Gel permeation chromatography

Nanocarriers were fabricated based on the controlled self-assembly of PEG-bl-PPS block copolymers. A variety of different morphologies can be obtained by controlling the molecular weight (MW) ratio of the hydrophilic PEG to hydrophobic PPS blocks. Block copolymers PEG₄₅-bl-PPS₂₆ were synthesized as previously described [19 (link), 22 (link)]. Briefly, PEG thioacetate was deprotected by sodium methoxide for initiation of anionic ring opening polymerization of poly-propylene sulfide. The reaction was run to completion and subsequently protonated with acetic acid to create the PPS thiol-end groups for subsequent fluorophore conjugation. The resulting block copolymer was purified by double precipitation in methanol and then characterized by 1 H NMR (CDCl₃) and gel permeation chromatography (ThermoFisher Scientific) using Waters Styragel columns with refractive index and UV–vis detectors in a tetrahydrofuran (THF) mobile phase.

Distinct NS were fabricated based on the controlled self-assembly of PEG-bl-PPS block copolymers. A variety of different architectures can be obtained by controlling the molecular weight (MW) ratio of the hydrophilic PEG to hydrophobic PPS blocks. The assembled size of each NS is influenced by the total MW of the block copolymer, with higher MWs producing thicker PPS membranes and PEG coronas. The diameters of vesicular NS can be further controlled via extrusion through nanopore membranes and solvent conditions that influence the aggregation number.^{63 (link),64 (link)} Block copolymers PEG_m-bl-PPS_n were synthesized as previously described.^{30 (link)} Briefly, PEG thioacetate initiator was deprotected by sodium methoxide to reveal the initiating thiolate. Propylene sulfide was added as necessary to polymerize the desired block lengths, and the polymerization was end-capped by 2,2′-dithiodipyridine or protonated with CH₃COOH to create the PPS thiol-end groups for subsequent fluorophore conjugation. The obtained block copolymers (PEG₁₇-bl-PPS₃₀, PEG₄₅-bl-PPS₂₀, and PEG₄₅-bl-PPS₄₄) were purified by double precipitation in cold diethyl ether or methanol and then characterized by ¹H NMR (CDCl₃) and gel permeation chromatography (ThermoFisher Scientific) using Waters Styragel columns with refractive index and UV–vis detectors in a tetrahydrofuran mobile phase.