Figure 1.

Dissolution method in abiotic flow cells (adapted from³⁷). The medium was selected to match the conditions of either the phagolysosomal (pH 4.5) or lung lining fluid (pH 7.4) microenvironment. Particles are in direct contact with the membrane. The choice of the ultrafiltration membrane permeation cutoff is essential; a range 3 kDa to 5 kDa is recommended. This represents a size cut-off of ~1–2 nm (Ren et al., 2006). Smaller cutoffs could induce excess pressure drops and are not recommended. Other options include (recommended): (1) especially for flow-through operation, anti-clogging filters on inlet tubing in the reservoir and elevation of the reservoir by roughly 30 cm, such that hydrostatic pressure compensates for the pressure drop by ultra-high molecular-weight polyethylene (UHMWPE) ultrafiltration membranes. (2) In one implementation, we operated five cells in parallel with a programmable autosampler. Each cell then has its own reservoir inlet tube, peristaltic pump tubing, and sampling.