Apatite/Chitosan Composites Formed by Cold Sintering for Drug Delivery and Bone Tissue Engineering Applications

In the biomedical field, nanocrystalline hydroxyapatite is still one of the most attractive candidates as a bone substitute material due to its analogies with native bone mineral features regarding chemical composition, bioactivity and osteoconductivity. Ion substitution and low crystallinity are also fundamental characteristics of bone apatite, making it metastable, bioresorbable and reactive. In the present work, biomimetic apatite and apatite/chitosan composites were produced by dissolution-precipitation synthesis, using mussel shells as a calcium biogenic source. With an eye on possible bone reconstruction and drug delivery applications, apatite/chitosan composites were loaded with strontium ranelate, an antiosteoporotic drug. Due to the metastability and temperature sensitivity of the produced composites, sintering could be carried out by conventional methods, and therefore, cold sintering was selected for the densification of the materials. The composites were consolidated up to ~90% relative density by applying a uniaxial pressure up to 1.5 GPa at room temperature for 10 min. Both the synthesised powders and cold-sintered samples were characterised from a physical and chemical point of view to demonstrate the effective production of biomimetic apatite/chitosan composites from mussel shells and exclude possible structural changes after sintering. Preliminary in vitro tests were also performed, which revealed a sustained release of strontium ranelate for about 19 days and no cytotoxicity towards human osteoblastic-like cells (MG63) exposed up to 72 h to the drug-containing composite extract.

Octacalcium phosphate phase forming cements as an injectable bone substitute materials: Preparation and in vitro structural study

In the realm of regenerating damaged or degenerated bones through minimally invasive techniques, injectable materials have emerged as exceptionally promising. Among these, calcium phosphate bone cements (CPCs) have garnered significant interest due to their remarkable bioactivity, setting it apart from non-degradable alternatives such as polymethyl methacrylate cements. α-Tricalcium phosphate (α-TCP) is a widely used solid phase component in CPCs. It can transform into calcium-deficient hydroxyapatite (CDHAp) when it comes in contact with water. In this study, we aimed to create an injectable, self-setting bone cement using low-temperature synthesized α-TCP powder as a single precursor of the powder phase. We found that changes in the pH of the liquid phase (pH 6.0, pH 6.2, pH 7.0 and pH 7.4) significantly altered the cement's setting, handling, and mechanical properties. The formation of the octacalcium phosphate (OCP) phase was identified in our study, which positively affects the osteoblastic cell response. Hardened OCP-forming bone cements prepared using a liquid phase with pH 7.0 and 7.4 showed better osteogenic cell attachment and proliferation than those prepared with pH 6.0 and 6.2. Our study suggests that changes in the pH of the liquid phase can significantly affect the properties of α-TCP-based bone cement, and the presence of the OCP phase is crucial for optimal cement performance.

Small organic molecules containing amorphous calcium phosphate: synthesis, characterization and transformation

As the primary solid phase, amorphous calcium phosphate (ACP) is a pivotal precursor in cellular biomineralization. The intrinsic interplay between ACP and Howard factor underscores the significance of understanding their association for advancing biomimetic ACP development. While organic compounds play established roles in biomineralization, this study presents the synthesis of ACP with naturally occurring organic compounds (ascorbate, glutamate, and itaconate) ubiquitously found in mitochondria and vital for bone remodeling and healing. The developed ACP with organic compounds was meticulously characterized using XRD, FTIR, and solid-state 13C and 31P NMR. The morphological analysis revealed the characteristic spherical morphology with particle size close to 20 nm of all synthesized ACP variants. Notably, the type of organic compound strongly influences true density, specific surface area, particle size, and transformation. The in vitro analysis was performed with MC3T3-E1 cells, indicating the highest cell viability with ACP_ASC (ascorbate), followed by ACP_ITA (itaconate). The lowest cell viability was observed with 10 %w/v of ACP_GLU (glutamate); however, 1 %w/v of ACP_GLU was cytocompatible. Further, the effect of small organic molecules on the transformation of ACP to low crystalline apatite (Ap) was examined in Milli-Q® water, PBS, and α-MEM.

The course of Autoimmune Thyroiditis in WOMEN

CONTEXT

Although, many studies have been made on the clinical course of autoimmune thyroiditis, this study focused on women and the factors effecting the natural course such as Selenium.

OBJECTIVE

The study aimed to determine Hashimoto's thyroiditis (HT) clinical course in adults and the factors that could affect it.

DESIGN

The study was in a retrospective manner between 2010-2018.

SUBJECTS AND METHODS

101 patients with HT were followed for 60.7±32.7 months. Biochemical and ultrasonographic data were collected. We investigated whether the age at diagnosis, family history, smoking habits, levothyroxine replacement therapy, and serum selenium (Se) levels influenced the disease course.

RESULTS

No relationship was observed between age and thyroid functions, thyroid volumes (TV), and autoantibody (Ab) levels at diagnosis. Ab levels were irrelevant with TV, echogenicity, and nodularity at diagnosis. However, initial TSH levels were significantly associated with anti-TPO levels (p=0.028, r=0.218). In the untreated group, thyroid functions seemed to be stable. TV decreased significantly in both treated and untreated patients (p<0.001). The decrease in TV was significantly higher in the treatment group (p=0.002). In euthyroid and subclinical hypothyroid patients, levothyroxine therapy did not affect the decrease in TV. Ab levels remained stable in untreated patients, but anti-TPO levels significantly decreased in treated patients (p<0.001). Smoking seemed to increase only anti-Tg levels (p=0.009). Family history was not associated with any of the studied parameters. Serum Se level was negatively correlated only with thyroid echostructure and only in treated patients. TV showed a "Gaussian distribution" in all patients at the diagnosis and at the end, independent of levothyroxine treatment.

CONCLUSIONS

Most euthyroid patients remained euthyroid during five years of follow-up. The decrease in TV was significantly prominent with LT4 treatment. Importantly, TV followed a normal distribution instead of the bimodal distribution that is classically described.