Search Results (450)

Protein–polyelectrolyte entities (complex, coacervates, flocs, gels, etc.) are of great interest due to their potential applications in biological and medical fields. This study focuses on investigating the interactions between a model protein, human serum albumin (HSA) and a newly synthesized hybrid thermoresponsive copolymer based on chitosan polysaccharide grafted with poly(N-isopropylacrylamide) synthetic polymer chains (Chit-g-PNIPAM), in aqueous media, by mixing the individual component aqueous solutions. Depending on the mixing molar ratio and the order of addition of the two components (protein and copolymer), either stable nanostructured suspension or macrostructures’ phase separation have been observed. Dynamic light scattering (T reveal that the Chit-g-PNIPAM/HSA_x (molar ratio 5:x, where x = 1, 2, 3, 5, 10 and 15) nanostructures’ and HSA/Chit-g-PNIPAM_x (molar ratio 100:x, where x = 1, 2, 3, 10, 20, 30, 40 and 50) structures’ formation depend on the molar ratio of the two components as well as on the order of addition, with first component amount being kept constant in aqueous solution and second component solution added drop-by-drop in the solution of the first component. Additional information regarding the thermoresponsiveness and stability vs time of the formed (nano)structures were acquired using turbidimetry and DLS measurements. Full article

Additive manufacturing of hydrogel-based scaffolds requires concurrent control of material rheology and extrusion dynamics, especially in multi-material architectures. In this work, we develop a modular multi-material extrusion-based 3D-printing platform that combines a filament-fed extruder for thermoplastic polymers with a piston-driven extruder for viscous gel inks, together with an empirical calibration procedure for gel dosing. The calibration algorithm optimizes the pre-extrusion and retraction displacement (E_Pr/R) based on stepwise extrusion experiments and reduces the discrepancy between theoretical and measured deposited mass for shear-thinning alginate gels to below the prescribed tolerance. The calibrated system is then used to fabricate two representative hybrid constructs: partially crosslinked sodium alginate scaffolds with an internal hollow channel supported by a removable polycaprolactone framework, and self-supporting structures based on a sodium alginate–chitosan polyelectrolyte complex obtained by sequential co-extrusion. The resulting constructs remain mechanically stable after ionic crosslinking and solvent treatment and can subsequently be converted into highly porous scaffolds by freeze- or supercritical drying. The proposed combination of hardware architecture and extrusion calibration enables reproducible multi-material 3D printing of hydrogel–thermoplastic hybrid scaffolds and can be readily adapted to other gel-based inks for tissue engineering applications. Full article

This article investigates the thermodynamic driving force of the interaction between lysozyme (Lys) and sulfated β-cyclodextrin (β-CDS), with a particular emphasis on the elusive role of hydration during polyelectrolyte–protein binding. Using isothermal titration calorimetry (ITC), the binding affinity was quantified across varying temperatures and salt concentrations, employing a recently developed thermodynamic framework that explicitly separates the contributions from counterion release and hydration effects. The study reveals that while counterion release is minimal in the Lys/β-CDS system, hydration effects become a dominant factor influencing the binding free energy ΔG_b, especially as experimental temperature deviates from the characteristic temperature T₀. It demonstrates that hydration contributions can substantially weaken binding at increased salt concentration c_s. The high characteristic temperature T₀ and the salt-dependent heat capacity change indicate a complex interplay of water structure and ion association—significantly departing from commonly linear interpretations of ΔG_b vs. log c_s based solely on counterion release effects. This work advances the understanding of polyelectrolyte–protein interactions by providing the first direct quantification of the hydration effect in such complexes and may have an impact on the rational design of biomolecular assemblies and therapeutic carriers. Full article

In this work, sodium alginate/chitosan (SA/CS) blend films were prepared by thermo-compression for the first time. Glycerol and lactic acid were used as de-structuring agents for SA and CS, respectively. The chemical structures, thermal stability, phase morphology, mechanical properties, water resistance, film opacity, film color, and soil burial test of thermo-compressed SA/CS films were investigated. The results indicate that intermolecular interactions in polyelectrolyte complexes in SA/CS blends were detected. Blending with CS improved the thermal stability of SA-based films. The SA/CS films showed excellent phase compatibility between SA and CS. The addition of CS improved the tensile properties of the SA-based films. The incorporation of CS in SA films resulted in enhanced water resistance and opacity and a decrease in biodegradability under soil burial. Thermo-compressed SA/CS films show promise for development and increased production capacity. These films can be tailored by varying the SA/CS ratios to display different properties. This versatility makes them suitable for a range of sustainable and diverse applications, including wound dressing, drug delivery, biosorbents, and packaging. Full article

Water-soluble poly-β-cyclodextrins (PCDs), crosslinked with ethylenediaminetetraacetic acid dianhydride (EDTADA), were synthesized at varying β-CD:EDTADA molar ratios (1:6, 1:9, 1:12, 1:15) to develop multifunctional nanocarriers with the ability to complex drugs, polymers, and ions. All PCDs exhibited nanometric particle sizes (14 to 28 nm), negative zeta potential (−18 to −27 mV), and adjustable content of free carboxyl groups controlled by crosslinker ratio. Functional evaluations demonstrated effective Ca²⁺ chelation and a linear inclusion complexation profile with acyclovir, but not with naproxen, highlighting pH-dependent solubility effects. Additionally, PCDs successfully formed polyelectrolyte complexes with poly-L-lysine, indicating their potential as components of advanced drug delivery systems. Among the analyzed variants, PCD 1:6 showed reduced yields, fewer reactive groups, and diminished ion-binding capacity compared to formulations with higher crosslinker content. These findings underscore the importance of crosslinking density in modulating physicochemical and functional properties and support the potential of EDTA-crosslinked PCDs as versatile platforms for advanced, ion-sensitive biomedical applications. Full article

Alginate [ALG] and chitosan [CS] are biomaterials of importance in drug-delivery because of their ability to form ionically-crosslinked nanosystems and polyelectrolyte-complexes under mild conditions. Here, a modified ionic-polyelectrolyte-pre-gelation method, with a controlled addition of reagents and sonication throughout the process, is reported to produce ALG¬¬-CS-based NPs. A mathematical study of the effects of the factors with influence in the process on the properties of NPs has been performed using a two-phase-design-of-experiment-based procedure, something never done to our knowledge. The concentration of ALG, CS and CaCl₂ and the ratio ALG:CS have significant influence on polydispersity (PDI), surface-charge (ZP) and encapsulation efficiency (EE%) of NPs. Moreover, CS flow rate has a significant effect over PDI and EE%. Thus, the values of ALG, CS and CaCl₂ concentration (mg/mL), ALG:CS (mL:mL) and CS flow rate (mL/min) to obtain the minimum-expected PDI (0.168) or the optimized EE% (86.7) are {0.30, 0.79, 1.00, 2.50:1.00, 0.86} or {0.30, 1.00, 1.00, 2.50:1.00, 2.00}, with ALG:CaCl₂ (mL:mL) and CaCl₂ flow rate (mL/min) fixed at 2.50:0.31 and 1.25. Although most of the conditions yielded highly-negative particles (minimum-expected of −67.8 mV using 0.69, 0.30 and 0.13 mg/mL of ALG, CS and CaCl₂ and ALG:CS of 2.50:0.59 mL:mL), varying the mass ratio of ALG:CS allowed for the generation of positively-charged particles (up to +21.1 mV with 0.30, 1.00 and 0.61 mg/mL of ALG, CS and CaCl₂ and ALG:CS of 2.50:1.00 mL:mL). In both cases, ALG:CaCl₂ (mL:mL), CaCl₂ and CS flow rates (mL/min) were fixed at 2.50:0.31, 1.25 and 1.25. The model for the NPs size depends only on CS and CaCl₂ concentrations, with the minimum- or maximum-expected (160 or 635 nm) at 0.30 and 1.00 or 1.00 and 0.30 of CS and CaCl₂, although the method allows a wide range of sizes (144.0–1965.0 nm). Full article

Biopolymeric films based on chitosan and starch offer an ecological alternative for food protection. Nevertheless, their practical application is often limited by their low mechanical properties and high solubility in aqueous solutions, due to weak interactions between the chains of the biopolymers. One approach to resolve this problem is to obtain biopolymeric films based on (bio)polyelectrolyte complex ((bio)PEC). These films exhibit stronger electrostatic interactions and homogeneous biopolymeric structure. In this study, films based on (bio)PEC were obtained by the casting method, using chitosan and carboxymethyl cassava starch with different degrees of substitution with a biopolymer concentration of 2.5 wt.% at pH = 6. The obtained films were analyzed using the optical and scanning microscopy, color method, ATR-FTIR spectroscopy, thermogravimetry, mechanical analysis under tension, solubility in water, simulated gastric fluid (SGF), and phosphate-buffered saline (PBS) solutions, and contact angle of water. The results demonstrated that the tensile strength and Young’s modulus of films based on (bio)PEC increased by 2–4 times, and the elongation at break by 20% compared to films based on a mixture chitosan and starch. This is due to the increase in the attraction between oppositely charged polyelectrolytes in (bio)PEC films. Additionally, the solubility of (bio)PEC films was reduced by ~40%, 35% and 70% in water, SGF and PBS solutions, respectively, when the carboxymethyl starch with highest degree of substitution was used, and z was near to 1. Full article

Polyelectrolyte-based complexes have attracted attention, as the interaction of the oppositely charged components results in nanoparticle formation through an easy but highly efficient method, avoiding the use of strong solvents, extreme temperatures, and toxic chemicals. Sodium oleate (NaOL) is a widely used surfactant in the pharmaceutical industry due to its availability, eco-friendliness, and low cost. In the present study, the neutral-cationic block copolymer poly(oligo(ethylene glycol) methyl ether methacrylate)–b–quaternized poly(2-(dimethylamino) ethyl methacrylate) (POEGMA-b-Q(PDMAEMA)) is mixed with the anionic surfactant sodium oleate for the formation of nanoscale polyelectrolyte complexes through electrostatic interactions. Different weight ratios of copolymer to surfactant are studied. Then, the co-solvent protocol was implemented, and curcumin is successfully loaded in the formed particles for drug delivery applications. The size and morphology of the macromolecular complexes are examined via Dynamic Light Scattering (DLS) and Cryogenic Transmission Electron Microscopy (cryo-TEM). The methods that we have used have indicated that the polymer–surfactant complexes form spherical complexes, worm-like and vesicle-like structures. When curcumin was introduced, encapsulation was effectively achieved into micelles, giving rise to vesicle-like shapes. The success of curcumin encapsulation is confirmed by Ultraviolet–Visible absorption (UV–Vis) and fluorescence (FS) spectroscopy. POEGMA-b-Q(PDMAEMA)–sodium oleate polyelectrolyte complexes revealed promising attributes as efficient drug carrier systems for pharmaceutical formulations. Full article

Background: Various thiolactones are known as biologically active compounds, capable of stimulating the development of several human diseases and quorum sensing of Gram–positive bacteria. The enzymatic hydrolysis of thiolactones represents a promising approach to preventing their action. Methods: Thirteen enzymes, including various lactonases and serine hydrolases were studied in this work using several substrates including the homocysteine thiolactone (HTL), and its derivatives the N–acetylhomocysteine thiolactone (C₂–HTL) and the isobutyryl–homocystein thiolactone (i–but–HTL). The potential interactions of the ligands with the surface of enzymes molecules were predicted in silico using computational modeling and checked in wet experiments in vitro. Results: Based on the data obtained several enzymes were selected with localization of the thiolactones near their active sites, indicating the possibility of effective catalysis. The lactonase (AiiA), metallo-β-lactamase (NDM-1) and the organophosphate hydrolase with hexahistidine tag (His₆–OPH) were among them. Determination of catalytic characteristics of enzymes in the hydrolytic reactions with the HTL and the C₂–HTL revealed the maximal value of catalytic efficiency constant for the NDM-1 in the hydrolysis of the HTL (826 M⁻¹ s⁻¹). The maximal activity in the hydrolysis of C₂–HTL was established for AiiA (137 M⁻¹ s⁻¹). The polyaspartic (PLD₅₀) and the polyglutamic (PLE₅₀) acids were used to obtain polyelectrolyte complexes with enzymes. The further combination of these complexes with the clotrimazole and polymyxin B possessing antimicrobial properties resulted in notable improvement of their action in relation to Staphylococcus cells. Conclusions: It was revealed that the antimicrobial activity of the polymyxin B is enhanced by 9–10 times against bacteria and yeast when combined with the His₆–OPH polyelectrolyte complexes. The antimicrobial activity of clotrimazole was increased by ~7 times against Candida tropicalis cells in the case of the AiiA/PLE₅₀/Clotrimazole combination. These results make the obtained biology attractive and promising for their further advancement to practical application. Full article

Background/Objectives: Paediatric patients continue to lack access to age-appropriate oral medicines for their treatment and have to depend on the off-label use of medicines approved for adults, which compromises dosing accuracy and exposes children to unpleasant bitterness. Building on previous proof-of-concept work with flucloxacillin sodium, this study investigated the effects of fatty-acid chain length on the formation, stability, dissolution, and sensory acceptability of diclofenac sodium (DS)–Eudragit® EPO (EE)–fatty acid (FA) polyelectrolyte complexes (PECs). Four saturated fatty acids, lauric (C12), myristic (C14), palmitic (C16), and stearic acid (C18), were evaluated at stoichiometric equimolar DS:EE:FA ratio (1:1:1). Methods: PEC microparticles were prepared by solvent evaporation. A stability-indicating RP-HPLC assay was developed and validated according to ICH guidelines to quantify DS content. Drug content and stability were monitored over 3 months at ambient storage. In vitro dissolution was performed in pH 5.5 medium at 37 °C. Taste acceptability and willingness to take again was assessed with 25 healthy adult volunteers using 11-point scale. Results: All PECs retained >90% of expected drug content after 3 months. Compared with neat DS, PECs markedly suppressed early drug release (32–39% vs. 94% at 2 min) but achieved >87% cumulative drug release in 60 min. Sensory evaluation showed significant differences across samples (p < 0.001): neat DS was least acceptable (20.8% willing to take again), while DS-EE-PA was most acceptable (92%), followed by DS-EE-SA and DS-EE-MA. DS-EE-LA was least favoured among PECs. Conclusions: Fatty-acid chain length influenced PEC formation and taste acceptability, but not the PEC stability and drug dissolution profile. Palmitic acid (DS-EE-PA) offered the best overall profile and represents a promising candidate for further development of paediatric-appropriate diclofenac formulations. Full article

The direct deposition of highly concentrated polyelectrolyte complexes based on poly(ethyleneimine) (PEI) and poly(sodium methacrylate) (PMANa) onto inorganic sand microparticles (F100 and F200) resulted in the formation of versatile core-shell composites with fast removal properties in dynamic conditions toward anionic charged pollutants. Herein, in situ-generated nonstoichiometric PEI/PMANa polyelectrolyte complexes were directly precipitated as a soft organic shell onto solid sand microparticles at a 5% mass ratio (organic/inorganic part = 5%, w/w%). The sorption of an anionic model pollutant (Indigo Carmine (IC)) onto the composite particles in dynamic conditions depended on the inorganic core size, the flow rate, the bed type (fixed or fluidized) and the initial dye concentration. The maximum sorption capacity, after 10 cycles of sorption/desorption of IC onto F100@P5% and F200@P5%, was between 16 and 18 mg IC/mL composite. The newly synthesized core-shell composites could immobilize IC at a high flow rate (8 mL/min), either from concentrated (C_IC = 60 mg/L) or very diluted (C_IC = 0.2 mg/L) IC aqueous solution, demonstrating that this type of material could be promising in water treatment or efficient in solid-phase extraction (concentration factor of 2000). Full article

A novel glucose biosensor is developed based on a tilted fiber Bragg grating (TFBG) functionalized with a pH-responsive polyelectrolyte multilayer membrane, onto which glucose oxidase (GOD) is immobilized. The sensing film is constructed via layer-by-layer self-assembly of poly(ethylenimine) (PEI) and poly(acrylic acid) (PAA), which undergoes reversible swelling and refractive index (RI) changes in response to local pH variations. These changes are transduced into measurable shifts in the resonance wavelengths of TFBG cladding modes. The catalytic action of GOD oxidizes glucose to gluconic acid, thereby modulating the interfacial pH and actuating the polyelectrolyte membrane. With an optimized (PEI/PAA)₄(PEI/GOD)₁ structure, the biosensor achieves highly sensitive glucose detection, featuring a wide measurement range (10⁻⁸ to 10⁻² M), a low detection limit of 27.7 nM, and a fast response time of ~60 s. It also demonstrates excellent specificity and robust performance in complex biological matrices such as rabbit serum and artificial urine, with recovery rates of 93–102%, highlighting its strong potential for point-of-care testing applications. This platform offers significant advantages in stability, temperature insensitivity, and miniaturization, making it well-suited for clinical glucose monitoring and disease management. Full article

Cardiac hypertrophy is a critical contributor to cardiac dysfunction and the development of heart failure, yet effective therapeutic strategies remain limited. Propylene glycol alginate sulfate sodium (PSS) is a marine sulfated polysaccharide drug used in the treatment of cardiovascular diseases and has shown cardiac function benefits. Here, we designed a pH-responsive PSS-loaded nanoparticle drug delivery system. It was self-assembled by negatively charged PSS with positively charged trimethyl chitosan glycocholic acid (TMC-GA) via electrostatic interaction, and further stabilized the nanoparticles with Hydroxypropyl methylcellulose phthalate (HP55) excipients. The prepared TMC-GA/HP55@PSS nanoparticles were spherical, with a mean particle size of 361.5 ± 1.26 nm, zeta potential of −30.3 ± 0.9 mV, and encapsulation efficiency of 92.52 ± 2.4%. In vitro release study demonstrated the pH-responsive property of TMC-GA/HP55@PSS under intestinal conditions and facilitated nanoparticles absorption in the intestinal epithelium. In vitro experiments confirmed the biocompatibility of PSS and its ability to improve myocardial cell hypertrophy. In vivo, both PSS and its nanoparticles significantly ameliorated pressure overload–induced cardiac hypertrophy in mice, with TMC-GA/HP55@PSS exhibiting better cardioprotective efficacy. This study is the first to integrate pH-responsiveness and bile acid transport-mediated uptake into PSS nanocarrier systems. The findings provide valuable data and enlightenment for designing novel formulations and expanding the clinical applications of PSS. Full article