Interaction of hydroxyapatite nanoparticles with endothelial cells: internalization and inhibition of angiogenesis in vitro through the PI3K/Akt pathway

In vitro/In vivo Evaluations of Hydroxyapatite Nanoparticles with Different Geometry

Purpose

Hydroxyapatite-based nanoparticles have found diverse applications in drug delivery, gene carriers, diagnostics, bioimaging and tissue engineering, owing to their ability to easily enter the bloodstream and target specific sites. However, there is limited understanding of the potential adverse effects and molecular mechanisms of these nanoparticles with varying geometries upon their entry into the bloodstream. Here, we used two commercially available hydroxyapatite nanoparticles (HANPs) with different geometries (less than 100 nm in size each) to investigate this issue.

Methods

First, the particle size, Zeta potential, and surface morphology of nano-hydroxyapatite were characterized. Subsequently, the effects of 2~2000 μM nano-hydroxyapatite on the proliferation, migration, cell cycle distribution, and apoptosis levels of umbilical vein endothelial cells were evaluated. Additionally, the impact of nanoparticles of various shapes on the differential expression of genes was investigated using transcriptome sequencing. Additionally, we investigated the in vivo biocompatibility of HANPs through gavage administration of nanohydroxyapatite in mice.

Results

Our results demonstrate that while rod-shaped HANPs promote proliferation in Human Umbilical Vein Endothelial Cell (HUVEC) monolayers at 200 μM, sphere-shaped HANPs exhibit significant toxicity to these monolayers at the same concentration, inducing apoptosis/necrosis and S-phase cell cycle arrest through inflammation. Additionally, sphere-shaped HANPs enhance SULT1A3 levels relative to rod-shaped HANPs, facilitating chemical carcinogenesis-DNA adduct signaling pathways in HUVEC monolayers. In vivo experiments have shown that while HANPs can influence the number of blood cells and comprehensive metabolic indicators in blood, they do not exhibit significant toxicity.

Conclusion

In conclusion, this study has demonstrated that the geometry and surface area of HANPs significantly affect VEC survival status and proliferation. These findings hold significant implications for the optimization of biomaterials in cell engineering applications.

Biocompatibility and Osteogenic Activity of Samarium-Doped Hydroxyapatite-Biomimetic Nanoceramics for Bone Regeneration Applications

In this study, we report on the development of hydroxyapatite (HAp) and samarium-doped hydroxyapatite (SmHAp) nanoparticles using a cost-effective method and their biological effects on a bone-derived cell line MC3T3-E1. The physicochemical and biological features of HAp and SmHAp nanoparticles are explored. The X-ray diffraction (XRD) studies revealed that no additional peaks were observed after the integration of samarium (Sm) ions into the HAp structure. Valuable information regarding the molecular structure and morphological features of nanoparticles were obtained by using Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The elemental composition obtained by using energy-dispersive X-ray spectroscopy (EDS) confirmed the presence of the HAp constituent elements, Ca, O, and P, as well as the presence and uniform distribution of Sm3+ ions. Both HAp and SmHAp nanoparticles demonstrated biocompatibility at concentrations below 25 μg/mL and 50 μg/mL, respectively, for up to 72 h of exposure. Cell membrane integrity was preserved following treatment with concentrations up to 100 μg/mL HAp and 400 μg/mL SmHAp, confirming the role of Sm3+ ions in enhancing the cytocompatibility of HAp. Furthermore, our findings reveal a positive, albeit limited, effect of SmHAp nanoparticles on the actin dynamics, osteogenesis, and cell migration compared to HAp nanoparticles. Importantly, the biological results highlight the potential role of Sm3+ ions in maintaining cellular balance by mitigating disruptions in Ca2+ homeostasis induced by HAp nanoparticles. Therefore, our study represents a significant contribution to the safety assessment of both HAp and SmHAp nanoparticles for biomedical applications focused on bone regeneration.

Biomaterial-Based Responsive Nanomedicines for Targeting Solid Tumor Microenvironments

Solid tumors are composed of a highly complex and heterogenic microenvironment, with increasing metabolic status. This environment plays a crucial role in the clinical therapeutic outcome of conventional treatments and innovative antitumor nanomedicines. Scientists have devoted great efforts to conquering the challenges of the tumor microenvironment (TME), in respect of effective drug accumulation and activity at the tumor site. The main focus is to overcome the obstacles of abnormal vasculature, dense stroma, extracellular matrix, hypoxia, and pH gradient acidosis. In this endeavor, nanomedicines that are targeting distinct features of TME have flourished; these aim to increase site specificity and achieve deep tumor penetration. Recently, research efforts have focused on the immune reprograming of TME in order to promote suppression of cancer stem cells and prevention of metastasis. Thereby, several nanomedicine therapeutics which have shown promise in preclinical studies have entered clinical trials or are already in clinical practice. Various novel strategies were employed in preclinical studies and clinical trials. Among them, nanomedicines based on biomaterials show great promise in improving the therapeutic efficacy, reducing side effects, and promoting synergistic activity for TME responsive targeting. In this review, we focused on the targeting mechanisms of nanomedicines in response to the microenvironment of solid tumors. We describe responsive nanomedicines which take advantage of biomaterials' properties to exploit the features of TME or overcome the obstacles posed by TME. The development of such systems has significantly advanced the application of biomaterials in combinational therapies and in immunotherapies for improved anticancer effectiveness.

Size-Dependent Cytotoxicity, Adhesion, and Endocytosis of Micro-/Nano-hydroxyapatite Crystals in HK-2 Cells

Nano-hydroxyapatite (nano-HAP) is often used as a crystal nest to induce calcium oxalate (CaOx) kidney stone formation, but the mechanism of interaction between HAP crystals of different properties and renal tubular epithelial cells remains unclear. In this study, the adhesion and endocytosis of HAP crystals with sizes of 40 nm, 70 nm, 1 μm, and 2 μm (HAP-40 nm, HAP-70 nm, HAP-1 μm, and HAP-2 μm, respectively) to human renal proximal tubular epithelial cells (HK-2) were comparatively studied. The results showed that HAP crystals of all sizes promoted the expression of osteopontin and hyaluronic acid on the cell surface, destroyed the integrity of the lysosomes, and induced the apoptosis and necrosis of cells. Nano-HAP crystals had a higher specific surface area, a smaller contact angle, a higher surface energy, and a lower Zeta potential than those of micro-HAP. Therefore, the abilities of HK-2 cells to adhere to and endocytose nano-HAP crystals were greater than their abilities to do the same for micro-HAP crystals. The order of the endocytosed crystals was as follows: HAP-40 nm > HAP-70 nm > HAP-1 μm > HAP-2 μm. The endocytosed HAP crystals entered the lysosomes. The more crystal endocytosis and adhesion there is, the more toxic it is to HK-2 cells. The results of this study showed that nanosized HAP crystals greatly promoted the formation of kidney stones than micrometer-sized HAP crystals.

Frontiers of Hydroxyapatite Composites in Bionic Bone Tissue Engineering

Bone defects caused by various factors may cause morphological and functional disorders that can seriously affect patient's quality of life. Autologous bone grafting is morbid, involves numerous complications, and provides limited volume at donor site. Hence, tissue-engineered bone is a better alternative for repair of bone defects and for promoting a patient's functional recovery. Besides good biocompatibility, scaffolding materials represented by hydroxyapatite (HA) composites in tissue-engineered bone also have strong ability to guide bone regeneration. The development of manufacturing technology and advances in material science have made HA composite scaffolding more closely related to the composition and mechanical properties of natural bone. The surface morphology and pore diameter of the scaffold material are more important for cell proliferation, differentiation, and nutrient exchange. The degradation rate of the composite scaffold should match the rate of osteogenesis, and the loading of cells/cytokine is beneficial to promote the formation of new bone. In conclusion, there is no doubt that a breakthrough has been made in composition, mechanical properties, and degradation of HA composites. Biomimetic tissue-engineered bone based on vascularization and innervation show a promising future.

Effective treatment of intractable diseases using nanoparticles to interfere with vascular supply and angiogenic process

Angiogenesis is a vital biological process involving blood vessels forming from pre-existing vascular systems. This process contributes to various physiological activities, including embryonic development, hair growth, ovulation, menstruation, and the repair and regeneration of damaged tissue. On the other hand, it is essential in treating a wide range of pathological diseases, such as cardiovascular and ischemic diseases, rheumatoid arthritis, malignancies, ophthalmic and retinal diseases, and other chronic conditions. These diseases and disorders are frequently treated by regulating angiogenesis by utilizing a variety of pro-angiogenic or anti-angiogenic agents or molecules by stimulating or suppressing this complicated process, respectively. Nevertheless, many traditional angiogenic therapy techniques suffer from a lack of ability to achieve the intended therapeutic impact because of various constraints. These disadvantages include limited bioavailability, drug resistance, fast elimination, increased price, nonspecificity, and adverse effects. As a result, it is an excellent time for developing various pro- and anti-angiogenic substances that might circumvent the abovementioned restrictions, followed by their efficient use in treating disorders associated with angiogenesis. In recent years, significant progress has been made in different fields of medicine and biology, including therapeutic angiogenesis. Around the world, a multitude of research groups investigated several inorganic or organic nanoparticles (NPs) that had the potential to effectively modify the angiogenesis processes by either enhancing or suppressing the process. Many studies into the processes behind NP-mediated angiogenesis are well described. In this article, we also cover the application of NPs to encourage tissue vascularization as well as their angiogenic and anti-angiogenic effects in the treatment of several disorders, including bone regeneration, peripheral vascular disease, diabetic retinopathy, ischemic stroke, rheumatoid arthritis, post-ischemic cardiovascular injury, age-related macular degeneration, diabetic retinopathy, gene delivery-based angiogenic therapy, protein delivery-based angiogenic therapy, stem cell angiogenic therapy, and diabetic retinopathy, cancer that may benefit from the behavior of the nanostructures in the vascular system throughout the body. In addition, the accompanying difficulties and potential future applications of NPs in treating angiogenesis-related diseases and antiangiogenic therapies are discussed.

Synthesis of Hybrid Polyphenol/Hydroxyapatite Nanomaterials with Anti-Radical Properties

Plant-derived natural bioactive molecules are of great therapeutic potential but, so far, their application in nanomedicine has scarcely been studied. This work aimed at comparing two methodologies, i.e., adsorption and in situ incorporation, to prepare hybrid polyphenol/hydroxyapatite nanoparticles. Two flavonoids, baicalin and its aglycone derivative baicalein, and two phenolic acids derived from caffeic acid, rosmarinic and chlorogenic acids, were studied. Adsorption of these polyphenols on pre-formed hydroxyapatite nanoparticles did not modify particle size or shape and loading was less than 10% (w/w). In contrast, presence of polyphenols during the synthesis of nanoparticles significantly impacted and sometimes fully inhibited hydroxyapatite formation but recovered particles could exhibit higher loadings. For most hybrid particles, release profiles consisted of a 24 h burst effect followed by a slow release over 2 weeks. Antioxidant properties of the polyphenols were preserved after adsorption but not when incorporated in situ. These results provide fruitful clues for the valorization of natural bioactive molecules in nanomedicine.

Nanoparticle Effects on Stress Response Pathways and Nanoparticle-Protein Interactions

Nanoparticles (NPs) are increasingly used in a wide variety of applications and products; however, NPs may affect stress response pathways and interact with proteins in biological systems. This review article will provide an overview of the beneficial and detrimental effects of NPs on stress response pathways with a focus on NP-protein interactions. Depending upon the particular NP, experimental model system, and dose and exposure conditions, the introduction of NPs may have either positive or negative effects. Cellular processes such as the development of oxidative stress, the initiation of the inflammatory response, mitochondrial function, detoxification, and alterations to signaling pathways are all affected by the introduction of NPs. In terms of tissue-specific effects, the local microenvironment can have a profound effect on whether an NP is beneficial or harmful to cells. Interactions of NPs with metal-binding proteins (zinc, copper, iron and calcium) affect both their structure and function. This review will provide insights into the current knowledge of protein-based nanotoxicology and closely examines the targets of specific NPs.

Synergistic effects of nanoattapulgite and hydroxyapatite on vascularization and bone formation in a rabbit tibia bone defect model

Hydroxyapatite (HA) is a promising scaffold material for the treatment of bone defects. However, the lack of angiogenic properties and undesirable mechanical properties (such as fragility) limits the application of HA. Nanoattapulgite (ATP) is a nature-derived clay mineral and has been proven to be a promising bioactive material for bone regeneration due to its ability to induce osteogenesis. In this study, polyvinyl alcohol/collagen/ATP/HA (PVA/COL/ATP/HA) scaffolds were printed. Mouse bone marrow mesenchymal stem/stromal cells (BMSCs) and human umbilical vein endothelial cells (HUVECs) were used in vitro to assess the biocompatibility and the osteogenesis and vascularization induction potentials of the scaffolds. Subsequently, in vivo micro-CT and histological staining were carried out to evaluate new bone formation in a rabbit tibial defect model. The in vitro results showed that the incorporation of ATP increased the printing fidelity and mechanical properties, with values of compressive strengths up to 200% over raw PC-H scaffolds. Simultaneously, the expression levels of osteogenic-related genes and vascularization-related genes were significantly increased after the incorporation of ATP. The in vivo results showed that the PVA/COL/ATP/HA scaffolds exhibited synergistic effects on promoting vascularization and bone formation. The combination of ATP and HA provides a promising strategy for vascularized bone tissue engineering.

Cell-Seeded Biomaterial Scaffolds: The Urgent Need for Unanswered Accelerated Angiogenesis

One of the most arduous challenges in tissue engineering is neovascularization, without which there is a lack of nutrients delivered to a target tissue. Angiogenesis should be completed at an optimal density and within an appropriate period of time to prevent cell necrosis. Failure to meet this challenge brings about poor functionality for the tissue in comparison with the native tissue, extensively reducing cell viability. Prior studies devoted to angiogenesis have provided researchers with some biomaterial scaffolds and cell choices for angiogenesis. For example, while most current angiogenesis approaches require a variety of stimulatory factors ranging from biomechanical to biomolecular to cellular, some other promising stimulatory factors have been underdeveloped (such as electrical, topographical, and magnetic). When it comes to choosing biomaterial scaffolds in tissue engineering for angiogenesis, key traits rush to mind including biocompatibility, appropriate physical and mechanical properties (adhesion strength, shear stress, and malleability), as well as identifying the appropriate biomaterial in terms of stability and degradation profile, all of which may leave essential trace materials behind adversely influencing angiogenesis. Nevertheless, the selection of the best biomaterial and cells still remains an area of hot dispute as such previous studies have not sufficiently classified, integrated, or compared approaches. To address the aforementioned need, this review article summarizes a variety of natural and synthetic scaffolds including hydrogels that support angiogenesis. Furthermore, we review a variety of cell sources utilized for cell seeding and influential factors used for angiogenesis with a concentrated focus on biomechanical factors, with unique stimulatory factors. Lastly, we provide a bottom-to-up overview of angiogenic biomaterials and cell selection, highlighting parameters that need to be addressed in future studies.

Inductive Materials for Regenerative Engineering

Regenerative engineering has pioneered several novel biomaterials to treat critical-sized bone injuries. However, despite significant improvement in synthetic materials research, some limitations still exist. The constraints correlated with the current grafting methods signify a treatment paradigm shift to osteoinductive regenerative engineering approaches. Because of their intrinsic potential, inductive biomaterials may represent alternative approaches to treating critical bone injuries. Osteoinductive scaffolds stimulate stem cell differentiation into the osteoblastic lineage, enhancing bone regeneration. Inductive biomaterials comprise polymers, calcium phosphate ceramics, metals, and graphene family materials. This review will assess the cellular behavior toward properties of inductive materials.

Investigation into the trophic transfer and acute toxicity of phosphorus-based nano-agromaterials in Caenorhabditis elegans

Biogenic phosphorus (P) based - nanomaterials (NMs) are currently being explored as nanofertilizers. In this study, the acute toxic effects and trophic transfer of multiple types of P-based NMs were examined on soil-dwelling nematode, Caenorhabditis elegans. The study involved four variants of nanohydroxyapatites (nHAPs) synthesized either via a biogenic or a chemical route and another NM, nanophosphorus (nP), biosynthesized from bulk rock phosphate (RP). The pristine NMs differed in their physicochemical properties with each possessing different shapes (biogenic nHAP: platelet-shaped, ˜35 nm; biogenic nP, ˜5-10 nm: dots; chemically synthesized nHAPs: spherical, ˜33 nm, rod, ˜80 nm and needle-shaped, ˜64 nm). The toxic effects of NMs' in C. elegans were assessed using survival, hatching and reproductive cycle as the key endpoints in comparison to bulk controls, calcium phosphate and RP. The interactions and potential uptake of fluorescent-tagged nHAP to E. coli OP50 and C. elegans were investigated using confocal microscopy. The transformation of NMs within the nematode gut was also explored using dynamic light scattering and electron microscopy. C. elegans exposed to all of the variants of nHAP and the nP had 88-100% survival and 82-100% hatch rates and insignificant effects on brood size as observed at the tested environmentally relevant concentrations ranging from 5 to 100 μg.mL^-1. Confocal microscopy confirmed the interaction and binding of fluorescent-tagged nHAP with the surface of E. coli OP50 and their trophic transfer and internalization into C. elegans. Interestingly, there was only a small reduction in the hydrodynamic diameter of the nHAP after their uptake into C. elegans and the transformed NMs did not induce any additional toxicity as evident by healthy brood sizes after 72 h. This study provides key information about the environmental safety of agriculturally relevant P-based NMs on non-target species.

Comparison of multi-walled carbon nanotubes and halloysite nanotubes on lipid profiles in human umbilical vein endothelial cells

Tubular nanomaterials (NMs), such as multi-walled carbon nanotubes (MWCNTs) and halloysite nanotubes (HNTs), may be used in biomedicine, but previous studies showed that MWCNTs induced toxicity to endothelial cells (ECs). However, the influence of tubular NMs on EC lipid profiles has gained little attention, probably because ECs are not traditionally considered to be involved in regulating lipid homeostasis. This study compared the different effects of MWCNTs and HNTs on lipid profile changes in human umbilical vein ECs (HUVECs). The results showed that MWCNTs but not HNTs of the same mass concentrations induced cytotoxicity, ultrastuctural changes and intracellular thiol depletion. Meanwhile, only MWCNTs promoted lipid accumulation due to the induction of ER stress leading to up-regulation of fatty acid synthase (FASN). Interestingly, lipidomics results showed that the main lipid classes induced by MWCNTs but not HNTs were ceramide (Cer) and phosphatidylinositol (PI), with most of the lipid classes unaltered or even decreased after NM exposure. Then, extra Cer and PI were added to explore the implications of increase of these lipids. Adding Cer promoted the cytotoxicity of MWCNTs to HUVECs, indicating the lipotoxic role of Cer. Whereas adding PI partially increased intracellular NO and decreased interleukin-6 (IL-6) release due to MWCNT exposure, indicating the signaling role of PI. These results indicated novel roles of lipid dysfunction in NM-induced toxicity to ECs, even though ECs are not the professional cells for controlling lipid homeostasis.

Application of nanoparticles in bone tissue engineering; a review on the molecular mechanisms driving osteogenesis

The introduction of nanoparticles into bone tissue engineering strategies is beneficial to govern cell fate into osteogenesis and the regeneration of large bone defects. The present study explored the role of nanoparticles to advance osteogenesis with a focus on the cellular and molecular pathways involved. Pubmed, Pubmed Central, Embase, Scopus, and Science Direct databases were explored for those published articles relevant to the involvement of nanoparticles in osteogenic cellular pathways. As multifunctional compounds, nanoparticles contribute to scaffold-free and scaffold-based tissue engineering strategies to progress osteogenesis and bone regeneration. They regulate inflammatory responses and osteo/angio/osteoclastic signaling pathways to generate an osteogenic niche. Besides, nanoparticles interact with biomolecules, enhance their half-life and bioavailability. Nanoparticles are promising candidates to promote osteogenesis. However, the interaction of nanoparticles with the biological milieu is somewhat complicated, and more considerations are recommended on the employment of nanoparticles in clinical applications because of NP-induced toxicities.

Potential Osteoinductive Effects of Hydroxyapatite Nanoparticles on Mesenchymal Stem Cells by Endothelial Cell Interaction

Nano-hydroxyapatite (nano-HA) has attracted substantial attention in the field of regenerative medicine. Endothelial cell (EC)-mesenchymal stem cell (MSC) interactions are necessary for bone reconstruction, but the manner in which nano-HA interacts in this process remains unknown. Herein, we investigated the cytotoxicity and osteoinductive effects of HA nanoparticles (HANPs) on MSCs using an indirect co-culture model mediated by ECs and highlighted the underlying mechanisms. It was found that at a subcytotoxic dose, HANPs increased the viability and expression of osteoblast genes, as well as mineralized nodules and alkaline phosphatase production of MSCs. These phenomena relied on HIF-1α secreted by ECs, which triggered the ERK1/2 signaling cascade. In addition, a two-stage cell-lineage mathematical model was established to quantitatively analyze the impact of HIF-1α on the osteogenic differentiation of MSCs. It demonstrated that HIF-1α exerted a dose-dependent stimulatory effect on the osteogenic differentiation rate of MSCs up to 1500 pg/mL, which was in agreement with the above results. Our data implied that cooperative interactions between HANPs, ECs, and MSCs likely serve to stimulate bone regeneration. Furthermore, the two-stage cell-lineage model is helpful in vitro system for assessing the potential influence of effector molecules in bone tissue engineering.

Potential roles of Kruppel-like factors in mediating adverse vascular effects of nanomaterials: A review

The development of nanotechnology leads to the exposure of human beings to nanomaterials (NMs), and there is a health concern about the adverse vascular effects of NMs. Current data from epidemiology, controlled human exposure, and animal studies suggested that exposure to NMs could induce cardiopulmonary effects. In support of in vivo findings, in vitro studies showed that direct contact of vascular cells with NMs could induce endothelial cell (EC) activation and promote macrophage foam cell formation, although only limited studies showed that NMs could damage vascular smooth muscle cells and promote their phenotypic switch. It has been proposed that NMs induced adverse vascular effects via different mechanisms, but it is still necessary to understand the upstream events. Kruppel-like factors (KLFs) are a set of C2H2 zinc finger transcription factors (TFs) that can regulate various aspects of vascular biology, but currently, the roles of KLF2 in mediating the adverse vascular effects of NMs have gained little attention by toxicologists. This review summarized current knowledge about the adverse vascular effects of NMs and proposed the potential roles of KLFs in mediating these effects based on available data from toxicological studies as well as the current understanding about KLFs in vascular biology. Finally, the challenges in investigating the role of KLFs in vascular toxicology were also summarized. Considering the important roles of KLFs in vascular biology, further studies are needed to understand the influence of NMs on KLFs and the downstream events.

An in vitro chondro-osteo-vascular triphasic model of the osteochondral complex

The generation of engineered models of the osteochondral complex to study its pathologies and develop possible treatments is hindered by the distinctly different properties of articular cartilage and subchondral bone, with the latter characterized by vascularization. In vitro models of the osteochondral complex have been mainly engineered as biphasic constructs containing just cartilage and bone cells, a condition very dissimilar from the in vivo environment. The different cellular components of the osteochondral complex are governed by interacting biochemical signaling; hence, to study the crosstalk among chondrocytes, osteoblasts, and endothelial cells, we have developed a novel triphasic model of the osteochondral tissue interface. Wet-spun poly(ε-caprolactone) (PCL) and PCL/hydroxyapatite (HA) scaffolds in combination with a methacrylated gelatin (gelMA) hydrogel were used as the polymeric backbone of the constructs. The scaffold components were engineered with human bone marrow derived mesenchymal stem cells (hMSCs) and human umbilical vein endothelial cells (HUVECs), and differentiated using a dual chamber microphysiological system (MPS) bioreactor that allows the simultaneous, separate flow of media of different compositions for induced differentiation of each compartment towards a cartilaginous or osseous lineage. Within the engineered Microphysiological Vascularized Osteochondral System, hMSCs showed spatially distinct chondrogenic and osteogenic markers in terms of histology and gene expression. HUVECs formed a stable capillary-like network in the engineered bone compartment and enhanced both chondrogenic and osteogenic differentiation of hMSCs, resulting in the generation of an in vitro system that mimics a vascularized osteochondral interface tissue.

The Morphology of Hydroxyapatite Nanoparticles Regulates Cargo Recognition in Clathrin-Mediated Endocytosis

The clathrin-associated protein adaptin-2 (AP2) is a distinctive member of the hetero-tetrameric clathrin adaptor complex family. It plays a crucial role in many intracellular vesicle transport pathways. The hydroxyapatite (HAp) nanoparticles can enter cells through clathrin-dependent endocytosis, induce apoptosis, and ultimately inhibit tumor metastasis. Exploring the micro process of the binding of AP2 and HAp is of great significance for understanding the molecular mechanism of HAp's anti-cancer ability. In this work, we used molecular modeling to study the binding of spherical, rod-shaped, and needle-shaped HAps toward AP2 protein at the atomic level and found that different nanoparticles' morphology can determine their binding specificity through electrostatic interactions. Our results show that globular HAp significantly changes AP2 protein conformation, while needle-shaped HAP has more substantial binding energy with AP2. Therefore, this work offers a microscopic picture for cargo recognition in clathrin-mediated endocytosis, clarifies the design principles and possible mechanisms of high-efficiency nano-biomaterials, and provides a basis for their potential anti-tumor therapeutic effects.

Osteosarcoma tissue-engineered model challenges oxidative stress therapy revealing promoted cancer stem cell properties

The use of oxidative stress generated by Cold Atmospheric Plasma (CAP) in oncology is being recently studied as a novel potential anti-cancer therapy. However, the beneficial effects of CAP for treating osteosarcoma have mostly been demonstrated in 2-dimensional cultures of cells, which do not mimic the complexity of the 3-dimensional (3D) bone microenvironment. In order to evaluate the effects of CAP in a relevant context of the human disease, we developed a 3D tissue-engineered model of osteosarcoma using a bone-like scaffold made of collagen type I and hydroxyapatite nanoparticles. Human osteosarcoma cells cultured within the scaffold showed a high capacity to infiltrate and proliferate and to exhibit osteomimicry in vitro. As expected, we observed significantly different functional behaviors between monolayer and 3D cultures when treated with Cold Plasma-Activated Ringer's Solution (PAR). Our data reveal that the 3D environment not only protects cells from PAR-induced lethality by scavenging and diminishing the amount of reactive oxygen and nitrogen species generated by CAP, but also favours the stemness phenotype of osteosarcoma cells. This is the first study that demonstrates the negative effect of PAR on cancer stem-like cell subpopulations in a 3D biomimetic model of cancer. These findings will allow to suitably re-focus research on plasma-based therapies in future.

A novel vertical aligned mesoporous silica coated nanohydroxyapatite particle as efficient dexamethasone carrier for potential application in osteogenesis

Bone defect is a common problem and inducing osteoblasts differentiation is the key process for the regenerative repair. Recently, the mesoporous silica (MS) coated nanohydroxyapatite particles nHA (nHA-MS) has shown enhanced intrinsic potency for bone regeneration, whereas whether the osteogenesis potency can be further enhanced after drug delivery has not been investigated. In this study, the nHA-MS was fabricated by a novel biphase stratification growth way. The cytotoxicity in MC3T3-E1 was validated by MTT assay, apoptosis analysis and cell cycle examination. The cell uptake was observed by confocal laser scanning microscope and transmission electron microscope respectively. After adsorption with dexamethasone (DEX), the osteogenic differentiation was determined both in vitro and in vivo. The synthesized nHA-MS showed a core-shell structure that the nanorod-like nHA was coated by a porous MS shell (~5 nm pores diameter, ~50 nm thickness). A dose-dependent cytotoxicity was observed and below 10 µg/ml was a safe concentration. The nHA-MS also showed efficient cell uptake efficiency and more efficient in DEX loading and release. After DEX adsorption, the nanoparticles exhibited enhanced osteogenic induction in MC3T3-E1 and rat calvarial bone defect regeneration. In conclusion, the nHA-MS is a favorable platform for drug delivery to obtain more enhanced osteogenesis capabilities.

Evaluating the Radiosensitization Effect of Hydroxyapatite Nanoparticles on Human Breast Adenocarcinoma Cell Line and Fibroblast

Background:

Nanohydroxyapatite (nHAP) exhibit anti-proliferative effects on various cancer cells. However, to date, there are only a few studies on the radiosensitization effect of nHAP. The present study aimed to investigate the possible enhancement of the radiosensitization effect of nHAP on human breast adenocarcinoma cancer (MCF-7) and fibroblast.

Methods:

nHAP was extracted from fish scales using the thermal alkaline method and characterized at Babol University of Medical Sciences (Babol, Iran) in 2017. The anti-proliferative and the radiosensitization effects of nHAP were investigated by 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-Diphenyltetrazolium Bromide (MTT), clonogenic assay, and apoptosis assay. MCF-7 cells and fibroblasts were incubated with different concentrations of nHAP and at different periods. The MTT solution was added and the absorbance was measured at 570 nm. The MCF-7 cells were exposed to 0, 1.5, 3.5, and 5 Gy X-ray irradiation and incubated for 10-14 days. The data were compared using the one-way analysis of variance (ANOVA) followed by the post hoc tests (Tukey’s method).

Results:

The results showed that nHAP significantly inhibited the growth of MCF-7 cells compared with controls (P<0.001), but the difference was not statistically significant for fibroblasts (P=0.686 at 400 µg/mL at 72 hours). After 48 hours, the proliferation of MCF-7 cells and fibroblasts was inhibited by about 81% and 34% at 400 µg/mL concentration, respectively. The radiosensitization enhancement factor for MCF-7 cells and fibroblasts at a dose of 3.5 Gy and 100 μg/mL concentration were 1.87 and 1.3, respectively.

Conclusion:

nHAP can be considered as a breast cancer radiosensitization agent with limited damage to the surrounding healthy tissue.

Size-Dependent Cytotoxicity of Hydroxyapatite Crystals on Renal Epithelial Cells

Background

Hydroxyapatite (HAP) is a common component of most idiopathic calcium oxalate (CaOx) stones and is often used as a nidus to induce the formation of CaOx kidney stones.

Methods

This work comparatively studies the cytotoxicity of four kinds of HAP crystals with different sizes (40 nm to 2 μm), namely, HAP-40 nm, HAP-70 nm, HAP-1 μm, and HAP-2 μm, on human renal proximal tubular epithelial cells (HK-2).

Results

HAP crystals reduce the viability and membrane integrity of HK-2 cells in a concentration-dependent manner and consequently cause cytoskeleton damage, cell swelling, increased intracellular reactive oxygen species level, decreased mitochondrial membrane potential, increased intracellular calcium concentration, blocked cell cycle and stagnation in G0/G1 phase, and increased cell necrosis rate. HAP toxicity to HK-2 cells increases with a decrease in crystal size.

Conclusion

Cell damage caused by HAP crystals increases the risk of kidney stone formation.

Understanding cellular interactions with nanomaterials: towards a rational design of medical nanodevices

Biomedical applications increasingly require fully characterized new nanomaterials. There is strong evidence showing that nanomaterials not only interact with cells passively but also actively, mediating essential molecular processes for the regulation of cellular functions, but we are only starting to understand the mechanisms of those interactions. Systematic studies about cell behavior as a response to specific nanoparticle properties are scarce in the literature even when they are necessary for the rational design of medical nanodevices. Information in the literature shows that the physicochemical properties determine the bioactivity, biocompatibility, and safety of nanomaterials. The information available regarding the interaction and responses of cells to nanomaterials has not been analyzed and discussed in a single document. Hence, in this review, we present the latest advances about cellular responses to nanomaterials and integrate the available information into concrete considerations for the development of innovative, efficient, specific and, more importantly, safe biomedical nanodevices. We focus on how physicochemical nanoparticle properties (size, chemical surface, shape, charge, and topography) influence cell behavior in a first attempt to provide a practical guide for designing medical nanodevices, avoiding common experimental omissions that may lead to data misinterpretation. Finally, we emphasize the importance of the systematic study of nano-bio interactions to acquire sufficient reproducible information that allows accurate control of cell behavior based on tuning of nanomaterial properties. This information is useful to guide the design of specific nanodevices and nanomaterials to elicit desired cell responses, like targeting, drug delivery, cell attachment, differentiation, etc, or to avoid undesired side effects.

Role of Sirtuins in Tumor Angiogenesis

Generally, changes in the metabolic status of cells under conditions like hypoxia and accumulation of lactate can be sensed by various sensing mechanisms, leading to modulation of a number of signal transduction pathways and transcription factors. Several of the proangiogenic cytokines like VEGF, FGF, PDGF, TGF-β, Ang-2, ILs, etc. are secreted by cancer cells, under hypoxic microenvironment. These cytokines bind to their receptors on the endothelial cells and activates a number of signaling pathways including Akt/PIP3, Src, p38/MAPK, Smad2/3, etc., which ultimately results in the proliferation and migration of endothelial cells. Transcription factors that are activated in response to the metabolic status of tumors include HIFs, NF-κb, p53, El-2, and FOXO. Many of these transcription factors has been reported to be regulated by a class of histone deacetylase called sirtuins. Sirtuins are NAD+ dependent histone deacetylases that play pivotal role in the regulation of tumor cell metabolism, proliferation, migration and angiogenesis. The major function of sirtuins include, deacetylation of histones as well as some non-histone proteins like NF-κB, FOXOs, PPAR⋎, PGC1-α, enzymes like acetyl coenzymeA and structural proteins like α tubulin. In the cell, sirtuins are generally considered as the redox sensors and their activities are dependent on the metabolic status of the cell. Understanding the intricate regulatory mechanisms adopted by sirtuins, is crucial in devising effective therapeutic strategies against angiogenesis, metastasis and tumor progression. Keeping this in mind, the present review focuses on the role of sirtuins in the process of tumor angiogenesis and the regulatory mechanisms employed by them.

Natural polysaccharide-incorporated hydroxyapatite as size-changeable, nuclear-targeted nanocarrier for efficient cancer therapy

Nuclear-targeted, size-changeable polysaccharide hybrid hydroxyapatite nanoparticles were prepared for the delivery of doxorubicin for cancer therapy, showing low toxicity to healthy tissue cells but strong killing effect on tumor cells.

Comprehensive In Vitro Testing of Calcium Phosphate-Based Bioceramics with Orthopedic and Dentistry Applications

Recently, a large spectrum of biomaterials emerged, with emphasis on various pure, blended, or doped calcium phosphates (CaPs). Although basic cytocompatibility testing protocols are referred by International Organization for Standardization (ISO) 10993 (parts 1-22), rigorous in vitro testing using cutting-edge technologies should be carried out in order to fully understand the behavior of various biomaterials (whether in bulk or low-dimensional object form) and to better gauge their outcome when implanted. In this review, current molecular techniques are assessed for the in-depth characterization of angiogenic potential, osteogenic capability, and the modulation of oxidative stress and inflammation properties of CaPs and their cation- and/or anion-substituted derivatives. Using such techniques, mechanisms of action of these compounds can be deciphered, highlighting the signaling pathway activation, cross-talk, and modulation by microRNA expression, which in turn can safely pave the road toward a better filtering of the truly functional, application-ready innovative therapeutic bioceramic-based solutions.

PEGylated gold nanorods are not cytotoxic to human endothelial cells but affect kruppel-like factor signaling pathway

Gold (Au) nanomaterials (NMs), particularly those with PEG surface functionalization, are generally considered to be biocompatible for biomedical applications due to relatively low cytotoxicity. Herein, we investigated the toxicity of PEGylated Au nanorods (NRs) to human umbilical vein endothelial cells (HUVECs), a commonly used in vitro model for human endothelium. We found a previously unknown effect that up to 10 μg/mL Au NRs, albeit not cytotoxic, decreased the mRNA and protein levels of kruppel-like factor 2 (KLF2), a transcription factor with well-documented vasoprotective effects. The results from PCR array showed that a number of genes associated with risk of cardiovascular diseases were altered by Au NRs, and several genes are downstream genes of KLF2 according to ingenuity pathway analysis (IPA). These effects could be observed with or without the presence of inflammatory stimuli lipopolysaccharide (LPS), which suggests a pre-existing inflammatory state is not required for Au NRs to alter KLF2 signaling pathway. We further identified that Au NRs significantly decreased eNOS mRNA/p-eNOS proteins as well as increased MCP-1 mRNA/sMCP-1 release, which are targets of KLF2. Combined, our data revealed a novel pathway that PEGylated Au NPs at non-cytotoxic concentrations might alter KLF leading to the increase of risk of cardiovascular diseases in human endothelial cells. Given the importance of KLF in vascular homeostasis, our data indicate that it is necessary to evaluate the influence of engineered NPs to KLF signaling pathways, especially for NPs with biomedical uses.

Antiangiogenic properties of nanoparticles: a systematic review

Nanoparticles appear to be one of the most promising agents that offer efficacy in angiogenesis-related disease therapy. The objective of this research is to systematically review studies that have probed into the effect of nanoparticles on angiogenesis. Selected inclusion criteria were used to extract articles, references that were cited in the initial search were sought to identify more potential articles, and articles that did not meet the inclusion criteria and duplicates were discarded. The spherical shape was shown to be the most common shape employed to investigate the role of nanoparticles in angiogenesis therapy. The size of nanoparticles appears to play a crucial role for efficacy on angiogenesis, in which 20 nm emerged as the preferred size. Gold nanoparticles exhibit the most promise as an antiangiogenesis agent, and the toxicity was adjustable based on the dosages applied.

Size effect of nano-hydroxyapatite on proliferation of odontoblast-like MDPC-23 cells

Nano-hydroxyapatite (nano-HAP) is supposed to be a promising candidate for apatite substitute in hard tissue engineering. We aimed to investigate the effect of nano-HAP particles on the proliferation of odontoblast-like MDPC-23 cells compared with conventional hydroxyapatite (c-HAP). HAP in diameter of ~20 nm (np20), ~70 nm (np70) and ~200 nm (c-HAP) were synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). Inverted microscope and MTT assay were used to detect the morphology and proliferation rate of MDPC-23 cells; TEM was used to reveal the internalization of HAP. We found that nano-HAP (np20 and np70), especially np20 expressed obvious growth-promoting effect on MDPC-23 cells compared with c-HAP, which caused the most vacuole in MDPC-23 cells. These results suggest that nano-HAP may be an optimal choice of apatite substitute for MDPC-23 cells on the aspect of cell proliferation.

The effect of glucose modification of hydroxyapatite nanoparticles on gene delivery

Surface modification techniques have been employed for the use of biocompatible and bioresorbable hydroxyapatite (HAp) nanoparticles in cell biology and medicine for the delivery of bioactive molecules. We demonstrated the effects of glucose modification of HAp (GlcHAp) on the transfection efficiency in endothelial cells. After preparing homogeneous HAp nanoparticles with a microemulsion technique, the particles with or without glucose modification and plasmid DNA (pDNA) complexes were transfected into endothelial cells. The transfection efficiency of GlcHAp/pDNA was higher than that of HAp/pDNA. To elucidate the mechanism underlying the improvement in the transfection efficiency following glucose modification, the uptake route into the cells and the inhibition of DNA degradation were investigated. GlcHAp/pDNA enhanced the transfection efficiency after interacting with the glucose transporter 1, as observed by the selective inhibitor assay. In addition, GlcHAp/pDNA was more stable than HAp/pDNA in the DNA degradation assay. Our results suggest that the glucose modification could promote the uptake of HAp nanoparticles by cells and protect the internalized DNA; properties essential for non-viral transfection carriers. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 61-66, 2019.

Vascular biosafety of commercial hydroxyapatite particles: discrepancy between blood compatibility assays and endothelial cell behavior

BACKGROUND

Vascular homeostasis is ensured by a dynamic interplay involving the endothelium, the platelets and the coagulation system. Thus, the vascular safety of particulate materials must address this integrated system, an approach that has been largely neglected. This work analysed the effects of commercial hydroxyapatite (HA) particles in blood compatibility and in endothelial cell behavior, due to their clinical relevance and scarcity of data on their vascular biosafety.

RESULTS

Particles with similar chemical composition and distinct size and morphology were tested, i.e. rod-like, nano dimensions and low aspect ratio (HAp1) and needle-shape with wider size and aspect ratio (HAp2). HAp1 and HAp2, at 1 to 10 mg/mL, did not affect haemolysis, platelet adhesion, aggregation and activation, or the coagulation system (intrinsic and extrinsic pathways), although HAp2 exhibited a slight thrombogenic potential at 10 mg/mL. Notwithstanding, significantly lower levels presented dose-dependent toxicity on endothelial cells' behavior. HAp1 and HAp2 decreased cell viability at levels ≥ 250 and ≥ 50 μg/mL, respectively. At 10 and 50 μg/mL, HAp1 did not interfere with the F-actin cytoskeleton, apoptotic index, cell cycle progression, expression of vWF, VECad and CD31, and the ability to form a network of tubular-like structures. Comparatively, HAp2 caused dose-dependent toxic effects in these parameters in the same concentration range.

CONCLUSION

The most relevant observation is the great discrepancy of HA particles' levels that interfere with the routine blood compatibility assays and the endothelial cell behavior. Further, this difference was also found to be dependent on the particles' size, morphology and aspect ratio, emphasizing the need of a complementary biological characterization, taking into consideration the endothelial cells' functionality, to establish the vascular safety of particulate HA.

Endocytic mechanisms and osteoinductive profile of hydroxyapatite nanoparticles in human umbilical cord Wharton's jelly-derived mesenchymal stem cells

Background

As a potentially bioactive material, the widespread application of nanosized hydroxyapatite (nano-HAP) in the field of bone regeneration has increased the risk of human exposure. However, our understanding of the interaction between nano-HAP and stem cells implicated in bone repair remains incomplete.

Methods

Here, we characterized the adhesion and cellular internalization of HAP nanoparticles (HANPs) with different sizes (20 nm np20 and 80 nm np80) and highlighted the involved pathway in their uptake using human umbilical cord Wharton's jelly-derived mesenchymal stem cells (hWJ-MSCs). In addition, the effects of HANPs on cell viability, apoptosis response, osteogenic differentiation, and underlying related mechanisms were explored.

Results

It was shown that both types of HANPs readily adhered to the cellular membrane and were transported into the cells compared to micro-sized HAP particles (m-HAP; 12 μm). Interestingly, the endocytic routes of np20 and np80 differed, although they exhibited similar kinetics of adhesion and uptake. Our study revealed involvement of clathrin- and caveolin-mediated endocytosis as well as macropinocytosis in the np20 uptake. However, for np80, clathrin-mediated endocytosis and some as-yet-unidentified important uptake routes play central roles in their internalization. HANPs displayed a higher preference to accumulate in the cytoplasm compared to m-HAP, and HANPs were not detected in the nucleolus. Exposure to np20 for 24 h caused a decrease in cell viability, while cells completely recovered with an exposure time of 72 h. Furthermore, HANPs did not influence apoptosis and necrosis of hWJ-MSCs. Strikingly, HANPs enhanced mRNA levels of osteoblast-related genes and stimulated calcium mineral deposition, and this directly correlated with the activation in c-Jun N-terminal kinases and p38 pathways.

Conclusion

Our data provide additional insight about the interactions of HANPs with MSCs and suggest their application potential in hard tissue regeneration.