Development of cassava starch-based films incorporated with phenolic compounds produced by an Amazonian fungus.

Drug-release systems have attracted attention over the last few years since they can be used as a substitute for traditional methods of drug delivery. These have the advantage of being directly administered at the treatment site and can maintain the drug at adequate levels for a longer period, thus increasing their efficacy. Starch-based films are interesting candidates for use as matrices for drug release, especially due to starch's non-toxic properties and its biocompatibility. Endophytic fungi are an important source of bioactive molecules, including secondary metabolites such as phenolic compounds with antioxidant activity. In the present study, cassava starch-based films were developed to act as release systems of phenolic compounds with antioxidant activity. The Amazonian endophytic fungus Aspergillus niger MgF2 was cultivated in liquid media, and the fungal extract was obtained by liquid-liquid partition with ethyl acetate. The starch-based films incorporated with the fungal extract were characterized in regards to their physicochemical properties. The release kinetics of the extract from the film and its antioxidant and cytotoxic properties were also evaluated. The films incorporated with the extract presented maximum release after 25 min at 37 °C and pH 6.8. In addition, it was observed that the antioxidant compounds of the fungal extract maintain their activity after being released from the film, and were non-toxic. Therefore, considering the promising physicochemical properties of the extract-incorporated films, and their considerable antioxidant capacity, the films demonstrate great biotechnological potential with diverse applications in the pharmacological and cosmetic industries.

Starch as a Matrix for Incorporation and Release of Bioactive Compounds: Fundamentals and Applications.

Due to its abundance in nature and low cost, starch is one of the most relevant raw materials for replacing synthetic polymers in a number of applications. It is generally regarded as non-toxic, biocompatible, and biodegradable and, therefore, a safe option for biomedical, food, and packaging applications. In this review, we focused on studies that report the use of starch as a matrix for stabilization, incorporation, or release of bioactive compounds, and explore a wide range of applications of starch-based materials. One of the key application areas for bioactive compounds incorporated in starch matrices is the pharmaceutical industry, especially in orally disintegrating films. The packaging industry has also shown great interest in using starch films, especially those with antioxidant activity. Regarding food technology, starch can be used as a stabilizer in nanoemulsions, thus allowing the incorporation of bioactive compounds in a variety of food types. Starch also presents potential in the cosmetic industry as a delivery system. However, there are still several types of industry that could benefit from the incorporation of starch matrices with bioactive compounds, which are described in this review. In addition, the use of microbial bioactive compounds in starch matrices represents an almost unexplored field still to be investigated.

Assessing the Influence of Dyes Physico-Chemical Properties on Incorporation and Release Kinetics in Silk Fibroin Matrices.

Silk fibroin (SF) is a promising and versatile biodegradable protein for biomedical applications. This study aimed to develop a prolonged release device by incorporating SF microparticles containing dyes into SF hydrogels. The influence of dyes on incorporation and release kinetics in SF based devices were evaluated regarding their hydrophilicity, molar mass, and cationic/anionic character. Hydrophobic and cationic dyes presented high encapsulation efficiency, probably related to electrostatic and hydrophobic interactions with SF. The addition of SF microparticles in SF hydrogels was an effective method to prolong the release, increasing the release time by 10-fold.

A review on orally disintegrating films (ODFs) made from natural polymers such as pullulan, maltodextrin, starch, and others.

In recent years, orally disintegrating films (ODFs) have been studied as alternative ways for drug administration. They can easily be applied into the mouth and quickly disintegrate, releasing the drug with no need of water ingestion and enabling absorption through the oral mucosa. The ODFs matrices are typically composed of hydrophilic polymers, in which the natural polymers are highlighted since they are polymers extracted from natural sources, non-toxic, biocompatible, biodegradable, and have favorable properties for this application. Besides that, natural polymers such as polysaccharides and proteins can be applied either alone or blended with other synthetic, semi-synthetic, or natural polymers to achieve better mechanical and mucoadhesive properties and fast disintegration. In this review, we analyzed ODFs developed using natural polymers or blends involving natural polymers, such as maltodextrin, pullulan, starch, gelatin, collagen, alginate, chitosan, pectin, and others, to overview the recent publications and discuss how natural polymers can influence ODFs properties.

Phase Diagram and Estimation of Flory-Huggins Parameter of Interaction of Silk Fibroin/Sodium Alginate Blends.

Silk fibroin (SF) and sodium alginate (SA) are natural polymers used to produce biomaterials. One of the strategies to improve the properties of these products is to prepare blends with them, which are partially miscible. Phase separation is observed, therefore, the thermodynamic analysis of this system is important to predict the final state and composition of this blends. This study explored blends with a different initial composition of SF, SA, and water (WA) at 25°C and neutral pH. After phase separation, two phases were identified, one rich in SF and other rich in SA. The Flory-Huggins parameters of interaction of polymer-solvent and polymer-polymer were estimated using the extended equation and data of phase equilibrium, their values indicates the partial miscibility of the polymers.

Silk fibroin/chitosan/alginate multilayer membranes as a system for controlled drug release in wound healing.

In this study, we proposed the use of the biopolymers silk fibroin, chitosan and alginate, which are recognized for their biocompatibility and biodegradability, for the preparation of multilayer membranes aiming at high performance wound dressings with controlled drug delivery. The rationale was to combine in one material the mechanical properties of fibroin, the antimicrobial action of chitosan and the ideal exudate absorption of alginate, reaching a synergic effect of each biopolymer, without losing their individual intrinsic properties. The membranes were prepared by casting and diclofenac sodium was incorporated as model drug into the chitosan solution before the solvent evaporation, being retained in the middle layer of the membrane. Morphological, thermal, mechanical, solubility and barrier properties of the membranes were evaluated, as well as cytotoxicity and microbiological permeation. Results show that the incorporation of the drug did not affect mechanical and barrier properties, as well as microbiological permeation. Drug release was evaluated in vitro using simulated solution of wound exudate at 37 °C and diclofenac sodium was released from the multilayer membrane in 7 h, in which Fickian diffusion was the main mechanism associated. The results show the potential application of the biopolymer multilayer membranes as high-performance wound dressings.

Characterization and in vitro evaluation of chitosan/konjac glucomannan bilayer film as a wound dressing.

A novel bilayer film of chitosan and konjac glucomannan were prepared by the two-step casting technique. Blend films were also prepared to investigate the interactions between the two polymers in the interfacial region of the bilayer structure. Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis showed that, unlike in the blends, the physicochemical properties of each biopolymer were preserved in the bilayer film. Differential scanning calorimetry and thermogravimetric analysis also indicated a good thermostability and miscibility for both polymers, probably due to strong hydrogen bonds between their polymer chains. Biological, mechanical and water vapor transmission tests showed a high biocompatibility, low cytotoxicity, and suitable mechanical and barrier properties of the bilayer films for wound dressing applications.

Freezing influence on physical properties of glucomannan hydrogels.

Freezing is an interesting technique to modify the mechanical properties and morphology of hydrogels. Konjac glucomannan (KGM) is a polysaccharide that has potential use in cutting-edge areas as biomaterials and tissue engineering. In this work, we deeply investigated the influence of freezing on KGM. For that, KGM hydrogels were frozen at several freezing rates and temperatures. Results show that the freezing rate was the most important factor in the final physical properties of the KGM hydrogels. Slow freezing rate produced structures with isotropic and large pores, while fast freezing resulted in hydrogels with small and aligned pores. In addition, hydrogels frozen at high temperature (-8 °C) exhibited higher penetration modulus than hydrogels frozen at low temperature (-28 °C), since dense polymer regions are formed due to higher molecules dehydration caused by slow freezing. KGM hydrogels that underwent freezing can be explored as scaffolds for tissue engineering, with improved structural and mechanical properties.

Factors controlling the deposition of silk fibroin nanofibrils during layer-by-layer assembly.

The layer-by-layer technique has been used as a powerful method to produce multilayer thin films with tunable properties. When natural polymers are employed, complicated phenomena such as self-aggregation and fibrilogenesis can occur, making it more difficult to obtain and characterize high-quality films. The weak acid and base character of such materials provides multilayer systems that may differ from those found with synthetic polymers due to strong self-organization effects. Specifically, LbL films prepared with chitosan and silk fibroin (SF) often involve the deposition of fibroin fibrils, which can influence the assembly process, surface properties, and overall film functionality. In this case, one has the intriguing possibility of realizing multilayer thin films with aligned nanofibers. In this article, we propose a strategy to control fibroin fibril formation by adjusting the assembly partner. Aligned fibroin fibrils were formed when chitosan was used as the counterpart, whereas no fibrils were observed when poly(allylamine hydrochloride) (PAH) was used. Charge density, which is higher in PAH, apparently stabilizes SF aggregates on the nanometer scale, thereby preventing their organization into fibrils. The drying step between the deposition of each layer was also crucial for film formation, as it stabilizes the SF molecules. Preliminary cell studies with optimized multilayers indicated that cell viability of NIH-3T3 fibroblasts remained between 90 and 100% after surface seeding, showing the potential application of the films in the biomedical field, as coatings and functional surfaces.

Silk fibroin and sodium alginate blend: miscibility and physical characteristics.

Films of silk fibroin (SF) and sodium alginate (SA) blends were prepared by solution casting technique. The miscibility of SF and SA in those blends was evaluated and scanning electron microscopy (SEM) revealed that SF/SA 25/75 wt.% blends underwent microscopic phase separation, resulting in globular structures composed mainly of SF. X-ray diffraction indicated the amorphous nature of these blends, even after a treatment with ethanol that turned them insoluble in water. Thermal analyses of blends showed the peaks of degradation of pristine SF and SA shifted to intermediate temperatures. Water vapor permeability, swelling capacity and tensile strength of SF films could be enhanced by blending with SA. Cell viability remained between 90 and 100%, as indicated by in vitro cytotoxicity test. The SF/SA blend with self-assembled SF globules can be used to modulate structural and mechanical properties of the final material and may be used in designing high performance wound dressing.

Effects of sterilization methods on the physical, chemical, and biological properties of silk fibroin membranes.

Silk fibroin has been widely explored for many biomedical applications, due to its biocompatibility and biodegradability. Sterilization is a fundamental step in biomaterials processing and it must not jeopardize the functionality of medical devices. The aim of this study was to analyze the influence of different sterilization methods in the physical, chemical, and biological characteristics of dense and porous silk fibroin membranes. Silk fibroin membranes were treated by several procedures: immersion in 70% ethanol solution, ultraviolet radiation, autoclave, ethylene oxide, and gamma radiation, and were analyzed by scanning electron microscopy, Fourier-transformed infrared spectroscopy (FTIR), X-ray diffraction, tensile strength and in vitro cytotoxicity to Chinese hamster ovary cells. The results indicated that the sterilization methods did not cause perceivable morphological changes in the membranes and the membranes were not toxic to cells. The sterilization methods that used organic solvent or an increased humidity and/or temperature (70% ethanol, autoclave, and ethylene oxide) increased the silk II content in the membranes: the dense membranes became more brittle, while the porous membranes showed increased strength at break. Membranes that underwent sterilization by UV and gamma radiation presented properties similar to the nonsterilized membranes, mainly for tensile strength and FTIR results.

Mechanical and biological performances of new scaffolds made of collagen hydrogels and fibroin microfibers for vascular tissue engineering.

A microstructured composite material made of collagen hydrogel (matrix) and silk fibroin microfibers (randomly oriented reinforcing fibers) is investigated in order to conjugate the mechanical resistance of fibroin with the suitable biological performance of collagen to design new scaffolds for vascular tissue engineering. Results show that fibroin microfibers and collagen fibrils have suitable interfacial adhesion, and the scaffold exhibits improved mechanical properties if compared with a pure collagen hydrogel. Furthermore, the overall biological performance is improved.