Predicting binding affinities of nitrogen-containing bisphosphonates on hydroxyapatite surface by molecular dynamics

A Comparative Study of Ultrasmall Calcium Carbonate Nanoparticles for Targeting and Imaging Atherosclerotic Plaque

Atherosclerosis is a complex disease that can lead to life-threatening events, such as myocardial infarction and ischemic stroke. Despite the severity of this disease, diagnosing plaque vulnerability remains challenging due to the lack of effective diagnostic tools. Conventional diagnostic protocols lack specificity and fail to predict the type of atherosclerotic lesion and the risk of plaque rupture. To address this issue, technologies are emerging, such as noninvasive medical imaging of atherosclerotic plaque with customized nanotechnological solutions. Modulating the biological interactions and contrast of nanoparticles in various imaging techniques, including magnetic resonance imaging, is possible through the careful design of their physicochemical properties. However, few examples of comparative studies between nanoparticles targeting different hallmarks of atherosclerosis exist to provide information about the plaque development stage. Our work demonstrates that Gd (III)-doped amorphous calcium carbonate nanoparticles are an effective tool for these comparative studies due to their high magnetic resonance contrast and physicochemical properties. In an animal model of atherosclerosis, we compare the imaging performance of three types of nanoparticles: bare amorphous calcium carbonate and those functionalized with the ligands alendronate (for microcalcification targeting) and trimannose (for inflammation targeting). Our study provides useful insights into ligand-mediated targeted imaging of atherosclerosis through a combination of in vivo imaging, ex vivo tissue analysis, and in vitro targeting experiments.

Nuclear Magnetic Resonance and Metadynamics Simulations Reveal the Atomistic Binding of l-Serine and O-Phospho-l-Serine at Disordered Calcium Phosphate Surfaces of Biocements

Interactions between biomolecules and structurally disordered calcium phosphate (CaP) surfaces are crucial for the regulation of bone mineralization by noncollagenous proteins, the organization of complexes of casein and amorphous calcium phosphate (ACP) in milk, as well as for structure-function relationships of hybrid organic/inorganic interfaces in biomaterials. By a combination of advanced solid-state NMR experiments and metadynamics simulations, we examine the detailed binding of O-phospho-l-serine (Pser) and l-serine (Ser) with ACP in bone-adhesive CaP cements, whose capacity of gluing fractured bone together stems from the close integration of the organic molecules with ACP over a subnanometer scale. The proximity of each carboxy, aliphatic, and amino group of Pser/Ser to the Ca²⁺ and phosphate species of ACP observed from the metadynamics-derived models agreed well with results from heteronuclear solid-state NMR experiments that are sensitive to the ¹³C-³¹P and ¹⁵N-³¹P distances. The inorganic/organic contacts in Pser-doped cements are also contrasted with experimental and modeled data on the Pser binding at nanocrystalline HA particles grown from a Pser-bearing aqueous solution. The molecular adsorption is driven mainly by electrostatic interactions between the negatively charged carboxy/phosphate groups and Ca²⁺ cations of ACP, along with H bonds to either protonated or nonprotonated inorganic phosphate groups. The Pser and Ser molecules anchor at their phosphate/amino and carboxy/amino moieties, respectively, leading to an extended molecular conformation across the surface, as opposed to an "upright standing" molecule that would result from the binding of one sole functional group.

Breast Cancer Bone Metastasis: A Narrative Review of Emerging Targeted Drug Delivery Systems

Bone is one of the most common metastatic sites among breast cancer (BC) patients. Once bone metastasis is developed, patients' survival and quality of life will be significantly declined. At present, there are limited therapeutic options for BC patients with bone metastasis. Different nanotechnology-based delivery systems have been developed aiming to specifically deliver the therapeutic agents to the bone. The conjugation of targeting agents to nanoparticles can enhance the selective delivery of various payloads to the metastatic bone lesion. The current review highlights promising and emerging advanced nanotechnologies designed for targeted delivery of anticancer therapeutics, contrast agents, photodynamic and photothermal materials to the bone to achieve the goal of treatment, diagnosis, and prevention of BC bone metastasis. A better understanding of various properties of these new therapeutic approaches may open up new landscapes in medicine towards improving the quality of life and overall survival of BC patients who experience bone metastasis.

A 3D Printed Composite Scaffold Loaded with Clodronate to Regenerate Osteoporotic Bone: In Vitro Characterization

Additive manufacturing (AM) is changing our current approach to the clinical treatment of bone diseases, providing new opportunities to fabricate customized, complex 3D structures with bioactive materials. Among several AM techniques, the BioCell Printing is an advanced, integrated system for material manufacture, sterilization, direct cell seeding and growth, which allows for the production of high-resolution micro-architectures. This work proposes the use of the BioCell Printing to fabricate polymer-based scaffolds reinforced with ceramics and loaded with bisphosphonates for the treatment of osteoporotic bone fractures. In particular, biodegradable poly(ε-caprolactone) was blended with hydroxyapatite particles and clodronate, a bisphosphonate with known efficacy against several bone diseases. The scaffolds' morphology was investigated by means of Scanning Electron Microscopy (SEM) and micro-Computed Tomography (micro-CT) while Energy Dispersive X-ray Spectroscopy (EDX) and X-ray Photoelectron Spectroscopy (XPS) revealed the scaffolds' elemental composition. A thermal characterization of the composites was accomplished by Thermogravimetric analyses (TGA). The mechanical performance of printed scaffolds was investigated under static compression and compared against that of native human bone. The designed 3D scaffolds promoted the attachment and proliferation of human MSCs. In addition, the presence of clodronate supported cell differentiation, as demonstrated by the normalized alkaline phosphatase activity. The obtained results show that the BioCell Printing can easily be employed to generate 3D constructs with pre-defined internal/external shapes capable of acting as a temporary physical template for regeneration of cancellous bone tissues.

A new alendronate doped HAP nanomaterial for Pb2+, Cu2+ and Cd2+ effect absorption

In this paper, a new nanobiomaterial, alendronate hydroxyapatite (AL-HAP), was synthesized by the conventional co-precipitation method with alendronate (AL) as dopant, and applied in the removal of heavy metal contaminants for the first time. The characterization results showed that the crystallinity of the AL-HAP nanocomposite biomaterials after doping has been greatly deteriorated, and the pore volume and pore size increased. When the doping amount of AL was 10 %, the maximum adsorption capacity of AL-HAP for Pb²⁺, Cd²⁺ and Cu²⁺ can reach 1431.8, 469 and 226.6 mg/g, respectively, which was much higher than that reported in other literature. Meanwhile, the adsorption mechanism of AL-HAP for heavy metal ions was discussed from both the views of experimental and Multiwfn program theoretical calculation based on density functional theory (DFT). Quantitative molecular surface analysis was carried out for the first time to study the minimum points and the positions of electrostatic potential (ESP) and average local ionization energy(ALIE), as well as the exact values, giving more accurate and reliable analysis conclusions for the reaction sites and binding mode. In addition, the independent gradient model (IGM) method was also firstly applied to investigate the interactions between AL and HAP or AL-HAP nanocomposite with metal ions. AL-HAP is a potential adsorption material for heavy metal wastewater treatment and soil remediation because of its advantages such as convenient synthesis, excellent adsorption performance and no secondary pollution.

Molecular docking and molecular dynamics simulation studies on the adsorption/desorption behavior of bone morphogenetic protein-7 on the β-tricalcium phosphate surface

The adsorption/desorption behavior, and conformational and orientational changes of proteins on the surface of biomaterials are significant parameters for understanding how biomaterials perform their biological functions. In this study, for the first time, the interactions between BMP-7 and β-TCP (001) surface models with different ion-rich terminations (Ca-rich and P-rich) were investigated by molecular dynamics simulation (MD) and steered molecular dynamics simulation (SMD). The results indicated that BMP-7 preferentially interacts with both Ca-rich and P-rich β-TCP (001) surfaces at its wrist epitope residues with certain conformational changes, which led to more exposure of BMP-7 knuckle epitope residues to the environment and facilitation for binding to the type II receptor. Compared to the P-rich surface, it is speculated that the Ca-rich surface was more conducive to BMP-7 signal transduction since the upright orientation of the protein adsorption would lead to smaller hindrance for receptor binding. This study provided more atomistic and molecular information for better understanding the process of Ca-P surfaces affecting BMP-7 biological properties and further interpreted the osteoinductive mechanism from the perspective of growth factor adsorption. Moreover, the docking screening method adopted in this study is of guiding significance to the design and development of bioactive materials.