Jukuan Zheng

Post-Assembly Derivatization of Electrospun Nanofibers via Strain-Promoted Azide Alkyne Cycloaddition

A primary amine-derivatized 4-dibenzocyclooctynol (DIBO) was used to initiate the ring-opening polymerization of poly(γ-benzyl-L-glutamate) (DIBO-PBLG). This initiator yields well-defined PBLG polymers functionalized with DIBO at the chain termini. The DIBO end group further survives an electrospinning process that yields nanofibers that were then derivatized post-assembly with azide-functionalized gold nanoparticles. The availability of DIBO on the surface of the fibers is substantiated by fluorescence, SEM, and TEM measurements. Post-assembly functionalization of nanofiber constructs with bioactive groups can be facilitated easily using this process.

4-Dibenzocyclooctynol (DIBO) as an initiator for poly(ε-caprolactone): copper-free clickable polymer and nanofiber-based scaffolds

Utilization of 4-dibenzocyclooctynol (DIBO) as an initiator for the ring-opening polymerization of [varepsilon]-caprolactone yields well-defined, high molecular weight poly([varepsilon]-caprolacton ...

Enhanced schwann cell attachment and alignment using one-pot "Dual Click" GRGDS and YIGSR derivatized nanofibers

Using metal-free click chemistry and oxime condensation methodologies, GRGDS and YIGSR peptides were coupled to random and aligned degradable nanofiber networks postelectrospinning in a one-pot reaction. The bound peptides are bioactive, as demonstrated by Schwann cell attachment and proliferation, and the inclusion of YIGSR with GRGDS alters the expression of the receptor for YIGSR. Additionally, aligned nanofibers act as a potential guidance cue by increasing the aspect ratio and aligning the actin filaments, which suggest that peptide-functionalized scaffolds would be useful to direct SCs for peripheral nerve regeneration.

Enzyme-catalyzed ring-opening polymerization of ε-caprolactone using alkyne functionalized initiators

Well-defined poly(caprolactone)s were generated using alkyne-based initiating systems catalyzed by Candida antarctica Lipase B (CALB). Propargyl alcohol and 4-dibenzocyclooctynol (DIBO) were shown to efficiently initiate the polymerizations under metal free conditions and yielded 4 to 24 KDa polymers with relatively narrow molecular mass distribution. The alkyne bonds in the strained and unstrained initiating systems survived the polymerization conditions and the purification process. The resulting bonds can be sequentially functionalized post-polymerization using metal free and copper catalyzed click chemistry conditions.

Concentration-Dependent hMSC Differentiation on Orthogonal Concentration Gradients of GRGDS and BMP-2 Peptides

Self-assembled monolayer substrates containing tethered orthogonal concentration profiles of GRGDS (glycine/arginine/glycine/aspartic acid/serine) and BMP-2 (bone morphogenetic protein) peptides are shown to accelerate or decelerate, depending on the concentrations, the proliferation and osteoblastic differentiation of human mesenchymal stem cell (hMSC) populations in vitro without the use of osteogenic additives in culture medium. Concurrently, the single peptide gradient controls (GRGDS or BMP-2 only) induce significantly different proliferation and differentiation behavior from the orthogonal substrates. Bone sialoprotein (BSP) and Runt-related transcription factor 2 (Runx2) PCR data acquired from hMSC populations isolated by laser capture microdissection correspond spatially and temporally to protein marker data obtained from immunofluorescent imaging tracking of the differentiation process. Although genomic and protein data at high concentrations area GRGDS (71-83 pmol/cm(2)):BMP-2 (25 pmol/cm(2)) reveal an implicit acceleration on the hMSC differentiation timeline relative to the individual peptide concentrations, most of the GRGDS and BMP-2 combinations displayed significant antagonistic behavior during the hMSC differentiation. These data highlight the utility of the orthogonal gradient approach to aid in identifying optimal concentration ranges of translationally relevant peptides and growth factors for targeting cell lineage commitment.