Editing Magnetic beads Preparation Methods (section)

== Polymer Brush-Modified Magnetic Nanoparticles ==

[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3153590/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3153590/]

Sigma: N,N-dimethylformamide (DMF, anhydrous, 99.8%), CuCl (99.999%), CuBr2 (99%), 2,2’-bipyridyl (bpy, 99%), 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide hydrochloride (EDC), N-hydroxysuccinimide (NHS), 4-dimethylaminopyridine (DMAP), imidazole (99%), 2-hydroxyethyl methacrylate (HEMA, 97%), TWEEN-20 surfactant

HEMA was passed through a column of activated basic alumina (Aldrich) prior to use. NiSO4·5H2O (Columbus Chemical), CuSO4·5H2O (CCI), NaH2PO4 (CCI), Na2HPO4 (Aldrich), tetraethyl orthosilicate (TEOS, Fluka), Nα,Nα-bis(carboxymethyl)-l-lysine hydrate (aminobutyl NTA, Fluka), succinic anhydride (SA, Matheson Coleman & Bell),

[https://ferrofluid.ferrotec.com/products/ferrofluid-emg/water/emg-308/ https://ferrofluid.ferrotec.com/products/ferrofluid-emg/water/emg-308/]

EMG 308 (1 mL, Ferrotec), a solution of Fe3O4 nanoparticles, was diluted with water (13.6 mL) prior to addition of isopropanol (80 mL) to precipitate the magnetite nanoparticles and remove excess surfactant. The supernatant was decanted, and the magnetically collected nanoparticles were then dispersed in 200 mL of 80% (v:v) ethanol (EtOH) in water. After sonication of this solution for 15 min, concentrated ammonia (5 mL) and TEOS (2 mL) were added to the solution,37, 38 and the mixture was mechanically stirred for 3 h. HCl (1 mL, 2M) was added to stop the reaction, and the silica-coated MNPs were magnetically collected and washed twice with 50 mL of EtOH (the same volume of solvent was used for all the washing steps), twice with water, and again with EtOH before drying under vacuum for 6 h.

'''Initiator attachment'''

SiO2-MNPs were dried at 120 °C overnight and then dispersed in toluene through sonication (0.2 g beads in 150 mL). Tricholorosilane initiator, '''(11-(2-bromo-2-methyl) propionyloxy)undecyltrichlorosilane'''39 was added (0.2 mL), and the mixture was stirred at 65 °C overnight while bubbling with N2. The initiator-modified beads were washed twice with 50 mL of toluene and twice with 50 mL of THF prior to drying in vacuum for 4 h.

'''(11-(2-bromo-2-methyl) propionyloxy)undecyltrichlorosilane'''

[[File:TETHERED INITIATOR.png|500px]]

tethered initiator for atrp on silicon surfaces.

2-Hydroxyethyl methacrylate:&nbsp; 500 G $33.90&nbsp;[https://www.sigmaaldrich.com/catalog/product/aldrich/128635 https://www.sigmaaldrich.com/catalog/product/aldrich/128635]

[[File:HEME.png]]

2,2′-Bipyridyl

[[File:BPY.png]]

DMAP

[https://www.sigmaaldrich.com/catalog/substance/4dimethylaminopyridine12217112258311 https://www.sigmaaldrich.com/catalog/substance/4dimethylaminopyridine12217112258311]



Growth of poly(2-hydroxyethyl methacrylate) (PHEMA) on beads

Initiator-modified beads (0.1 g) were dispersed by sonication in purified HEMA (10 mL), and the mixture was degassed via 3 freeze-pump-thaw cycles. In another Schlenk flask, HEMA (10 mL) was mixed with water (10 mL) and bpy (366 mg), and after 3 degassing cycles CuCl (82.5 mg) and CuBr2 (54 mg) were added and another 2 degassing cycles were performed. In a glove bag, the two degassed HEMA mixtures were combined and magnetically stirred for 1 h. Subsequently, air was bubbled through the polymerization solution until its color turned from dark brown to dark green, and the beads were then washed sequentially with 20 mL of DMF (the same volume of solvent was used for all the washing steps), EtOH (twice), water, and EtOH, and dried in vacuum.

Derivatization

40 PHEMA-MNPs (200 mg) were dispersed in 10 mL DMF by sonication and mixed with 10 mL DMF containing SA (200 mg) and DMAP (200 mg) prior to stirring at 55 °C overnight. The SA-MNPs were washed with 20 mL of DMF (the same volume of solvent was used for all the washing steps), EtOH (twice) and then water (twice). Subsequently, an aqueous solution (20 mL) containing EDC (0.1 M) and NHS (0.1 M) was mixed with the SA-MNPs for 30 min followed by washing with EtOH three times. Then, the EDC/NHS-activated beads were exposed to a pH 10, '''aminobutyl-NTA '''(0.1 M) aqueous solution for 1 h with magnetic stirring and washed with water three times. Finally, the NTA-SA-PHEMA-MNPs were immersed in CuSO4 (0.05 M) for 1 h, washed with water three times and EtOH twice and dried under vacuum for 5 h.