Statistical analysis
Statistical analysis was performed using the SciPy library (Python 3.6; www.scipy.org31). Data was presented as mean and standard deviation and compared with Student’s t-test. According to the tests of statistical hypothesis used, the average values of the compared samples differ non-significant (the difference between their mean values is random) if the p-value of the statistical test is higher than the significance level (alpha-error). An alpha error of 5% was accepted for all cases.