Haake

Measurements of the blood samples were done with the AcCellerator instrument (Zellmechanik Dresden, Dresden, Germany) as described previously^{18 (link),19 (link)}. For maximum quality, measurements were done no longer than 4 h after blood collection to minimize cell lysis. In preparation for the measurement, citrate blood was diluted 1:20 with phosphate buffered saline (PBS) containing methylcellulose and viscosity was adjusted to 60 mPa s at 24 °C using a falling ball viscometer (Haake, Thermo Scientific). 1 ml of cell suspension was loaded into a syringe, placed in a syringe pump and connected to the microfluid chip made of polydimethylsiloxane (PDMS) attached to cover glass. The inlet of the chip led to a square channel of 20 × 20 µm and 300 µm length. Pure measurement buffer administered via a second inlet to the microfluidic chip induced a focused constant flow of the cell suspension through the channel. The total flow rate was 0.02 µL/s, of which the sheath flow rate was 0.015 µL/s and the sample flow rate was 0.005 µL/s. Images of the cells were taken at the last third of the channel with a high-speed microscope at 3000 fps in a region of 250 × 80 pixels. Cell analysis was focused on RBCs applying filters for object length and heights from 1.0 µm to 80.0 µm and limited to 10 000 events (Fig. 1b).

The phenol-sulfuric acid method was used to determine the total polysaccharide content of POP extract, using D-glucose as the standard[22 ]. Protein content of POP extract was determined by Lowery method, using BSA as the standard[23 (link)]. The m-hydroxybiphenyl assay was used to measure uronic acid content of POP extract, using glucuronic acid as reference material [24 ]. The moisture content of POP was measured, referring to the method outlined in Kong et al (22). The pH values of the POP at the 2 mg/mL of POP were determined using a pH meter and the relative viscosity of POP (10 mg/mL) was determined using viscometer (Thermo Scientific HAAKE, 388–0100) at 25°C[25 (link)].