Impact of Dopants on the Electrical and Optical Properties of Hydroxyapatite

This chapter deals with the effect of alternating electrical current on hydroxyapatite [HAp, Ca10(PO4)6(OH)2] and doped HAp along with their optical response and the processes involved. The dielectric constant, permittivity and ac conductivity were analyzed to have an insight into the surface charge polarization phenomenon. Further, the magnitude and the polarity of the surface charges, microstructure, and phases also play significant role in the cell proliferation and growth on the implants. Besides, the mechanism behind the electrical properties and the healing of bone fracture are discussed. The influence of various dopants on the optical properties of HAp viz., absorbance, transmission, band gaps and defects energy levels are analyzed along with the photoluminescence and excitation independent emission. In the future outlook, the analysis of effect of doping is summarized and its impact on the next generation biomaterials are elucidated

Extremely Fast and Efficient Removal of Congo Red Using Cationic-Incorporated Hydroxyapatite Nanoparticles (HAp: X (X = Fe, Ni, Zn, Co, and Ag))

Congo red (CR) is a stable anionic diazo dye that causes allergic reactions with carcinogenic properties. The rapid removal of CR using cation-incorporated nanohydroxyapatite (pristine HAp: X (X = Fe, Ni, Zn, Co, and Ag)) was investigated. The pristine and cation ion-doped HAp adsorbents were coprecipitated and subjected to hydrothermal and ultrasound treatments and subsequent microwave drying. The dopant ions significantly engineered the crystallite size, crystallinity, particle size (decreased 38–77%), shape (a rod to sphere modification by the incorporation of Ag+, Ni2+, and Co2+ ions), and colloidal stability (CS) of the adsorbent. These modifications aided in the rapid removal of the CR dye (98%) within one minute, and the CR adsorption rate was found to be significantly higher (93–99%) compared to previously reported rates. Furthermore, the kinetic, Langmuir, Freundlich, and DKR isotherms and thermodynamic results confirmed that the CR adsorption on the HAp was due to the strong chemical adsorption process. The order of the maximum CR adsorption capacity was Fe-HAp > HAp > Ag-HAp > Co-HAp > Zn-HAp. Whereas the CR regeneration efficiency was Fe-HAp (92%) > Ag-HAp (42%) > Ni-HAp (30%), with the other adsorbents exhibiting a poor recycling efficiency (1–16%). These results reveal Fe-HAp as a potential adsorbent for removing CR without the formation of byproducts

Extremely Fast and Efficient Removal of Congo Red Using Cationic-Incorporated Hydroxyapatite Nanoparticles (HAp: X (X = Fe, Ni, Zn, Co, and Ag))

Congo red (CR) is a stable anionic diazo dye that causes allergic reactions with carcinogenic properties. The rapid removal of CR using cation-incorporated nanohydroxyapatite (pristine HAp: X (X = Fe, Ni, Zn, Co, and Ag)) was investigated. The pristine and cation ion-doped HAp adsorbents were coprecipitated and subjected to hydrothermal and ultrasound treatments and subsequent microwave drying. The dopant ions significantly engineered the crystallite size, crystallinity, particle size (decreased 38–77%), shape (a rod to sphere modification by the incorporation of Ag+, Ni2+, and Co2+ ions), and colloidal stability (CS) of the adsorbent. These modifications aided in the rapid removal of the CR dye (98%) within one minute, and the CR adsorption rate was found to be significantly higher (93–99%) compared to previously reported rates. Furthermore, the kinetic, Langmuir, Freundlich, and DKR isotherms and thermodynamic results confirmed that the CR adsorption on the HAp was due to the strong chemical adsorption process. The order of the maximum CR adsorption capacity was Fe-HAp > HAp > Ag-HAp > Co-HAp > Zn-HAp. Whereas the CR regeneration efficiency was Fe-HAp (92%) > Ag-HAp (42%) > Ni-HAp (30%), with the other adsorbents exhibiting a poor recycling efficiency (1–16%). These results reveal Fe-HAp as a potential adsorbent for removing CR without the formation of byproducts

Induction Heating Efficiency of Water-Dispersible Mn_0.5Fe_2.5O₄@YVO₄:Eu³⁺ Magnetic-Luminescent Nanocomposites in an Acceptable ac Magnetic Field: Hemocompatibility and Cytotoxicity Studies

Not many reports are available on magnetic-luminescent nanocomposites for cancer hyperthermia applications. Further, such nanocomposites on Mn²⁺-doped iron oxide may be available rather rarely. Studies on the induction heating properties within the threshold magnetic field and frequency factors are still rare. In most cases, magnetic nanoparticles are studied for hyperthermia and lanthanide-doped luminescent nanoparticles for certain biomedical applications. Here, we report on water-dispersible superparamagnetic manganese-doped iron oxide (Mn_0.5Fe_2.5O₄) nanoparticles and a polyethylene glycol6000-coated magnetic-luminescent nanocomposite. The nanocomposite is composed of magnetic Mn_0.5Fe_2.5O₄ (average size 10–20 nm) nanoparticles and red-emitting YVO₄:Eu³⁺ (average size 40–50 nm) nanoparticles. These magnetic nanoparticles and nanocomposites are studied for their induction heating abilities at different acceptable <i>Hf</i> values (<i>H</i>, strength of alternating magnetic field and <i>f</i>, the operating frequency). The operational <i>Hf</i> values lie in the ranges of 2.15 × 10⁶ to 4.58 × 10⁶ kA m^–1 s^–1 that are well below the threshold limit of 5 × 10⁶ kA m^–1 s^–1. A specific absorption rate as high as 132 and 63 W/g, respectively, for Mn_0.5Fe_2.5O₄ and Mn_0.5Fe_2.5O₄@YVO₄:Eu³⁺, can be achieved. The rate of heating and the temperature achieved with time can be tuned with concentrations as well as magnetic constituents in the nanocomposites. Hemocompatibility analysis revealed high blood compatibility with <5% hemolysis. The cytotoxicity analysis in the MCF-7 cell line showed that the cell viability is 74–85% for 0.2–0.5 mg of the magnetic-luminescent nanocomposites. Beyond this concentration, the percentage of cell death is very high. The red-emitting magnetic-luminescent nanocomposites will be useful for in vitro optical imaging and tracking of magnetic nanoparticles. The magnetization analysis showed that the samples have high enough saturation magnetization and low residual magnetization, which is quite suitable for clinical applications. The water dispersibility, hemocompatibility, and cytotoxicity assay in conjunction with their efficient induction heating abilities have shown that these magnetic-luminescent nanocomposites will have potential applications in magnetic fluid hyperthermia and optical imaging

Adipose tissue derived stromal cells in a gelatin-based 3D matrix with exclusive ascorbic acid signalling emerged as a novel neural tissue engineering construct: an innovative prototype for soft tissue

[EN] The current study investigated a triad, which comprises of adipose tissue derived stem cells isolated from infrapatellar fat pad and gelatin/polyvinyl alcohol (PVA)-based matrix with exclusive ascorbic acid signalling. Though, the bio-mechanical properties of the gelatin-PVA blended scaffolds in wet condition are equivalent to the ECM of soft tissues in general, in this study, the triad was tested as a model for neural tissue engineering. Apart from being cytocompatible and biocompatible, the porosity of the scaffold has been designed in such a manner that it facilitates the cell signalling and enables the exchange of nutrients and gases. The highly proliferative stem cells from Passage 2 were characterized using both, mesenchymal and embryonic stem cell markers. As an initial exploration the mesenchymal stem cells at Passage 4 were exposed to ascorbic acid and basic fibroblast growth factor signalling for neuronal differentiation in 2D environment independently. The MSCs successfully differentiated and acquired neuron specific markers related to cytoskeleton and synapses. Subsequently, three phases of experiments have been conducted on the 3D gelatin/PVA matrix to prove their efficacy, the growth of stem cells, growth of differentiated neurons and the in situ growth and differentiation of MSCs. The scaffold was conducive and directed MSCs to neuronal lineage under specific signalling. Overall, this organotypic model triad could open a new avenue in the field of soft tissue engineering as a simple and effective tissue construct.The authors thank National Foundation for Liver Research (NFLR) for financially supporting the cell-based work in this project. CIBER-BBN is an initiative funded by the VI National R&D & I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program. CIBER actions are financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund. One of the authors (N.K.S.) thanks the University Grants Commission, India for the award of the Basic Scientific Research (UGC-BSR) Faculty Fellowship [No. F.4-5(11)2019 (BSR)].Martin, CA.; Radhakrishnan, S.; Gómez Ribelles, JL.; Trentz, OA.; Nivethaa, E.; Reddy, MS.; Rela, M.... (2022). Adipose tissue derived stromal cells in a gelatin-based 3D matrix with exclusive ascorbic acid signalling emerged as a novel neural tissue engineering construct: an innovative prototype for soft tissue. Regenerative Biomaterials (Online). 9:1-16. https://doi.org/10.1093/rb/rbac031116