Gel: PEG-nb - Nucleus

Overview¶

Gel: PEG-nb is a poly(ethylene glycol) hydrogel made from 4-arm PEG-norbornene (PEG-nb) and a 4-arm PEG-thiol crosslinker, with the photoinitiator lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP). The precursor does not set in response to temperature. The network sets when the precursor is exposed to 405 nm light, so a sample can be loaded and checked before the gel forms. It is set by Embedding: Photocrosslinking.

Reference Composition¶

Module Dependencies

Precursor Solution

Precursor of Gel: PEG-nb.

Component	Molecular weight (g/mol)	Concentration
4-arm PEG-norbornene	5000	80 mM
4-arm PEG-thiol	2000	20 mM
LAP	294.21	16.9 mM
Outer solution		Solution

The precursor is mixed 1:1 with the sample. Final after the 1:1 mix: PEG-nb 40 mM.

Expected Behavior¶

Gel: PEG-nb is expected to stay liquid until it is exposed to 405 nm light, and to set under a 60 s exposure from a projector. It is easy to pipette as a precursor.

Gel: PEG-nb shows higher autofluorescence than Gel: ULGA and Gel: LGA in fluorescence microscopy. This lowers the signal-to-background ratio of a green fluorescent reporter in it. The comparison is GFP-channel microscopy of GUVs and LUVs embedded in each gel (Figure 6).

Requirements¶

Requires a light source at 405 nm (e.g. a digital light processing projector).

Requires an outer solution to dissolve into. For liposomes, use the outer solution used to prepare the liposomes.

Outer-solution framing is not settled for this gel

Editor: confirm that the precursor solvent must match the sample’s own outer solution, not a generic compatible buffer. This page’s source describes the solvent as PBS, deionized water or any buffer. A stock-sheet note records that PBS failed in one set of GUVs. That reads as a looser rule than matching the sample’s own outer solution. Unlike ULGA, the DevNote does not state the matching rule directly for PEG-nb. The wording above, and the Outer solution entries in Reference Composition and Constituent Modules, follow the ULGA and LGA convention. Say whether that convention applies here. Once a published result exists showing what happens with a mismatched solvent, cite it. See also the matching open question on Embedding: Photocrosslinking.

Processes¶

Embedding: Photocrosslinking prepares the precursor and sets the gel.

Materials¶

Materials of Gel: PEG-nb.

Name	Category	Product	Manufacturer	Part #	Price	Storage	Link
4-arm PEG-norbornene	Polymer	4-arm PEG-norbornene	Creative Pegworks	`PSB-4110`	—	−20 °C, dark	Creative PEGWorks PSB-4110
4-arm PEG-thiol	Crosslinker	4-arm PEG-thiol	Creative Pegworks	`PSB-440-5g`	—	−20 °C, dark	Creative PEGWorks PSB-440
LAP	Photoinitiator	Lithium phenyl-2,4,6-trimethylbenzoylphosphinate	Sigma-Aldrich	900889-1G	—	2 °C to 8 °C, dark	Sigma-Aldrich 900889

Constituent Modules¶

4-arm PEG-norbornene — the polymer
4-arm PEG-thiol — the crosslinker
LAP — the photoinitiator
Outer solution — the solution the precursor dissolves into

Credits¶

Developed by Ojaswita Pant (Northwestern University, DevCells Chicago Node, Truby Lab) and Manuel Bibrowski (Imperial College London, DevCells London Node, Elani Lab).

Supported by¶

DevNotes that support this specification include:

Understanding Liposome Behaviour in Hydrogel Matrices

TetO-Regulated PLA1 Sensor in Vesicles: aTc Titration and Spatial Patterning