Osmotic pressure-dependent release profiles of payloads from nanocontainers by co-encapsulation of simple salts

The encapsulation of payloads in micro- to nano-scale capsules allows protection of the payload from the surrounding environment and control of its release profile. Herein, we program the release of hydrophilic payloads from nanocontainers by co-encapsulating simple inorganic salts for adjusting the osmotic pressure. The latter either leads to a burst release at high concentrations of co-encapsulated salts or a sustained release at lower concentrations. Osmotic pressure causes swelling of the nanocapsule's shell and therefore sustained release profiles can be adjusted by crosslinking it. The approach presented allows for programing the release of payloads by co-encapsulating inexpensive salts inside nanocontainers without the help of stimuli-responsive materials.

Table S1 Composition of the dispersed phase for the dispersion of nanocapsules used in the experiments.NP means nanocapsules and D is added for samples containing 2-nitrophenol sodium salt (dye).X refers to the addition of diethylentriamine (crosslinker) and [Salt] c indicates that the concentration of encapsulated salt in aqueous dispersed phase is equal to "c".Table S3 Composition of the dispersed phase for the dispersion of nanocapsules used in the experiments.NP means nanocapsules and X refers to the addition of diethylentriamine (crosslinker) and [Salt] c indicates that the concentration of encapsulated salt in aqueous dispersed phase is equal to "c".

Characterization methods
The morphology of the NCs was examined with a transmission electron microscope (TEM) (Jeol 1400) operating at an accelerating voltage of 120 kV and a Gemini 1530 (Carl Zeiss AG, Oberkochem, Germany) scanning electron microscope (SEM) operating at 0.35 kV.Droplets of 10 μL of the diluted dispersions were placed on small silica platelets for scanning electron microscopy and on copper grids for TEM measurements.The UV-Vis absorption spectra were recorded with a Perkin Elmer Lambda 25 UV/VIS spectrometer.All dynamic light scattering (DLS) measurements were carried out at 22 °C on a commercially available instrument from ALV GmbH (Langen, Germany) consisting of a goniometer and an ALV-5000 multiple tau full-digital correlators with 320 channels.A helium-neon laser from JDS Uniphase (Milpitas, USA) with an operating intensity of 25 mW and a laser wavelength of λ = 632.8nm was used as a light source.All solutions for the light scattering experiments were prepared in dustfree quartz cuvettes from Hellma (Müllheim, Germany) with an inner diameter of 18 mm, which were cleaned before with distilled acetone.For the measurements of NCs size, their dispersion was diluted against an aqueous SDS solution (X=40, the same dilution condition with the release experiment).The amount of dispersed phase percentage in the NCs dispersion was ~ 0.05wt% after dilution.Samples were very slightly hazy after dilution.
Samples were then withdrawn at two certain times, at t = 0 min and t = 240 min.Dust was removed from the withdraw samples via filtration using 5 micrometer filter LS (PTFE) (Merck Millipore, Germany) before measurements.The Stokes-Einstein equation was applied to calculate diffusion coefficient while viscosity value was set for water at 22 °C.The values of hydrodynamic average diameters of the samples were calculated by independent extrapolation for q = 0 (zero angle).An Activa M spectrometer (Horiba Jobin Yvon, Bernsheim, Germany) equipped with a Meinhardt-type nebulizer and a cyclone chamber was used for ICP-OES measurements.
The device was controlled by an ACTIVAnalyst 5.4 software.For the measurement the following conditions were chosen: 1250 W forward plasma power, 12 L•min-1 Ar flow, and 15 rpm pump flow.The Ar emission at 404.442 nm was employed as a reference line t.The emission lines chosen for calibration and quantification of potassium were 766.490 nm and 769.896 nm with a 5 s integration time.For calibration and quantification of calcium, the emission lines 373.690 and 422.673 with a 5 s integration time were chosen.The emission lines 213.618 and 253.560 were selected for calibration and quantification of phosphorus with a 5 s integration time.For the calibration 5 different standard concentrations were used, baseline correction, and a dynamic underground correction were provided by the software.Each measurement was an average of three repetitions and repeated two times.S1).The average shell thickness for these NCs was calculated to be 36 ± 13 nm.

Fig. S1
Fig. S1 UV-Vis spectra of 2-nitrophenol sodium salt dissolved in water with different concentration (a).Calibration

Fig. S6
Fig. S6 DLS results of sample NP (a and b), NP[KCl] 1 (c and d), NPX (e and f), and NPX[KCl] 1 (g and h) after dilution at time t = 0 and t = 240 min.The values of the hydrodynamic avarage radii were calculated by independent

Fig. S7 .
Fig. S7.Photograph of the dispersion of nanocontainers with encapsulated KSCN before (a) and after (b) addition