Design of manganese-based nanomaterials for pharmaceutical and biomedical applications

In the past few years, manganese-based nanostructures have been extensively investigated in the biomedical field particularly to design highly biocompatible theranostics, which can not only act as efficient diagnostic imaging contrast agents but also deliver the drugs to the target sites. The nanoscale size, large surface area-to-volume ratio, availability of cheap precursors, flexibility to synthesize nanostructures with reproducible properties and high yield, and easy scale up are the major reasons for the attraction towards manganese nanostructures. Along with these properties, the nontoxic nature, pH-sensitive degradation, and easy surface functionalization are additional benefits for the use of manganese nanostructures in biomedical and pharmaceutical sciences. Therefore, in this review, we discuss the recent progress made in the synthesis of manganese nanostructures, describe the attempts made to modify their surfaces to impart biocompatibility and stability in biological fluids, and critically discuss their use in magnetic resonance imaging, drug and gene delivery, hyperthermia, photothermal/photodynamic, immunotherapy, biosensing and tumor diagnosis.

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.

N-Doped carbon dots for the fluorescence and colorimetry dual-mode detection of curcumin

Nitrogen doped carbon dots (N-CDs) were synthesized by a one-step hydrothermal method with dopamine and ethylenediamine. The as-prepared N-CDs were characterized via transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), fluorescence spectrophotometer, UV-Vis spectrophotometry and Fourier transform infrared spectroscopy (FTIR). The average particle dimension of the as-prepared N-CDs was 2.68 nm, and the best excitation and emission wavelengths were 405 nm and 535 nm, separately. N-CDs exhibits excellent selectivity and sensitivity to detect the curcumin (Cur), attaining a wider linear range of 97.5 nM-67.9 μM and a limit of detection (LOD) of as low as 94 nM. Interestingly, N-CDs can also give responsive signals of a visible colour change (yellow to red). Moreover, a novel fluorescent/colorimetric dual-mode method has been successfully employed for the determination of Cur in real samples with good recoveries (94%-110%) and precision (RSD = 0.3-2.9%).

Ultrasmall Fe@Fe3O4 nanoparticles as T1-T2 dual-mode MRI contrast agents for targeted tumor imaging

Targeted T₁-T₂ MRI contrast agents, which can eliminate the difficulty of image matching across multiple imaging instruments and permit specific localization of lesions, are promising candidates for more accurate diagnosis of tumors. In this study, ultrasmall Fe@Fe₃O₄ nanoparticles were designed and synthesized as T₁-T₂ dual-mode MRI contrast agents for accurate tumor imaging. First, to investigate the influence of nanoparticle size, Fe@Fe₃O₄ nanoparticles with diameters of 4, 8, and 12 nm were prepared, among which the 8 nm 3-(3,4-dihydroxyphenyl)propionic acid (DHCA)-modified nanoparticles exhibited the optimal T₁-T₂ dual-mode MRI performance. Next, to develop a tumor-targeted contrast agent, the DHCA-Fe@Fe₃O₄ nanoparticles were conjugated with the F56 peptide, which targets the vascular endothelial growth factor receptor, and the resulting F56-DHCA-Fe@Fe₃O₄ nanoparticles were found to exhibit good T₁-T₂ dual-mode imaging and tumor-targeting performance both in vitro and in vivo, indicating the nanoparticles represent a new research tool for accurate tumor diagnosis.

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.

Facile synthesis of Silicon quantum dot-Gadolinium: A potential fluorescent/T1-T2 multimodal imaging agent

Highly stable and multifunctional fluorescent quantum dots are particularly attractive in practical applications. Here, a new kind of ultra-small-sized silicon quantum dot-gadolinium (SiQD-Gd) was successfully fabricated by a newly-designed facile hydrothermal growth and chelating method. The obtained SiQD-Gd exhibited outstanding water dispersibility, stability and good fluorescent property with the quantum yield of 11.6%. SiQD-Gd displayed a low cytotoxicity in normal cell lines (HELF, HEK293F) and tumor cell lines (H1299, A549). Meanwhile, SiQD-Gd showed excellent magnetic resonance response with r₁ relaxation rate of 10.5 mmol L^-1·s^-1 and r₂ relaxation rate of 47.5 mmol L^-1·s^-1, which are 2.5 and 7.4 times enhanced comparing to that of the commercial MR agent Magnevist. In vivo studies showed significant contrast enhancement effect of its T₁- and T₂-weighted MR imaging. In addition, in vivo fluorescent imaging for mice and zebrafish indicated its potential applications in fluorescent tracking. Thus, the excellent multimodal imaging capacity and biocompatibility of SiQD-Gd make it a potential imaging agent for clinic applications.

Construction of Hybrid Alginate Nanogels Loaded with Manganese Oxide Nanoparticles for Enhanced Tumor Magnetic Resonance Imaging

Development of sensitive contrast agents for positive magnetic resonance (MR) imaging of biosystems still remains a great challenge. Herein, we report a facile process to construct hybrid alginate (AG) nanogels (NGs) loaded with manganese oxide (Mn₃O₄) nanoparticles (NPs) for enhanced tumor MR imaging. The obtained AG/PEI-Mn₃O₄ NGs with a mean size of 141.6 nm display excellent colloidal stability in aqueous solution and good cytocompatibility in the studied concentration range. Moreover, the hybrid NGs have a high r₁ relaxivity of 26.12 mM^-1 s^-1, which is about 19.5 times higher than that of PEI-Mn₃O₄ NPs with PEI surface amine acetylated (PEI.Ac-Mn₃O₄ NPs). Furthermore, the AG/PEI-Mn₃O₄ NGs presented longer blood circulation time and better tumor MR imaging performances in vivo than PEI.Ac-Mn₃O₄ NPs. With the good biosafety confirmed by histological examinations, the developed AG/PEI-Mn₃O₄ NGs may be potentially used as an efficient contrast agent for enhanced MR imaging of different biosystems.

Construction of iron oxide nanoparticle-based hybrid platforms for tumor imaging and therapy

This review highlights the most recent progress in the construction of iron oxide nanoparticle-based hybrid platforms for tumor imaging and therapy.

Aqueous-phase synthesis of iron oxide nanoparticles and composites for cancer diagnosis and therapy

The design and development of multifunctional nanoplatforms for biomedical applications still remains to be challenging. This review reports the recent advances in aqueous-phase synthesis of iron oxide nanoparticles (Fe₃O₄ NPs) and their composites for magnetic resonance (MR) imaging and photothermal therapy of cancer. Water dispersible and colloidally stable Fe₃O₄ NPs synthesized via controlled coprecipitation route, hydrothermal route and mild reduction route are introduced. Some of key strategies to improve the r₂ relaxivity of Fe₃O₄ NPs and to enhance their uptake by cancer cells are discussed in detail. These aqueous-phase synthetic methods can also be applied to prepare Fe₃O₄ NP-based composites for dual-mode molecular imaging applications. More interestingly, aqueous-phase synthesized Fe₃O₄ NPs are able to be fabricated as multifunctional theranostic agents for multi-mode imaging and photothermal therapy of cancer. This review will provide some meaningful information for the design and development of various Fe₃O₄ NP-based multifunctional nanoplatforms for cancer diagnosis and therapy.

New developments and clinical transition of hyaluronic acid-based nanotherapeutics for treatment of cancer: reversing multidrug resistance, tumour-specific targetability and improved anticancer efficacy

This review aims to overview and critically analyses recent developments in achieving tumour-specific delivery of anticancer agents, maximizing anticancer efficacy, and mitigating tumour progression and off-target effects. Stemming from critical needs to develop target-specific delivery vehicles in cancer therapy, various hyaluronic acid (HA)-conjugated nanomedicines have been fabricated owing to their biocompatibility, safety, tumour-specific targetability of drugs and genes, and proficient interaction with cluster-determinant-44 (CD44) receptors over-expressed on the surface of tumour cells. HA-based conjugation or surface modulation of anticancer drugs encapsulated nanocarriers have shown promising efficacy against the various types of carcinomas of liver, breast, colorectal, pancreatic, lung, skin, ovarian, cervical, head and neck and gastric. The success of this emerging platform is assessed in achieving the rapid internalization of anticancer payloads into the tumour cells, impeding cancer cells division and proliferation, induction of cancer-specific apoptosis and prevention of metastasis (tumour progression). This review extends detailed insight into the engineering of HA-based nanomedicines, characterization, utilization for the diagnosis or treatment of CD44 over-expressing cancer subtypes and emphasizing the transition of nanomedicines to clinical cancer therapy.

A facile synthesis of size- and shape-controlled Gd(OH)3 nanoparticles and Gd(OH)3@Au core/shell nanostars

A facile hydrothermal route was developed to generate size- and shape-controlled (Gd(OH)₃) nanoparticles and polyethylenimine-stabilized Gd(OH)₃@Au core/shell nanostars with photothermal properties.

Core@shell Fe3O4@Mn2+-doped NaYF4:Yb/Tm nanoparticles for triple-modality T1/T2-weighted MRI and NIR-to-NIR upconversion luminescence imaging agents

Core@shell structures of Fe₃O₄@Mn²⁺-doped NaYF₄:Yb/Tm nanoparticles (NPs) were prepared and then used for in vivo NIR to NIR (980 nm to 800 nm) imaging, and as dual-mode T₁/T₂-weighted MRI because of the co-existence of Fe₃O₄ and Mn²⁺ in the NPs.

Fe3O4–Mn3O4 nanocomposites with moderate magnetism for in vitro cytotoxicity studies on macrophages

Reduced magnetism of Fe₃O₄–Mn₃O₄ nanocomposites synthesised by alkaline hydrolysis has been explored for in vitro cytotoxicity studies on splenic macrophages.