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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.

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.

The novelty of this study was to investigate for the first time in literature the influence of Bombyx mori silkworm cocoon’s age on the properties of silk fibroin-based materials, during all stages of cocoon processing to obtain the fibroin film. The study started with the premise that the cocoon age could cause modifications on fibroin properties during processing and, consequently, a possible interference on the characteristics of the final product. Characterizations were performed using batches of cocoons produced in different years, named C0 (fresh cocoons) and C6 (six-year-old cocoons). The influence of cocoon’s aging was observed on dialyzed dispersion regarding the molecular weight, particle size, and conformation. C6 films showed a more crystalline structure and higher thermal resistance than C0 films. The findings reported in this work are relevant for the reproducibility of fibroin-based materials, and the cocoon age is a key factor that should be considered in the preparation of fibroin-based materials.

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.

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.

Background COVID-19 is caused by the SARS-CoV-2 virus, an emerging respiratory pathogen. The work environment represents a high-risk factor for health professionals. Given the scarcity of protective personal equipment due to global demand, decontamination and reuse studies should be carried out. Thus, the aim of this study was to evaluate the safety of a method of decontamination of N95/PFF2 respirators, especially regarding structural integrity. Methods N95/PFF2 respirators were subjected to hydrogen peroxide decontamination and analyzed using scanning electron microscopy and thermogravimetric analysis. Seven respirators of the same brand and lot were used, one being a control and the other six subjected to decontamination process. As for the sealing, a qualitative test was applied, in order to identify the changes in the structure that could damage the sealing of respirators. Results Indicated that the fiber morphology in all layers was not affected by the six decontamination cycles. Also, the thermal stability in the different layers was very similar. Fit testing showed that the respiradors submitted to all cycles of decontamination were approved. Conclusions Thus, it is possible to conclude that the hydrogen peroxide decontamination method is effective, since it does not alter the physical properties of the respirators.

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.

Chitosan films have been extensively studied as dressings in formulations for the treatment of chronic wounds. The incorporation of aloe vera (Aloe barbadensis Miller) into chitosan dressings could potentialize the healing process since aloe vera shows several pharmacological activities. This work aimed to evaluate the effect of aloe vera and chitosan concentrations on the physicochemical properties of the developed films. The films were obtained by casting technique and characterized with respect to their color parameters, morphology, barrier and mechanical properties, and thermal analysis. Results showed that the presence of aloe vera modified the films color parameters, changed barrier properties, increased fluid handling capacity (FHC), and decreased water-vapor permeability (WVP). The reduced elongation at break resulted in more rigid films. Aloe vera concentration did not significantly change film properties, but the presence of this gel increased the films stability at temperatures below 200 °C, showing similar behavior as chitosan films above 400 °C. The results suggest a crosslinking/complexation between chitosan and aloe vera, which combine appropriate physicochemical properties for application as wound dressing materials., This work was supported by São Paulo Research Foundation (FAPESP) (2010/17.721-4), Portuguese Science and Technology Foundation (FCT) through the projects M-ERA-NET/0004/2015 (PAIRED) and UIDB/04469/2020 (strategic fund) funded by national funds, and co-financed Education (FCT/MEC) from national funds and FEDER, under the Partnership Agreement PT202, info:eu-repo/semantics/publishedVersion

Asymmetric membranes present promising characteristics for wound dressing applications. A porous structure uptakes the wound exudate, whereas an occlusive layer (upper film) inhibits the microbial penetration and prevents an excessive loss of water. Konjac glucomannan (KGM) is a natural polysaccharide that has been investigated as wound dressings in the form of films, sponges, and hydrogels due to its flexibility, swelling capacity, biocompatibility, and low cost. However, there are no studies on literature regarding the development of KGM asymmetric membranes. In this study, we investigated a new casting—freezing process for the production of KGM asymmetric membranes. The scanning electron microscopy and thermogravimetric analyses indicated an asymmetric morphology and a good thermal stability of the membrane samples, respectively. Moreover, biological, mechanical, and fluid-handling capacity tests showed that the membrane is biocompatible and resistant to handling structure, which was also able to retain the ideal moist conditions for wound healing.

In this chapter, a full overview of the main characterization techniques of biopolymer membranes and films is presented, focusing on the fundamentals and methods of analysis of each technique applied to biopolymers. First, a complete publications search on the main characterizations of biopolymer films and membranes is reported, specifying the number of published papers per technique from 1999 to 2018. Then, the characterizations are sorted by type. In the physicochemical characterization section, microscopy techniques, Fourier transform infrared spectroscopy, Raman spectroscopy, nuclear magnetic resonance spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and thermal analysis are addressed. Then, physical characterizations, such as swelling, degradation/erosion degree, mechanical and barrier properties, contact angle, and textural analysis applied to biopolymer membranes and films are elucidated. Finally, the main biological characterizations are reported, such as cytotoxicity, sensitization capacity, and irritation potential.

Chitosan is a semisynthetic biopolymer made from chitin which is the second most abundant biopolymer on Earth. In addition to being abundant, chitosan exhibits properties such as biodegradability and nontoxicity that make it very attractive for applications in diverse fields. However, the mechanical properties of chitosan devices represent one of the challenges in the use of chitosan in many areas such as medical, packaging, and the environment. The production of chitosan composites (or biocomposites) may represent a strategy to overcome problems related to mechanical properties, for example, without losing properties like their positive charges. Nevertheless, in the case of a biodegradable matrix such as chitosan, the use of some synthetic fillers may alter the features mentioned above due to the nonbiodegradability of the filler. In this sense, the use of natural fillers to obtain biocomposites of chitosan has grown in recent years, mainly due to the appeal of the two natural materials (chitosan and filler). In this chapter, we focus on (bio)composites of chitin and chitosan only with natural fillers that have fibrous morphology, focusing on different raw materials and applications. First, we show an introduction to the increase in publications in the field; then, we discuss natural fibers, their properties and treatments. Finally, we review in depth the publications about (bio)composites with chitin/chitosan, which were classified by raw material.

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.

In this study, we proposed the use of the biopolymer alginate to produce membranes with diclofenac sodium incorporated as model-drug aiming at wound dressing application with drug delivery. The membranes were prepared by casting and the drug was incorporated directly into alginate solution, being retained within the membrane. Morphological, chemical, mechanical and barrier properties were evaluated, as well as the release kinetics in vitro using simulated exudate fluid at 37 °C. Results show that the membranes are malleable in the glycerol presence and more resistant to water after crosslinking. The incorporation of diclofenac sodium did not affect barrier properties, but influenced the mechanical properties, increasing the total thickness (from 0.108 to 0.209 mm) and reducing tensile strength (from 40.85 to 21.76 MPa). Drug release evaluation shows that anomalous transport is the major rate-controlling mechanism, where the swelling or erosion of the alginate matrix is the major responsible for the diclofenac sodium release, with a small contribution of Fickian diffusion mechanism. The results show the potential of application of the alginate membranes for wound dressings with drug delivery for enhancing healing process.

Silk fibroin (SF) and sodium alginate (SA) are natural polymers with many applications as biomaterials. It is possible to make blends with them in order to improve their properties. Those blends are partially miscible; therefore, understanding the mechanism and phase equilibrium of this system is important to better understand the interaction between these natural polymers. This work analyzed the mechanism of phase separation of SF and SA blends with different composition in solution and in the solid state (as membranes) using small angle light scattering with a He-Ne laser. Polymer interaction and conformation were investigated by Fourier-Transform Infrared Spectroscopy with Attenuated Total Reflectance (FTIR-ATR) and X-Ray Diffraction (XRD), and membrane morphology was analyzed by Scanning Electron Microscopy (SEM). SEM images showed interpenetrated globules in the matrix. Light scattering profile for blends in solution and in the solid state showed a peak of intensity suggesting that phase separation occurs by spinodal decomposition.

Chitosan (CS) is a semi-synthetic biopolymer obtained from chitin that is the second most abundant biopolymer. Many devices produced from CS have been widely used for drug delivery systems and biomaterials. Biocompatibility, biodegradability, nonallergenicity, and antimicrobial activity are advantageous properties of CS; moreover, CS has also exhibited healing properties. Some properties can be potentiated by using the CS to produce CS-based nanocomposites. In this sense, this chapter intends to give some CS nanodevices with different kind of fillers (reinforcements) and their application to the drug delivery systems. Fillers such as nanoparticles, nanolayer, and nanofibrous are discussed.

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.

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.

After publication of the paper, the authors realized that the affiliation of the fourth author (Tiberiu Esanu) was given incorrectly. Its correct version appears above. Moreover, a second funding grant was missed in the acknowledgements. We give their complete correct version below.

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.

Chitin is a natural copolymer found in crustacean shells and has potential for use in a wide range of faculties. During the chitin obtainment process, effluents with high organic charge are generated. These should be treated before discharge in order to avoid environmental problems. This work aimed to investigate the treatment of effluents from chitin obtainment process using chitin (CH) and aluminum sulfate (Al 2 (SO 4 ) 3 ) as coagulants. The effects of coagulant type (CH and Al 2 (SO 4 ) 3 ), coagulant concentration (150 and 300 mg L −1 ) and pH (6.0 and 8.5) were evaluated by a full 2 3 experimental design. The considered responses were: total solids reduction (TSR), suspended solids reduction (SSR) and turbidity reduction (TR). It was found that the use of 300 mg L −1 of Al 2 (SO 4 ) 3 under pH 6.0 or 8.5 favored the treatment of effluents from chitin obtainment process. The proposed treatment provided reductions of 20, 89 and 85% in the total solids, suspended solids and turbidity respectively.

The use of natural resources, especially processing wastes, as low cost and environmentally friendly alternative aiming high value-added applications is a subject of broad interest. Since the Brazilian silk production annually generates a large amount of waste during the silk fibers processing, this work explores the preparation and characterization of silk fibroin hydrogels using spinning waste silk fibers from textile processing and the processed ones. Hydrogels were obtained directly by dialyzing silk fibroin solutions against frequent changes of water until the gelation point and then lyophilized and characterized in terms of their morphology, crystallinity, thermal resistance and secondary structure. X-ray diffraction analysis revealed the presence of β-sheet conformation related to sol-gel transition. FT-IR spectra indicated the coexistence of random coil (silk I) and β-sheet (silk II) structures, with predominance of β-sheet conformation for hydrogels from processed silk fibers. From thermogravimetric analysis the presence of β-sheet secondary conformation was demonstrated by a degradation peak around 292 °C for both hydrogels. Freeze-dried hydrogels presented sheet or leaf like morphology and no significant change was observed among the hydrogels from waste silk fibers and processed ones. These characteristics suggest that silk fibroin hydrogels prepared from spinning waste silk fibers and obtained directly by dialysis can be potential candidates for biomaterials application, such as drug delivery systems and for wound dressings.

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.

Silk fibroin (SF) films have been largely studied as biomaterials due to their biocompatibility and biodegradability. Casting a SF aqueous solution at room temperature is a common technique to produce SF films at relative low cost and processing time; however, their brittleness and solubility in water make them unsuitable for certain biomedical applications. In this study, the incorporation of additives, ethanol and glycerin, are presented as an alternative to both improve mechanical properties of SF films and decrease their solubility in water. SF films with additives were further characterized using scanning electron microscopy, X-ray diffraction, Fourier transformed infrared spectroscopy with attenuated total reflection, analysis of water solubility, mechanical test of traction, and in vitro cytotoxicity experiments. The results show that SF films containing additives are stable in water due to the effect of glycerin and ethanol, and do not require post-treatments. Furthermore, great improvements on elongation of the films were achieved, mainly in the presence of both additives. In addition, all films were not toxic to cells, which is a first indication of their biocompatibility. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

The use of membranes prepared with alginate and chitosan to adsorb paraquat aqueous solution was evaluated as a potential alternative technique for remediation of contaminated water. Production of bilayer membranes was based on the electrostatic interaction between alginate (a polyanion) and chitosan (a polycation). Herbicide adsorption experiments were performed using three different membranes, consisting of pure alginate, pure chitosan, and a chitosan/alginate bilayer. Adsorption was characterized using the Langmuir and Freundlich isotherm models, as well as by applying pseudo-first order and pseudo-second order kinetic models. The potential use of the membranes in environmental applications was evaluated using water collected from the Sorocabinha River in Sao Paulo State, Brazil. The results indicated that interactions between the membranes and the herbicide were strongly related to the type of biopolymer and the physical–chemical characteristics of the herbicide.

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Silk fibroin (SF) is a protein fiber spun by Bombyx mori silkworm. SF fibers are about 10-25 μm wide in diameter and a single cocoon may provide over 1000 m of SF fibers. SF can present several conformations regarding protein secondary structure which ultimately define the structural properties of SF-based materials. For this reason, a rigorous control on its processing conditions shall be performed. It is known that SF has excellent properties to be used in biomaterials field, controlled release and scaffolds for tissue engineering. In addition, SF can be processed in several forms, such as films, fibers, hydrogels or microparticles. This work seeks to provide an overview on SF processing conditions, regarding the preparation of SF membranes (dense and porous), hydrogels and biocomposites, focusing on biomaterials application.

Silk fibroin (SF) hydrogels were obtained from the dialysis of a SF metastable solution. Temperature and calcium concentration in SF solution/hydrogel were measured, as critical variables for SF gelation phenomenon. Gelation time of SF solution was increased by decreasing the dialysis temperature, whereas the residual calcium concentration was higher when higher dialysis temperatures were applied. Hydrogels obtained at 20 °C were characterized after freeze-drying. SEM micrographs showed porous structures, of ca. 20 μm (in cross-sectional area) and 5 μm (on surface). XRD indicated the presence of a β-sheet structure that is formed during SF gelation. In hydrogel formation, SF molecules in solution are dehydrated and interact by intra and intermolecular hydrogen bonds, forming a stable hydrogel. DSC measurements showed the decomposition peak for SF at 290 °C, characteristic of SF β-sheet structure, which is in accordance with the XRD results and demonstrate its high thermal resistance. SF hydrogels were found not to be toxic to cells using in vitro cytotoxicity tests. Results indicate that silk fibroin hydrogels hold promise for use in the biomaterial field.

The moisture equilibrium isotherms of chitosan were determined at 20, 30, 40, 50 and 60 � C, using the gravimetric static method. Experimental data were analyzed by the GAB, Oswin, Halsey and Smith equations. Isosteric heat and differential entropy of sorption were determined from the GAB model using the Clausius-Clapeyron and Gibbs-Helmholtz equations, and pore size distribution was calculated by the Kelvin and Halsey equations. The GAB and Oswin equations showed best fit to the experimental data with R 2 z 99% and low mean relative deviation values (E% < 10%). Monolayer moisture content values (from 0.12 to 0.20 kg kg � 1 ) and water surface area values (from 450 to 700 m 2 g �1 ) decrease with increasing temperature. Isosteric heat and differential entropy of sorption were estimated as a function of moisture content. The Kelvin and Halsey equations were adequate for calculation of pore size distribution, which varied from 0.5 to 30 nm.

The moisture equilibrium isotherms of garlic and apple were determined at 50, 60 and 70 °C using the gravimetric static method. The experimental data were analysed using GAB, BET, Henderson-Thompson and Oswin equations. The isosteric heat and the differential entropy of desorption were determined by applying Clausius-Clapeyron and Gibbs-Helmholtz equations, respectively. The GAB equation showed the best fitting to the experimental data (R 2 > 99% and E% < 10%). The monolayer moisture content values for apple were higher than those for garlic at the studied temperatures; the values varied from 0.050 to 0.056 and from 0.107 to 0.168 for garlic and apple, respectively. The isosteric heat and the differential entropy of desorption were estimated in function of the moisture content. The values of these thermodynamic properties were higher for apple (in range 48-100 kJ mol -1 and 14-150 J mol -1 K -1 ) than for garlic (in range 43-68 kJ mol -1 and 0-66 J mol -1 K -1 ). The water surface area values decreased with increasing temperature. The Kelvin and the Halsey equations were used to calculate the pore size distribution.

The aim of this work was to study the drying of Spirulina platensis, evaluating the final product characteristics about its phycocyanin content and its protein solubility in water. Two drying techniques were used: the spouted bed and the thin layer. For drying in a spouted bed, the cone-cylindrical geometry was chosen, namely type conventional spouted bed (CSB) and jet-spouted bed, with a paste concentration of 5%. The thin-layer drying was performed at temperatures of 50 and 60C, with a load of material of 4 kg/m2 in the tray. The spouted bed dryer type CSB demonstrated good functionality, not presenting a collapse during the experiments. The solubility in aqueous mean was similar in all the drying techniques used, being the values found around 37%. The largest phycocyanin values were found in the thin-layer temperature of 50C and in the spouted bed type CSB; however, the thin layer was excluded so as not to reach the commercial moisture content. PRACTICAL APPLICATIONS Phycocyanin is the major phycobiliprotein in Spirulina. Phycocyanin has significant antioxidant, anti-inflammatory, hepatoprotective and radical scavenging properties. It is used as colorant in food and cosmetics. It was also shown to have therapeutic value (immunomodulating activity and anticancer activity). The drying operation is commonly used to prolong the shelf life of microbial biomasses. Preservation of cyanobacteria is a difficult process, since the cells are small and, moreover, the cultures are usually diluted. Drying of liquids and pastes in spouted beds with inert bodies has been presented as an alternative to spray drying in an attempt to obtain high-quality powdered products at a low cost.

Silk hydrogels are interesting materials to be used as matrix in controlled drug delivery devices. However, methods to accelerate fibroin gelation and allow the drug incorporation during the hydrogel preparation are needed in literature. In this article we report the preparation of silk fibroin hydrogels with addition of several contents of ethanol, used to accelerate fibroin gelation kinetics, and we also evaluate the potential of these hydrogels to be used as matrices for drug delivery. Chemical and conformational properties did not change despite the amount of ethanol incorporated in the hydrogel. Hydrogels containing diclofenac sodium dissolved in ethanol showed a faster initial release of the drug than hydrogels with the drug dissolved in water but equilibrium was reached later. This indicates a more sustained drug delivery from hydrogels in which the model drug was dissolved in ethanol. Fibroin hydrogels confirm their promising use as biopolymeric matrices for controlled drug release. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41802.

This work presents a novel composite hydrogel consisting of silk fibroin (SF) and nanohydroxyapatite (nanoHA) prepared by a new and innovative method using ethanol as gelling agent capable of forming hydrogels in few minutes. The properties of the composite material, such as the microstructure as well as the chemical and physical properties were studied. Moreover in␣vitro studies of osteoblastic citocompatibility were performed. The microporosity and macroporosity obtained combined with interconnected porous structure and a uniform dispersion of nanoHA particles throughout the fibroin matrix makes composite hydrogel suitable for bone regeneration. The compression modulus of composite hydrogels was increased as the nanoHA concentration increased from 10 to 15 wt.% and the water uptake ability of these materials decreased with the incorporation of nanoHA. The metabolic and alkaline phosphatase activities of osteoblastic cells were improved with the incorporation of nanoHA in the SF matrix providing a more promising material for bone tissue engineering.

Miscibility is an important issue in biopolymer blends for analysis of the behavior of polymer pairs through the detection of phase separation and improvement of the mechanical and physical properties of the blend. This study presents the formulation of a stable and one-phase mixture of collagen and regenerated silk fibroin (RSF), with the highest miscibility ratio between these two macromolecules, through inducing electrostatic interactions, using salt ions. For this aim, a ternary phase diagram was experimentally built for the mixtures, based on observations of phase behavior of blend solutions with various ratios. The miscibility behavior of the blend solutions in the miscible zones of the phase diagram was confirmed quantitatively by viscosimetric measurements. Assessing the effects of biopolymer mixing ratio and salt ions, before and after dialysis of blend solutions, revealed the importance of ion-specific interactions in the formation of coacervate-based materials containing collagen and RSF blends that can be used in pharmaceutical, drug delivery, and biomedical applications. Moreover, the conformational change of silk fibroin from random coil to beta sheet, in solution and in the final solid films, was detected by circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR), respectively. Scanning electron microscopy (SEM) exhibited alterations of surface morphology for the biocomposite films with different ratios. Surface contact angle measurement illustrated different hydrophobic properties for the blended film surfaces. Differential scanning calorimetry (DSC) showed that the formation of the beta sheet structure of silk fibroin enhances the thermal stability of the final blend films. Therefore, the novel method presented in this study resulted in the formation of biocomposite films whose physico-chemical properties can be tuned by silk fibroin conformational changes by applying different component mixing ratios.