Cyclohexanone

Microfluidic devices were fabricated in polydimethylsiloxane (PDMS) using the standard soft lithography process with dry photoresist masters, as we detailed previously [31 (link)]. Briefly, 3″ silicon wafers were dehydrated for 15 min on a 225 °C hotplate, laminated with a 50 μm thick ADEX film (DJ Microlaminates Inc., Sudbury, MA, USA) and baked for 5 min on a 65 °C hotplate. Next, the wafers were exposed to UV light (I-line 365 nm, Optical Associates Inc., San Jose, CA, USA) for 33 s at 10 mW/cm² through a mask plate in hard contact. The wafers were developed in cyclohexanone (98%, Acros Organics, Pittsburg, PA, USA), washed with isopropyl alcohol (IPA) and deionized (DI) water, air dried and baked for 90 min on a 170 °C hotplate. A mixture of a 10:1 ratio of PDMS (Sylgard 184, Dow Corning, Midland, MI, USA) and curing agent was cast on the master, degassed for 90 min in a vacuum oven and cured for 120 min at 80 °C. Devices were cut out using a scalpel and inlet and outlet ports were cored using a biopsy punch with a diameter of 1.5 mm. Finally, devices were bonded to standard microscope glass slides using an oxygen plasma treatment at 10 W for 20 s (PE-50, Plasma Etch Inc., Carson City, NV, USA), baked for 60 min at 80 °C and allowed to cool to room temperature before use.

Throughout the experiments, poly(d,l-lactic acid) (PDLLA), Mn 47,000 gmol⁻¹, from Evonik Rohm GmbH (Darmstadt, Germany), poly(vinyl acetate-co-alcohol) (PVA) M_w 25 kDa, 88% hydrolysed from Sigma-Aldrich (St. Louis, MO, USA,)and ethyl acetate from Fisher Scientific (Waltham, MA, USA) were used, without modification.
Surfmers were produced in house using poly(ethylene glycol) methyl ether methacrylate (mPEGMA), Mn = 300, ethylene glycol phenyl ether acrylate (EGPEA), tetrahydrofurfuryl acrylate (THFuA), and 2,2′-azobis (2-methylpropionitrile) (AIBN, 98%). These materials were purchased from Sigma Aldrich and used without further purifications. The catalytic CTA, bis[(difluoroboryl)diphenylglyoximato] cobalt (II) (PhCoBF) (DuPont, DE, USA). Cyclohexanone and heptane used as solvents for the synthesis and precipitations, respectively, were used as received and supplied by Fisher Scientific.

Never-dried softwood kraft pulp fibers (Metsä Board Husum mill, Sweden) were used to prepare TCNF following the method of (Saito et al. 2007 (link)). Sulfur-free birch lignin produced by BLN process (named after the company that initially developed the technology) was provided by CH Bioforce Oy (Finland). Briefly, the process involves hot water (150 °C) extraction of hemicelluloses from biomass followed by alkali cooking to extract lignin, all in oxygen-starved conditions (von Schoultz 2015 ). The LNPs were prepared by anti-solvent nanoprecipitation in acetone and water (Figueiredo et al. 2021 (link)). These LNPS were cationized by coating with glycidyltrimethylammonium chloride (GTAC)-treated lignin to produce cationic LNPs (cLNPs) (Agustin et al. 2022 (link); Sipponen et al. 2017 (link)). The detailed preparation of TCNF, LNPs, and cLNPs and their basic characteristics are available in the Supporting Information (Fig. S2). Hexadecane, GTAC, cyclohexanone, and acetone were purchased from Fisher Scientific (Finland). The pharmaceutical compounds, which are certified reference materials, dialysis membrane tubing (Spectra/Por 7, 6–8 kDa molecular weight cut-off (MWCO), Spectra/Por 1, 1 kDa MWCO), glass microfibre filters with a 0.7 µm pore size (Whatman GF/F), chromasolv-grade acetonitrile and methanol were obtained from Sigma-Aldrich (Finland).