Formation Of Electrostatic Complexes Research Articles

Enhancing encapsulation of curcumin by pH-driven and sodium alginate blending with ovalbumin as a carrier

Curcumin is a hydrophobic polyphenol with various health benefits, but its poor water solubility and stability limit its application in the food and pharmaceutical industries. In this study, a pH-driven method was developed to prepare ovalbumin (OVA)-curcumin nanocomplexes without organic solvents, reducing the environmental impact. The results showed that curcumin was encapsulated in OVA with a high efficiency of over 95% and remained in an amorphous state within the protein molecules. Molecular docking and spectroscopic analyses revealed that curcumin was mainly bound and stabilized by hydrogen bonds and hydrophobic interactions in the hydrophobic core of OVA. The binding strength of the intermediate stage of the pH-driven method was stronger than that of the final stage, due to the exposure of OVA molecular binding sites and the involvement of electrostatic attraction. Furthermore, the potential of polysaccharide blending to enhance the stability of the nanocomplexes was investigated. The results showed that sodium alginate effectively enhanced the photostability and thermal stability of the OVA-curcumin nanocomplexes by co-solubilization and electrostatic complex formation. In addition, simulated in vitro digestion also demonstrated that the pH-driven method combined with polysaccharide blending increased the bioaccessibility of curcumin in nanocomplexes from 17.79% to 52.54%. Therefore, the pH-driven method coupled with polysaccharide blending ensures the encapsulation and stabilization of hydrophobic bioactive substances for use in their delivery systems to improve bioaccessibility.

Thermally stabilized chondroitin sulfate-hemoglobin nanoparticles and their interaction with bioactive compounds

The preparation of nanoparticles (NPs) based on hemoglobin (Hb) with a fully biocompatible methodology is presented. The spontaneous formation of electrostatic complexes of Hb with chondroitin sulfate (CS) at pH 4 in the polysaccharide/protein mass ratio regime where charge neutrality is met leads to spherical nanostructures with monomodal hydrodynamic radii distribution in the range of 50–100 nm. The integrity of the electrostatic complexes is disturbed at pH 7 as the net electric charge of Hb is very low. Treating the NPs at mildly elevated temperature stabilizes them against the pH increase taking advantage of Hb's ability of unfolding and self-associating upon thermal treatment. The NPs surface charge is pH-tunable and changes from positive to strongly negative upon pH increase to 7 proving the presence of negative surface patches of Hb and CS segments in their exterior. The α-helix content of Hb does not change significantly by thermal treatment. The NPs are found to bind the bioactive compounds curcumin and β-carotene and are stable in solutions with high salt content. This investigation introduces a straightforward method to formulate Hb in NPs with possibilities in the nanodelivery of nutrients and drugs.

Polysaccharide-based polyampholyte complex formation: Investigating the role of intra-chain interactions

The difference in inter-chain and intra-chain electrostatic attraction was investigated in polyelectrolyte and polyampholyte electrostatic complex formation. Three polymers with similar backbone molecular structures including chitosan (Ch) polycation, carboxymethyl cellulose (CMCe) polyanion, and carboxymethyl chitosan (CMCh) polyampholyte were used for this purpose. The turbidimetric, water content, and rheological measurements for polyampholyte self-complex showed more dependence on the ionic strength rather than the polyelectrolyte one. The degree of dissociation (α), dissociation constant (pKa), and intrinsic persistence length were calculated by applying the Katchalsky-Lifson model to potentiometric data. We studied the gyration radii as a function of Debye length and observed the polyampholyte chain contractions due to the intra-chain electrostatic attractions, which minimize the entropic gain of the inter-chain complex formation. This is in accordance with the decrease in pKa by αc for CMCh which is the opposite of that for the Ch and CMCe samples. We also found that the polyampholyte has less intrinsic and electrostatic persistence length compared with both polyanion and polycation with similar chain structures indicating the impact of the inter-chain electrostatic interaction on the complex properties. This study deepens our insight about the behavior of CMCh and the nature of difference between CMCh and Ch/CMCe electrostatic complexes.

Foaming properties are improved by interactions between brewer's spent grain proteins and carrageenans in aqueous solution.

Foaming properties and macromolecular interactions in solution among brewer's spent grain proteins (CP) and iota and lambda carrageenans (i-CG and l-CG, respectively) as a function of aqueous medium pH (2-6) and protein-polysaccharide ratio, RCP:CG (1:1, 2:1 and 4:1), were studied. At these conditions, the CP colloidal stability was favored by the formation of soluble electrostatic complexes with CG. Fluorescence (intrinsic and extrinsic) spectroscopy and dynamic light scattering techniques, including particle size and ζ-potential analysis, were applied to know the phase behavior of the biopolymer systems. The bubbling method was used to produce foams, and the foam expansion (%) and half-life time (t1/2 ) were determined. Both CG promoted an increased Trp fluorescence emission depending on the pH, suggesting conformational changes in CP. The CG in mixed systems produced a significant decrease in the extrinsic fluorescence intensity, mainly at low pH values, highlighting a reduction in CP surface hydrophobicity. At the examined pH range, the ζ-potential values for mixed-systems were negative, and their magnitudes were intermediate between CP and CG, revealing the associative electrostatic nature of biopolymer interactions, which were dependent on the RCP:CG . The particle size analysis confirmed the formation of soluble electrostatic complexes in solution. Finally, using i-CG at pH 2 or 3 and 2:1 RCP:CG , the best foaming properties for mixed systems were observed. The formation of electrostatic complexes with a compact assembly among biopolymers, high negative net charge, and colloidal stability convert the CP-CG mixed solutions into promising biopolymer systems for food foams production. © 2022 Society of Chemical Industry.

Impact of heat treatment in whey proteins-soluble soybean polysaccharides electrostatic complexes in different pH and biopolymer mass ratio conditions

The formation of electrostatic complexes between whey protein isolate (WPI) and soluble soybean polysaccharide (SSPS) was firstly studied to select the suitable conditions of pH and WPI:SSPS mass ratio. Then, the influence of a heat treatment (90 °C, 20 min) on the characteristics of WPI-SSPS complexes was studied in the selected conditions of pH (3.0, 3.5, and 4.0) and WPI:SSPS ratio (1:0.50 to 1:0.17) by ζ-potential, particle size distribution, surface hydrophobicity, and physical stability in a 3 × 2 design by statistical response surface methodology. This analysis showed that the heat treatment significantly increased the Z-average and surface hydrophobicity of complexes and increased their size and physical stability over time. This work provides new information on the impact of heat treatment on molecular interactions in WPI-SSPS systems. The obtained data is useful to design heat-treated WPI-SSPS complexes with specific characteristics of size, charge, hydrophobicity, and physical stability. Furthermore, this work provides an optimized WPI-SSPS nanocomplex that could be implemented as a delivery system for hydrophobic bioactive compounds in food matrices.

Using Lipid Nanoparticles for the Delivery of Chemically Modified mRNA into Mammalian Cells

In recent years, chemically modified messenger RNA (mRNA) has emerged as a potent nucleic acid molecule for developing a wide range of therapeutic applications, including a novel class of vaccines, protein replacement therapies, and immune therapies. Among delivery vectors, lipid nanoparticles are found to be safer and more effective in delivering RNA molecules (e.g., siRNA, miRNA, mRNA) and a few products are already in clinical use. To demonstrate lipid nanoparticle-mediated mRNA delivery, we present an optimized protocol for the synthesis of functional me1Ψ-UTP modified eGFP mRNA, the preparation of cationic liposomes, the electrostatic complex formation of mRNA with cationic liposomes, and the evaluation of transfection efficiencies in mammalian cells. The results demonstrate that these modifications efficiently improved the stability of mRNA when delivered with cationic liposomes and increased the eGFP mRNA translation efficiency and stability in mammalian cells. This protocol can be used to synthesize the desired mRNA and transfect with cationic liposomes for target gene expression in mammalian cells.

The physicochemical stability of oat-based drinks

The popular dairy alternative oat-based drink (OBD) is made from hydrolysed oat. However, natural OBD is inherently unstable. OBD is commonly made from wholemeal oat and considered to have health benefits due to the β-glucan content. β-glucan is also a hydrocolloid with stabilizing potential and stored mainly in the bran. This study investigated the effect of bran substitution, to traditional wholemeal oat on the stability and physicochemical properties of OBD. In addition, the effect of the loss of the β-glucan network at neutral and acidified pH are also assessed. Products with intact β-glucan from bran were highly viscous and, thus, stable throughout storage at 20 °C for 14 days, but showed a viscous gel-like tendency that is unsuitable for thin beverage applications. The loss of the β-glucan network made thin beverage-like products that were unstable. The instabilities observed were phase separation due to thermodynamic incompatibility (bran pH 6.4), gravity separation-based creaming (wholemeal pH 6.4 and 4.2), and electrostatic complex formation (bran pH 4.2). The complex formation highlighted the slight anionic tendency of hydrolysed β-glucan. The use of bran fraction leads to higher protein and β-glucan content. The physicochemical balance of the products greatly influenced the stability of the product.

Chitin nanofibers improve the stability and functional performance of Pickering emulsions formed from colloidal zein

There is growing interest in formulating Pickering emulsions from biopolymer particles due to consumer demand for more natural products. Protein-based colloidal particles can be used for this purpose, but they are prone to aggregate at pH values around their isoelectric point (pI), which limits their application. In this study, the possibility of using chitin nanofibers (ChNFs) to improve the pH stability of Pickering emulsions prepared from zein colloidal particles (ZCPs) was investigated. Initially, the morphology and interfacial properties of the complexes formed between ChNFs and ZCPs were studied as a function of pH (3–9). The tendency of the ZCPs to aggregate and sediment at pH ≥ pI was reduced in the presence of ChNFs, which was attributed to the formation of electrostatic complexes. The contact angle of the composite particles could be optimized by altering their composition. For instance, the contact angle increased from 74° for ZCPs to 85° for ZCP/ChNF (5:1 ratio) at pH 6, which improved their tendency to stabilize the oil droplets. Brewster angle microscopy indicated that ZCP/ChNF complexes had rod-like and/or particulate structures at an air-water interface, which were different from those observed in the bulk aqueous phase. Pickering emulsions formed from ZCP/ChNF complexes had better stability than those formed from ZCPs or ChNFs, especially when the pH was close to or greater than the pI. An in vitro digestion study showed that the presence of the interfacial complexes reduced the lipolysis of the oil droplets by about 11% in a simulated gastrointestinal tract. High internal phase Pickering emulsions (HIPPEs) could be formed from ZCP/ChNF complexes at pH ≥ pI, which were able to protect unsaturated lipids from oxidation. Overall, our results show that chitin nanofibers can be used to improve the pH stability of Pickering emulsions formed from colloidal zein, as well as to modulate their functional performance.

Method of casein obtaining from skimmilk using oligochitosans

The interaction of milk proteins and oligochitosans is based on formation of electrostatic complex between negatively charged casein micelles and positively charged polysaccharide groups. At low concentrations of oligochitosans, partial interaction with milk proteins occurs. Maximum protein coagulation (90 %) is achieved in equivalence zone at the concentration of oligochitosans: 45.3 kDa-0.88×10−4 M; 25.4 kDa-1.57×10−4 M; 7.7 kDa – 5.19×10−4 M; 1.5 kDa-26.67×10−4 M. In these concentrations, taking into account the molecular weight and degree of deacetylation of oligochitosans, the total content of protonated amino groups is equal 2.4×10−4 M. When t protein content in skimmed milk is 3.0 % - 3.2%, oligochitosans of any molecular weight and degree of deacetylation can be used for casein coagulation, important that the final concentration of amino groups should be 2.4×10−4 M. It was determined that the use of the studied samples of oligochitosan allows to obtain coacervate where 1 g of oligochitosan binds 6.0 – 6.2 g of milk proteins.

Modulating properties of polysaccharides nanocomplexes from enzymatic hydrolysis of chitosan

Synthesis of nanocomplexes is a simple and low-cost technique for the production of encapsulation systems aiming industrial applications, based on the interaction of at least two oppositely charged molecules. Gellan gum (anionic) is a water-soluble biopolymer resistant to stomach pH conditions, therefore an interesting alternative as an encapsulating matrix. Chitosan (cationic) is also widely used due to its biocompatibility and mucoadhesive properties, although its low water solubility is an important step to be overcome for the production of the complexes. To improve this property, many techniques have been employed, but most of them use unsustainable techniques and chemical agents. The enzymatic hydrolysis of chitosan using proteases emerges as an alternative to these drawbacks and, therefore, this study aimed to evaluate the electrostatic nanocomplexation of native (C) or hydrolyzed (HC) chitosan (by porcine pepsin protease) with gellan gum (G). Polysaccharides and nanocomplexes formed with different G:C or G:HC ratio were evaluated by zeta potential measurements, particle size distribution, X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Transmission Electron Microscopy (STEM), intrinsic viscosity and turbidity analyses. Chitosan hydrolysis allowed the formation of a smaller (445.3 nm in pH 4.5) and more soluble structure (3 kDa), which positively influenced the formation of the complexes. The ratios G:HC of 7:3 and 8:2 formed complexes with lower values of zeta potential (13.9 mV and −5.0 mV, respectively), particle size (635.8 nm and 533.6 nm, respectively) and polydispersity (0.28 and 0.23) compared to complexes formed with native chitosan. Overall, our results show that enzymatic hydrolysis of chitosan favored the formation of electrostatic complexes with reduced size and low polydispersity, which can be used as efficient encapsulating matrices for improved targeted delivery and controlled release of bioactive compounds.

Long-term glycemic control and prevention of diabetes complications in vivo using oleic acid-grafted-chitosan‑zinc-insulin complexes incorporated in thermosensitive copolymer

Daily injections for basal insulin therapy are far from ideal resulting in hypo/hyperglycemic episodes associated with fatal complications in type-1 diabetes patients. Here we report a delivery system that provides controlled release of insulin closely mimicking physiological basal insulin requirement for an extended period following a single subcutaneous injection. Stability of insulin was significantly improved by formation of zinc-insulin hexamers, further stabilized by electrostatic complex formation with chitosan polymer. Insulin complexes were homogenously incorporated into PLA-PEG-PLA, a biodegradable thermogel copolymer, that instantaneously forms a subcutaneous gel-depot following injection. Chitosan polymer was hydrophobically modified using oleic acid prior to complex formation with insulin to enable distribution of oleic acid-grafted-chitosan‑zinc-insulin complexes into the hydrophobic core of PLA-PEG-PLA thermogel-copolymer micelles. In vivo, daily administration of marketed long-acting insulin, glargine, resulted in fluctuating blood glucose levels between 91 and 443 mg/dL in type 1 diabetic rats. However, single administration of thermogel copolymeric formulation successfully demonstrated slow diffusion of insulin complexes maintaining peak-free basal insulin level of 21 mU/L for 91 days. Sustained release of basal insulin also correlated with efficient glycemic control (blood glucose <120 mg/dL), prevention of diabetic ketoacidosis and absence of cataract development, unlike other treatment groups. Moreover, there was no sign of inflammation, tissue damage, or collagen deposition around depot site, suggesting exceptional biocompatibility of the formulation for long-term use.

Complex coacervation between oak protein isolate and gum Arabic: optimization & functional characterization

ABSTRACT In this research, complex coacervation between oak protein isolate (OPI) and gum arabic (GA) at different pH values (7.0–1.6) and mixing ratios (8:1 to 1:8 protein: polysaccharide), and a constant biopolymer concentration (0.125% w/w) was studied by turbidimetric analysis. The findings revealed that the pH = 3.2 and 4:1 mixing ratio were the optimum conditions for electrostatic complex formation. The functional properties (e.g., solubility, surface hydrophobicity, capacity of water and oil absorption, foam formation, and emulsifying properties) of the OPI-GA complexes were better than OPI. The FTIR spectra revealed that the complex coacervation between the amine groups of OPI and the carboxyl groups of GA caused the formation of the coacervate, with hydrogen bonding also being involved. The results of DSC and TGA showed that the complex coacervate had better thermal stability in comparison with OPI and GA.

All-inorganic perovskite quantum dots CsPbX3 (Br/I) for highly sensitive and selective detection of explosive picric acid

As a new family of fluorescent materials, all inorganic perovskite quantum dots (PQDs) CsPbX3 (Cl, Br, I) have attracted rising attention due to their intrinsic optical superiorities and potential applications in various fields. This work takes advantage of the bright fluorescence of PQDs and the strong electrophilic properties of picric acid (PA) to construct an analytical method for sensitive and selective discrimination of PA against other nitroaromatic explosives, and the limit of detection is as low as 0.8 nM. The quenching mechanism was elucidated as the formation of electrostatic complex and the electron transfer between PA and PQDs. To facilitate visual and on-site detection, the CsPbBr3 PQDs were printed onto microfiltration membrane by inkjet printing to fabricate test papers for rapid and on-site detections of explosive and pollutant PA, showing a great research prospect in the detection of ultratrace PA at different sites.

Effect of pH on the formation of electrostatic complexes between lentil protein isolate and a range of anionic polysaccharides, and their resulting emulsifying properties

This research investigated the effect of pH on forming electrostatic complexes between lentil protein isolate (LPI) and a range of anionic polysaccharides [carboxymethyl cellulose (CMC), gum Arabic (GA), alginate (AL), and ι-carrageenan (CAR)] at 4:1 LPI-polysaccharide mixing ratio, and their resulting emulsifying abilities. Maximum optical densities were found to be 0.486, 0.716, 0.310, and 0.190 for LPI-CMC, LPI-GA, LPI-AL, and LPI-CAR, respectively indicating the level of aggregate size and growth. LPI-CAR emulsion displayed the highest emulsion stability (ES) because of its higher continuous phase and emulsion viscosities, lower mean droplet sizes, and negatively charged droplets. They also formed much smaller complexes within solution due to their high negative charge. All other LPI-polysaccharide systems formed less stable emulsions than LPI alone due to the larger sizes of both complexes and oil droplets.

A Supramolecular Crosslinker To Give Salt-Resistant Polyion Complex Micelles and Improved MRI Contrast Agents.

Three-component mixtures (diblock copolymer/metal ion/oligoligand) can assemble into micellar particles owing to a combination of supramolecular polymerization and electrostatic complex formation. Such particles cover a large range of compositions, but the electrostatic forces keeping them together make them rather susceptible to disintegration by added salt. Now it is shown how the salt stability can be tuned continuously by employing both a bis-ligand and a tris-ligand, and varying the ratio of these in the mixture. For magnetic ions such as MnII and FeIII , the choice of the multiligand also affects the ion/water interaction and, hence, the magnetic relaxivity. As an example, MnII -based nanoparticles with a very high longitudinal relaxivity (10.8 mm-1 s-1 ) were investigated that are not only biocompatible but also feature strong contrast enhancement in target organs (liver, kidney), as shown by T1 -weighted in vivo magnetic resonance imaging (MRI).

A Supramolecular Crosslinker To Give Salt‐Resistant Polyion Complex Micelles and Improved MRI Contrast Agents

AbstractThree‐component mixtures (diblock copolymer/metal ion/oligoligand) can assemble into micellar particles owing to a combination of supramolecular polymerization and electrostatic complex formation. Such particles cover a large range of compositions, but the electrostatic forces keeping them together make them rather susceptible to disintegration by added salt. Now it is shown how the salt stability can be tuned continuously by employing both a bis‐ligand and a tris‐ligand, and varying the ratio of these in the mixture. For magnetic ions such as MnII and FeIII, the choice of the multiligand also affects the ion/water interaction and, hence, the magnetic relaxivity. As an example, MnII‐based nanoparticles with a very high longitudinal relaxivity (10.8 mm−1 s−1) were investigated that are not only biocompatible but also feature strong contrast enhancement in target organs (liver, kidney), as shown by T1‐weighted in vivo magnetic resonance imaging (MRI).

Application of Response Surface Methodology in the Preparation of Pectin-Caseinate Nanocomplexes for Potential Use as Nutraceutical Formulation: A Statistical Experimental Design Analysis

Background: The formation of electrostatic complexes between two types of biopolymers, sodium Caseinate (a derivative from most abundant milk protein) and Pectin (a natural hetro polysaccharide), was studied as a function of biopolymers concentrations and pH of solutions (3.9- 4.3). Method: The size and morphology of the resulted complexes were investigated by using of laser light scattering and transmission electron microscopy, respectively. Response surface methodology (A three-factor, three levels Box-Behnken design) was used for the optimization procedure with pH, pectin and sodium Caseinate concentrations as independent variables. Particle size and polydispersity index of nanocomplexes were considered as dependent variables. Results: Negatively charged nanocomplexes were produced below the isoelectric point of protein (5.4), at pH 4.1 with a suitable colloidal stability and average particle size of about 100 nm. It was found that the particle size of nanocomplexes could be controlled by changing in variables. Conclusion: In conclusion response surface methodology are simple, rapid and beneficial approach for preparation, optimization and investigation of the effect of independent variables on the properties of products.

DPPC monolayer response to non-spanning cobalt-cage metallosurfactants: Electrostatic complex formation

A novel series of amphiphilic cobalt-cage derivatives (ACCD), bearing a diaza-crown bridge and varying alkyl chains, facilitate ion transport across biomembrane models via self-aggregation. In this study, compression isotherm analyses and atomic force microscopy (AFM) were used to assess the interactions of these amphiphiles with Langmuir monolayers of dipalmitoylphosphatidylcholine (DPPC) in order to elucidate electrostatic and steric contributions to ion transport. The stability and compressibility of DPPC monolayers are disrupted by ACCD molecules with short (C12) alkyl chains. These top-heavy amphiphiles (large cone angles) create voids at the interface of the hydrophobic/aqueous layer leading to monolayer expansion and packing efficiency of the aliphatic chains is disrupted. Long-tailed analogues (C16, C18) are cohesively integrated into DPPC monolayers due to their smaller cone angles at the interfacial region and increased hydrocarbon compatibility in the hydrophobic region. Thermodynamic data indicate the formation of electrostatic complexes between DPPC and longer-tailed amphiphiles consistent with AFM observations of aggregate structures at the corresponding concentrations.

Interactions between hsian-tsao gum and chitosan in aqueous solution

The interactions of 0.05 wt% chitosan (CS) in admixture with different amounts of hsian-tsao gum (HG) in aqueous solutions were studied under different pH and ionic strength by the analysis of state diagram, turbidity, particle size and distribution, zeta potential and microstructure. Results obtained suggested that interactions between CS and HG could form soluble/insoluble complexes mainly through electrostatic attractions which significantly affected by HG concentration, pH and ionic strength. Particularly, varying pH or increasing HG concentration affected the zeta potential of CS-HG mixtures, which further influenced the complexes formation and caused phase separation. Furthermore, the formation of soluble complexes occurred between individual CS and HG molecules at pH away form pKa of CS, near which insoluble complexes with bigger size formed between HG and aggregate CS, except the 0.005 wt% HG molecules interacted with aggregate CS to form soluble complexes with smaller size than CS alone at pH 6.5. Additionally, added NaCl ions changing the charge density of two biopolymers further affected their electrostatic interactions, which were enhanced at lower concentrations but suppressed at higher concentrations. Optical measurements indicated the CS-HG complexes formed at pH 6.5 presented a coarsening phenomenon with increase of HG concentration. This study provided information regarding the effects of HG concentration, pH and ionic strength on the formation of electrostatic complexes between CS and HG in aqueous solution, which could be an available reference for preparation of electrostatic complexes.

Label-free ECL immunosensor for the early diagnosis of rheumatoid arthritis based on asymmetric heterogeneous polyaniline-gold nanomaterial

Specific and sensitive detection method for anti-cyclic citrullinated peptide antibody (anti-CCP) is highly in demand for the early diagnosis of rheumatoid arthritis (RA). In this work, a label-free electrogenerated chemiluminescence (ECL) immunosensor for the detection of anti-CCP was proposed based on the application of an interfacially synthesized asymmetric heterogeneous nanomaterial. Dumbbell-like polyaniline-gold (PANI-Au) nanocomposite show excellent synergetic enhancement effect on the ECL behaviors of graphite-like carbon nitride (g-C3N4). The formation of electrostatic complex between g-C3N4 and PANI-Au composite improves the interfacial stability of hydrophilic g-C3N4. The synergetic enhancement effect of PANI and Au NPs was confirmed by tailoring the morphology of the nanocomposite. An ECL immunosensor was constructed using asymmetric PANI-Au incorporated g-C3N4 as a sensing platform. The presence of Au NPs enables the facile immobilization of the recognition element for anti-CCP antibody. The simple preparation method endows the good reproducibility and stability for the proposed ECL immunosensor. A wide linear range of 0.001∼15ngmL−1 with a lower detection limit of 0.2pgmL−1 was obtained for the determination of anti-CCP antibody. The proposed ECL method may has promising application in other bioassays.