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Creators/Authors contains: "Fan, Jingwei"

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  1. Fundamental synthetic methodology was advanced to allow for the preparation of a reactive glucose-based block copolycarbonate, which was conveniently transformed into a series of amphiphilic block copolymers that underwent aqueous assembly into functional nanoparticle morphologies having practical utility in biomedical and other applications. Two degradable d -glucose carbonate monomers, with one carrying alkyne functionality, were designed and synthesized to access well-defined block polycarbonates ( Đ < 1.1) via sequential organocatalytic ring opening polymerizations (ROPs). Kinetic studies of the organocatalyzed sequential ROPs showed a linear relationship between the monomer conversion and the polymer molecular weight, which indicated the controlled fashion during each polymerization. The pendant alkyne groups underwent two classic click reactions, copper-catalyzed azide–alkyne dipolar cycloaddition (CuAAC) and thiol–yne addition reactions, which were employed to render hydrophilicity for the alkyne-containing block and to provide a variety of amphiphilic diblock poly( d -glucose carbonate)s (PGCs). The resulting amphiphilic PGCs were further assembled into a family of nanostructures with different sizes, morphologies, surface charges and functionalities. These non-ionic and anionic nanoparticles showed low cytotoxicity in RAW 264.7 mouse macrophage cells and MC3T3 healthy mouse osteoblast precursor cells, while the cationic nanoparticles exhibited significantly higher IC 50 (162 μg mL −1 in RAW 264.7;more »199 μg mL −1 in MC3T3) compared to the commercially available cationic lipid-based formulation, Lipofectamine (IC 50 = 31 μg mL −1 ), making these nanomaterials of interest for biomedical applications.« less
  2. A polypeptide-based hydrogel system, when prepared from a diblock polymer with a ternary copolypeptide as one block, exhibited thermo-, mechano- and enzyme-responsive properties, which enabled the encapsulation of naproxen (Npx) during the sol–gel transition and its release in the gel state. Statistical terpolymerizations of l -alanine (Ala), glycine (Gly) and l -isoleucine (Ile) NCAs at a 1 : 1 : 1 feed ratio initiated by monomethoxy monoamino-terminated poly(ethylene glycol) afforded a series of methoxy poly(ethylene glycol)- block -poly( l -alanine- co -glycine- co - l -isoleucine) (mPEG- b -P(A-G-I)) block polymers. β-Sheets were the dominant secondary structures within the polypeptide segments, which facilitated a heat-induced sol-to-gel transition, resulting from the supramolecular assembly of β-sheets into nanofibrils. Deconstruction of the three-dimensional networks by mechanical force (sonication) triggered the reverse gel-to-sol transition. Certain enzymes could accelerate the breakdown of the hydrogel, as determined by in vitro gel weight loss profiles. The hydrogels were able to encapsulate and release Npx over 6 days, demonstrating the potential application of these polypeptide hydrogels as an injectable local delivery system for small molecule drugs.
  3. A strategy for reversible patterning of soft conductive materials is described, based upon a combination of peptide-based block copolymer hydrogelators and photo-thermally-active carbon nanotubes. This composite displays photo-responsive gelation at application-relevant timescales (<10 s), allowing for rapid and spatially-defined construction of conductive patterns (>100 S m −1 ), which, additionally, hold the capability to revert to sol upon sonication for reprocessing.