Appendix A

Supporting Information

Responsive Foams for Nanoparticle Delivery

Christina Tang1, Edward Xiao1, Patrick J. Sinko2, Zoltan Szekely2 and Robert K. Prud’homme1

1Department of Chemical Engineering, Princeton University, Princeton, NJ 08544

2Department of Pharmaceutics, Rutgers, The State University of New Jersey,

Piscataway, NJ 08854

Figure A.1. Temperature responsive foam structure stabilized by solifided particulates (at room temperature) of long-chain alochols stabilized in the ethanol/water liquid phase of the foam by the amphiphilic polysorbate 60. At 37°C, the long-chain alcohols melt and are soluble in the ethanol-water liquid phase, destabilizing the foam structure.

Figure A.2. Temperature-responsive foams at room temperature and when applied to a surface initially heated to 37°C. The foam formulation is listed in Table 1. Yellow tape was used to adhere the thermocouple to the plate during the heated plate experiment

Figure A.3. Foam formulations visualized between crossed polarizers (a) at room temperature heated without polysorbate 60, (b) heated without polysorbate 60, (c) at room temperature with polysorbate 60 and (d) heated with polysorbate 60 with a 100 micron scale bar. Photographs of the corresponding bulk samples are included as insets.

Figure A.4. Foam volume to liquid volume ratios for temperature sensitive foams with up to 10 wt.% PEG in the formulation.

Figure A.5. PAA-based nanoparticle loaded nitrous oxide based foams (A) initially applied to a surface at 37°C, (B) after 60 seconds and (C) particle size distributions measured by dynamic light scattering in water, in 60% ethanol and after foam break.

Table A.1. Approximate foam volume to liquid volume ratios for various Tween surfactants and PEG5K.

Composition / Foam/Liquid Volume / CMC
2 wt.% Tween 20 / 10. / 0.0074 wt%
2 wt.% Tween 60 / 1.4 / 0.0027 wt.%
2 wt.% Tween 80 / 3. / 0.0016 wt.%
2 wt.% PEG5K / 1.4 / N/A

Table A.2. Foam to liquid volume ratios for surfactant based foams with various PEG5K loadings

Composition / Foam/Liquid Volume
2 wt.% Tween 20 / 10.7 ± 0.6
0.5 wt.% Tween 20, 5% PEG5K loading / 10.3 ± 0.6
0.5 wt.% Tween 20, 10% PEG5K loading / 10.4 ± 0.3
0.5 wt.% Tween 20, 50% PEG5K loading / 9.9 ± 0.4
5 wt.% Tween 20, 10% PEG5K loading / 10.6 ± 0.3

Figure A.6 Moisture-responsive foam structure: steric stabilization of Tween 20 micelles in liquid phase of foam stabilizes the foam. When in contact with a moist surface, local dilution of the micelles destabilizes the foam.

Figure A.7. PEG-based nanoparticle loaded surfactant based foam when applied to a dry surface or moist surface. Particle size distributions of the nanoparticles in water (dialyzed), in a 2 wt.% Tween 20 solution (foam formulation), and after foam break. Nanoparticles contain hostasol yellow dye for visualization.

Figure A.8. PMMA nanoparticle loaded Tween 20 foams (A) initially applied to a moist surface (B) after 30 minutes and (C) particle size distributions measured by dynamic light scattering of the formulation (2 wt. % Tween 20 and 34 wt.% PMMA nanoparticles) and after foam break.