Synthesis and application of nanometer hydroxyapatite in biomedicine

Nano-hydroxyapatite (nano-HA) has been widely studied as a promising biomaterial because of its potential mechanical and biological properties. In this article, different synthesis methods for nano-HA were summarized. Key factors for the synthesis of nano-HA, including reactant concentration, effects of temperature, PH, additives, aging time, and sintering, were separately investigated. The biological performances of the nano-HA depend strongly on its structures, morphology, and crystallite sizes. Nano-HA with different morphologies may cause different biological effects, such as protein adsorption, cell viability and proliferation, angiogenesis, and vascularization. Recent research progress with respect to the biological functions of the nano-HA in some specific biological applications are summarized and the future development of nano-sized hydroxyapatite is prospected.

Synthesis and Characterization of Antibiotic–Loaded Biodegradable Citrate Functionalized Mesoporous Hydroxyapatite Nanocarriers as an Alternative Treatment for Bone Infections

The continuing growth of bacterial resistance makes the top challenge for the healthcare system especially in bone-infections treatment. Current estimates reveal that in 2050 the death ratio caused by bacterial infections can be higher than cancer. The aim of this study is to provide an alternative to currently available bone-infection treatments. Here we designed mesoporous hydroxyapatite nanocarriers functionalized with citrate (Ctr–mpHANCs). Amoxicillin (AMX) is used as a model drug to load in Ctr–mpHANCs, and the drug loading was more than 90% due to the porous nature of nanocarriers. Scanning electron microscopy shows the roughly spherical morphology of nanocarriers, and the DLS study showed the approximate size of 92 nm. The Brunauer–Emmett–Teller (BET) specific surface area and pore diameter was found to be about 182.35 m²/g and 4.2 nm, respectively. We noticed that almost 100% of the drug is released from the AMX loaded Ctr–mpHANCs (AMX@Ctr–mpHANCs) in a pH-dependent manner within 3 d and 5 d at pH 2.0 and 4.5, respectively. The sustained drug release behaviour was observed for 15 d at pH 7.4 and no RBCs hemolysis by AMX@Ctr–mpHANCs. The broth dilution and colony forming unit (CFU) assays were used to determine the antimicrobial potential of AMX@Ctr–mpHANCs. It was observed in both studies that AMX@Ctr–mpHANCs showed a significant reduction in the bacterial growth of S. aureus, E. coli, and P. aeruginosa as compared to Ctr–mpHANCs with no bacteria-killing. Thus, we proposed that Ctr–mpHANCs can be used as a drug carrier and a treatment option for bone infections caused by bacteria.

UV-assisted synthesis of hydroxyapatite from eggshells at ambient temperature: cytotoxicity, drug delivery and bioactivity

Hydroxyapatite [Ca10(PO4)6(OH)2], an important biomaterial, retains a chemical structure that is similar to the mineral phase of bone. Consequently, the ability of hydroxyapatite (Hap) to augment bone growth within bone tissue has made it a potential candidate for use as a hard tissue-implant material. In this work, adopting a UV-mediated solid-state method for the first time, hydroxyapatite was synthesized from eggshells and no thermal treatment was used but ambient temperature was maintained. This simple synthesis process involved a combination of ball milling of the starting materials followed by UV-irradiation. UV-excitation of the Ca and P precursors resulted in the desired Hap and X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) and Raman spectroscopic techniques were used for characterization. The potency of UV-Hap as a biomaterial was examined via the bioactivity, cytotoxicity and the drug (ciprofloxacin) loading-releasing response, which was encouraging. The results of the cell viability assays complied an insignificant cytotoxicity and the simulated body fluid immersion test indicated the bioactivity was within the acceptable range. On the other hand, to better understanding the drug ejection and associated transport phenomenon, two kinetic models (Higuchi and Ritger-Peppas models) were used and a diffusion controlled ciprofloxacin release mechanism was observed using the Higuchi model. However, the experimental outcomes of a drug delivery response exposed UV-Hap as a favorable vehicle for drug loading and release. Hence, this research highlights the prospects of a UV-assisted synthesis method as a green route for the synthesis of Hap to be applied in biomedical fields.

A new kind of nanocomposite Xuan paper comprising ultralong hydroxyapatite nanowires and cellulose fibers with a unique ink wetting performance

In the history of civilization, Xuan paper with its superior texture, durability and suitable characteristics for writing and painting, has played an important role in the dissemination of culture and art. Xuan paper has won the reputation of "the king of paper that lasts for 1000 years" and was inscribed on the Representative List of the Intangible Cultural Heritage of Humanity by the Educational, Scientific and Cultural Organization of the United Nations in 2009. However, the surface of the commercial unprocessed Xuan paper has a large number of large-sized pores with a poor resistance to water, allowing ink droplets to easily spread during the writing and painting process. In this study, we report a new kind of nanocomposite Xuan (HNXP) paper comprising ultralong hydroxyapatite (HAP) nanowires and plant cellulose fibers with unique ink wetting performance, high whiteness and excellent durability. The as-prepared HNXP paper sheets with various weight ratios of ultralong HAP nanowires ranging from 10% to 100% are all superhydrophilic with a water contact angle of zero. In contrast, the ink contact angle of the HNXP paper can be well controlled by adjusting the weight ratio of ultralong HAP nanowires, and the ink contact angle of the HNXP paper increases with increasing weight ratio of ultralong HAP nanowires. The experimental results show the unique ink wetting behavior of the as-prepared HNXP paper, which is absent in the traditional Xuan paper. This new kind of nanocomposite Xuan paper comprising ultralong hydroxyapatite nanowires and plant cellulose fibers is promising for applications in calligraphy and painting arts.

Research progress of novel inorganic nanometre materials carriers in nanomedicine for cancer diagnosis and treatment

Nanomedicine, as the new achievement in combination of nanotechnology and medical science, has the potential to accurately monitor tumor for early diagnosis and dramatically improve the targeted, long-lasting and combinational therapy. Compared with traditional chemotheraphy, nanomedicine would effectively improve the drug accumulation and controlled release in the tumor sites to improve the therapeutic effect. Recently, all kinds of nanomedicines are designed and synthesized for tumor diagnosis and treatment based on inorganic nanocarriers, such as quantum dots, gold nanoparticles, silicon nanoparticles and so on. They might be adjusted and promoted their properties by core-shell structure, surface modification and other strategies. In this review, the inorganic nanometre materials as nanodrug carriers applied in tumor diagnosis and treatment were summarized; nanodrug carriers design strategies and mechanisms of tumor diagnosis and treatment were introduced in detail, the future and several questions still need to resolve about inorganic nanodrugs in tumor diagnosis and treatment of clinical application was prospected.

Covalent immobilization of doxorubicin in glycine functionalized hydroxyapatite nanoparticles for pH-responsive release

Development and therapeutic evaluation of glycine functionalized hydroxyapatite nanoparticles having a covalently conjugated anticancer drug, doxorubicin hydrochloride.

Influence of carbon nanotubes and graphene nanosheets on photothermal effect of hydroxyapatite

Herein we present a successful strategy for enhancement of photothermal efficiency of hydroxyapatite (HAP) by its conjugation with carbon nanotubes (CNTs) and graphene nanosheets (GR). Owing to excellent biocompatibility with human body and its non-toxicity, implementation of HAP based nanomaterials in photothermal therapy (PTT) provides non-replaceable benefits over PTE agents. Therefore, in this report, it has been experimentally exploited that the photothermal effect (PTE) of HAP has significantly improved by its assembly with CNTs and GR. It is found that the type of carbon nanomaterial used to conjugate with HAP has influence on its PTE in such a way that the photothermal efficiency of GR-HAP was higher than CNTs-COOH-HAP under exposure to 980nm near-infrared (NIR) laser. The temperature attained by aqueous dispersions of both CNTs-COOH-HAP and GR-HAP after illuminating to NIR radiations for 7min was found to be above 50°C, which is beyond the temperature tolerance of cancer cells. So that the rise in temperature shown by both CNTs-COOH-HAP and GR-HAP is enough to induce the death of tumoral or cancerous cells. Overall, this approach in modality of HAP with CNTs and GR provide a great potential for development of future nontoxic PTE agents.

Bioinspired negatively charged calcium phosphate nanocarriers for cardiac delivery of MicroRNAs

Aim: To develop biocompatible and bioresorbable negatively charged calcium phosphate nanoparticles (CaP-NPs) as an innovative therapeutic system for the delivery of bioactive molecules to the heart. Materials & methods: CaP-NPs were synthesized via a straightforward one-pot biomineralization-inspired protocol employing citrate as a stabilizing agent and regulator of crystal growth. CaP-NPs were administered to cardiac cells in vitro and effects of treatments were assessed. CaP-NPs were administered in vivo and delivery of microRNAs was evaluated. Results: CaP-NPs efficiently internalized into cardiomyocytes without promoting toxicity or interfering with any functional properties. CaP-NPs successfully encapsulated synthetic microRNAs, which were efficiently delivered into cardiac cells in vitro and in vivo. Conclusion: CaP-NPs are a safe and efficient drug-delivery system for potential therapeutic treatments of polarized cells such as cardiomyocytes.

Processing, characterization and hemostatic mechanism of a ultraporous collagen/ORC biodegradable composite with excellent biological effectiveness

To overcome the hemostatic limitations, ultraporous Col/ORC composites were prepared in this paper.

Citrate-functionalized hydroxyapatite nanoparticles for pH-responsive drug delivery

Development of biocompatible citrate-functionalized hydroxyapatite nanoparticles for pH responsive delivery of doxorubicin.

Design of a novel wound dressing consisting of alginate hydrogel and simvastatin-incorporated mesoporous hydroxyapatite microspheres for cutaneous wound healing

Wound dressings consisting of alginate hydrogel and simvastatin-incorporated mesoporous hydroxyapatite microspheres stimulated angiogenesis and accelerated cutaneous wound healing.

Mesoporous Hydroxyapatite as Olanzapine Carrier Provides a Long-Acting Effect in Antidepression Treatment

An antidepressant carrier was designed to maintain over 2 weeks of constant medication release. The carrier was injected into muscle, where cellular activity was employed to achieve the goal of constant release. Mesoporous hydroxyapatite (mesoHAP) was synthesized into an adequate size by a coprecipitation method; it then went through a series of hydrophobic surface modifications for olanzapine (OLZ) loading by physical absorption to produce mesoHAP-OLZ. Because of its hydrophobic nature, OLZ was not effectively released from mesoHAP-OLZ in an aqueous environment. However, once engulfed by macrophages, the lysosome/endosome hybrid ruptured due to alterations in osmotic pressure, resulting in the release of OLZ into the cytoplasm. OLZ was then exocytosed to the extracellular space due to a high calcium ion (Ca(2+)) concentration and finally reached the blood circulation. Our findings provide a useful treatment strategy to achieve long-term drug release with a single intramuscular (IM) injection, helping to solve the problem of nonadherent medication intake that often occurs in antidepressant therapy.