diagnostic purposes whose three-dimensional imaging in high resolution helps physicians to obtain detailed image of investigated regions. Researchers in biological sciences and engineering use X-ray tomography because it is a nondestructive method to assess the structure of their samples. In both medical and biological applications, visualization of soft tissues and structures requires special treatment, in which special contrast agents are used. In this detailed report, molecule-based and nanoparticle-based contrast agents used in biological applications to enhance the image quality were compiled and reported. Special contrast agent applications and protocols to enhance the contrast for the biological applications and works to develop nanoparticle contrast agents to enhance the contrast for targeted drug delivery and general imaging applications were also assessed and listed.

Applications of nanoparticles in biomedical imaging

An urgent need for early detection and diagnosis of diseases continuously pushes the advancements of imaging modalities and contrast agents. Current challenges remain for fast and detailed imaging of tissue microstructures and lesion characterization that could be achieved via development of nontoxic contrast agents with longer circulation time. Nanoparticle technology offers this possibility. Here, we review nanoparticle-based contrast agents employed in most common biomedical imaging modalities, including fluorescence imaging, MRI, CT, US, PET and SPECT, addressing their structure related features, advantages and limitations. Furthermore, their applications in each imaging modality are also reviewed using commonly studied examples. Future research will investigate multifunctional nanoplatforms to address safety, efficacy and theranostic capabilities. Nanoparticles as imaging contrast agents have promise to greatly benefit clinical practice.

Enzyme/pH-sensitive polyHPMA-DOX conjugate as a biocompatible and efficient anticancer agent

In this study, to enhance the therapeutic function and reduce the side-effects of doxorubicin (DOX), a biodegradable N-(2-hydroxypropyl) methacrylamide (HPMA) polymer-DOX conjugate has been prepared through reversible addition fragmentation chain transfer (RAFT) polymerization and conjugation chemistry, and the anticancer agent DOX was covalently linked to the polymeric vehicle through a pH-responsive hydrazone bond. The cellular mechanisms of the conjugate were explored, and the therapeutic indexes were studied as well. The high molecular weight (MW) polymeric conjugate (94 kDa) was degraded into products with low MW (45 kDa) in the presence of lysosomal cathepsin B and also showed pH-responsive drug release behavior. In vitro cellular mechanism studies revealed that the polymeric conjugate was uptaken by the 4T1 cells, leading to cell apoptosis and cytotoxicity to cancer cells, while the polymeric conjugate demonstrated excellent in vivo biosafety even at a high dose. Compared to free DOX, the conjugate has a much longer half-life in pharmacokinetics and accumulates in tumors with a much higher amount. The conjugate therefore has a much greater in vivo anticancer efficacy against 4T1 xenograft tumors and shows subtle side-effects, which were confirmed via tumor size and weight, immunohistochemistry and histological studies. Overall, this polymeric conjugate may be used as an enzyme/pH-sensitive anticancer agent.

Multimodal Molecular Imaging: Current Status and Future Directions

Molecular imaging has emerged at the end of the last century as an interdisciplinary method involving in vivo imaging and molecular biology aiming at identifying living biological processes at a cellular and molecular level in a noninvasive manner. It has a profound role in determining disease changes and facilitating drug research and development, thus creating new medical modalities to monitor human health. At present, a variety of different molecular imaging techniques have their advantages, disadvantages, and limitations. In order to overcome these shortcomings, researchers combine two or more detection techniques to create a new imaging mode, such as multimodal molecular imaging, to obtain a better result and more information regarding monitoring, diagnosis, and treatment. In this review, we first describe the classic molecular imaging technology and its key advantages, and then, we offer some of the latest multimodal molecular imaging modes. Finally, we summarize the great challenges, the future development, and the great potential in this field.

A unique nanogel-based platform for enhanced dual mode tumor MR/CT imaging

Alginate nanogels loaded with gold nanoparticles and gadolinium can be synthesized via a nanoparticle-crosslinking approach for enhanced tumor MR/CT imaging.