Oxidative stress and apoptosis induced by hydroxyapatite nanoparticles in C6 cells

Hydroxyapatite nanoparticles induced calcium overload-initiated cancer cell-specific apoptosis through inhibition of PMCA and activation of calpain

Hydroxyapatite nanoparticles (HAPNs) have been reported to specifically induce apoptosis and sustained elevation of intracellular Ca2+ concentration ([Ca2+]i) in cancer cells. However, it remains unclear whether calcium overload, the abnormal intracellular accumulation of Ca2+, is the intrinsic cause of cell apoptosis, how HAPNs specifically evoke calcium overload in cancer cells, and which potential pathways were involved in apoptosis initiation in response to calcium overload. In this study, using various cancer and normal cells, we observed a positive correlation between the degree of increased [Ca2+]i and the specific toxicity of HAPNs. Moreover, chelating intracellular Ca2+ with BAPTA-AM inhibited HAPN-induced calcium overload and apoptosis, thus demonstrating that calcium overload was the main cause of HAPN-induced cytotoxicity in cancer cells. Notably, the dissolution of particles outside the cells did not affect cell viability or [Ca2+]i. In contrast, internalized HAPNs dissolved more readily in cancer cells than in normal cells and inhibited the activity of plasma membrane calcium-ATPase solely in cancer cells to prevent extrusion of excessive Ca2+, hence leading to calcium overload in tumor cells. Upon exposure to HAPNs, the Ca2+-sensitive cysteine protease calpain was activated and then cleaved the BH3-only protein Bid. Consequently, cytochrome c was released, and caspase-9 and -3 were activated, leading to mitochondrial apoptosis. However, these effects were alleviated by the calpain inhibitor calpeptin, confirming the involvement of calpain in HANP-induced apoptosis. Therefore, our results demonstrated that calcium overload induced by HAPNs caused cancer cell-specific apoptosis by inhibiting PMCA and activating calpain in tumor cells and thus may contribute to a more comprehensive understanding of biological effects of this nanomaterial and facilitate the development of calcium overload cancer therapy.

The toxicity of nanoparticles and their interaction with cells: an in vitro metabolomic perspective

Nowadays, nanomaterials (NMs) are widely present in daily life due to their significant benefits, as demonstrated by their application in many fields such as biomedicine, engineering, food, cosmetics, sensing, and energy. However, the increasing production of NMs multiplies the chances of their release into the surrounding environment, making human exposure to NMs inevitable. Currently, nanotoxicology is a crucial field, which focuses on studying the toxicity of NMs. The toxicity or effects of nanoparticles (NPs) on the environment and humans can be preliminary assessed in vitro using cell models. However, the conventional cytotoxicity assays, such as the MTT assay, have some drawbacks including the possibility of interference with the studied NPs. Therefore, it is necessary to employ more advanced techniques that provide high throughput analysis and avoid interferences. In this case, metabolomics is one of the most powerful bioanalytical strategies to assess the toxicity of different materials. By measuring the metabolic change upon the introduction of a stimulus, this technique can reveal the molecular information of the toxicity induced by NPs. This provides the opportunity to design novel and efficient nanodrugs and minimizes the risks of NPs used in industry and other fields. Initially, this review summarizes the ways that NPs and cells interact and the NP parameters that play a role in this interaction, and then the assessment of these interactions using conventional assays and the challenges encountered are discussed. Subsequently, in the main part, we introduce the recent studies employing metabolomics for the assessment of these interactions in vitro.

Biomaterial-assisted tumor therapy: A brief review of hydroxyapatite nanoparticles and its composites used in bone tumors therapy

Malignant bone tumors can inflict significant damage to affected bones, leaving patients to contend with issues like residual tumor cells, bone defects, and bacterial infections post-surgery. However, hydroxyapatite nanoparticles (nHAp), the principal inorganic constituent of natural bone, possess numerous advantages such as high biocompatibility, bone conduction ability, and a large surface area. Moreover, nHAp's nanoscale particle size enables it to impede the growth of various tumor cells via diverse pathways. This article presents a comprehensive review of relevant literature spanning the past 2 decades concerning nHAp and bone tumors. The primary goal is to explore the mechanisms responsible for nHAp's ability to hinder tumor initiation and progression, as well as to investigate the potential of integrating other drugs and components for bone tumor diagnosis and treatment. Lastly, the article discusses future prospects for the development of hydroxyapatite materials as a promising modality for tumor therapy.

Hydroxyapatite Biobased Materials for Treatment and Diagnosis of Cancer

Great advances in cancer treatment have been undertaken in the last years as a consequence of the development of new antitumoral drugs able to target cancer cells with decreasing side effects and a better understanding of the behavior of neoplastic cells during invasion and metastasis. Specifically, drug delivery systems (DDS) based on the use of hydroxyapatite nanoparticles (HAp NPs) are gaining attention and merit a comprehensive review focused on their potential applications. These are derived from the intrinsic properties of HAp (e.g., biocompatibility and biodegradability), together with the easy functionalization and easy control of porosity, crystallinity and morphology of HAp NPs. The capacity to tailor the properties of DLS based on HAp NPs has well-recognized advantages for the control of both drug loading and release. Furthermore, the functionalization of NPs allows a targeted uptake in tumoral cells while their rapid elimination by the reticuloendothelial system (RES) can be avoided. Advances in HAp NPs involve not only their use as drug nanocarriers but also their employment as nanosystems for magnetic hyperthermia therapy, gene delivery systems, adjuvants for cancer immunotherapy and nanoparticles for cell imaging.

Hydroxyapatite Nanoparticles for Improved Cancer Theranostics

Beyond their well-known applications in bone tissue engineering, hydroxyapatite nanoparticles (HAp NPs) have also been showing great promise for improved cancer therapy. The chemical structure of HAp NPs offers excellent possibilities for loading and delivering a broad range of anticancer drugs in a sustained, prolonged, and targeted manner and thus eliciting lower complications than conventional chemotherapeutic strategies. The incorporation of specific therapeutic elements into the basic composition of HAp NPs is another approach, alone or synergistically with drug release, to provide advanced anticancer effects such as the capability to inhibit the growth and metastasis of cancer cells through activating specific cell signaling pathways. HAp NPs can be easily converted to smart anticancer agents by applying different surface modification treatments to facilitate the targeting and killing of cancer cells without significant adverse effects on normal healthy cells. The applications in cancer diagnosis for magnetic and nuclear in vivo imaging are also promising as the detection of solid tumor cells is now achievable by utilizing superparamagnetic HAp NPs. The ongoing research emphasizes the use of HAp NPs in fabricating three-dimensional scaffolds for the treatment of cancerous tissues or organs, promoting the regeneration of healthy tissue after cancer detection and removal. This review provides a summary of HAp NP applications in cancer theranostics, highlighting the current limitations and the challenges ahead for this field to open new avenues for research.

Mitochondrial targeting of potent nanoparticulated drugs in combating diseases

Mitochondrial dysfunction, characterized by the electron transport chain (ETC) leakage and reduced adenosine tri-phosphate synthesis, occurs primarily due to free radicals -induced mutations in either the mitochondrial deoxyribonucleic acid (mtDNA) or nuclear (n) DNA caused by pathogenic infections, toxicant exposures, adverse drug-effects, or other environmental exposures, leading to secondary dysfunction affecting ischemic, diabetic, cancerous, and degenerative diseases. In these concerns, mitochondria-targeted remedies may include a significant role in the protection and treatment of mitochondrial function to enhance its activity. Coenzyme Q10 pyridinol and pyrimidinol antioxidant analogues and other potent drug-compounds for their multifunctional radical quencher and other anti-toxic activities may take a significant therapeutic effectivity for ameliorating mitochondrial dysfunction. Moreover, the encapsulation of these bioactive ligands-attached potent compounds in vesicular system may enable them a superb biological effective for the treatment of mitochondria-targeted dysfunction-related diseases with least side effects. This review depicts mainly on mitochondrial enzymatic dysfunction and their amelioration by potent drugs with the usages of nanoparticulated delivery system against mitochondria-affected diseases.

The Antioxidant Supplementation with Filipendula ulmaria Extract Attenuates the Systemic Adverse Effects of Nanosized Calcium Phosphates in Rats

The aim of this study was to investigate and compare the systemic toxicity of three nanosized calcium phosphates (CaPs): hydroxyapatite (HA), tricalcium phosphate (TCP), and amorphous calcium phosphate (ACP) in rats. Since those metallic compounds are widely used as bone replacement materials, including their use in oral surgery, CaPs were applied (per os) equimollary (17.8 mg/kg, 11 mg/kg, and 9.65 mg/kg b.w., respectively) for 30 days in order to mimic the previously described release rate from dental composites. Also, we employed antioxidant supplementation with Filipendula ulmaria (FU) extract. All the applied CaPs significantly increased serum calcium, triglycerides, LDL, and LDH, while serum levels of testosterone and LH declined, with no alterations in the liver enzymes. The evaluation of oxidative stress markers (in the liver, kidney, and testicle) showed an increase in TBARS values, while SOD and CAT activities and GSH levels were significantly reduced. The relative gene expression of Bax and Bcl-2 was shifted to proapoptotic action, accompanied by intense characteristic histological changes in architecture in all investigated organs. The toxic effects were most prominent in groups treated by ACP. FU administration attenuated the majority of nanosized CaP-induced adverse effects, thus recommending this therapeutic approach to minimize nano-CaP systemic toxicities.

The Antioxidant Supplementation with Filipendula ulmaria Extract Attenuates the Systemic Adverse Effects of Nanosized Calcium Phosphates in Rats

The aim of this study was to investigate and compare the systemic toxicity of three nanosized calcium phosphates (CaPs): hydroxyapatite (HA), tricalcium phosphate (TCP), and amorphous calcium phosphate (ACP) in rats. Since those metallic compounds are widely used as bone replacement materials, including their use in oral surgery, CaPs were applied (per os) equimollary (17.8 mg/kg, 11 mg/kg, and 9.65 mg/kg b.w., respectively) for 30 days in order to mimic the previously described release rate from dental composites. Also, we employed antioxidant supplementation with Filipendula ulmaria (FU) extract. All the applied CaPs significantly increased serum calcium, triglycerides, LDL, and LDH, while serum levels of testosterone and LH declined, with no alterations in the liver enzymes. The evaluation of oxidative stress markers (in the liver, kidney, and testicle) showed an increase in TBARS values, while SOD and CAT activities and GSH levels were significantly reduced. The relative gene expression of Bax and Bcl-2 was shifted to proapoptotic action, accompanied by intense characteristic histological changes in architecture in all investigated organs. The toxic effects were most prominent in groups treated by ACP. FU administration attenuated the majority of nanosized CaP-induced adverse effects, thus recommending this therapeutic approach to minimize nano-CaP systemic toxicities.

An understanding of mitochondria and its role in targeting nanocarriers for diagnosis and treatment of cancer

Nanotechnology has changed the entire paradigm of drug targeting and has shown tremendous potential in the area of cancer therapy due to its specificity. In cancer, several targets have been explored which could be utilized for the better treatment of disease. Mitochondria, the so-called powerhouse of cell, portrays significant role in the survival and death of cells, and has emerged as potential target for cancer therapy. Direct targeting and nanotechnology based approaches can be tailor-made to target mitochondria and thus improve the survival rate of patients suffering from cancer. With this backdrop, in present review, we have reemphasized the role of mitochondria in cancer progression and inhibition, highlighting the different targets that can be explored for targeting of disease. Moreover, we have also summarized different nanoparticulate systems that have been used for treatment of cancer via mitochondrial targeting.

Novel Strategies for Disrupting Cancer-Cell Functions with Mitochondria-Targeted Antitumor Drug-Loaded Nanoformulations

Any variation in normal cellular function results in mitochondrial dysregulation that occurs in several diseases, including cancer. Such processes as oxidative stress, metabolism, signaling, and biogenesis play significant roles in cancer initiation and progression. Due to their central role in cellular metabolism, mitochondria are favorable therapeutic targets for the prevention and treatment of conditions like neurodegenerative diseases, diabetes, and cancer. Subcellular mitochondria-specific theranostic nanoformulations for simultaneous targeting, drug delivery, and imaging of these organelles are of immense interest in cancer therapy. It is a challenging task to cross multiple barriers to target mitochondria in diseased cells. To overcome these multiple barriers, several mitochondriotropic nanoformulations have been engineered for the transportation of mitochondria-specific drugs. These nanoformulations include liposomes, dendrimers, carbon nanotubes, polymeric nanoparticles (NPs), and inorganic NPs. These nanoformulations are made mitochondriotropic by conjugating them with moieties like dequalinium, Mito-Porter, triphenylphosphonium, and Mitochondria-penetrating peptides. Most of these nanoformulations are meticulously tailored to control their size, charge, shape, mitochondriotropic drug loading, and specific cell-membrane interactions. Recently, some novel mitochondria-selective antitumor compounds known as mitocans have shown high toxicity against cancer cells. These selective compounds form vicious oxidative stress and reactive oxygen species cycles within cancer cells and ultimately push them to cell death. Nanoformulations approved by the FDA and EMA for clinical applications in cancer patients include Doxil, NK105, and Abraxane. The novel use of these NPs still faces tremendous challenges and an immense amount of research is needed to understand the proper mechanisms of cancer progression and control by these NPs. Here in this review, we summarize current advancements and novel strategies of delivering different anticancer therapeutic agents to mitochondria with the help of various nanoformulations.

Synergistic Combination of Bioactive Hydroxyapatite Nanoparticles and the Chemotherapeutic Doxorubicin to Overcome Tumor Multidrug Resistance

Multidrug resistance (MDR) is one of the biggest obstacles in cancer chemotherapy. Here, a remarkable reversal of MDR in breast cancer through the synergistic effects of bioactive hydroxyapatite nanoparticles (HAPNs) and doxorubicin (DOX) is shown. DOX loaded HAPNs (DHAPNs) exhibit a 150-fold reduction in IC₅₀ compared with free DOX for human MDR breast cancer MCF-7/ADR cells, and lead to almost complete inhibition of tumor growth in vivo without obvious side effects of free DOX. This high efficacy and specificity could be attributed to multiple action mechanisms of HAPNs. In addition to acting as the conventional nanocarriers to facilitate the cellular uptake and retention of DOX in MCF-7/ADR cells, more importantly, drug-free HAPNs themselves are able to prevent drug being pumped out of MDR cells through targeting mitochondria to induce mitochondrial damage and inhibit ATP production and to trigger sustained mitochondrial calcium overload and apoptosis in MDR cancer cells while not affecting normal cells. The results demonstrate that this simple but versatile bioactive nanoparticle provides a practical approach to effectively overcome MDR.

Ameliorating quercetin constraints in cancer therapy with pH-responsive agarose-polyvinylpyrrolidone -hydroxyapatite nanocomposite encapsulated in double nanoemulsion

Despite quercetin (QC) promising features for cancer therapy, low solubility, poor permeability, and short biological half-life time significantly confine its application in cancer therapy. In this study, a novel approach is developed to improve loading efficiency and attain quercetin sustained-release concurrently. In this direction, hydrogel nanocomposite of agarose (AG)-polyvinylpyrrolidone (PVP)-hydroxyapatite (HAp) was loaded with QC. Incorporating HAp nanoparticles in the AG-PVP hydrogel improved the loading efficiency up to 61%. Also, the interactions between nanoparticle, drug, and hydrogel polymers rendered the nanocomposite pH-responsive at acidic conditions and controlled the burst release at neutral conditions. Then, QC-loaded hydrogel was encapsulated into the water in oil in water nanoemulsions to further sustain the drug release. As a result, the pH-responsive release of QC with prolonged-release over 96 h was observed. In more detail, according to the Korsmeyer-Peppas mathematical model, the mechanism of release was anomalous (diffusion-controlled) at pH 7.4 and anomalous transport (dissolution-controlled) at pH 5.4. The presence of all nanocomposite components was confirmed with FTIR analysis, and XRD results approved the incorporation of QC in the fabricated nanocomposite. The homogeneous surface of the nanocomposite in FESEM images showed good compatibility between components. The zeta potential analysis confirmed the good stability of the nanocarriers. Besides, the fabricated AG-PVP-HAp-QC platform showed significant cytotoxicity on MCF-7 cells compared to QC as a free drug (p < 0.001) and to quercetin-loaded AG-PVP (AG-PVP-QC) (p < 0.001) with enhanced apoptosis induction after the addition of HAp. Accordingly, this delivery platform ameliorated loading and sustained-release of QC, as well as its anticancer activity by releasing the drug at an effective therapeutic level over a long period to induce apoptosis. Thus, turning this drug delivery system into a potential candidate for further biomedical applications.

Does an Alteration in Nociceptive Response to Mineral Components of Dental Composites Involve Changes in Oxidative Status? a Brief Report

Since that use of bioactive mineral components of dental composites have been accompanied with various toxicities, including neurotoxicity, the aim of the study was to examine the effect of chronic application of hydroxyapatite, tricalcium phosphate and amorphous calcium phosphate in nanoparticles (nHA, nTCP, nACP) to parameters of sensitivity to thermal pain stimuli. Although the systemic toxicity of those compounds is frequently attributed to an oxidative damage, we also decided to examine the potential effects of Filipendula ulmaria extract on nociception alterations induced by the nano-sized mineral components of dental composites. Forty-two Wistar albino rats were divided into control and six experimental (equal) groups that orally received either nHA, nTCP, nACP alone, or simultaneously with FU extract for 30 days. Nociceptive alterations were quantified in the hot plate and tail flick test. The chronic administration of nHA and nACP resulted in significant increase in reactivity to thermal stimulus, with no significant change observed in nTCP group when compared to the control in the hot plate test, while simultaneous application of FU extract prevented any significant alteration of time to respond. The reaction time in the tail flick test for all three groups that received only nano calcium phosphates was reduced, with no changes in the groups treated with FU extract. The results of this study confirmed that calcium phosphates of mineral components of dental composites produced hyperalgesic effects, and this side effect were significantly attenuated by antioxidant supplementation.

The Beneficial Role of Filipendula ulmaria Extract in Prevention of Prodepressant Effect and Cognitive Impairment Induced by Nanoparticles of Calcium Phosphates in Rats

Mineral components of dental composites are used in many medical and dental applications, including preventive, restorative, and regenerative dentistry. To evaluate the behavioural alterations induced by nanosized particles of novel dental composites, by means of depressive level and cognitive functions, experimental groups of rats were chronically administered with nanosized hydroxyapatite (HA), tricalcium phosphate (TCP), and amorphous calcium phosphate (ACP) with or without simultaneous application of Filipendula ulmaria L. (FU) methanolic extract. The significant prodepressant action was observed in groups solely treated with HA and ACP. Besides, prolonged treatment with ACP also resulted in a significant decline in cognitive functions estimated in the novel object recognition test. The adverse impact of calcium phosphates on estimated behavioural functions was accompanied by increased oxidative damage and apoptotic markers in the prefrontal cortex, as well as diminished specific neurotrophin (BDNF) and gabaergic expression. The results of our investigation showed that simultaneous antioxidant supplementation with FU extract prevented calcium phosphate-induced behavioural disturbances, as well as prooxidative and apoptotic actions, with the simultaneous restoration of BDNF and GABA-A receptors in the prefrontal cortex. These findings suggest that FU may be useful in the prevention of prodepressant impact and cognitive decline as early as the manifestation of calcium phosphate-induced neurotoxicity.

Fabrication of nanoparticles for bone regeneration: new insight into applications of nanoemulsion technology

Introducing synthetic bone substitutes into the clinic was a major breakthrough in the regenerative medicine of bone. Despite many advantages of currently available bone implant materials such as biocompatiblity and osteoconductivity, they still suffer from relatively poor bioactivity, osteoinductivity and osteointegration. These properties can be effectively enhanced by functionalization of implant materials with nanoparticles such as osteoinductive hydroxyapatite nanocrystals, resembling inorganic part of the bone, or bioactive polymer nanoparticles providing sustained delivery of pro-osteogenic agents directly at implantation site. One of the most widespread techniques for fabrication of nanoparticles for bone regeneration applications is nanoemulsification. It allows manufacturing of nanoscale particles (<100 nm) that are injectable, 3D-printable, offer high surface-area-to-volume-ratio and minimal mass transport limitations. Nanoparticles obtained by this technique are of particular interest for biomedical engineering due to fabrication procedures requiring low surfactant concentrations, which translates into reduced risk of surfactant-related in vivo adverse effects and improved biocompatibility of the product. This review discusses nanoemulsion technology and its current uses in manufacturing of nanoparticles for bone regeneration applications. In the first section, we introduce basic concepts of nanoemulsification including nanoemulsion formation, properties and preparation methods. In the next sections, we focus on applications of nanoemulsions in fabrication of nanoparticles used for delivery of drugs/biomolecules facilitating osteogenesis and functionalization of bone implants with special emphasis on biomimetic hydroxyapatite nanoparticles, synthetic polymer nanoparticles loaded with bioactive compounds and bone-targeting nanoparticles. We also highlight key challenges in formulation of nanoparticles via nanoemulsification and outline potential further improvements in this field.

Preclinical evaluation of platinum-loaded hydroxyapatite nanoparticles in an embryonic zebrafish xenograft model

Hydroxyapatite (HA) nanoparticles are commonly used as building blocks in the design of bone-substituting biomaterials. Recently, these nanoparticles have been considered for the treatment of metastasis disease, since their pH-dependent dissolution behavior allows for precise tuning of release kinetics of loaded cargo. Herein we show that the capacity of drug-loaded nanoparticles stabilized with citrate ions reduce cancer cell survival in an embryonic zebrafish xenograft model. In particular, in vitro studies demonstrate that PtPP-loaded HA nanoparticles exhibit anti-proliferative activity against breast cancer cells at reduced pH. In vivo studies using an embryonic zebrafish xenograft model reveal that PtPP co-delivered with human breast cancer cells strongly reduce cancer cell survival. Similarly, co-injection of breast cancer cells with citrate-functionalized and PtPP-loaded HA nanoparticles into zebrafish significantly reduces survival of cancer cells due to release of chemotherapeutically active kiteplatin species. These results demonstrate the preclinical efficacy of drug-loaded nanoparticles against human breast cancer cells in a xenogenic embryonic in vivo model.

Hydroxyapatite as a biomaterial - a gift that keeps on giving

The synthetic analogue to biogenic apatite, hydroxyapatite (HA) has a number of physicochemical properties that make it an attractive candidate for diagnosis, treatment of disease and augmentation of biological tissues. Here we describe some of the recent studies on HA, which may provide bases for a number of new medical applications. The content of this review is divided to different medical application modes utilizing HA, including tissue engineering, medical implants, controlled drug delivery, gene therapies, cancer therapies and bioimaging. A number of advantages of HA over other biomaterials emerge from this discourse, including (i) biocompatibility, (ii) bioactivity, (iii) relatively simple synthesis protocols for the fabrication of nanoparticles with specific sizes and shapes, (iv) smart response to environmental stimuli, (v) facile functionalization and surface modification through noncovalent interactions, and (vi) the capacity for being simultaneously loaded with a wide range of therapeutic agents and switched to bioimaging modalities for uses in theranostics. A special section is dedicated to analysis of the safety of particulate HA as a component of parenterally administrable medications. It is concluded that despite the fact that many benefits come with the usage of HA, its deficiencies and potential side effects must be addressed before the translation to the clinical domain is pursued. Although HA has been known in the biomaterials world as the exemplar of safety, this safety proves to be the function of size, morphology, surface ligands and other structural and compositional parameters defining the particles. For this reason, each HA, especially when it comes in a novel structural form, must be treated anew from the safety research angle before being allowed to enter the clinical stage.

Anti-osteosarcoma effect of hydroxyapatite nanoparticles both in vitro and in vivo by downregulating the FAK/PI3K/Akt signaling pathway

Schematic representing the anti-cancer effects of nano-HAPs both in vitro and in vivo by downregulating the FAK/PI3K/Akt signaling pathway.

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.

Application of hydroxyapatite nanoparticles in tumor-associated bone segmental defect

Hydroxyapatite (HA) has been widely applied in bone repair because of its superior biocompatibility. Recently, a proliferation-suppressive effect of HA nanoparticles (n-HA) against various cancer cells was reported. This study was aimed at assessing the translational value of n-HA both as a bone-regenerating material and as an antitumor agent. Inhibition of tumor growth, prevention of metastasis, and enhancement of the survival rate of tumor-bearing rabbits treated with n-HA were demonstrated. Activated mitochondrial-dependent apoptosis in vivo was confirmed, and we observed that a stimulated immune response was involved in the n-HA-induced antitumor effect. A porous titanium scaffold loaded with n-HA was fabricated and implanted into a critical-sized segmental bone defect in a rabbit tumor model. The n-HA-releasing scaffold not only showed a prominent effect in suppressing tumor growth and osteolytic lesion but also promoted bone regeneration. These findings provide a rationale for using n-HA in tumor-associated bone segmental defects.

The protective role of CsNPs and CurNPs against DNA damage, oxidative stress, and histopathological and immunohistochemical alterations induced by hydroxyapatite nanoparticles in male rat kidney

Hydroxyapatite nanoparticles (HAP-NPs) are an inorganic component of natural bone and are mainly used in the tissue engineering field due to their bioactivity, osteoconductivity, biocompatibility, non-inflammatory, and non-toxicity properties. However, the current toxicity data for HAP-NPs regarding human health are limited, and only a few results from basic studies have been published. Therefore, the present study was designed to investigate the beneficial role of chitosan nanoparticles (CsNPs) and curcumin nanoparticles (CurNPs) in alleviating nephrotoxicity induced by HAP-NPs in male rats. The results showed that HAP-NPs caused a reduction in antioxidant enzymes and induced lipid peroxidation, nitric oxide production and DNA oxidation. Moreover, HAP-NP administration was associated with intense histologic changes in kidney architecture and immunoreactivity to proliferating cell nuclear antigen (PCNA). However, the presence of CsNPs and/or CurNPs along with HAP-NPs reduced the levels of oxidative stress through improving the activities of antioxidant enzymes. Also, the rats administered the nanoparticles showed a moderate improvement in glomerular damage which matched that of the control group and showed mild positive reactions to PCNA-ir in glomeruli and renal tubules in the cortical and medullary portions. These novel insights confirm that the presence of chitosan and curcumin in nanoforms has powerful biological effects with enhanced bioactivity and bioavailability phenomena compared to their microphase counterparts. Also, they were able to ameliorate the nephrotoxicity induced by HAP-NPs.

In vitro and in vivo mechanism of hepatocellular carcinoma inhibition by β-TCP nanoparticles

Background: Studies have showed that nanoparticles have a certain anti-cancer activity and can inhibit many kinds of cancer cells. β-tricalcium phosphate nanoparticles (nano-β-TCP) displays better biodegradation, but the application and mechanism of nano-β-TCP in anti-cancer activity are still not clear. Purpose: The objective of this study was to synthesize nano-β-TCP and investigate its inhibitory properties and mechanism on hepatocellular carcinoma (HepG2) cells in vitro and in vivo. Methods: Nano-β-TCP was synthesized using ethanol-water system and characterized. The effects of nano-β-TCP on cell viability, cell uptake, intracellular oxidative stress (ROS), cell cycle and apoptosis were also investigated with HepG2 cells and human hepatocyte cells (L-02). Intratumoral injection of nano-β-TCP was performed on the xenograft liver cancer model to explore the inhibitory effect and mechanism of nano-β-TCP on liver tumors. Results: In vitro results revealed that nano-β-TCP caused reduced cell viability of HepG2 cells in a time-and dose-dependent manner. Nano-β-TCP was internalized through endocytosis and degraded in cells, resulting in obvious increase of the intracellular Ca²⁺ and PO₄ ^3- ions. Nano-β-TCP induced cancer cells to produce ROS and induced apoptosis of tumor cells by an apoptotic signaling pathways both in extrinsic and intrinsic pathway. In addition, nano-β-TCP blocked cell cycle of HepG2 cells in G0/G1 phase and disturbed expression of some related cyclins. In vivo results showed that 40 mg/kg of nano-β-TCP had no significant toxic side effects, but could effectively suppress hepatocellular carcinoma growth. Conclusion: These findings revealed the anticancer effect of nano-β-TCP and also clarified the mechanism of its inhibitory effect on hepatocellular carcinoma.

Combinational effect of curcumin and metformin against gentamicin-induced nephrotoxicity: Involvement of antioxidative, anti-inflammatory and antiapoptotic pathway

Gentamicin (GM) is an antibiotic related to aminoglycoside group that is used in treating Gram-negative bacterial infections. However, treatment with gentamicin is considered to be limited as it induces an oxidative stress-mediated apoptosis in kidney which causes a nephrotoxicity. Metformin is a well-known biguanide that is used for treating diabetes mellitus, especially type 2. Supplement with plant metabolites or natural antioxidants produce a protective activity against many types of diseases in vivo. Curcumin is a main medicinal constituent of Curcuma longa, has reported for number of biological effects, such as antioxidant, anti-inflammatory, and antitumor. The study aims at evaluating the metformin and curcumin alone or in combination on nephrotoxicity induced by GM. The outcome of the study shows that both metformin and curcumin, when used unaided, were effectively decreasing GM-induced nephrotoxicity. The two drugs combination was showed synergistic effect in ameliorating a GM-induced kidney injury, as supported by expressively improved renal dysfunction. Metformin and curcumin showed strong protection against oxidative stress in GM treated animals through decreasing the activities and expression of various antioxidative enzymes. Moreover, combination of two drugs showed an anti-inflammatory response through reducing a level of pro-inflammatory cytokines including tumor necrosis factor-alpha, interleukin 1-beta, and interleukin 6 in GM intoxicated group of animals. Furthermore, GM agitated apoptosis was affectedly diminished by the combinational treatment of metformin and curcumin via down-regulating activity of cleaved Caspase-3 and pro-apoptotic factor Bax, whereas increasing anti-apoptotic factor Bcl-2 signaling pathways. The above results suggested that combinational treatment of metformin and curcumin might be have a synergizing effect and substantial potential against nephrotoxicity induced by GM. PRACTICAL APPLICATIONS: Curcumin and metformin combination exhibited substantial synergistic effect against GM-induced nephrotoxicity through reducing oxidative stress, inflammation, as well as apoptosis in kidney cells. Therefore, the method of combination of curcumin and metformin might be functional to treat or inhibit GM prompted nephrotoxicity in future.

Nano hydroxyapatite induces glioma cell apoptosis by suppressing NF-κB signaling pathway

Nano-sized hydroxyapatite (nHA) particles have been demonstrated to exert anti-cancer effects on multiple cancer cell lines and animal models of cancer biology. However, the molecular mechanism underlying the effects of nHA particles on glioma cells remains unclear. The present study aimed to examine the effects of nHA on the behavior of glioma cells and investigate its underlying molecular mechanism. Rat glioma C6 cells and human glioma U87MG ATCC cells were exposed to nHA (20–100 µg/ml), and its effects on cell morphology, viability, apoptosis, cell cycle, invasion and nuclear factor (NF)-κB signaling were analyzed. Exposure of C6 and U87MG ATCC cells to 20 µg/ml nHA for 24 h caused cell detachment. Viability of C6 and U87MG ATCC cells were significantly reduced by nHA in a dose-dependent manner (P<0.05). Nuclear staining with Hoechst 33258 exhibited clear chromatin condensation in C6 cells following 24 h exposure to ≥25 µg/ml nHA. Flow cytometry revealed that nHA (20–100 µg/ml) significantly induced apoptosis and cell cycle G2/M arrest in C6 and U87MG ATCC cells (P<0.05). Transwell invasion assay demonstrated that nHA (20–60 µg/ml) significantly inhibited invasion of U87MG ATCC cells (P<0.05). Furthermore, western blotting and confocal immunofluorescence microscopy revealed that nHA (20–100 µg/ml) decreased NF-κB p65 protein expression and blocked NF-κB p65 nuclear translocation in C6 cells. The protein expression of NF-κB target molecules, such as B cell lymphoma 2, cyclooxygenase-2 and survivin, were also significantly reduced by nHA in a dose-dependent manner in both C6 and U87MG ATCC cells (P<0.05). In conclusion, it was demonstrated that the inhibitory effect of nHA on glioma cells is likely associated with the downregulation of NF-κB signaling.

Genotoxicity of amorphous silica nanoparticles: Status and prospects

Amorphous silica nanoparticles (SNPs) are widely used in biomedical applications and consumer products. Little is known, however, about their genotoxicity and potential to induce gene expression regulation. Despite recent efforts to study the underlying mechanisms of genotoxicity of SNPs, inconsistent results create a challenge. A variety of factors determine particle-cell interactions and underlying mechanisms. Further, high-throughput studies are required to carefully assess the impact of silica nanoparticle physicochemical properties on induction of genotoxic response in different cell lines and animal models. In this article, we review the strategies available for evaluation of genotoxicity of nanoparticles (NPs), survey current status of silica nanoparticle gene alteration and genotoxicity, discuss particle-mediated inflammation as a contributing factor to genotoxicity, identify existing gaps and suggest future directions for this research.

Regeneration of sciatic nerve crush injury by a hydroxyapatite nanoparticle-containing collagen type I hydrogel

The current study aimed to enhance the efficacy of peripheral nerve regeneration using a hydroxyapatite nanoparticle-containing collagen type I hydrogel. A solution of type I collagen, extracted from the rat tails, was incorporated with hydroxyapatite nanoparticles (with the average diameter of ~212 nm) and crosslinked with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) to prepare the hydrogel. The Schwann cell cultivation on the prepared hydrogel demonstrated a significantly higher cell proliferation than the tissue culture plate, as positive control, after 48 h (n = 3, P < 0.005) and 72 h (n = 3, P < 0.01). For in vivo evaluation, the prepared hydrogel was administrated on the sciatic nerve crush injury in Wistar rats. Four groups were studied: negative control (with injury but without interventions), positive control (without injury), collagen hydrogel and hydroxyapatite nanoparticle-containing collagen hydrogel. After 12 weeks, the administration of hydroxyapatite nanoparticle-containing collagen significantly (n = 4, P < 0.005) enhanced the functional behavior of the rats compared with the collagen hydrogel and negative control groups as evidenced by the sciatic functional index, hot plate latency and compound muscle action potential amplitude measurements. The overall results demonstrated the applicability of the produced hydrogel for the regeneration of peripheral nerve injuries.

Antitumor Effect by Hydroxyapatite Nanospheres: Activation of Mitochondria-Dependent Apoptosis and Negative Regulation of Phosphatidylinositol-3-Kinase/Protein Kinase B Pathway

Hydroxyapatite nanoparticles (HA NPs) have been acknowledged for their benign biocompatibility and proliferation inhibition effect on tumor cells, attracting considerable attention for tumor therapeutics without late effects. However, unnoticeable tumor cytotoxicity of HA NPs limited the final clinical therapeutic efficacy. Herein, a two-phase synthetic approach was developed to synthesize sphere-like HA NPs by varying the conventional growth habit of HA precipitate. We present our in vitro and in vivo experimental evidence that spherical HA NPs have surprisingly high inhibitory activities against tumor cells. We demonstrate further, based on our experimental data, that the underlying cause for the death of the tumor cells is related to two concurrent pathways, the mitochondria-dependent apoptosis pathway and negative regulation of the phosphatidylinositol-3-kinase/protein kinase B (PIK3/AKT) pathway. The present study indicated that HA nanospheres can be engineered as nontoxic specific inhibitors for efficient tumor therapeutics with nanobiomaterials.

Mitochondria: promising organelle targets for cancer diagnosis and treatment

Mitochondrial-mediated tumor monitoring provides a new perspective on mitochondria-based therapy.

Nanopreparations for mitochondria targeting drug delivery system: Current strategies and future prospective

Mitochondria are a novel and promising therapeutic target for diagnosis, treatment and prevention of a lot of human diseases such as cancer, metabolic diseases and neurodegenerative disease. Owing to the mitochondrial special bilayer structure and highly negative potential nature, therapeutic molecules have multiple difficulties in reaching mitochondria. To overcome multiple barriers for targeting mitochondria, the researchers developed various pharmaceutical preparations such as liposomes, polymeric nanoparticles and inorganic nanoparticles modified by mitochondriotropic moieties like dequalinium (DQA), triphenylphosphonium (TPP), mitochondrial penetrating peptides (MPPs) and mitochondrial protein import machinery that allow specific targeting. The targeted formulations exhibited enhanced pharmacological effect and better therapeutic effect than their untargeted counterpart both in vitro and in vivo. Nanocarriers may be used for bio-therapeutic delivery into specific mitochondria that possess a great potential treatment of mitochondria related diseases.

Hybrid nanofibers based on poly-caprolactone/gelatin/hydroxyapatite nanoparticles-loaded Doxycycline: Effective anti-tumoral and antibacterial activity

Cancer is one of the leading causes of morbidity and mortality Worldwide, 19.3 million new cancer cases are expected to be identified in 2025. Among the therapeutic arsenal to cancer control one could find the Doxycycline and the nano hydroxyapatite. The Doxycycline (Dox) not only shown antibiotic effect but also exhibits a wide range of pleiotropic therapeutic properties as the control of the invasive and metastatic cancer cells characteristics. The purpose of the present study was to evaluate both cytotoxicity in vitro and antibacterial activity of electrospun Dox-loaded hybrid nanofibrous scaffolds composed by hydroxyapatite nanoparticles (nHA), poly-ε-caprolactone (PCL) and gelatin (Gel) polymers. Both nHA and Dox were dispersed into different PCL/Gel ratios (70:30, 60:40, 50:50wt%) solutions to form electrospun nanofibers. The nHA and Dox/nHA/PCL-Gel hybrid nanofibers were characterized by TEM microscopy. In vitro Dox release behavior from all of these Dox-loaded nHA/PCL-Gel nanofibers showed the same burst release profile due to the high solubility of Gel in the release medium. Antibacterial properties of nanofiber composites were evaluated using Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Porphyromonas gingivalis (P. gingivalis) bacteria. The co-delivery of nHA particles and Dox simultaneously exhibited inhibition of bacterial growth more efficiently than the delivery of either Dox or nHA at the same concentrations, indicating a synergistic effect. The results showed that cancer cell tested had different sensibility to co-delivery system. On the whole, A-431 cells were found exhibited the most pronounced synergistic effect compared to CACO-2 and 4T1 cancer cells. Based on the anticancer as well as the antimicrobial results in this study, the developed Dox/nHA/PCL-Gel composite nanofibers are suitable as a drug delivery system with potential applications in the biomedical fields.

Inhibition of prostate cancer RM1 cell growth in vitro by hydroxyapatite nanoparticle‑delivered short hairpin RNAs against Stat3

The present study investigated the effect of signal transducer and activator of transcription 3 (Stat3) interference on RM1 prostate cancer cell viability in vitro, using plasmid‑based Stat3 specific short hairpin RNA (sh‑Stat3) delivered by hydroxyapatite nanoparticles (HAP). HAP carrying sh‑Stat3 plasmids were transfected into tumor cells. MTT assays were used to measure RM1 cell viability 24 and 48 h following transfection, and the apoptosis rate and cell cycle phase distribution were determined by flow cytometry. Stat3 mRNA expression levels were measured by reverse transcription‑quantitative polymerase chain reaction and Stat3, Cyclin D1, B cell lymphoma 2 apoptosis regulator (Bcl‑2), vascular endothelial growth factor (VEGF), Bcl‑2 associated X apoptosis regulator (Bax) and cleaved‑caspase‑3 protein expression levels were detected using western blot analysis. The results demonstrated that HAP‑delivered sh‑Stat3 significantly decreased RM1 cell viability through the promotion of cell cycle arrest and apoptosis. Stat3 mRNA and protein expression levels were significantly downregulated in RM1 cells. Bcl‑2, VEGF and Cyclin D1 were also significantly downregulated, but cleaved‑caspase‑3 and Bax mRNA and protein expression levels were significantly upregulated. HAP‑delivered sh‑Stat3 decreased RM1 cell viability in vitro, and HAP assisted plasmid‑based delivery of shRNA into tumor cells. The present results suggest that HAP may be a useful method for successful shRNA delivery into tumors.

The effects of titanium dioxide nanoparticles on ultrastructure of zebrafish testis (Danio rerio)

INTRODUCTION

Nanotechnology investigates materials at nanoscale level (0.1-100nm in diameter). There are many commercially nanoproducts such as silver, silicon, titanium, zinc, and gold. They are used in a variety of applications and released to the environment. Titanium dioxide (TiO₂) is one of the most commonly used nanoparticles (NP). In this study, the ultrastructural effects of TiO₂-NP on zebrafish testis tissue were evaluated.

MATERIAL AND METHOD

Zebrafish were divided into four groups (N=60) as one control and 3 experimental groups (1mg/L, 2mg/L and 4mg/L TiO₂). Testis tissues were dissected after 5days of the exposure. Tissues were fixed with 2.5% glutaraldehyde at 4°C. After routine electron microscopy tissue processing, the testis were embedded in epon resin. Ultrathin sections were counterstained with 1% uranyl acetate and lead citrate and examined using a transmission electron microscope.

RESULTS

Mitochodrial degeneration with swelling and cristae loss were detected in Sertoli cells and spermatogonial cells of TiO2-NP treated groups in a dose-dependent manner. Moreover, autophagic vacuole accumulation were seen in Sertoli cell cytoplasms of the experimental groups. Necrosis was also detected in the 4mg TiO2-NP-treated group.

CONCLUSION

TiO2-NP has been used in crop production, food additives, medicine, toothpastes, sunscreens, cosmetics, and in waste water treatment, which contaminated the environment. Our findings showed TiO₂-NP-induced autophagy and necrosis at higher doses in Sertoli cells, which consequently negatively affected spermatogenic cells and testicular morphology of Zebrafish. It is important to give much more attention to the use of this NP to minimise the possible effects on nature and organisms.

Mitochondria-Targeted Hydroxyapatite Nanoparticles for Selective Growth Inhibition of Lung Cancer in Vitro and in Vivo

Lung cancer is the leading cause of cancer-related mortality worldwide. Most patients have metastases at the time of diagnosis, thus demanding development of more effective and specific agents. In this study, the specific anticancer effect of hydroxyapatite nanoparticles (HAPNs) to human lung cancer cells (A549) and the underlying mechanisms were investigated, using normal bronchial epithelial cells (16HBE) as the control. Rod-shaped HAPNs (∼10 nm in width and 50 nm in length) were prepared by aqueous precipitation method. Without any further functionalization and drug loading, HAPNs selectively inhibited cancer-cell proliferation. Their efficient mitochondrial targeting correlated strongly with decreased mitochondrial membrane potential and induction of mitochondria-dependent apoptosis in A549 cells. Caveolae-mediated endocytosis via lysosome trafficking was observed to be a prominent internalization pathway for HAPNs in both A549 and 16HBE cells. However, more nanoparticles were taken up into A549 cells. HAPNs triggered a sustained elevation of intracellular calcium concentration ([Ca²⁺]_i) in cancer cells but only a transitory increase in normal control cells. In a nude mouse lung cancer model with xenotransplanted A549 cells, HAPN treatment demonstrated nearly 40% tumor growth inhibition without apparent side effect. These results demonstrated that the enhanced cellular uptake and mitochondrial targeting of HAPNs, together with the prolonged elevation of [Ca²⁺]_i in A549 cells, could result in the cancer-specific cytotoxicity of HAPNs. Thus, HAPNs might be a promising agent or mitochondria-targeted delivery system for effective lung cancer therapy.

Toxicity assessment of hydroxyapatite nanoparticles in rat liver cell model in vitro

Hydroxyapatite nanoparticles (HAP NPs) are widely used for preparations of biomedical and biotechnological fields such as drug delivery, gene therapy, and molecular imaging. However, the current toxicological knowledge about HAP NPs is relatively limited. The present study was designed to investigate the toxicity potentials of various concentrations (0–1000 µg cm−2) of HAP NPs in cultured primary rat hepatocytes. Cell viability was detected by 3-(4,5-dimethyl-thiazol-2-yl) 2,5-diphenyltetrazolium bromide (MTT) assay and lactate dehydrogenase (LDH) release, while total antioxidant capacity (TAC) and total oxidative stress (TOS) levels were determined to evaluate the oxidative injury. The DNA damage was also analyzed via scoring liver micronuclei rates and determining 8-oxo-2-deoxyguanosine (8-OH-dG) levels. The results of MTT and LDH assays showed that the higher concentrations of dispersed HAP NPs (300, 500, and 1000 µg cm−2) decreased cell viability. Also, HAP NPs increased TOS (500 and 1000 µg cm−2) levels and decreased TAC (300, 500, and 1000 µg cm−2) levels in cultured hepatocytes. On the basis of increasing doses, the NPs as depending on dose caused significant increases of the number of micronucleated hepatocytes and 8-OH-dG levels as compared to control culture. Furthermore, the highest concentration of HAP NPs (1000 µg cm−2) exhibited cytotoxic activity. Based on these results, HAP NPs have a dose-dependent toxic effect in rat hepatocytes. Further extensive research in this field is promising and reasonable.

Mitochondria and nuclei dual-targeted heterogeneous hydroxyapatite nanoparticles for enhancing therapeutic efficacy of doxorubicin

Dual-targeted nanoparticles have been increasingly used to realize greater anti-proliferation effect by attacking double key sites of tumor cells. In order to retain nuclei inhibition effect and enhance DOX-induced apoptosis by mitochondrial pathway simultaneously, hyaluronic acid (HA) modified hydroxyapatite (HAP) nanoparticles (HAP-HA), the functional calcium-based tumor targeting nanoparticles, have been developed. In this nanosystem, HA acts as an active tumor-targeting ligand to bind the CD44 receptors which are overexpressed on the surface of tumor cells while HAP can load and deliver DOX to both nuclei and mitochondria of tumor cells. In this study, DOX-loaded HAP-HA nanoparticles (DOX/HAP-HA) exhibited satisfactory drug loading efficiency which was up to 214.55 ± 51.05 μg mg(-1) and showed a uniform nano-scaled particle size. The mitochondrial and nuclei targetability of DOX/HAP-HA was confirmed by confocal laser scanning microscopy analyses. Besides, western blot assay demonstrated that DOX/HAP-HA could markedly enhance mitochondrial cytochrome C leakage and thereby activate apoptotic cascade associated with it. In addition, in vivo anti-tumor efficacy and toxicity evaluation of DOX/HAP-HA indicated that DOX/HAP-HA was more effective and less harmful compared to other groups. DOX/HAP-HA might be a new promising targeted delivery system for effective cancer therapy.

Systematic investigation and in vitro biocompatibility studies on mesoporous europium doped hydroxyapatite

This paper reports the systematic investigation of europium doped hydroxyapatite (Eu:HAp). A set of complementary techniques, namely Fourier Transform Infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and the Brunauer-Emmett-Teller (BET) technique were used towards attaining a detailed understanding of Eu:HAp. The XPS analysis confirmed the substitution of Ca ions by Eu ions in the Eu:HAp samples. Secondly, Eu:HAp and pure HAp present type IV isotherms with a hysteresis loop at a relative pressure (P/P0) between 0.4 and 1.0, indicating the presence of mesopores. Finally, the in vitro biological effects of Eu:HAp nanoparticles were evaluated by focusing on the F-actin filament pattern and heat shock proteins (Hsp) expression in HEK293 human kidney cell line. Fluorescence microscopy studies of the actin protein revealed no changes of the immunolabelling profile in the renal cells cultured in the presence of Eu:HAp nanoparticles. Hsp60, Hsp70 and Hsp90 expressions measured by Western blot analysis were not affected after 24 and 48 hours exposure. Taken together, these results confirmed the lack of toxicity and the biocompatibility of the Eu:HAp nanoparticles. Consequently, the possibility of using these nanoparticles for medical purposes without affecting the renal function can be envisaged.

Differential cytotoxicity and particle action of hydroxyapatite nanoparticles in human cancer cells

Aim: While hydroxyapatite nanoparticles (HAPNs) have been reported to exhibit anticancer effects on several types of human cancer cells, no investigation has been performed to compare their cytotoxicity with different types of cancer cells. The objective of the present study is to investigate the cytotoxic action of HAPNs in different types of human cancer cell and to explore the possible mechanisms involved. Materials & methods: Rod-shaped HAPNs were prepared by the aqueous precipitation method and then labeled with ?uorescein isothiocyanate to visualize the cellular uptake and distribution. Their cytotoxicity to three human carcinoma cell lines (gastric cancer cells [MGC80-3], cervical adenocarcinoma epithelial cells [HeLa] and hepatoma cells [HepG2], as well as to normal human hepatocyte cells [L-02]) was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell apoptosis was characterized by the changes in nuclear morphology with 4’,6-diamidino-2-phenylindole staining and by ?ow cytometric analysis with Annexin V-?uorescein isothiocyanate/propidium iodide double staining. Furthermore, the activity of apoptotic proteins (caspase-3, -8 and -9), intracellular reactive oxygen species and glutathione levels were analyzed in HAPN-treated cells. The cellular uptake of HAPNs was studied using flow cytometry analysis, and changes in intracellular calcium levels were investigated using the Ca2+-sensitive fluorescent dye, fluo-3 AM. Results: HAPNs significantly inhibited cell proliferation and induced apoptosis of cancer cells with an order of MGC80-3 > HepG2 > HeLa, but had no impact on normal hepatic cells (L-02). The increase in apoptosis was accompanied by the activation of caspase-3 and -9, but not activation of caspase-8. Moreover, HAPN treatment led to reactive oxygen species generation and decreased intracellular glutathione in cancer cells, with the most remarkable reactive oxygen species burst in HeLa cells. The degree of cytotoxicity did not correlate with the cellular uptake efficiency of HAPNs. However, more HAPNs were found inside the nucleus of MGC80-3 cells, and an increase in the intracellular calcium level was observed in all cancer cells, with the highest level also detected in MGC80-3. Conclusion: Varying cytotoxicity of HAPNs was observed in different cancer cell types. Our results suggest that possible mechanisms of cytotoxicity in various types of cancer cells could be different. The elevated calcium concentration and nuclear localization of the particles might be the main mechanism of growth inhibition by HAPNs in cancer cells.

Original submitted 18 April 2012; Revised submitted 14 September 2012; Published online 24 April 2013

Global gene expression analysis of cellular death mechanisms induced by mesoporous silica nanoparticle-based drug delivery system

Mesoporous silica nanoparticles (MSNs), as one of the most promising inorganic drug carriers, have attracted ever increasing attention due to their unique structural, physicochemical, and biochemical features. Drug delivery systems (DDSs) based on MSNs could easily escape from endosomes after endocytosis and protect the loaded drugs from bioerosion by stable MSN carriers, efficiently deliver drugs intracellularly in a sustained release way, and consequently kill cancer cells at enhanced efficacy. However, the underlying pathways and mechanisms of cancer cell death induced by MSN-mediated drug delivery have not been well explored. In this study, we introduce gene expression analyses to evaluate the pathways and mechanisms of cancer cell death induced by a MSN-based drug delivery system. Unique changes in gene expressions and gene ontology terms, which were caused only by the MSN-based DDS (DOX-loaded MSNs, DOX@MSNs) but not by free drug doxorubicin (DOX) and/or the carrier MSNs, were discovered and proposed to be responsible for the varied cell death mechanisms, including the greatly enhanced necrosis due to amplified oxidative stress and the apoptosis related with DNA/RNA synthesis and cell cycle inhibitions. By virtue of a certain kind of synergetic biological effect between the drug and the carrier, the DOX@MSNs DDS was found capable of increasing the intracellular levels of reactive oxygen species and triggering the mitochondria-related autophagic lysosome pathway, consequently activating a specific pathway of necrosis, which is different from those by the free drug and the carrier.