Vista mpx

Samples of plant materials (1.0 g) was digested with spectrally pure nitric acid 69% m/m (5 mL), (Suprapur, Merck, Kenilworth, NJ, USA) at the temperature 200 °C in a microwave digestion system Start D, Milestone (Sorisole, Italy) equipped with the advanced reaction sensors for temperature and pressure control. Parameters of the process were optimized to assure complete digestion of samples. After digestion, samples were diluted 10 times with ultrapure water (Millipore Simplicity) to perform multielemental ICP-OES analysis.
The concentration of elements in digested biomass was determined by ICP-OES spectrometer Vista MPX, Varian (Sydney, Australia), optimized and calibrated for multielemental analysis taking into account the effect of the acid matrix. The analyses were carried out in laboratory Accredited by Polish Centre of Accreditation (PCA) according to PN-EN ISO/IEC 17025:2005. Quality assurance of the test results was achieved by using Combined Quality Control Standard from Ultra Scientific, North Kingstown, RI, USA. All samples were analyzed in three repeats (results of analyses were arithmetic mean, the relative standard deviation was <5%).

An aliquot (0.2 g) of each sample was mixed with 3.5 mL HNO₃ (65%) and 3.5 mL H₂O₂ (30%). Thereafter, microwave digestion for complete combustion of organic matrix was carried out using a MARS 6 system (CEM, Orsay, France, 1200 W, 10 min at 55 °C; 10 min at 75 °C; and 45 min at 120 °C). Ca, Mg, K and Na concentrations (mg/kg dry weight (DW)) were subsequently determined in the diluted digests via ICP-OES (Varian Vista MPX, Palo Alto, CA, USA). External calibration was used. Accuracy and precision were monitored by periodic evaluation of a calibration blank, re-analyzing standards during sample runs, and analysis of certified reference materials (including rice flour NIST1568a, sea lettuce BCR279 and spinach leaves SRM 1570a), spiked samples and analytical duplicates.

In vitro bioactivity of the cylindrical scaffolds (Ф 12 × 2 mm²) was assessed with the mineralization of hydroxyapatite by immersing the samples in simulated body fluid (SBF, pH = 7.4) at 37°C. The preparation of SBF was according to our previous research [28 (link)]. Scaffolds C0, C20 and C40 were soaked in SBF solution in a polyethylene container at 37°C (the ratio of SBF volume to scaffolds mass was 200 ml/g). After immersion for 1, 3, 5, 7 and 14 days, the Ca, P, Si and Mg ionic concentration, respectively, of SBF in containers were analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES; Vista-MPX, Varian, USA). After soaked for 2 weeks, the scaffolds were removed from SBF and rinsed with distilled water, then vacuum-dried. The surface morphology of the scaffolds after immersion, as well as the chemical composition at some specific sites, was determined by SEM, EDS and XRD.