Biology subjects

Valadao Cardoso, A.

Publications and source records attributed to Valadao Cardoso, A..

3 recordsLinked to original sources

bioRxiv2026

Phosphate and Carbonate in the Biomineralization of Chicken Eggshells and the Increase in Eggshell Thickness through Nanodroplet Addition

The presence of hydroxyapatite (HAp) in the Cuticle of laying hen eggshells was investigated through an extensive and detailed study combining scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS), as well as micro-Raman, micro-FTIR, X-ray diffraction (XRD), and thermogravimetric analysis (TG). Additionally, Raman and FTIR spectra of Cuticle HAp were compared with those obtained from the internal surface of chicken femur fragments and from a bovine HAp sample. Examination of the same region by SEM in SE (topographic) and BSE (subsurface compositional contrast) modes revealed unidirectional (nanofibrous) calcite growth within the Vertical Layer (VL) and Palisade Layer (PL), which together constitute nearly the entire eggshell thickness. Shell thickening in the VL and PL layers appears to proceed via an additive mechanism characterized by the successive deposition of nanodroplets containing, according to our hypothesis, the mineral phase, water, and organic components. This multiphasic system generates lamellae that progressively increase in thickness through the continuous incorporation of new nanodroplets onto the pre-existing surface. This additive nanodroplet-mediated growth contributes to understanding how micropores form in the PL and VL. Biomineralization via an additive mechanism is strongly supported by the presence of nano-hemispheres attached to growing lamellae in the VL and PL. Statistical analyses corroborate the relationship between the diameter of Cuticle nanospheres and that of nano-hemispheres in the Vertical Layer. Fractures observed in the VL indicate structural continuity between the Cuticle and the Vertical Layer, suggesting that additive growth involves a continuous supply of HAp -- possibly across the entire uterine surface -- which, through a yet undescribed mechanism, dissolves and/or transforms calcium phosphate nanospheres into calcium carbonate nanofibers.

bioengineering↗

bioRxiv2024

Dissolution of Phosphate and Precipitation of Carbonate in the Bio-mineralization of the Bivalve Shell Limnoperna fortunei

The mantle of bivalves plays a crucial role in the formation and maintenance of their shells through biomineralization. Detailed studies using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis have revealed the presence of phosphorus (P) compounds as the primary phase during biomineralization at the growing edge of the periostracum of the bivalve shell Limnoperna fortunei (Dunker, 1857). The presence of a crystal morphology like hydroxyapatite (HAp) at the growing edge of the shell has also been identified, and the Ca/P ratio compatible with HAp. Carbonic anhydrase (CA), whose presence in the shell was investigated in this work, and/or bivalve proteins with identical capability are likely responsible for the dissolution phosphate and calcium carbonate precipitation. Other experimental techniques (ICP-OES, WDXRF) were used to quantify the main chemical elements in the shell of L. fortunei and the marine bivalve P. perna. The concentration of P in the shells suggests that phosphate is confined to the growing regions. FTIR and FTIR-ATR spectroscopies indicate aragonite as the main phase at the shell edges but also show the presence of phosphate absorption bands. X-ray diffraction (XRD) analyses revealed aragonite and calcite phases at the shell edges, with the presence of one of the main peaks of crystalline calcium phosphate both in L. fortunei and P. perna. The presence of phosphate as the primary phase in the biomineralization process of L. fortunei rekindles the discussion about the importance of the co-occurrence of phosphate and carbonate in the bivalve biomineralization dynamics and suggests an important evolutionary advantage in acquiring phosphate compounds essential for energy production and organism function.

bioengineering↗

bioRxiv2022

Characterization of magnetic nanoparticles from the shells of freshwater mussel L fortunei and marine P perna mussels

The presence of magnetic nanoparticles in animal species, including humans, has been growing steadily, but none have reported the presence in mollusks apart from the radula of chitons, in 1962. In shells this is the first time. Magnetite (Fe3O4) nanoparticles were extracted (using three distinct and rather simple protocols) from the shells of freshwater Limnoperna fortunei (Dunker 1857) and marine Perna perna (Linnaeus 1758) mussels and were fully physically-chemically characterized. Due to the spatial distribution, the ferrimagnetic particles in the shells are in low concentration and present a superparamagnetic behavior characteristic of materials of nanometric sizes. Transmission electron microscopy (TEM, especially HRTEM) indicated that the 50-100 nm round magnetic particles are in fact aggregates of 5-10 nm nanoparticles. Using analysis TEM techniques on the shell of the L fortunei we have not found any iron oxide particle at the periostracum layer nor in the calcite layer. Nevertheless, roughly round nanoparticle aggregates of iron hydroxy/oxide were found in the nacar layer, the aragonite layer. Being the aragonite layer responsible for more than 97% of the shell of the L fortunei and considering the estimated size of magnetic nanoparticles we could infer that they might be distributed throughout the nacar layer.

bioengineering↗