Controlled superficial assembly of DNA–amorphous calcium phosphate nanocomposite spheres for surface-mediated gene delivery

Calcium Phosphate-Based Biomaterials for Bone Repair

Traumatic, tumoral, and infectious bone defects are common in clinics, and create a big burden on patient's families and society. Calcium phosphate (CaP)-based biomaterials have superior properties and have been widely used for bone defect repair, due to their similarities to the inorganic components of human bones. The biological performance of CaPs, as a determining factor for their applications, are dependent on their physicochemical properties. Hydroxyapatite (HAP) as the most thermally stable crystalline phase of CaP is mostly used in the form of ceramics or composites scaffolds with polymers. Nanostructured CaPs with large surface areas are suitable for drug/gene delivery systems. Additionally, CaP scaffolds with hierarchical nano-/microstructures have demonstrated excellent ability in promoting bone regeneration. This review focuses on the relationships and interactions between the physicochemical/biological properties of CaP biomaterials and their species, sizes, and morphologies in bone regeneration, including synthesis strategies, structure control, biological behavior, and the mechanisms of CaP in promoting osteogenesis. This review will be helpful for scientists and engineers to further understand CaP-based biomaterials (CaPs), and be useful in developing new high-performance biomaterials for bone repair.

Bisphosphonate type-dependent cell viability suppressive effects of carbon nanohorn-calcium phosphate-bisphosphonate nanocomposites

In the process of bone metastasis, tumor cells spread to the bones to activate osteoclasts, which cause pathological bone resorption and destruction. Bisphosphonates (BPs) inhibit osteoclast activation to resorb bone, reducing bone pain and fracture. We previously developed a nanocomposite for potential localized treatment of bone metastasis by loading a BP compound, ibandronate, onto oxidized carbon nanohorns (OxCNHs), a next-generation drug carrier, using calcium phosphates (CaPs) as mediators to generate OxCNH-CaP-BP nanocomposites. The objective of the present study was to determine nanocomposite formation and biological properties of nanocomposites constructed from two BPs, zoledronate and pamidronate. In vitro tests using murine macrophages (RAW264.7 cells) and osteoclasts differentiated from RAW264.7 cells revealed that the resulting OxCNH-CaP-BP nanocomposites suppressed cell viability in a BP type-dependent manner and more effectively than OxCNHs or BPs alone. The mechanism for the potent and BP type-dependent suppression of cell viability by OxCNH-CaP-BP nanocomposites, based on their relative cellular uptake and reactive oxygen species generation, is also discussed. The present study supports the conclusions that BPs can be loaded onto OxCNHs using CaPs as mediators, and that OxCNH-CaP-BP nanocomposites are putative medicines for localized treatment of metastatic bone destruction.

Synthetic amorphous calcium phosphates (ACPs): preparation, structure, properties, and biomedical applications

Amorphous calcium phosphates (ACPs) represent a metastable amorphous state of other calcium orthophosphates (abbreviated as CaPO₄) possessing variable compositional but rather identical glass-like physical properties, in which there are neither translational nor orientational long-range orders of the atomic positions. In nature, ACPs of a biological origin are found in the calcified tissues of mammals, some parts of primitive organisms, as well as in the mammalian milk. Manmade ACPs can be synthesized in a laboratory by various methods including wet-chemical precipitation, in which they are the first solid phases, precipitated after a rapid mixing of aqueous solutions containing dissolved ions of Ca²⁺ and PO₄^3- in sufficient amounts. Due to the amorphous nature, all types of synthetic ACPs appear to be thermodynamically unstable and, unless stored in dry conditions or doped by stabilizers, they tend to transform spontaneously to crystalline CaPO₄, mainly to ones with an apatitic structure. This intrinsic metastability of the ACPs is of a great biological relevance. In particular, the initiating role that metastable ACPs play in matrix vesicle biomineralization raises their importance from a mere laboratory curiosity to that of a reasonable key intermediate in skeletal calcifications. In addition, synthetic ACPs appear to be very promising biomaterials both for manufacturing artificial bone grafts and for dental applications. In this review, the current knowledge on the occurrence, structural design, chemical composition, preparation, properties, and biomedical applications of the synthetic ACPs have been summarized.

Bio-multifunctional noncovalent porphyrin functionalized carbon-based nanocomposite

Herein, in a one-pot method, the reduced graphene oxide layers with the assistance of multiwalled carbon nanotubes were decorated to provide a suitable space for the in situ growth of CoNi₂S₄, and the porphyrins were incorporated into the layers as well to increase the sensitivity of the prepared nanostructure. The prepared nanocomposite can establish π-π interactions between the genetic material and on the surface of porphyrin rings. Also, hydrogen bonds between genetic domains and the porphyrin' nitrogen and the surface hydroxyl groups are probable. Furthermore, the potential donor-acceptor relationship between the d⁷ transition metal, cobalt, and the genetic material provides a suitable way to increase the interaction and gene loading , and transfections. The reason for this phenomenon was optimized to increase the EGFP by up to 17.9%. Furthermore, the sensing ability of the nanocomposite towards H₂O₂ was investigated. In this regard, the limit of detection of the H₂O₂ obtained 10 µM. Also, the in situ biosensing ability in the HEK-293 and PC12 cell lines was evaluated by the addition of PMA. The nanocomposite showed the ability to detect the released H₂O₂ after adding the minimum amount of 120 ng/mL of the PMA.

Fabrication of gold-calcium phosphate composite nanoparticles through coprecipitation mediated by amino-terminated polyethylene glycol

Calcium phosphate (CaP) nanoparticles immobilizing gold (Au) nanocrystals (Au-CaP composite nanoparticles) would be useful in diagnoses and/or treatments with Au nanocrystals. In this study, we achieved the rapid one-pot fabrication of such nanoparticles via coprecipitation in labile supersaturated CaP solutions by using appropriate Au sources, namely, Au nanocrystals coated with amino-terminated polyethylene glycol (PEG). In this process, amino groups at the PEG terminal played a crucial role in the coprecipitation with CaP through affinity interactions, and thus in the formation of Au-CaP composite nanoparticles; however, the molecular weight of the PEG chain was not a controlling factor in the coprecipitation. The important role of the functional groups at the PEG terminal was suggested by comparison with Au nanocrystals coated with carboxyl- and methoxy-terminated PEG, both of which barely coprecipitated with CaP and failed to form Au-CaP composite nanoparticles. Au nanocrystals coated with amino-terminated PEG were immobilized on the CaP nanoparticles, thereby regulating their size (∼140 nm in hydrodynamic diameter) and their dispersion in water. This coprecipitation process and the resulting Au-CaP composite nanoparticles have great potential in biomedical applications.

Biomolecule-assisted green synthesis of nanostructured calcium phosphates and their biomedical applications

Calcium phosphates (CaPs) are ubiquitous in nature and vertebrate bones and teeth, and have high biocompatibility and promising applications in various biomedical fields. Nanostructured calcium phosphates (NCaPs) are recognized as promising nanocarriers for drug/gene/protein delivery owing to their high specific surface area, pH-responsive degradability, high drug/gene/protein loading capacity and sustained release performance. In order to control the structure and surface properties of NCaPs, various biomolecules with high biocompatibility such as nucleic acids, proteins, peptides, liposomes and phosphorus-containing biomolecules are used in the synthesis of NCaPs. Moreover, biomolecules play important roles in the synthesis processes, resulting in the formation of various NCaPs with different sizes and morphologies. At room temperature, biomolecules can play the following roles: (1) acting as a biocompatible organic phase to form biomolecule/CaP hybrid nanostructured materials; (2) serving as a biotemplate for the biomimetic mineralization of NCaPs; (3) acting as a biocompatible modifier to coat the surface of NCaPs, preventing their aggregation and increasing their colloidal stability. Under heating conditions, biomolecules can (1) control the crystallization process of NCaPs by forming biomolecule/CaP nanocomposites before heating; (2) prevent the rapid and disordered growth of NCaPs by chelating with Ca2+ ions to form precursors; (3) provide the phosphorus source for the controlled synthesis of NCaPs by using phosphorus-containing biomolecules. This review focuses on the important roles of biomolecules in the synthesis of NCaPs, which are expected to guide the design and controlled synthesis of NCaPs. Moreover, we will also summarize the biomedical applications of NCaPs in nanomedicine and tissue engineering, and discuss their current research trends and future prospects.

Dendrimer-grafted bioreducible polycation/DNA multilayered films with low cytotoxicity and high transfection ability

Controlled release of incorporated foreign DNA from multilayered films plays an important role in surface-mediated gene delivery. Herein, multilayered polyelectrolyte complex thin films, composed of dendrimer-grafted bio-reducible cationic poly(disulfide amine) and plasmid DNA, were fabricated via layer-by-layer (LBL) assembly for in vitro localized gene delivery. The UV absorbance and thickness of the LBL films were found to have linear correlation with the numbers of poly(disulfide amine)/DNA bilayers. Although LBL films were stable in PBS buffer, their degradation could be triggered by reducing agents (i.e. glutathione, GSH). The degradation rate of the films is directly proportional to the GSH concentration, which in turn affected the corresponding gene expression. All poly(disulfide amine)/DNA films exhibited lower cytotoxicity and higher transfection activity in comparison with PEI/DNA multilayered films. Moreover, LBL films showed the highest transfection efficiency in the presence of 2.5 mM GSH when cultured with 293T cells, with ~36% GFP-positive 293T cells after 5-days of co-culture. These DNA-containing reducible films could potentially be useful in gene therapy and tissue engineering by controlling the release of incorporated DNA.

Preliminary in vivo magnetofection data using magnetic calcium phosphate nanoparticles immobilizing DNA and iron oxide nanocrystals

The data reported herein are in association with our research article entitled "Rapid one-pot fabrication of magnetic calcium phosphate nanoparticles immobilizing DNA and iron oxide nanocrystals using injection solutions for magnetofection and magnetic targeting" (Shubhra et al. 2017) [1]. This article reports morphological and gene delivery (in vitro and preliminary in vivo) data of those calcium phosphate (CaP) naonparticles (NPs) with various iron oxide (IO) contents, named as CaP-Fe(1), CaP-Fe(2), CaP-Fe(3), CaP-Fe(4), and CaP-Fe(5), which were prepared via coprecipitation in supersaturated CaP solutions with nominal Fe concentrations 6.97, 13.94, 27.87, 55.74, and 139.35 μg/mL, respectively. Morphological data of four different NPs: CaP-Fe(1), CaP-Fe(2), CaP-Fe(4), and CaP-Fe(5) are shown here. Data of the luciferase reporter gene expression assay show the effects of the coprecipitation time and the dosage of the CaP-Fe(3) NPs on gene expression levels of CHO-K1 cells transfected by the NPs without external magnetic field. It is demonstrated using digital and microscopic images that the CaP-Fe(3) NPs localize near the periphery of the external magnet that was placed under the cell culture plate. Using the CaP-Fe(3) NPs, animal experiments were conducted to obtain preliminary in vivo magnetofection data.

Facile one-pot fabrication of calcium phosphate-based composite nanoparticles as delivery and MRI contrast agents for macrophages

We developed a facile one-pot fabrication process for magnetic iron oxide-calcium phosphate (IO-CaP) composite nanoparticles via coprecipitation in labile supersaturated CaP solutions containing IO nanocrystals. All the source solutions used were clinically approved for injection, including water and magnetic IO nanocrystals (ferucarbotran, used as a negative magnetic resonance imaging (MRI) contrast agent). This ensured that the resulting nanoparticles were pathogen- and endotoxin-free. The dispersants used were clinically approved heparin sodium (heparin) or adenosine triphosphate disodium hydrate (ATP), which were added to the IO-containing labile supersaturated CaP solutions. Both heparin and ATP coprecipitated with CaP and ferucarbotran to form heparin- and ATP-modified IO-CaP nanoparticles, respectively, with a hydrodynamic diameter of a few hundred nanometers. Both the resulting nanoparticles exhibited relatively large negative zeta potentials, caused by the negatively charged functional groups in heparin and ATP, which improved the particle dispersibility when compared to non-modified IO-CaP nanoparticles. The heparin-modified IO-CaP nanoparticles were effectively ingested by murine macrophages (RAW264.7) without showing significant cytotoxicity but barely ingested by non-phagocytotic human umbilical vein endothelial cells, indicating the potential of these nanoparticles for targeted delivery to macrophages. The heparin-modified IO-CaP nanoparticles exhibited a negative contrast enhancing ability for MRI. Our results show that IO-CaP nanoparticles have potential as delivery and MRI contrast agents for macrophages.

Bioactive Polymeric Materials for Tissue Repair

Bioactive polymeric materials based on calcium phosphates have tremendous appeal for hard tissue repair because of their well-documented biocompatibility. Amorphous calcium phosphate (ACP)-based ones additionally protect against unwanted demineralization and actively support regeneration of hard tissue minerals. Our group has been investigating the structure/composition/property relationships of ACP polymeric composites for the last two decades. Here, we present ACP's dispersion in a polymer matrix and the fine-tuning of the resin affects the physicochemical, mechanical, and biological properties of ACP polymeric composites. These studies illustrate how the filler/resin interface and monomer/polymer molecular structure affect the material's critical properties, such as ion release and mechanical strength. We also present evidence of the remineralization efficacy of ACP composites when exposed to accelerated acidic challenges representative of oral environment conditions. The utility of ACP has recently been extended to include airbrushing as a platform technology for fabrication of nanofiber scaffolds. These studies, focused on assessing the feasibility of incorporating ACP into various polymer fibers, also included the release kinetics of bioactive calcium and phosphate ions from nanofibers and evaluate the biorelevance of the polymeric ACP fiber networks. We also discuss the potential for future integration of the existing ACP scaffolds into therapeutic delivery systems used in the precision medicine field.

Calcium phosphate nanoparticles prepared from infusion fluids for stem cell transfection: process optimization and cytotoxicity analysis

The preparation of calcium phosphate nanoparticles from infusion fluids for gene delivery to stem cells and CHO-K1 cells is reported.