Physicochemical Properties and Cell Viability of Shrimp Chitosan Films as Affected by Film Casting Solvents. I-Potential Use as Wound Dressing

Abstract

Chitosan solubility in aqueous organic acids has been widely investigated. However, most of the previous works have been done with plasticized chitosan films and using acetic acid as the film casting solvent. In addition, the properties of these films varied among studies, since they are influenced by different factors such as the chitin source used to produce chitosan, the processing variables involved in the conversion of chitin into chitosan, chitosan properties, types of acids used to dissolve chitosan, types and amounts of plasticizers and the film preparation method. Therefore, this work aimed to prepare chitosan films by the solvent casting method, using chitosan derived from Litopenaeus vannamei shrimp shell waste, and five different organic acids (acetic, lactic, maleic, tartaric, and citric acids) without plasticizer, in order to evaluate the effect of organic acid type and chitosan source on physicochemical properties, degradation and cytotoxicity of these chitosan films. The goal was to select the best suited casting solvent to develop wound dressing from shrimp chitosan films. Shrimp chitosan films were analyzed in terms of their qualitative assessment, thickness, water vapor permeability (WVP), water vapor transmission rate (WVTR), wettability, tensile properties, degradation in phosphate buffered saline (PBS) and cytotoxicity towards human fibroblasts using the resazurin reduction method. Regardless of the acid type employed in film preparation, all films were transparent and slightly yellowish, presented homogeneous surfaces, and the thickness was compatible with the epidermis thickness. However, only the ones prepared with maleic acid presented adequate characteristics of WVP, WVTR, wettability, degradability, cytotoxicity and good tensile properties for future application as a wound dressing material. The findings of this study contributed not only to select the best suited casting solvent to develop chitosan films for wound dressing but also to normalize a solubilization protocol for chitosan, derived from Litopenaeus vannamei shrimp shell waste, which can be used in the pharmaceutical industry.

Keywords: chitosan; film; organic acids; solubility; solvent casting; wound dressing.

Figure 1

Images of the shrimp chitosan films manufactured with acetic, lactic, maleic, tartaric and citric acids as film casting solvent. A logotype was placed below the samples to better demonstrate the appearance of the films.

Figure 2

Phosphate buffered saline (PBS) and water contact angle values (average ± standard deviation) for the surface of shrimp chitosan films prepared with acetic, lactic, maleic, tartaric and citric acids. Values labeled with the same letter do not statistically differ from each other (p > 0.05).

Figure 3

Stress-strain curves of shrimp chitosan films prepared with acetic, lactic, maleic, tartaric and citric acids (CS-AA, CS-LA, CS-MA, CA-TA and CS-CA, respectively).

Figure 4

Molecular weight loss percentage in shrimp chitosan films as a function of degradation time. Values labeled with the same letter do not statistically differ from each other (p > 0.05).

Figure 5

X-ray diffractograms of shrimp chitosan (CS) powder, CS-AA, CS-LA, CS-MA and CS-CA films.

Figure 6

Cytotoxicity of shrimp chitosan films prepared with acetic, citric, lactic, and maleic acids (CS-AA, CS-CA, CS-LA, and CS-MA) in BJh-TERT human fibroblast cells for 7 days after cell seeding at five different concentrations of the film extract in PBS medium (2%, 4%, 6%, 8% and 10%). Same letter indicates that there is no significant difference (p > 0.05) by the Tukey’s test.