Tryptophan complexed hydroxyapatite nanoparticles for immunoglobulin adsorption

Hybrid Hydroxyapatite-Metal Complex Materials Derived from Amino Acids and Nucleobases

Calcium phosphates (CaPs) and their substituted derivatives encompass a large number of compounds with a vast presence in nature that have aroused a great interest for decades. In particular, hydroxyapatite (HAp, Ca10(OH)2(PO4)6) is the most abundant CaP mineral and is significant in the biological world, at least in part due to being a major compound in bones and teeth. HAp exhibits excellent properties, such as safety, stability, hardness, biocompatibility, and osteoconductivity, among others. Even some of its drawbacks, such as its fragility, can be redirected thanks to another essential feature: its great versatility. This is based on the compound's tendency to undergo substitutions of its constituent ions and to incorporate or anchor new molecules on its surface and pores. Thus, its affinity for biomolecules makes it an optimal compound for multiple applications, mainly, but not only, in biological and biomedical fields. The present review provides a chemical and structural context to explain the affinity of HAp for biomolecules such as proteins and nucleic acids to generate hybrid materials. A size-dependent criterium of increasing complexity is applied, ranging from amino acids/nucleobases to the corresponding macromolecules. The incorporation of metal ions or metal complexes into these functionalized compounds is also discussed.

Neodymium doped hydroxyapatite theranostic nanoplatforms for colon specific drug delivery applications

Theranostic nanoplatforms integrate therapeutic payloads with diagnostic agents, and help monitor therapeutic response. In this regard, stimuli responsive nanoplatforms further favour combinatorial therapeutic approach that can considerably improve efficacy and specificity of treatment. Herein, we present the engineering of a smart theranostic nanoplatform based on neodymium doped hydroxyapatite (HAN). The presence of neodymium endows the HAN nanoplatforms with near-infrared fluorescence capability. These HAN nanoparticles were then subsequently modified with alginic acid (HANA) to confer pH responsiveness to the synthesized nanoplatforms delivering them to the colon after oral administration. These nanoplatforms possessing optimum size, needle shaped morphology and negative zeta potential, are conducive to cellular internalization. On excitation at 410nm they exhibit near infrared emission at 670nm unraveling their theranostic capabilities. Cytotoxic effects systematically assessed using MTT and live dead assays reveal excellent viability. Raman microscopic imaging technique used to visualize uptake in HeLa cells demonstrate increased uptake from 4 to 16h, with growing cluster size and localization in the cytoplasm. Moreover the concomitant presence of alginic acid manifested advantages of augmented loading and pH dependent release profiles of the model drug, 4 acetyl salicylic acid (4ASA). We could thus establish a theranostic system for early tumour detection, targeted tumour therapy and monitoring of colon cancer that can be administered via the oral route.

Characterization and Stability of Tanshinone IIA Solid Dispersions with Hydroxyapatite

Solid dispersions of tanshinone IIA (TanIIA) using hydroxyapatite (HAp) as the dispersing carrier (TanIIA-HAp SDs) were prepared by the solvent evaporation method. The formed solid dispersions were characterized by scanning electron microscopy (SEM), differential scanning calorimetry analysis (DSC), X-ray powder diffraction (XRPD) and Fourier transforms infrared (FTIR) spectroscopy. The in vitro dissolution rate and the stability of TanIIA-HAp SDs were also evaluated. DSC and XRPD showed that TanIIA was changed from a crystalline to an amorphous form. FTIR suggested the presence of interactions between TanIIA and HAp in solid dispersions. The result of an in vitro dissolution study showed that the dissolution rate of TanIIA-HAp SDs was nearly 7.11-folds faster than free TanIIA. Data from stability studies for over one year of TanIIA-HAp SDs performed under room temperature revealed no significant differences in drug content and dissolution behavior. All these results indicated that HAp may be a promising carrier for improving the oral absorption of TanIIA.