Functional Biopolymer Particles: Design, Fabrication, and Applications

Complex coacervates between bovine serum albumin and anionic polysaccharides: formation and characterization

Abstract The comparative study regarding complexes coacervated between Bovine Serum Albumin (BSA) and different polysaccharides, Pectin (PEC) and Gum Acacia (GA), was carried out by evaluating the influence of different ratios (protein:polysaccharide) and sodium chloride (NaCl) concentrations on turbidity and zeta potential. The BSA:PEC complexes were formed in a 10:1 ratio whereas BSA:GA at 3:1. The complexation pH showed different behavior, BSA: PEC complexes exhibited maximum turbidity in a wide pH range (4.9 to 1.5), while BSA: GA had maximum turbidity at pH 3.5. The increase in the concentration of NaCl negatively influenced the complexation. The NaCl concentration of 0.40 mol L-1 suppressed the interaction in BSA:PEC (10:1) and reduced the range formation of BSA:GA (3:1). The Fourier Transform Infrared (FTIR) demonstrated the participation not only of electrostatic interactions, but also of hydrogen bonds in the complexation. This initial study elucidated fundamental aspects about the formation of coacervate complexes between BSA:GA/PEC that assist in directing its application in food products especially, in acidic matrices (pH~4.0) as well as with low concentration of salts, in view of the effect of pH on maximum formation and sensitivity to NaCl. These complexes can be added directly to products in order to add nutritional value or even be used as a new matrix for the encapsulation of bioactive compounds.

The impact of pH and biopolymer ratio on the complex coacervation of Spirulina platensis protein concentrate with chitosan

Spirulina platensis is one of the most significant multicellular blue-green Cyanobacterium microalgae with a high protein content. The complex coacervation as an encapsulation technique allows the formation of proteins with improved functional properties and thermal stability. In this study, the effects of pH and Spirulina platensis protein concentrate (SPPC)-chitosan ratio on complex coacervation formation were examined in terms of ζ-potential, turbidity, visual observation and microscopic images. Based on the results, the strongest interaction between SPPC and chitosan occurred at pH of 5.5 and SPPC-chitosan ratio of 7.5:1 with a precipitation in the test tubes. Stable dispersions were obtained at a pH range of 2-4 for the SPPC-chitosan ratio of 7.5:1 inhibiting the precipitation which occurs at individual SPPC solutions at this pH range. Characteristic organic groups in the individual SPPC and chitosan solutions as well as the SPPC-chitosan coacervate formed at the optimal conditions were identified by using Fourier Transform Infrared (FT-IR) spectroscopy technique. Furthermore, thermal stability of the individual SPPC and chitosan solutions and the SPPC-chitosan coacervates were investigated using differential scanning calorimetry (DSC). The glass transition temperature and enthalpy were 209.5 °C and - 3.414 W/g for the complex coacervates and 180.5 °C and - 0.877 W/g for SPPC. It means that complex coacervation provided more thermally-stable SPPC in chitosan-SPPC coacervate than that of the individual SPPC. Our results might have important implications for the utilization of Spirulina platensis proteins especially for acidic beverage applications.

Ultrasound-assisted modification of functional properties and biological activity of biopolymers: A review

In this review, the recent applications of power ultrasound technology in improving the functional properties and biological activities of biopolymers are reviewed. The basic principles of ultrasonic technology are briefly introduced, and its main effects on gelling, structural, textural, emulsifying, rheological properties, solubility, thermal stability, foaming ability and foaming stability and biological activity are illustrated with examples reviewing the latest published research papers. Many positive effects of ultrasound treatment on these functional properties of biopolymers have been confirmed. However, the effectiveness of power ultrasound in improving biopolymers properties depends on a variety of factors, including frequency, intensity, duration, system temperature, and intrinsic properties of biopolymers such as macromolecular structure. In order to obtain the desired outcomes, it is best to apply optimized ultrasound processing parameters and use the best conditions in terms of frequency, amplitude, temperature, time, pH, concentration and ionic strength related to the inherent characteristics of each biopolymer. This will help employ the full potential of ultrasound technology for generating innovative biopolymers functionalities for various applications such as food, pharmaceuticals, and other industries.

Synergistic interactions in dilute aqueous solutions between alginate and tropical vegetal hydrocolloids

Encapsulation in alginate beads has always been limited by the leakage due to the too wide distribution of pore sizes. Mixing alginate with other polymers have sometimes reduced the problem. Hydrocolloids from seven tropical vegetal species (barks of Triumfetta cordifolia and Bridelia thermifolia, seeds of Irvingia gabonensis and Beilschmiedia obscura, and leaves of Ceratotheca sesamoides, Adansonia digitata and Corchorus olitorius) were screened for synergistic interactions with alginate in dilute aqueous solution. Mixtures with alginate were made at different volume proportions and deviations from the initial viscosity set at 1 were evaluated. In distilled water, the gums from T. cordifolia, B. obscura, C. sesamoides and C. olitorius presented synergies with alginate. In 2 mM calcium chloride, the seven gums showed positive synergy. Interactions are favored by gum flexibility and the presence of charges, although high charges reduced the interactions. Alginate fraction of maximum viscosity enhancement depends on the ability to conformational order of the gum. The measure by laser diffraction of alginate-gum particles sizes at different fractions showed that the cooperative interactions did not always involve the largest complexes formed in gums associations. The occurrence of these interactions predicts the formation of homogeneous mixed gels at higher polymer and calcium concentrations.

Influence of Partial Acid Hydrolysis on Size, Dispersity, Monosaccharide Composition, and Conformation of Linearly-Branched Water-Soluble Polysaccharides

The effect of partial acid hydrolysis on the physical and chemical properties of galactomannan, arabinoxylan, and xyloglucan was investigated. Polysaccharides were treated at 50 °C with hydrochloric acid for 3-48 h. Portions of isopropanol (i-PrOH) were added sequentially to the hydrolyzates, resulting in fractions that were collected by centrifugation. As expected, a significant reduction of weight-average molecular weight (Mw) was observed with increasing hydrolysis time. Fractional precipitation was successfully applied to collect at least one polymer fraction with dispersity (Đ) close to one for each polysaccharide. The monosaccharide composition analysis showed that the partial hydrolysis usually lowered the relative amount of side chains, with the exception of galactomannan, where the composition remained largely unaffected. Estimation of the polymer conformation in solution, through evaluation of the Mark-Houwink parameter coefficient (α), confirmed that acid hydrolysis influenced the polysaccharides' conformation. It was demonstrated that acid treatment in dilute solution followed by fractional isopropanol precipitation is a method, extendible to a variety of polysaccharides, to obtain materials of decreased molecular weight and low dispersity with slightly altered overall composition and conformation.

Preparation, characterization and release studies of folic acid from inulin conjugates

Folic acid a synthetic form of folate, is the oxidized form of folate which acts as a coenzyme in one carbon transfer reactions required in the biosynthesis of DNA and RNA and its deficiency could be related to diseases such as neural tube defects, Alzheimer's disease, pregnancy complications and cancer. Inulin is a polydisperse polysaccharide comprising mostly of fructosyl fructose units. An oxidized derivative of this inulin was prepared and used as a complexing agent for folic acid to obtain a polysaccharide bound folic acid conjugate. The aldehyde content and degree of oxidation of the oxidized inulin were determined by acid-base titrations. All the products were characterized by sophisticated spectroscopic and thermal methods of analysis. Release studies of folic acid from conjugates were carried out in different pH media and the results demonstrate the pH-sensitive behavior of the inulin-based delivery system towards the controlled release of folic acid.

Biopolymer Microparticles Prepared by Microfluidics for Biomedical Applications

Biopolymers are macromolecules that are derived from natural sources and have attractive properties for a plethora of biomedical applications due to their biocompatibility, biodegradability, low antigenicity, and high bioactivity. Microfluidics has emerged as a powerful approach for fabricating polymeric microparticles (MPs) with designed structures and compositions through precise manipulation of multiphasic flows at the microscale. The synergistic combination of materials chemistry afforded by biopolymers and precision provided by microfluidic capabilities make it possible to design engineered biopolymer-based MPs with well-defined physicochemical properties that are capable of enabling an efficient delivery of therapeutics, 3D culture of cells, and sensing of biomolecules. Here, an overview of microfluidic approaches is provided for the design and fabrication of functional MPs from three classes of biopolymers including polysaccharides, proteins, and microbial polymers, and their advances for biomedical applications are highlighted. An outlook into the future research on microfluidically-produced biopolymer MPs for biomedical applications is also provided.

Physicochemical and antibacterial properties of fabricated ovalbumin–carvacrol gel nanoparticles

The applications of carvacrol are limited due to its poor stability, water solubility and high volatility. Herein we fabricated ovalbumin–carvacrol gel nanoparticles and then improved solubility, stability and antibacterial property of carvacrol.

Use of molecular interactions and mesoscopic scale transitions to modulate protein-polysaccharide structures

Mixed protein-polysaccharide structures have found widespread applications in various fields, such as in foods, pharmaceuticals or personal care products. A better understanding and a more precise control over the molecular interactions between the two types of macromolecules leading to an engineering of nanoscale and colloidal building blocks have fueled the design of novel structures with improved functional properties. However, these building blocks often do not constitute the final matrix. Rather, further process operations are used to transform the initially formed structural entities into bulk matrices. Systematic knowledge on the relation between molecular structure design and subsequent mesoscopic scale transitions induced by processing is scarce. This article aims at establishing a connection between these two approaches. Therefore, it reviews not only studies on the underlying molecular interaction phenomena leading to either a segregative or associative phase behavior and nanoscale or colloidal structures, but also looks at the less systematically studied approach of using macroscopic processing operations such as shearing, heating, crosslinking, and concentrating/drying to transform the initially generated structures into bulk matrices. Thereby, a more comprehensive look is taken at the relationship between different influencing factors, namely solvent conditions (i.e. pH, ionic strength), biopolymer characteristics (i.e. type, charge density, mixing ratio, biopolymer concentration), and processing parameters (i.e. temperature, mechanical stresses, pressure) to generate bulk protein-polysaccharide matrices with different morphological features. The need for a combinatorial approach is then demonstrated by reviewing in detail current mixed protein-polysaccharide applications that increasingly make use of this. In the process, open scientific questions that will need to be addressed in the future are highlighted.

Physico-Chemical Properties of Sugar Beet Pectin-Sodium Caseinate Conjugates via Different Interaction Mechanisms

Polysaccharides and proteins are frequently conjugated through electrostatic attraction, enzymatic cross-linking, and heat treatment (Maillard reaction) to obtain food structuring ingredients, mostly for their application as emulsifiers. The conjugate partners and their interaction type affect performance at acidic or neutral pH and during thermal processing, thus requiring careful selection. Here, the aggregate properties (particle size, conjugate charge, shear viscosity) of three types of sugar beet pectin (SBP)-sodium caseinate (SC) 1:1 conjugates, at acidic and neutral pH (4.5; 7), as well as their thermal processing stability (80 °C), were investigated. The enzymatically cross-linked SBP:SC was more acid tolerant than the electrostatically interacting conjugates. Maillard cross-linked conjugates aggregated at pH 4.5, suggesting poor emulsifier performance in acidic conditions. At pH 7, the three conjugate types showed similar aggregate properties. The results are discussed in terms of structural re-arrangement.

Biopolymers for Biomedical and Pharmaceutical Applications: Recent Advances and Overview of Alginate Electrospinning

Innovative solutions using biopolymer-based materials made of several constituents seems to be particularly attractive for packaging in biomedical and pharmaceutical applications. In this direction, some progress has been made in extending use of the electrospinning process towards fiber formation based on biopolymers and organic compounds for the preparation of novel packaging materials. Electrospinning can be used to create nanofiber mats characterized by high purity of the material, which can be used to create active and modern biomedical and pharmaceutical packaging. Intelligent medical and biomedical packaging with the use of polymers is a broadly and rapidly growing field of interest for industries and academia. Among various polymers, alginate has found many applications in the food sector, biomedicine, and packaging. For example, in drug delivery systems, a mesh made of nanofibres produced by the electrospinning method is highly desired. Electrospinning for biomedicine is based on the use of biopolymers and natural substances, along with the combination of drugs (such as naproxen, sulfikoxazol) and essential oils with antibacterial properties (such as tocopherol, eugenol). This is a striking method due to the ability of producing nanoscale materials and structures of exceptional quality, allowing the substances to be encapsulated and the drugs/ biologically active substances placed on polymer nanofibers. So, in this article we briefly summarize the recent advances on electrospinning of biopolymers with particular emphasis on usage of Alginate for biomedical and pharmaceutical applications.

Fabrication of Stable and Self-Assembling Rapeseed Protein Nanogel for Hydrophobic Curcumin Delivery

Food-dervied biopolymer nanogels have recently received considerable attention as favorable carrier systems for nutraceuticals and drugs. In the present study, new biocompatible and self-assembled acylated rapeseed protein isolate (ARPI)-based nanogels were fabricated for potential hydrophobic drug delivery by chemical acylation and heat-induced protein denaturation. The effects of the ARPI concentration, pH, heat temperature, and heat time on the physiochemical properties of self-assembled ARPI nanogels were investigated. The optimized ARPI nanogels were characterized by a hydrodiameter of 170 nm in size, spherical morphology, and light core-dark shell structure. In comparison to native rapeseed protein isolates and ARPI without the heat treatment, ARPI nanogels as a result of dual acylation and heat processes exhibited significantly altered spatial secondary and tertiary structures, increased surface hydrophobicity, and decreased free sulfhydryl contents of the protein. Such properties endow amphilic ARPI with the self-aggregating ability, resulting in the hydrophobic core with formations of covalent disulfide bonds and the hydrophilic shell with succinyl moieties exposed to the water side. Such a cross-linked structure allowed for ARPI nanogels to be resistant against a broad array of pH and ionic strength as well as lyophilization and dilution. ARPI nanogels demonstrated 95% encapsulation efficiency of hydrophobic compound curcumin and significantly increased its anticancer activity against multiple cancer cell lines.

Preparation and Application in Drug Storage and Delivery of Agarose Nanoparticles

In this work, monodisperse agarose gel nanoparticles were prepared using a W/O microemulsion as a template to control the size of the obtained particles. The combination of this template method with a temperature-induced gelling and a solvent exchange methodology has allowed preparing stable aqueous dispersions of monodisperse agarose gel nanoparticles in water. The average size, measured as an apparent hydrodynamic diameter, of the obtained particles was around 150 nm. The ability of the obtained hydrogel particles for the encapsulation and release of a synthetic insecticide (azamethiphos) was tested. The results evidence that the insecticide molecules encapsulated in the fabricated nanoparticles are released following a diffusion-controlled mechanism. These results combined with the biodegradability of the agarose provide the bases for the design of a new vector with application in the control of parasites in water reservoirs.

The correlation between gelatin macroscale differences and nanoparticle properties: providing insight into biopolymer variability

From therapeutic delivery to sustainable packaging, manipulation of biopolymers into nanostructures imparts biocompatibility to numerous materials with minimal environmental pollution during processing. While biopolymers are appealing natural based materials, the lack of nanoparticle (NP) physicochemical consistency has decreased their nanoscale translation into actual products. Insights regarding the macroscale and nanoscale property variation of gelatin, one of the most common biopolymers already utilized in its bulk form, are presented. Novel correlations between macroscale and nanoscale properties were made by characterizing similar gelatin rigidities obtained from different manufacturers. Samples with significant differences in clarity, indicating sample purity, obtained the largest deviations in NP diameter. Furthermore, a statistically significant positive correlation between macroscale molecular weight dispersity and NP diameter was determined. New theoretical calculations proposing the limited number of gelatin chains that can aggregate and subsequently get crosslinked for NP formation were presented as one possible reason to substantiate the correlation analysis. NP charge and crosslinking extent were also related to diameter. Lower gelatin sample molecular weight dispersities produced statistically smaller average diameters (<75 nm), and higher average electrostatic charges (∼30 mV) and crosslinking extents (∼95%), which were independent of gelatin rigidity, conclusions not shown in the literature. This study demonstrates that the molecular weight composition of the starting material is one significant factor affecting gelatin nanoscale properties and must be characterized prior to NP preparation. Identifying gelatin macroscale and nanoscale correlations offers a route toward greater physicochemical property control and reproducibility of new NP formulations for translation to industry.

Modulation of the bitterness of pea and potato proteins by a complex coacervation method

The incorporation of novel plant-based proteins into foods is often challenging due to an unacceptable bitter sensation. Typically, a combination of electrostatic and hydrophobic forces contributes to the proteins' bitterness. The current study therefore focuses on the development of electrical properties on cationic plant proteins to reduce their overall bitterness in order to improve the perceived sensorial acceptance. As such, we utilized a simple mixing process to induce complex coacervation of oppositely charged biopolymers under acidic conditions. Pea and potato protein stock solutions were mixed with apple pectin (DE 71%) solutions at various biopolymer ratios to modulate the electrical, rheological, and sensorial properties of the complexes. Whey protein hydrolyzate was used as a control sample. Surface charge measurements revealed a transition from positive to negative values as the pectin concentration was increased regardless of the plant protein, whereas stable dispersions without sedimentation were observed above a critical pectin : protein ratio of 1. Low and intermediate biopolymer ratios (<1) promoted aggregation and led to rapid sedimentation. Sensory evaluation showed that bitterness scores depended on protein type and decreased from pea protein > potato protein > whey protein. Moreover, bitter off-notes were increasingly reduced with increasing pectin : protein ratios; however, high dispersion viscosities above 0.05 Pa s led to undesirable texture and mouthfeel of the biopolymer dispersions. Our results might have important implications for the utilization of novel plant proteins in food and beverage applications.

Preparation of starch nanoparticles loaded with quercetin using nanoprecipitation technique

Nanoparticles of starches from different botanical origin were prepared by nanoprecipitation using 0.1M hydrochloric acid as non-solvent. The morphology and the particle size were analyzed using field emission scanning electron microscopy and dynamic light scattering. The nanoparticles were spherical and their sizes vary depending on the origin and the concentration of the starch solution. Starch nanoparticles loaded with quercetin were prepared. In-vitro release studies of the quercetin from the starch nanoparticles were performed in 35% ethanol as a release medium. The starch origin affects the quercetin loading percentage, the release kinetics and the antioxidant activity of the produced nanoparticles. The starch-quercetin nanoparticles from cereal origin showed the lowest loading percentage and the lowest fraction released of quercetin in comparison with nanoparticles from tuber and legume origin. The release kinetics seem to be controlled mainly by Fickian diffusion which have been revealed fitting the release data to the Peppas-Sahlin model.