Finely crafted quasi-core–shell gadolinium/layered double hydroxide hybrids for switching on/off bimodal CT/MRI contrasting nanodiagnostic platforms

Layered double hydroxide-based nanomaterials for biomedical applications

Against the backdrop of increased public health awareness, inorganic nanomaterials have been widely explored as promising nanoagents for various kinds of biomedical applications. Layered double hydroxides (LDHs), with versatile physicochemical advantages including excellent biocompatibility, pH-sensitive biodegradability, highly tunable chemical composition and structure, and ease of composite formation with other materials, have shown great promise in biomedical applications. In this review, we comprehensively summarize the recent advances in LDH-based nanomaterials for biomedical applications. Firstly, the material categories and advantages of LDH-based nanomaterials are discussed. The preparation and surface modification of LDH-based nanomaterials, including pristine LDHs, LDH-based nanocomposites and LDH-derived nanomaterials, are then described. Thereafter, we systematically describe the great potential of LDHs in biomedical applications including drug/gene delivery, bioimaging diagnosis, cancer therapy, biosensing, tissue engineering, and anti-bacteria. Finally, on the basis of the current state of the art, we conclude with insights on the remaining challenges and future prospects in this rapidly emerging field.

Topology dependent modification of layered double hydroxide for therapeutic and diagnostic platform

Layered double hydroxide is a family of two-dimensional materials with wide range of compositions. Recently, its ability to accommodate various chemical species and biocompatibility have been attracted in the biomedical applications to develop drug delivery system and nanodiagnostics. In this review, we categorized biomedical approaches of layered double hydroxide with respect to the three topologies of, namely, interlayer space, outer surface with particle edge, and the lattice points. There have been extensive researches on the intercalation of drug or tracing to make use of interlayer space of layered double hydroxide for drug stabilization, sustained release, cellular delivery and etc. Outer surface or edge has been utilized to immobilization of large therapeutic moieties and to attach tracing moiety. Lattice points consisting of various metal species could be utilized for the specific metal species like paramagnetic elements or radioisotopes. Based on these topologies in layered double hydroxide, both the synthetic routes and the achieved functionalities in terms of biomedical application will be discussed.

Physicochemical Properties and Hematocompatibility of Layered Double Hydroxide-Based Anticancer Drug Methotrexate Delivery System

A layered double hydroxide (LDH)-based anticancer delivery system was investigated in terms of crystalline phase, particle size, hydrodynamic radius, zeta potential, etc. through in vitro and in vivo study. Size controlled LDH with anticancer drug methotrexate (MTX) incorporation was successfully prepared through step-by-step hydrothermal reaction and ion-exchange reaction. The MTX-LDH was determined to have a neutral surface charge and strong agglomeration in the neutral aqueous condition due to the surface adsorbed MTX; however, the existence of proteins in the media dramatically reduced agglomeration, resulting in the hydrodynamic radius of MTX-LDH being similar to the primary particle size. The protein fluorescence quenching assay exhibited that MTX readily reduced the fluorescence of proteins, suggesting that the interaction between MTX and proteins was strong. On the other hand, MTX-LDH showed much less binding constant to proteins compared with MTX, implying that the protein interaction of MTX was effectively blocked by the LDH carrier. The in vivo hemolysis assay after intravenous injection of MTX-LDH showed neither significant reduction in red blood cell number nor membrane damage. Furthermore, the morphology of red blood cells in a mouse model did not change upon MTX-LDH injection. Scanning electron microscopy showed that the MTX-LDH particles were attached on the blood cells without serious denaturation of cellular morphology, taking advantage of the cell hitchhiking property.

Recent Advances of Bioresponsive Nano-Sized Contrast Agents for Ultra-High-Field Magnetic Resonance Imaging

The ultra-high-field magnetic resonance imaging (MRI) nowadays has been receiving enormous attention in both biomaterial research and clinical diagnosis. MRI contrast agents are generally comprising of T1-weighted and T2-weighted contrast agent types, where T1-weighted contrast agents show positive contrast enhancement with brighter images by decreasing the proton's longitudinal relaxation times and T2-weighted contrast agents show negative contrast enhancement with darker images by decreasing the proton's transverse relaxation times. To meet the incredible demand of MRI, ultra-high-field T2 MRI is gradually attracting the attention of research and medical needs owing to its high resolution and high accuracy for detection. It is anticipated that high field MRI contrast agents can achieve high performance in MRI imaging, where parameters of chemical composition, molecular structure and size of varied contrast agents show contrasted influence in each specific diagnostic test. This review firstly presents the recent advances of nanoparticle contrast agents for MRI. Moreover, multimodal molecular imaging with MRI for better monitoring is discussed during biological process. To fasten the process of developing better contrast agents, deep learning of artificial intelligent (AI) can be well-integrated into optimizing the crucial parameters of nanoparticle contrast agents and achieving high resolution MRI prior to the clinical applications. Finally, prospects and challenges are summarized.