Interactions between hydroxyapatite and cholesterol associated with calcification in age-related macular degeneration

Ocular Side Effects of Bisphosphonates: A Review of Literature

In rare cases, bisphosphonates are well established to cause ocular inflammation, presenting as uveitis, episcleritis, scleritis, orbital inflammation, and/or conjunctivitis. Some reports of bisphosphonate-associated neuro-ophthalmic complications also exist. We identified 101 reports in the literature relating to bisphosphonate-associated ocular complications. In a great majority of cases, symptoms resolve after discontinuation of the drug and anti-inflammatory treatment. Many cases recur if rechallenged with the same bisphosphonate. First-generation nonamino bisphosphonates, including clodronate and etidronate, are not associated with ocular inflammation. Only 2nd- and 3rd-generation amino bisphosphonates, including pamidronate, alendronate, risedronate, ibandronate, and zoledronate are associated with these complications. The mechanism of bisphosphonate-induced ocular inflammation may be related to activation of γ/δ T cells or M1 macrophages. Intravenous forms, such as pamidronate and zoledronate, tend to have higher rates and faster onset of ocular inflammation, generally presenting within days of infusion. In oral bisphosphonates, such as alendronate and risedronate, these complications present with more sporadic timing. Rates of complications are also higher when bisphosphonates are used for malignancy, as doses tend to be higher compared with doses for osteoporosis.

Solid-state NMR methods for the characterization of bioconjugations and protein-material interactions

Protein solid-state NMR has evolved dramatically over the last two decades, with the development of new hardware and sample preparation methodologies. This technique is now ripe for complex applications, among which one can count bioconjugation, protein chemistry and functional biomaterials. In this review, we provide our account on this aspect of protein solid-state NMR.

Interactions Between Amyloid-β (1-42) and Hydroxyapatite-Cholesterol Spherules Associated with Age-Related Macular Degeneration

Drusen deposition on sub-retinal pigment epithelium is the causal factor for age-related macular degeneration for the old-aged individuals. These deposits contain hydroxyapatite-cholesterol spherules on which several proteins and lipids accumulate to cover the retina and choroid, causing blurred vision and blindness. Amyloid-β, the known culprit in Alzheimer's disease, is one among the few major proteins known to occur in these deposits. In the present article, we report preliminary analyses of interactions between amyloid-β and hydroxyapatite-cholesterol composites using Thioflavin-T binding kinetics, solid-state NMR and transmission electron microscopy (TEM). Thioflavin-T fluorescence kinetics shows that amyloid-β (1-42) aggregates only under certain conditions of concentration of cholesterol in the hydroxyapatite-cholesterol composites prepared by two different methods. These results were confirmed by 1D ¹³C CPMAS solid-state NMR. TEM imaging revealed that there is an exposure of the cholesterol surface in the composites prepared by sonication method. These imaging experiments explain the dependence of aggregation kinetics on the exposure and availability of cholesterol surface in the composites to a certain extent.

The Impact of Oxidative Stress on Blood-Retinal Barrier Physiology in Age-Related Macular Degeneration

The blood retinal barrier (BRB) is a fundamental eye component, whose function is to select the flow of molecules from the blood to the retina and vice-versa, and its integrity allows the maintenance of a finely regulated microenvironment. The outer BRB, composed by the choriocapillaris, the Bruch's membrane, and the retinal pigment epithelium, undergoes structural and functional changes in age-related macular degeneration (AMD), the leading cause of blindness worldwide. BRB alterations lead to retinal dysfunction and neurodegeneration. Several risk factors have been associated with AMD onset in the past decades and oxidative stress is widely recognized as a key factor, even if the exact AMD pathophysiology has not been exactly elucidated yet. The present review describes the BRB physiology, the BRB changes occurring in AMD, the role of oxidative stress in AMD with a focus on the outer BRB structures. Moreover, we propose the use of cerium oxide nanoparticles as a new powerful anti-oxidant agent to combat AMD, based on the relevant existing data which demonstrated their beneficial effects in protecting the outer BRB in animal models of AMD.

Studies on physiochemical modifications on biologically important hydroxyapatite materials and their characterization for medical applications

Crystalline Hydroxyapatite (Ca10 (PO₄)₆(OH)₂) non linear optical crystal plays a major role in biomedical applications. Crystalline Hydroxyapatite was synthesized using natural human bone sample by thermal methods. This Hydroxyapatite was characterized by Fourier Transform infra-red spectroscopy (FTIR), scanning electron microscope, UV-Vis spectroscopy, X-ray diffraction and conductivity studies. It was found that compared to bovine bone, the changes to the molecular structure associated with the mineral (carbonate) and the organic content (collagen) was good. The sintering methods showed that the synthesized Hydroxyapatite has remarkable heat stability up to 750 °C. The XRD and FTIR results showed a high purity of the synthesized HA powders, in terms of the electronic transitions, in UV-Vis which require a certain amount of energy it is proportional to the wavelength absorbed and absorption coefficient, the optical band energy of the natural human bone is found to be 4.65 eV and the electrical conductivity of the bone material is 9.11 × 10^-6 Ω ^-1 cm^-1. Natural bone Hydroxyapatite gives superior results.