Permeation Study of Polymer Nanoparticles

The study started after 22 days of culture to get the desired TEER value. A Krebs-Ringer buffer (KRB) was prepared to perform this permeation study. First, the cells were rinsed three times with KRB, and 1.0 mL was added to the apical side and 2.0 mL to the basolateral side. The plates were kept in an incubator (37°C, 5% CO₂) for 30 min. After, around 3 milligrams of each powder (pure PP, SCNPs, CCNPs, and ChCNPs) were deposed on the apical side. Each powder was introduced into three different inserts to perform the test in triplicate and diffused for three hours. The apparent permeability coefficient (P_app) was calculated for each powder formulation by the following equation and expressed in cm/s50 (link),54 (link) (Equation 5):
(5)\documentclass[12pt]{minimal}
\usepackage{wasysym}
\usepackage[substack]{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage[mathscr]{eucal}
\usepackage{mathrsfs}
\DeclareFontFamily{T1}{linotext}{}
\DeclareFontShape{T1}{linotext}{m}{n} {linotext }{}
\DeclareSymbolFont{linotext}{T1}{linotext}{m}{n}
\DeclareSymbolFontAlphabet{\mathLINOTEXT}{linotext}
\begin{document}
$${P_{app}} = {\rm{ }}{{\left[{{C_b}} \right] \times V} \over {A \times \left[{{C_0}} \right] \times \Delta t}}{\rm{ }}$$
\end{document}where (µg/mL) is the concentration of PP in the basolateral compartment at the end of the experiment, (µg/mL) is the initial apical concentration of PP, V (mL) is the volume of the basolateral compartment, A is the surface area (cm²) and is the duration of the experiment (s).
The Transport Enhancement Ratio (TER) of the formulation compared to the pure PP was calculated from the P_app values (Equation 6):
6\documentclass[12pt]{minimal}
\usepackage{wasysym}
\usepackage[substack]{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage[mathscr]{eucal}
\usepackage{mathrsfs}
\DeclareFontFamily{T1}{linotext}{}
\DeclareFontShape{T1}{linotext}{m}{n} {linotext }{}
\DeclareSymbolFont{linotext}{T1}{linotext}{m}{n}
\DeclareSymbolFontAlphabet{\mathLINOTEXT}{linotext}
\begin{document}
$$TER = {\rm{}}\left({{{{P_{app{\rm{}}\left({formulation} \right)}}} \over {{P_{app{\rm{}}\left({PP} \right)}}}}} \right)$$
\end{document}where P_{app(formulation)} corresponds to the Papp of SCNPs, CCNPS, and ChCNPs formulations and where P_app(PP) corresponds to the P_app of PP.
The TEER was measured again 24 hours after the experiment to evaluate the integrity of the epithelium cells.