CC BY
3
UDC 54
DOI: 10.18698/1812-3368-2023-4-175-193
PREPARATION AND CHARACTERIZATION OF BIOCOMPOSITE FILMS OF SODIUM ALGINATE/KAPPA-CARRAGEENAN/IOTA-CARRAGEENAN LOADED WITH AMINOETHOXYVINYLGLYCINE
N.A. Villacrés1 É.T.G. Cavalheiro2 A.P.G. Ferreira2 T. Venancio3 H.A. Alarcón1 A.C. Valderrama1
1 National University of Engineering, Lima, Peru
2 University of Säo Paulo, Säo Paulo, Brazil
3 Federal University of Säo Carlos, Säo Paulo, Brazil
Abstract
This work focused on the development of a new biomaterial from polysaccharides. Thus composite films of sodium alginate, k-carrageenan, and i-carra-geenan plasticized with glycerol and poly(ethylene glycol) 400 (PEG 400) were prepared. The surface properties of the resulting films in terms of surface morphology were investigated. The best ratio between glycerol and PEG 400 used as plasticizers to prepare sodium alginate films was determined. Opacity, water content, SEM, TGA, and FTIR studies determined the optimal ratio between glycerol and PEG 400. The addition of carrageenans in the composite films showed differences in the TGA curves and on surface of the films. The composite film was loaded with an ethanolic solution of aminoethoxyvinylglycine (AVG). The AVG loaded in the composite film exhibited improved surface area, increased percent of crystallinity, and higher percent release at a lower temperature and its release kinetics were studied
Keywords
Alginate, carrageenan, plasticizers, films, aminoethoxyvinylglycine
Received 16.02.2023 Accepted 07.04.2023 © Author(s), 2023
The research was funded by the Peruvian government through Prociencia/World Bank Program (project grant 01-2018-FONDECYTBM-IADTUM)
Introduction. The environmental pollution generated by dumping and accumulating synthetic plastics has created the need to develop biodegradable
materials [1]. These materials, called biopolymers, are prepared from renewable sources such as polysaccharides, proteins, and mixtures [2].
Polysaccharides are used to produce biopolymers due to their highwater retention, non-toxicity, biocompatibility, and ability to act as drug carriers [3]. The mixture of polysaccharides is used to improve the physicochemical properties of biopolymers, obtain films with functional activities [4], and design controlled and sustained release formulations [5]. Among the various polysaccharides, the most used are cellulose, starch, chitosan, alginate, and carrageenan [6].
Sodium alginate is a water-soluble, biodegradable, and biocompatible polysaccharide extracted from brown algae and composed of linear (1-4) bonds of a-L-guluronic acid and P-D-mannuronic acid [7] (Fig. 1, a). Due to its good mechanical resistance, this polysaccharide is used to produce edible films and coatings. However, it is highly soluble in water [8], limiting its application in food packaging [9].
Carrageenans are polysaccharides extracted from red algae. Chemically, carrageenans are considered as the partially sulfated galactans [10]. They are formed by a linear backbone of repeating units of D-galactose and 3,6-anhydro-D-galactose (3,6-AG) linked through alternating a-(1-3) and P-(1-4) glycosidic [11], which allows them to be used in the production of biodegradable films [12]. The number and position of the sulfate ester groups and the 3,6-AG content allow carrageenan to be classified into X (lambda), k (kappa), i (iota), u (nu), (mu), 9 (theta) and E, (xi). For example, kappa-carrageenan (k-carrageenan) has a sulfate group at O-4 of P-D-galactopyranose (Fig. 1, b), which contains 25-30 % sulfate ester and 28-35 % 3,6-AG, and iota-carrageenan (i-carrageenan) has an additional sulfate group residue at O-2 of a-D-galactopyranose (Fig. 1, c) and contains 28-35 % sulfate ester and 25-30 % 3,6-AG [13].
Plasticizers are low molecular weight, non-volatile, and high boiling liquid additives. They are used to increase the flexibility or plasticity of polymers and to facilitate the processing of polymeric films [14]; commonly used plasticizers include glycerol, sorbitol, polyethylene glycol, xylitol, and urea [15]. Glycerol is a non-volatile polyol used as a plasticizer because it increases the mechanical and permeability properties of the films; due to the hydrogen bonds between the polymer chains that expand the intermolecular spaces and lead to an increase in the permeability and flexibility of the films [16]. Polyethylene glycol (PEG) is commercially available in a wide range of molecular weights, from 300 to 10,000 g • mol-1, and due to its excellent biocompatibility and non-toxicity, it is used in film production. The increase in the molecular weight of PEG causes
NaOOC
с
d °
Fig. 1. Structural representation of sodium alginate (a), k-carrageenan (b), i-carrageenan (c) and structural formula of aminoethoxyvinylglycine (d)
a decrease in its polarity and solubility, as well as its ability to interact with polymer chains, so PEGs with lower molecular weights exhibit a better plasticizing effect [17]. When the plasticizer is added to aqueous polymer dispersion, it disperses within the aqueous phase and diffuses between the polymeric matrices. However, when a mixture of polymers is present, its distribution within the coating dispersions and films may not be homogeneous [18].
The films made with polysaccharides are loaded with different active agents because these substances can migrate from the material to the food [19]. These films can be loaded with ethylene inhibitors and used to prevent the negative
effects caused by the ripening process induced by ethylene in foods, prolonging the shelf life of foods [20]. Ethylene inhibitors are classified as biosynthesis inhibitors, e.g., aminoethoxyvinylglycine (AVG), and action inhibitors, e.g., 1-methyl-cyclopropene (1-MCP) [21]. Aminoethoxyvinylglycine — AVG ((S)-trans-2-amino-4-(2-aminoethoxy)-3-butenoic acid hydrochloride) (Fig. 1, d) is an ethoxy analog of rhizobitoxine that inhibits ethylene biosynthesis by blocking the action of the 1-aminocyclopropane-1-carboxylic acid synthase enzyme [22].
Considering the need and importance of the development of new materials made from natural resources, this research focused on the study of the proportion between plasticizers and the addition of carrageenan derivatives in a sodium alginate solution to prepare composite films loaded with an ethylene inhibitor and study its release kinetics.
Materials. Sodium alginate, glycerol 99 % GC, average weight poly(ethylene glycol) Mn 400 (PEG 400), k-carrageenan (sulfated plant polysaccharide), i-carrageenan (commercial grade, type II, predominantly iota carrageenan) and aminoethoxyvinylglycine hydrochloride were purchased from Sigma — Aldrich. Ethanol from Merck was also used.
Experimental methods and analysis. Preparation of composite films loaded with AVG. The preparation of the composite films loaded was performed in three stages. In the first stage, the relationship between plasticizers (glycerol and PEG 400) and sodium alginate in the production of films was determined; in the second stage, composite films of sodium alginate with k-carrageenan and i-carrageenan were prepared, and in the third stage the composite film loaded with AVG was prepared. Table 1 details the parameters used in the preparation of the films.
Table 1
Parameters used in the preparation of the films
Film [NaAlg], mL Glycerol, g PEG-400, g [к-carra-geenan], mL [i-carra-geenan], mL AVG, mL
NaAlgCG9P1 30 0.9 0.1 - - -
NaAlgCG7P3 0.7 0.3
NaAlgCG5P5 0.5 0.5
NaAlgCG9P1k 0.9 0.1 5.0
NaAlgCG9P1i - 5.0 -
NaAlgCG9P1ki 5.0
NaAlgCG9P1kiA 10
Determination of the ratio of plasticizers. In this case 30 mL of 1.5 % w • v-1 sodium alginate (NaAlg) and 1 g of glycerol and poly(ethylene glycol) (PEG 400) mixture in different ratios (9:1, 7:3, and 5:5 w • w-1; respectively) was prepared. These solutions were kept under constant stirring for 30 minutes at 50 °C and poured into Petri dishes, and dried at 50 °C for 24 h.
Addition of carrageenans. Thus, 30 mL of sodium alginate (NaAlg) at 1.5 % w • v-1 was mixed with 5 mL of к-carrageenan (1.0 % w • v-1) and/or 5 mL of i-carrageenan (1.0 % w • v-1) and kept under constant stirring for 60 min at 70 °C. Then 1 g of the mixture of glycerol and PEG 400 in a 9:1 w • w-1 ratio was added and stirred for 30 min at 50 °C. Finally, the solutions were molded into a petri dish and dried at 50 °C for 24 h.
Loaded AVG. In this case 30 mL of sodium alginate (NaAlg) at 1.5 % w • v-1 was mixed with 5 mL of к-carrageenan (1.0 % w • v-1) and 5 mL of i-carrageenan (1.0 % w • v-1) for 60 min at 70 °C. Then 1 g of the mixture of glycerol and PEG 400 in a 9:1 w • w-1 ratio was added to the mixture of polysaccharides and stirred for 30 minutes at 50 °C. Subsequently, 10 mL of an ethanolic solution of aminoethoxyvinylglycine (AVG) (20 mg • L-1) was added and for 30 min at 50 °C was stirred. Finally, the solution was poured into a petri dish and dried at 50 °C for 24 h.
AVG Release. The loaded films were immersed in 25 mL of a 70 % ethanolic solution with constant stirring at 100 RPM at 10 and 25 °C. For measurement purposes, 2 ml of release medium were withdrawn at predetermined times, and its absorbance was measured at 197.5 nm using a UV-1800 UV-V is spectrophotometer (Shimadzu). This aliquot was returned after each reading, and the system was kept under stirring until the next reading.
To evaluate whether Fick's law governs the diffusion processes, the equations of Higuchi [23]
Ml ,0.5
Ma
= KHt05, (1)
and Korsmeyer — Peppas [24]
Mt
Щ = Ktn (2)
were used. These equations describe the release process from one of the faces of the film and the release from erosion or dissolution of the polymeric matrix, respectively. In Eq. (1), (2) Mt / Mx is the fraction of solute released at time t, Kh is the Higuchi diffusion constant. In Eq. (2) K is the system constant, n is the diffusion exponent.
Opacity. The opacity of the films containing different proportions in the mixture of plasticizers was obtained using equation
^ • " logT
Opacity =-2—,
d
where T is the light transmittance of the film at 600 nm; d is the thickness of the film (mm).
Film thickness images were collected using a Zeiss-LSM780 laser scanning microscope with an inverted confocal fluorescence, 40x objective lens, a numerical aperture of 0.8, and a resolution at x of rx = 165 nm, and using the ImageJ software, the thickness value was obtained by taking 10 measurements. In addition, the transmittance value was recorded on Varian Cary% 50 UV-Vis spectrophotometer.
Water content. The water content of the films made with different proportions of glycerol and PEG 400 was obtained by cutting the films into rectangular pieces and then weighing them before and after being dried at 105 °C for 24 h in an oven
Wi - Wf
Water content =-—,
Wf
where Wi , Wf are the initial (g) and the final masses of the film (g). Water content was expressed as g (H2O) g-1 (dry solids).
Characterization. Fourier transform infrared (FTIR). FTIR spectra were obtained on the Shimadzu IRPrestige 21 spectrophotometer with attenuated total reflectance (ATR) module.
Thermogravimetric analysis (TGA). The thermogravimetric curves were collected in a SDT Q600 simultaneous TG/DTA modulus managed by the Thermal Advantage for Q Series software (v. 5.5.24) both from TA Instruments. Measurements were performed in open a-alumina sample holders using sample mass of 5.0 ± 0.1 mg in a dynamic N2 atmosphere flowing at 50 mL • min-1; the temperature range was selected as 25-1000 °C with a heating rate of 10 °C • min-1.
X-ray diffraction (XRD). The diffractograms were obtained in a range of 20 from 5° to 100° in a D8 Advance diffractometer equipment (Bruker) equipped with a Cu source (Ka = 1.5418 A) operating at a voltage of 40 kV and 40 mA (1600 W) and a LynxEye model PSD type detector.
Scanning electron microscopy (SEM). Images were obtained with an LEO 440 microscope (Cambridge) equipped with a 7060 detector (Oxford) and
at resolutions of 10 and 1 ^m at 1000x and 5000x magnification, respectively. The samples were gold-plated in a MED 020 high vacuum metallizer (Bal-Tec).
Results and discussions. Preparation of films. First stage. Three films of sodium alginate plasticized with a mixture of glycerol and PEG 400 at different proportions were prepared: the first film was named NaAlgCG9P1 (Fig. 2, a), the second film NaAlgCG7P3 (Fig. 2, b), and the third film NaAlgCG5P5 (Fig. 2, c). The increase of PEG 400 in the ratio of the plasticizers increased the opacity (Table 2), decreased the percentage of transmittance at 600 nm, and modified the surface of the films, making them rougher (Fig. 2, d-f, Fig. 3, a). The whitish appearance of the films may be due to the high molecular weight and relatively low content of hydroxyl groups of PEG 400, which caused phase separation and incompatibility with the NaAlg polymeric matrix and increased surface roughness and heterogeneity of the films [25]. On the contrary, glycerol has a greater number of polar groups (-OH), which generates an increase in the moisture content in the films (see Table 2), and greater compatibility by forming hydrogen bonds with the hydroxyl groups of NaAlg [26], which creates large spaces between the polymer chains and improves the homogeneity on the surface of the films [27].
Fig. 2. Films obtained from sodium alginate plasticized with glycerol and PEG 400 and their respective SEM images with a magnification of 1.00 KX (10 |^m) and 5.00 KX (1 ^m): NaAlgCG9P1 (a, d), NaAlgCG7P3 (b, e) and NaAlgCG5P5 (c, f)
Table 2
Values of thickness, transmittance at 600 nm, opacity, and moisture content of the films obtained at different proportions of plasticizers
Film Thickness, |am T600, % Opacity, AU — nm ■ mm-1 Water content, g (H2O) g-1 (d.S.)
NaAlgCG9P1 173.43 ± 4.18 90.18 0.26 0.8975 ± 0.2719
NaAlgCG7P3 102.92 ± 2.59 64.93 1.82 0.7654 ± 0.0942
NaAlgCG5P5 NB. Тбоо (%) is p 164.57 ± 2.08 >ercent of transmittan 19.33 ce at 600 4.34 nm. 0.3145 ± 0.0702
300 400 500 600 700 800 900 1000 Wavelength, nm
100
4000
3000 2000 Wavelength, cm с
1000
200 400 600 800 1000 Temperature, °C b
Fig. 3. Light transmittance (a), TG curves (b), and FTIR spectrum (c) of NaAlgCG9P1 (—), NaAlgCG7P3 ( ), and NaAlgCG5P5 ( ) films
-l
Figure 3, b presents the TG curves of the films whose mass losses were assigned to the thermal events of dehydration, film degradation, polymer degradation, and carbonization [28]. The larger amount of glycerol in the mixture of plasticizer resulted in an increased mass loss during dehydration step, due to the higher hydrophobicity resulting from the presence of hydroxylated glycerol in the samples [29]. The thermal events and the mass loss with their respective temperature ranges of these films are summarized in Table 3.
Table 3
Mass loss values from TGA of NaAlgCG9P1, NaAlgCG7P3, and NaAlgCG5P5 films
Film Weight, mg Thermal event AT, °C Mass loss, %
NaAlgCG9P1 5.176 Dehydration 22.0-120.3 22.8
Film degradation 120.3-321.3 61.1
Polymer degradation 321.3-615.0 5.10
Carbonization 615.0-989.5 5.41
Carbonaceous residue 989.5 5.59
NaAlgCG7P3 5.051 Dehydration 21.0-108.2 20.3
Film degradation 108.2-378.0 61.0
Polymer degradation 378.0-616.0 3.76
Carbonization 616.0-991.5 12.92
Carbonaceous residue 991.5 2.02
NaAlgCG5P5 5.470 Dehydration 22.1-105.0 17.0
Film degradation 105.0-379.4 62.0
Polymer degradation 379.4-630.3 3.79
Carbonization 630.3-990.1 11.58
Carbonaceous residue 990.1 5.63
The FTIR spectra of the films prepared with different ratios of the plasticizers are presented in Fig. 3, c. The bands at 2931 and 2879 cm-1 are associated with C-H stretching [30]. On the other hand, the increase of PEG 400 generates more intense bands at 1605, 1409, 1244, and 1090 cm-1, which correspond to the asymmetric and symmetric stretching of the carboxylate [31] and C-OH and C-O-C stretches [32]; respectively. However, the increase of glycerol in the mixture of plasticizers increases the band corresponding to the hydroxyl group (-OH) (3292 cm-1), as well as those from water. Therefore, it is assumed that the hydrogen bonds between water and sodium alginate were weakened due to the higher water-plasticizer affinity. Being partially replaced by the relatively weaker hydrogen bonds between the polar groups of the plasticizers and those corresponding to the polymeric matrix [33].
Second stage. Three films composed of sodium alginate with carrageenan (k-carrageenan and/or i-carrageenan) and plasticized with glycerol/PEG 400 in a 9:1 ratio were prepared. The films were called NaAlgCG9P1k (Fig. 4, a), NaAlgCG9P1i (Fig. 4, b), and NaAlgCG9P1ki (Fig. 4, c). The SEM images
Fig. 4. Sodium alginate/carrageenan/glycerol/PEG 400 composite films, and their respective SEM images at 1.00 KX (10 ^.m) and 5.00 KX (1 ^.m) magnification: NaAlgCG9P1k (a, d), NaAlgCG9P1i (b, e) and NaAlgCG9P1ki (c, f)
(Fig. 4, d, f, and g) show that the surface of these films is rougher and more heterogeneous compared to the film containing only sodium alginate and the 9:1 mixture of plasticizers (see Fig. 2, d). For example, at a scale of 1 ^.m, the surface of the NaAlgCG9P1k film (see Fig. 4, d) has wide slits, and the NaAlgCG9P1i film (Fig. 4, e) has a greater number of thin striations on the surface. However, the film NaAlgCG9P1ki (see Fig. 4, f) presents aggregates not as refined as the film containing only i-carrageenan. This is due to the rapid gelation of i-carrageenan, which is induced by temperature and/or the presence of salts [34].
The presence of i-carrageenan in the films leads to a greater hydrophilic character represented by the greater mass loss during the dehydration process, and it showed a higher amount of carbonaceous residues compared to the film prepared with k-carrageenan. Sulfate groups are highly polar, which could increase the hydrophilic character and induce the thermostability in the films. This possibility can be supported by the fact that the residual weights in neat k-, and i-carrageenans are 16 and 21 %, respectively [35-37] (Fig. 5, a). The thermal events and the mass loss with their respective temperature intervals of these films are summarized in Table 4.
0 200 400 600 800 1000 4000 3000 2000 1000 Temperature, °C Wavelength, cm"1
a b
Fig. 5. TG curves (a) and FTIR spectrum (b) of NaAlgCG9P1k (—), NaAlgCG9P1i ( ), and NaAlgCG9P1ki (-) films
Table 4
Mass loss values from TGA of NaAlgCG9P1k, NaAlgCG9P1i, and NaAlgCG9P1ki films
Film Weight, mg Thermal event AT, °C Mass loss, %
NaAlgCG9P1k 5.131 Dehydration 21.1-113.9 16.4
Film degradation 113.9-581.9 72.1
Polymer degradation 581.9-909.5 9.32
Carbonization 909.5-991.3 1.21
Carbonaceous residue 991.3 0.97
NaAlgCG9P1i 4.740 Dehydration 22.2-109.0 20.2
Film degradation 109.0-594.8 67.5
Polymer degradation 594.8-901.5 9.71
Carbonization 901.5-992.2 1.28
Carbonaceous residue 992.2 1.31
NaAlgCG9P1ki 5.187 Dehydration 20.9-115.5 21.1
Film degradation 111.5-599.7 59.0
Polymer degradation 599.7-937.0 10.01
Carbonization 937.0-992.4 0.13
Carbonaceous residue 992.4 9.76
In the FTIR spectra (Fig. 5, b), no additional bands are evident concerning the FTIR spectrum of the NaAlgCG9P1 film (see Fig. 3, c), which was used as base film; however, the bands at 1029 and 923 cm-1 are associated with the S = O vibrational mode [38] and the C-O-C stretching of 3,6-anhydro-D-galactose [39, 40] of carrageenan derivatives, respectively. Therefore, it is assumed that the additional sulfate ester group that contains the i-carrageenan
interacts with a greater number of -OH groups, forming hydrogen bonds and, with it, greater interaction with the polymeric matrix of sodium alginate.
Third stage. Figure 6, a shows the NaAlgCG9P1kiA film, and the SEM image of the film's surface is depicted in Fig. 6, b. In the SEM image, the film loaded with AVG presents a homogeneous surface compared to the surface of the NaAlgCG9P1ki film (see Fig. 4, f); this is because ethanol positively impacts the homogeneity and visual appearance of alginate films. Since sodium alginate is not soluble in ethanol, a packed polymer matrix was formed, thus the degree of swelling of the films was decreased and less shrinkage was obtained during the film drying process [41].
Fig. 6. NaAlgCG9P1kiA film (a), SEM image at 1.00 KX (10 ^m) and 5.00 KX (1 ^m) magnification (b)
Figure 7, a shows the XRD diffractograms of the NaAlgCG9P1, NaAlgCG9P1ki, and NaAlgCG9P1kiA films, which offer a diffraction peak close to 21° in the diffraction pattern corresponding to the mannuronate unit of sodium alginate [42]. The crystallinity index of the films was calculated using the ratio of the crystalline region and the total diffraction area. The NaAlgCG9P1 film has a crystallinity percentage of 23.75 % due to the interaction between the plasticizers and the NaAlg polymer matrix. This indicates that the microstructure of this film is homogeneous [33]. The NaAlgCG9P1ki film presents a crystallinity percentage of 25.97 %; however, loading an ethanolic AVG solution causes the crystallinity of the NaAlgCG9P1kiA film to be 45.73 %. This can be attributed to the polarity of the ethanol molecules, which rearranges the intermolecular hydrogen bonds within the polymeric matrix [43].
Figure 7, b shows the TG curve (TGA) of the NaAlgCG9P1kiA film, which offers a higher percentage of mass loss during the dehydration process (25.6 %) compared to the NaAlgCG9P1ki film (see Table 4). This is due to the increase in polar groups in the ethanolic solution of AVG. On another hand, the presence
3000 3 2500 1 2000 •t 1500 | 1000 & 500
40 60 20, degree a
200 400 600 Temperature, °C
1000
Fig. 7. XRD diffractograms (a), TG curves (b), and FTIR spectrum of NaAlgCG9P1kiA film (c)
4000 3000
2000
1000
Wavelength, cm
-l
of AVG in the composite seems to interfere in the interchain interactions and leaded to a degradation profile similar to those observed for the individual carrageenan, with higher polymer degradation that resulted in a low carbonaceous residue. The thermal events and the mass loss with their respective temperature intervals of this film are summarized in Table 5.
Table 5
Mass loss values from thermogravimetric analysis of NaAlgCG9P1kiA films, weight 6.474 mg
Thermal event AT, °C Mass loss, %
Dehydration 18.9-117.3 25.6
Film degradation 117.3-318.2 58.8
Polymer degradation 318.2-566.0 4.87
Carbonization 566.0-992.3 9.59
Carbonaceous residue 992.3 1.14
The FTIR spectrum of the NaAlgCG9P1kiA film (Fig. 7, c) does not show the disappearance of bands concerning the FTIR spectrum of the NaAlgCG9P1ki film (see Fig. 4, b), so it is assumed that there are no structural changes in the polymer matrices.
Kinetic behavior of aminoethoxyvinylglycine release. The AVG release profiles (Fig. 8) show that at 10 °C the film released 18.89 mg • L-1 (94.45 %) of AVG, while at 25 °C only 8.64 mg • L-1 (43.2 %) was released, which suggests that this system has a faster release response at low temperatures. Table 6 shows the values of the correlation coefficient R2 and the diffusion exponent n calculated from Eq. (1), (2). The Korsmeyer — Peppas model has a higher R2 value than the Higuchi model in both release profiles, so it better describes the release of AVG. Additionally, the value of n is greater than 0.5 and less than 1.0, so it is assumed that the release is carried out by an anomalous or non-Fickian diffusion [44].
0.50 1.15 2.00 3.30 6.00 Time, h
Fig. 8. Release profiles at 10 and 25 °C of AVG
Table 6
Kinetic parameters obtained by the method of Higuchi and Korsmeyer — Peppas for NaAlgCG9P1kiA film
Temperature, °C Higuchi Korsmeyer — Peppas
R2 n R2
10 0.8211 0.9513 0.9367
25 0.9322 0.6585 0.9628
Conclusion. Thus, we can conclude that the 9:1 w • w-1 ratio of glycerol and PEG 400 makes it possible to obtain sodium alginate films with a homogeneous surface, lower opacity, and higher moisture content. The mixture of k-carra-
geenan and i-carrageenan reduces the heterogeneity on the surface of the film and the loss of mass during the degradation process in the TG, compared to the films containing the carrageenans separately. Adding an ethanolic solution of AVG generates a positive impact on the film's surface, and the ethanolic solution is a good release medium for AVG release at low temperatures.
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Villacrés Nelson Adrián — Post-Graduate Student, Faculty of Sciences, National University of Engineering (Tupac Amaru av. 210, Rimac, Lima, Peru).
Cavalheiro Éder Tadeu Gomes — Dr. Sc., Professor, Sao Carlos Institute of Chemistry, University of Sao Paulo (Sao Carlos, Sao Paulo CEP 13566-590, Brazil).
Ferreira Ana García — Dr. Sc., Sao Carlos Institute of Chemistry, University of Sao Paulo (Sao Carlos, Sao Paulo CEP 13566-590, Brazil).
Venancio Tiago — Dr. Sc., Professor, Nuclear Magnetic Resonance Laboratory, Department of Chemistry, Federal University of Sao Carlos (Sao Carlos, Sao Paulo, Brazil).
Alarcon Hugo — Dr. Sc., Professor, Faculty of Sciences, National University of Engineering (Tupac Amaru av. 210, Rimac, Lima, Peru).
Valderrama Ana — Dr. Sc., Professor, Faculty of Sciences, National University of Engineering (Tupac Amaru av. 210, Rimac, Lima, Peru).
Please cite this article as:
Villacrés N.A., Cavalheiro É.T.G., Ferreira A.P.G., et al. Preparation and characterization of biocomposite films of sodium alginate/kappa-carrageenan/iota-carrageenan loaded with aminoethoxyvinylglycine. Herald of the Bauman Moscow State Technical University, Series Natural Sciences, 2023, no. 4 (109), pp. 175-193. DOI: https://doi.org/10.18698/1812-3368-2023-4-175-193
