4-Arm PEG-Norbornene undergoes thiol-ene reaction to prepare hydrogels and other biocompatible materials. Photopolymerization is one that permits facile control over polymerization kinetics because light irradiation precisely controls the initiation and termination of crosslinking reaction. These hydrogels cross-linked through light mediated orthogonal reactions between multi-functional norbornene-modified macromers and sulfhydryl-containing linkers. Include dithiothreitol, PEG-dithiol, bis-cysteine peptides, 4-arm PEG-SH and 8-arm PEG-thiol.
Norbornene is conjugated to PEG through stable amide bonds in our standard catalog products. Norbornene attachment to PEG via hydrolytic ester bonds can be offered through custom synthesis. The norbornene starting material is typically a mixture of endo and exo isomers, predominantly endo isomer. Both isomers have almost identical reactivity in thiol-ene reactions.
Molecular weight: 4-Arm PEG MW refers to the MW of the entire PEG molecule. The MW of each arm is 1/4 of the MW indicated in the product name. MW of PEG was measured by MALDI-MS or GPC. PDI (polydispersity index) of our 4-Arm PEG is 1.02-1.05 with very narrow MW distribution. The number of repeating ethylene oxide units (CH2CH2O) or the degree of polymerization is calculated dividing the PEG MW by 44 (44 is the molecular mass of one repeating unit).
Solubility: Soluble in water and aqueous buffer, chloroform, methylene chloride, DMF, DMSO, and less soluble in alcohol, toluene. Not soluble in ether.
Density: PEG density is approximately 1.125 g/mL.
Physical form: PEG products generally appear as white or off-white powder, and for very low MW 4-Arm PEG such as MW 2k, it may appear as wax-like, semi-solid material due to the low MW and the type of functional groups.
Storage condition: PEG product shall be stored in the original form as received in a freezer at -20C or lower for long term storage. Stock solution of PEG reagents that do not contain oxygen or moisture sensitive functional groups may be temporarily stored in a refrigerator or ambient temperature for multiple days. Stock solution should avoid repeated freeze-and-thaw cycles. See Documents section for detailed storage and handling conditions.
1. A microfluidic-based cell encapsulation platform to achieve high long-term cell viability in photopolymerized PEGNB (PEG norbornene) hydrogel microspheres, J. Mater. Chem. B, 2017, 5, 173-180, Text.
2. Thiol-norbornene photo-click hydrogels for tissue engineering applications, J Appl Polym Sci. 2015 Feb 20; 132(8): 41563, Text.
3. Dynamic, Bioresponsive Hydrogels via Changes in DNA Aptamer Conformation, Macromolecular Bioscience, 2018, DOI: mabi.201800353.
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