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. Author manuscript; available in PMC: 2016 Nov 1.
Published in final edited form as: Eur Polym J. 2015 Feb 28;72:386–412. doi: 10.1016/j.eurpolymj.2015.02.022

Table 1.

Strategies for particle encoding and corresponding synthesis techniques

Encoding strategies Synthesis technique Hydrogel material Pre-polymer composition* Biomolecule immobilization if reported Ref.
anisotropic graphical code shape

  • contact photolithography

  • UV crosslinked (365nm)

 PEG PEGDA700 25% v/v, Darocur1173 2%, aqueous buffer with probe 73%

  • methacrylated oligonucleotide (covalent)

  • during synthesis

 [33]
PEG PEGDA700 25% v/v, Darocur1173 1%, aqueous buffer with probe 74%

  • bacteria (physical entrapment)

  • during synthesis

 [33]
shape

  • contact photolithography

  • UV crosslinked (365nm)

 PEG PEGDA3400 or 8000, DMPA 1.5mg/ml, enzyme 1mg ml−1

  • enzyme (physical entrapment)

  • during synthesis

 [67]
PEG 1:1 dilution of PEGDA700 in PBS, HOMPP 1%, functionalized magnetic nanoparticles (NP)

  • magnetic NP functionalized with enzyme (encapsulation)

  • during synthesis

 [36]
PEG PEGDA575 50% v/v, acrylic acid 25% v/v, HOMPP 2%, aqueous buffer

  • protein (covalent; EDC/NHS-mediated reaction)

  • post synthesis

 [74]
shape

  • replica molding using soft lithography

  • UV crosslinked (365nm)

 PEG varying ratio of PEGDA700, PEG200, Darocur1173 and aqueous buffer with probe

  • acrylated oligonucleotide (covalent)

  • during synthesis

 [37]
PEG- chitosan hybrid PEGDA700 30 48% v/v, chitosan oligomer 0 1.2% w/v, Darocur1173 2% v/v, water

  • functionalized oligonucleotide (covalent, Cu-free click chemistry reaction)

  • post synthesis

 [48]
bit-code (extruded holes)

  • stop-flow projection lithography

  • UV crosslinked (365nm)

 PEG varying ratio of PEGDA700, PEG200 or 600, Darocur1173 and aqueous buffer with probe or fluorescent dye

  • acrylated oligonucleotide (covalent)

  • during synthesis

 [35, 45, 70, 71, 92]
PEG PEGDA700 18% v/v, PEG200 36% v/v, Darocur1173 4.5% v/v, aqueous buffer with probe 41.5% v/v

  • acrylated antibody (covalent)

  • during synthesis

 [51, 72]
graphical and spectral encoding shape and structural color

  • contact photolithography

  • UV crosslinked (365nm)

 PEG - acrylamide

  • 1st polymerization: PEGDA700 10% v/v, HMPPO 1% v/v, colloid crystal array in aqueous buffer

  • 2nd polymerization: acrylamide/bisacrylamide (29:1) 10% w/v, APS 1% w/v, TEMED 0.1% v/v, probe in aqueous buffer

  • acryl-modified oligonucleotide (covalent, copolymerization of a second gel layer on particle)

  • post synthesis

 [50]
bit-code and structural color

  • flow projection lithography using dynamic masking

  • UV crosslinked (365nm)

 PEG

  • code: superparamagnetic colloidal nanocrystal clusters dispersed in PEGDA700 75% v/v, water 25% v/v, DMPA 10% wt

  • probe: PEGDA700 75% v/v, aqueous buffer with probe 25%, DMPA 10% wt

  • acrylated oligonucleotide (covalent)

  • during synthesis

 [38]
spectral encoding down- converting nanocrystals up-converting nanoparticles

  • droplet synthesis: herringbone mixer with T-junction

  • UV crosslinked (365nm)

  • stop-flow projection lithography

  • UV crosslinked (365nm)

 PEG

  • PEGDA700 42.8% v/v, Irgacure 2959 6%, nanocrystals 5%

  • oil: light mineral oil with 2% AbilEM90 and 0.05% Span-80

  • none

 [40]
PEG

  • code: PEGDA700 45% v/v, nanoparticles solution (0.5mg μl-1) 40% v/v, poly(styrenesulphonate) 10% v/v, Darocur1173 5% v/v

  • probe: PEGDA700 18% v/v, PEG200 36% v/v, Darocur1173 4.5% v/v, aqueous buffer with probe 41.5% v/v

  • acrylated oligonucleotide (covalent)

  • during synthesis

 [81]
quantum dots (QD)

  • droplet synthesis: flow- focusing, double T-junction, fusion chamber

  • chemically crosslinked

 alginate

  • 4% (w/w) and aqueous OPA:QDs in a 1:1 ratio (octylamine- modified polyacrylic acid-capped CdSe/ZnS QDs (OPA-QDs))

  • crosslinker: barium acetate (50 mM)

  • oil: Soybean

  • IgG antibody (non-specific adsorption)

  • post-synthesis

 [53, 65]
quantum dots

  • droplet synthesis: T-junction with PTFE tubing

  • UV crosslinked (365nm)

 PEG

  • PEG (PEGDA700, Darocur-1173, with silica colloidal particles)

  • oil: oly (1,1,1-trifluoropropylmethylsiloxane) (x-22-821)

  • oligonucleotides (covalent)

  • post-synthesis

 [107, 110]
structural color (colloid nanocrystals)

  • droplet synthesis: capillary device with co-flows and flow- focusing

  • UV crosslinked (365nm)

 PEG

  • PEGDA700 with SDS and Pluronic F-108

  • inner oil phase: ETPTA with QDs and silica nanoparticles to prevent QD aggregation; outer phase: hexadecane with AbilEM90

  • none

 [110]
*

UV-sensitive photoiniators are typically hydroxyalkylphenones: (HMOPP or Darocur1173 (=2-hydroxy-2-methylpropiophenone), DMAP (= 2-dimethoxy-2-phenylacetophenone), Irgacure2959 (=2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone). Irgacure is more water soluble than Darocur but requires longer exposure times.