In Vitro and Sensory Evaluation of Capsaicin-Loaded Nanoformulations

Capsaicin has known health beneficial and therapeutic properties. It is also able to enhance the permeability of drugs across epithelial tissues. Unfortunately, due to its pungency the oral administration of capsaicin is limited. To this end, we assessed the effect of nanoencapsulation of capsaicin, under the hypothesis that this would reduce its pungency. Core-shell nanocapsules with an oily core and stabilized with phospholipids were used. This system was used with or without chitosan coating. In this work, we investigated the in vitro release behavior of capsaicin-loaded formulations in different physiological media (including simulated saliva fluid). We also evaluated the influence of encapsulation of capsaicin on the cell viability of buccal cells (TR146). To study the changes in pungency after encapsulation we carried out a sensory analysis with a trained panel of 24 students. The in vitro release study showed that the systems discharged capsaicin slowly in a monotonic manner and that the chitosan coating had an effect on the release profile. The cytotoxic response of TR146 cells to capsaicin at a concentration of 500 μM, which was evident for the free compound, was reduced following its encapsulation. The sensory study revealed that a chitosan coating results in a lower threshold of perception of the formulation. The nanoencapsulation of capsaicin resulted in attenuation of the sensation of pungency significantly. However, the presence of a chitosan shell around the nanoformulations did not mask the pungency, when compared with uncoated systems

Cytotoxicity of different formulations against TR146 cells determined using the MTT assay.

<p>Relative cell viability following treatment with free capsaicin at increasing concentrations (Left). Relative cell viability following treatment with the different nanoformulations or their constituents at a universal concentration of 500 μM capsaicin (Right). For all experiments, cells were incubated for 3 h. Mean values ± SD. (n = 3, * p < 0.05, **** p < 0.0001). NC = nanocapsules; NE = nanoemulsion.</p

Pungency intensity tests of the nanoformulations in comparison to free capsaicin.

<p>Sensory evaluation of pungency of the different nanoformulations in comparison to the free compound at different concentrations (scale: 0–10; 0 = “not detectable”, 10 = “extremely pungent”). C = free capsaicin; NC = nanocapsules; NE = nanoemulsion. For statistical analysis refer to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0141017#pone.0141017.t004" target="_blank">Table 4</a>.</p

HPLC gradient profile for the detection of capsaicin.

<p>HPLC gradient profile for the detection of capsaicin.</p

Mean pungency ratings of the three kinds of formulations.

<p>C: unencapsulated; NC: nanocapsules, NE: nanoemulsion.</p><p>^a a, b, c, d, e, f–<i>I</i>_max mean values with different letters in columns are significantly different</p><p><i>p</i> < 0.05.</p><p>Mean pungency ratings of the three kinds of formulations.</p

Individual best estimate threshold (BET) of capsaicin-loaded nanoformulations.

<p>Individual BET of each panelist in comparison to the group BET for the capsaicin-loaded nanoemulsion and nanocapsules.</p

Number of correct answers during best estimate threshold (BET) study.

<p>Number of correct answers according to different concentrations of capsaicin for the nanoemulsion and the nanocapsules.</p

Physicochemical properties of chitosan-coated nanocapsules and nanoemulsions with or without capsaicin.

<p>NC: nanocapsules, NE: nanoemulsion.</p><p>Physicochemical properties of chitosan-coated nanocapsules and nanoemulsions with or without capsaicin.</p

Individual best estimate threshold (BET) of unloaded nanoformulations.

<p>Individual BET of each panelist in comparison to the group BET for the unloaded nanoemulsion and nanocapsules.</p