Highly Porous Curcumin-Loaded Polymer Mats for Rapid Detection of Volatile Amines

Abstract

Here, the development of highly porous colorimetric indicators that are able to rapidly sense the presence of amine vapors is presented. Specifically, porous, curcumin-loaded polycaprolactone fibers are formed by electrospinning through non-solvent-induced phase separation. In comparison to the non-porous fibers, the developed system shows significantly higher sensitivity and responsivity to the presence of dimethylamine vapors, with a distinct color change at very low vapor concentrations (2.33 ppm compared to 9.26 ppm) within the first 5 s of exposure. Indeed, CIELAB analysis proves that the induced color changes can be easily perceived visually, as the differences between the initial and the final color of the indicator after its interaction with the modified environment are well above the limit for visual perception, even by inexperienced users. Furthermore, the color changes are reversible, enabling the use of the same indicator several times, making it, thus, a sustainable colorimetric indicator system that can be used in applications where the rapid detection of low concentration of alkaline vapors is necessary.

Colorimetric Indicators Based on Anthocyanin Polymer Composites: A Review

“…Although both RGB and UV-visible spectroscopic studies effectively show the color modification of the films, they do not represent the perception of the color changes by the human eye [ 31 , 85 , 176 ]. This is a crucial parameter that should be taken into consideration when evaluating a colorimetric indicator, since a color change is not always perceivable by an inexperienced user [ 181 ]. In order to understand whether the color changes of the colorimetric indicators are visually perceivable by the human eye, CIELAB color space analysis should be adopted as it is specifically designed to approximate human color perception [ 176 ].…”

“…In order to understand whether the color changes of the colorimetric indicators are visually perceivable by the human eye, CIELAB color space analysis should be adopted as it is specifically designed to approximate human color perception [ 176 ]. Once the experimental verification that the color change is perceivable by a human observer is reached, no hardware or technological tools are needed for the assessment of the deployed materials, since the assessment can be done by naked eyes [ 181 ].…”

“…Their advantages derive from their high surface area and mainly focus on three criteria: the real-time response of the indicator, its capacity to present color changes that are perceivable by the human eye, and its ability to respond even when small concentrations of gases are present (low detection limit). Indeed, a recent study by Kossyvaki et al [ 181 ] showed that the more porous—thus with higher surface area—the indicator is, the lower is the detection limit and the faster and more intense the color change upon exposure to amine vapors. More specifically, a direct comparison was made between two different PCL/curcumin based fibrous structures—one with intrafibrillar pores on/in the fibers and one without them—by exposing them to vapors of dimethylamine exactly under the same conditions.…”

“…Hence, alternative structures have been proposed such as anthocyanin-based surface coatings [ 112 , 118 , 147 ], or fibrous mats and foams with a high surface to volume ratio ( Figure 6 d) and porosity [ 23 , 31 , 72 , 91 , 113 , 116 , 118 , 147 , 181 , 200 , 201 , 202 ], which allow faster response and higher sensitivity with respect to compact films fabricated by the same starting materials [ 202 ] ( Figure 6 b–d). Due to their porosity, fibrous and foam-based colorimetric indicators do not present high barrier properties, so it is difficult to be proposed as an integrated smart packaging system.…”

Polyhedral Oligomeric Silsesquioxane as a Polarity Mediator and Reinforced Nanofiller for Fabricating Robust and Hierarchical Porous Film for Cell Bioengineering

“…11 Various methods have been applied to generate porous polymer film including solution casting, 12 photopatterning, 13 salting leaching, 14 gas foaming, 15 freeze-drying, 16 templating, 17 and electrospinning. 18 However, most are not applicable for variable pore size and connectivity. An interconnected porous structure is critical in developing porous materials for tissue engineering.…”