Self-assembled Polyelectrolyte Complex Research Articles

Nanofibrous polyelectrolyte complex incorporated BSA-alginate composite bioink for 3D bioprinting of bone mimicking constructs

Although several bioinks have been developed for 3D bioprinting applications, the lack of optimal printability, mechanical properties, and adequate cell response has limited their practical applicability. Therefore, this work reports the development of a composite bioink consisting of bovine serum albumin (BSA), alginate, and self-assembled nanofibrous polyelectrolyte complex aggregates of gelatin and chitosan (PEC-GC). The nanofibrous PEC-GC aggregates were prepared and incorporated into the bioink in varying concentrations (0 % to 3 %). The bioink samples were bioprinted and crosslinked post-printing by calcium chloride. The average nanofiber diameter of PEC-GC was 62 ± 15 nm. It was demonstrated that PEC-GC improves the printability and cellular adhesion of the developed bioink and modulates the swelling ratio, degradation rate, and mechanical properties of the fabricated scaffold. The in vitro results revealed that the bioink with 2 % PEC-GC had the best post-printing cell viability of the encapsulated MG63 osteosarcoma cells and well oragnized stress fibers, indicating enhanced cell adhesion. The cell viability was >90 %, as observed from the MTT assay. The composite bioink also showed osteogenic potential, as confirmed by the estimation of alkaline phosphatase activity and collagen synthesis assay. This study successfully fabricated a high-shape fidelity bioink with potential in bone tissue engineering.

Development of a novel thermogelling PEC-based ECM mimicking nanocomposite bioink for bone tissue engineering

Non-union of large bone defects has been an existing clinical problem. 3D extrusion-based bioprinting provides an efficient approach to tackle such problems. This approach enables the use of various biomaterials, cell types and growth factors in developing a superior bone graft that is specific to the defect. In this article, we have designed and printed an ECM mimicking, self-assembled polyelectrolyte complex (PEC) based fibrous bioink using natural polymers like chitosan-polygalacturonic acid (PGA) and other biomaterials – gelatin, laponite and nanohydroxyapatite with a modified 3D printer. The developed bioink possesses a thermo-reversible sol-gel transition at physiological pH and temperature. Here, we demonstrated that post-printing, our fiber-reinforced bioink had significant cell proliferation with cell viability of >80% and negligible cell morbidity. The practicability of developing this self-assembled PEC-based bioink was assessed. Bioink with 4% gelatin (PECHLG4) had optimal printability with a minimal swelling ratio of approximately 3%. The printed scaffold had integrity for a period of 8 days under 0.5 mg/mL lysozyme concentration. We also evaluated the mechanical property of the bioink using compression analysis which gave an elastic modulus of 16 KPa. This combination of natural polymers and nanocomposite, along with a fibrous network of PECs, is itself a novel approach for 3D bioprinting and can be a preliminary proposition for the treatment of large bone defects.

Self-assembled polyelectrolyte complexes of chitosan and fucoidan for sustained growth factor release from PRP enhance proliferation and collagen deposition in diabetic mice.

Diabetic wound management is a serious health care challenge due to higher rates of relapse, expensive treatment approaches, and poor healing outcomes. Among cell-based therapies, use of platelet-rich plasma (PRP) has been shown to be effective for diabetic wounds, but its poor shelf-life limits its clinical use. Here, we demonstrate a simple but effective polymer system to increase the shelf-life of PRP by developing a polyelectrolyte complex with dropwise addition of chitosan solution containing PRP by simple mixing at room temperature. Thus, prepared chitosan-fucoidan (CF) carrier complex encapsulated more than 95% of the loaded PRP. The resulting CF/PRP colloids were spherical in shape and ensured extended PRP release up to 72h at 37°C. Routine characterization (FT-IR, XRD, SEM) showed the material properties. The biological assays showed that CF complexes were biocompatible while CF/PRP enhanced the proliferation of fibroblasts and keratinocytes via higher Ki67expression and fibroblast migration. Further investigations using a diabetic mouse model demonstrated significantly higher wound contraction and histopathological observations showed increased fibroblast migration, and collagen and cytokeratin deposition in treatment groups. The results are suggestive of the efficacy of CF/PRP as a cost-effective topical formulation for the sustained delivery of growth factors in treating chronic diabetic wounds.

Fast acting hemostatic agent based on self-assembled hybrid nanofibers from chitosan and casein

Hemorrhage is a leading cause of preventable death in both military combat and civilian accidents. To overcome these challenges, an affordable and effective bandage is must required substance. A novel strategy is reported for developing chitosan-casein (CC) based self-assembled nanofibrous polyelectrolyte complex (PEC) for rapid blood clotting. The amide group (1630 cm−1) and phosphate group (910 cm−1) of chitosan-casein can form PEC at pH 8.2 ± 0.2. The PECs contain intertwined nanofibers (≤100 nm diameter) with a high surface area. Increasing chitosan percentage from 30% (CC30) to 50% (CC50) or 70% (CC70) results, increase in zeta potential of PEC from -9.14 ± 3.3 to 7.46 ± 3.7 and 14.8 ± 3.3 mV, respectively. Under in vitro conditions, the CC30, CC50, and CC70 PECs allow platelet adhesion and rapidly absorbs blood fluid to form mechanically stable blood clots within 9 ± 3, 16 ± 3, and 30 ± 4 s, respectively, which are better than Celox™ (90 ± 3 s). In vivo application of PEC (CC50) causes clotting within 37 ± 6 s of large (1 cm) arterial incision in rabbit models. The PEC is biocompatible with promising hemostatic efficiency. This is the first report of nanofibrous PEC from chitosan and casein for rapid clotting, to the best of our knowledge.

SAXS methods for investigating macromolecular and self-assembled polyelectrolyte complexes.

Polyelectrolyte complexation is driven by associative interactions between oppositely charged polyelectrolytes, resulting in formation of a macroscopic polymer dense phase and a polymer dilute phase with applications in coatings, adhesives, and purification membranes. Beyond macroscale phase separation, precision polymer synthesis has enabled further development of polyelectrolyte complex (PEC)-based self-assembled micelles and hydrogels with applications in biotechnology. Interestingly, it has been suggested that mechanisms similar to polyelectrolyte complexation drive formation of biological condensates that play an indispensable role in cellular biogenesis. The formation pathways and functionality of these complex materials is dependent on the physical properties that are built into polymer structure and the resulting physical conformation in the dilute and dense phase. Scattering techniques have enabled in situ investigation of structure-function relationships in PEC materials that may address unresolved biophysical questions in cellular processes as well as catalyze the development of novel materials for diverse applications. We describe preparation of PEC materials with controlled polymer characteristics (length, blockiness, charge density), small-angle X-ray scattering (SAXS) techniques employed to probe appropriate length scales, and the data analysis routines from a practical standpoint for new users. This article deals with bulk complexes and not with the related, important and interesting area of non-equilibrium layer-by-layer assembly of polyelectrolytes.

Designer Self-Assembled Polyelectrolyte Complex Nanoparticle Membrane for a Stable Lithium–Sulfur Battery at Lean Electrolyte Conditions

Lithium–sulfur batteries can displace lithium-ion batteries owing to their superior theoretical capacity and specific energy density. Presently, however, high specific capacities do not translate t...

Formation of self-assembled polyelectrolyte complex hydrogel derived from salecan and chitosan for sustained release of Vitamin C

Vitamin C (VC) is an indispensable nutrient for human health. However, poor chemical stability in gastric environment restricts its full assimilation by intestine. It is important to construct a safe carrier that can protect VC from the gastric fluid and sustainably release it in intestine. Herein, we designed a novel polyelectrolyte complex (PEC) hydrogel through self-assembly of salecan and chitosan. PEC structure formed by electrostatic interactions was confirmed by FT-IR, XRD, XPS and TGA. Their swelling, morphology, rheology, cytocompatibility and biodegradation were well investigated. In particular, VC released in a controlled and pH-dependent manner. The release amount in simulated intestinal fluid (SIF) was significantly higher than simulated gastric fluid (SGF), and can be maintained at high level in blood after 6 h. Release mechanism agreed well with Ritger-Peppas model. The purpose of this study was to develop a smart nutrient delivery platform for targeted release of VC in intestinal condition.

Effect of Sodium Alginate Type on Drug Release from Chitosan-Sodium Alginate-Based In Situ Film-Forming Tablets.

Natural polymers are promising as the carrier of matrix-based sustained release tablets but limited by their diversity in source and structure properties. Our previous studies found that chitosan (CS)- and alginate (SA)-based tablets can form self-assembled polyelectrolyte complex (PEC) film on the surface, which controlled drug release with a novel mechanism. To elucidate whether PEC-based sustained drug delivery system could weaken the influence of single-matrix material diversity on drug release behavior, taking theophylline as a drug model, the effect of SA structure properties, including viscosity, G/M ratio, SA salt type, and degree of esterification on drug release profiles, swelling, and erosion of CS-SA composite system was investigated. The results showed that the viscosity, G content, salt type, and esterification degree of SA had a remarkable influence on drug release when SA alone was used as a matrix, but little effect of these parameters on drug release was observed in CS-SA combination system. SA of low viscosity is superior in controlling drug release from CS-SA combination system. Potassium, magnesium salt of SA, and esterified SA can help form PEC of higher thickness with different swelling and erosion extent. In conclusion, this study demonstrated that drug release diversity due to SA structure difference can be well eradicated by using CS-SA combination system, which is a promising strategy to manufacture natural polymer-based products with constant quality.

Construction of self-assembled polyelectrolyte complex hydrogel based on oppositely charged polysaccharides for sustained delivery of green tea polyphenols

In this study, we have developed a novel polyelectrolyte complex (PEC) hydrogel that could be easily prepared by self-assembly of two food-grade polysaccharides salecan and N,N,N-trimethyl chitosan (TMC). The electrostatic interactions between two polysaccharides were driving force in complexation processes and have been demonstrated by FTIR, XRD, XPS and TGA. The swelling capacity, morphology and rheological property of the hydrogels could be well tuned by controlling salecan/TMC ratio. Green tea polyphenols (GTP) was efficiently encapsulated into PEC hydrogels and liberated in a sustained pattern. The amount of GTP released in simulated intestinal fluid (SIF) was significantly higher than simulated gastric fluid (SGF). Increasing salecan/TMC ratio also markedly enhanced GTP release amount. Release exponent n obtained in SGF indicated a Fickian diffusion, while in SIF an anomalous transport occurred. The release mechanism was well-fitted with Ritger-Peppas model. Taken together, these PEC hydrogels could be suitable carriers for intestinal targeted nutrient delivery.

Self-assembled polyelectrolyte complex nanoparticles as a potential carrier in protein delivery systems

BSA as a protein model was encapsulated in the alginate-based self-assembled polyelectrolyte complex nanoparticles using two distinct approaches. In the first approach, a mixture of bovine serum albumin (BSA) and alginate (ALG) solutions was added to the synthesized poly(2-(acryloyloxyethyl) trimethylammonium chloride) p(AETMACl) cationic polyelectrolyte, and the resulting polyelectrolyte complex was named as p(AETMACl)@BSA/ALG. In the second approach, the mixture of BSA and Ca2+ was added to the ALG solution. The pre-gel was formed rapidly through physical crosslinking followed by complexing with p(AETMACl) cationic polyelectrolyte and named as p(AETMACl)@BSA/ALG-Ca2+. To achieve the maximum encapsulation efficiency (EE%) for BSA, the interactions between different polymeric pairs including BSA/ALG, p(AETMACl)/BSA, and p(AETMACl)/ALG have been studied by UV–Vis spectroscopy. Maximum EE% of BSA was obtained around 100% for both approaches. Analyzing the BSA circular dichroism spectra showed a similar α-helical secondary structure for both free and released BSA after 24 h. The presence of Ca2+ in the formulations led to a decrease in the particle size from 400 to 300 nm for p(AETMACl)@ALG-Ca2+, and 1 μm to 800 nm for p(AETMACl)@BSA/ALG-Ca2+. Analyzing the release results from the Korsmeyer-Peppas kinetic model showed that the release mechanism of BSA was non-Fickian with calcium and Fickian without calcium.

Non-equilibrium phenomena and kinetic pathways in self-assembled polyelectrolyte complexes.

Polyelectrolyte complexation has been conventionally focused on the thermodynamic states, where assemblies have equilibrated in solutions. Far less attention has been given to complex systems that are kinetically trapped at non-equilibrium states. A combination of time-resolved dynamic light scattering, small angle X-ray scattering (SAXS), and cryogenic transmission electron microscopy (Cryo-TEM) was employed here to investigate the internal structures and morphological evolution of non-equilibrium aggregates forming from a pair of two strong block polyelectrolytes over wide time and length scales. The role of formation pathways of electrostatically driven aggregates was assessed using two processing protocols: direct dissolution and salt annealing. The former led to thermodynamically stable products, while the latter resulted in kinetically trapped transient structures. After adding salt, the metastable structures gradually transformed into stable products. Cryo-TEM images showed the interconnected irregular morphologies of the aggregates, and SAXS data revealed the presence of fuzzy globular complexes with R g ∼ 10 nm within them. A two-step process in the time-dependent structural transformation was found and characterized by a fast breakdown of interconnected transient aggregates followed by a slow redistribution of the incipient individual electrostatic assemblies. Furthermore, the prolonged aggregate disintegration process fitting to a stretched exponential function unveiled the broad relaxation distribution and significant structural heterogeneity in these polyelectrolyte complex nanoaggregates. This work brings new insight into the comprehension of non-equilibrium phenomena in self-assembled electrostatic assemblies and represents a first step toward constructing far-from-equilibrium polyelectrolyte complexes de novo for future applications.

Tunable and sustained-release characteristics of venlafaxine hydrochloride from chitosan–carbomer matrix tablets based on in situ formed polyelectrolyte complex film coating

The objective of this study is to design sustained-release tablets using matrix technology, which can well control the release of highly water-soluble drugs with good system robustness and simple preparation process. Taking venlafaxine hydrochloride (VH) as a drug model, the feasibility of using chitosan (CS), carbomer (CBM) combination system to achieve this goal was studied. Formulation and process variables influencing drug release from CS–CBM matrix tablets were investigated. It was found that CS–CBM combination system weakened the potential influence of CS, CBM material properties and gastric emptying time on drug release profile. Demonstrated by direct observation, differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR), in situ self-assembled polyelectrolyte complex (PEC) film was formed on the tablet surface during gastrointestinal tract transition, which contributed to the tunable and robust control of drug release. The sustained drug release behavior was further demonstrated in vivo in Beagle dogs, with level A in vitro and in vivo correlation (IVIVC) established successfully. In conclusion, CS–CBM matrix tablets are promising system to tune and control the release of highly water-soluble drugs with good system robustness.

Self-assembled soft nanoparticle membranes with programmed free volume hierarchy

A self-assembled polyelectrolyte complex nanoparticle membrane was prepared, featuring programed free volume hierarchy, 8 times enhanced fractional free volume, and highly improved molecular separation performance in ethanol dehydration.

Self-assembled polyelectrolyte complexes films as efficient compression coating layers for controlled-releasing tablets.

Currently, polysaccharide-based hydrogels are widely studied macromolecular networks to modify drug dissolution from controlled-releasing matrix tablets. Among them, polyelectrolyte complexes (PEC) films consisted of chitosan (CS) and sodium alginate (SA) could be obtained via spontaneously assembling under physiological gastrointestinal environment. Here, we utilized these self-assembled PEC films as an efficient coating materials to develop controlled-released matrix tablets through compression coating process, with paracetamol (APAP) as model drug. The constitutive and morphology characteristic studies on these PEC films illustrated that the mixture of CS and SA with the weight ratio of 1:1 would be an promising outer layer for compression-coating tablets. In addition, the in vitro drug releasing behavior experiments demonstrated that the optimized compression coating tablets displayed satisfied zero-order drug releasing profits. Furthermore, the in vivo pharmacokinetic studies of these APAP loaded compression-coated tablets in New Zealand rabbits gave that the Tmax (12.32 ± 1.05 h) was significantly prolonged (p < 0.01), compared to that (0.89 ± 0.26 h) of common APAP tablets (Jinfuning®) after oral administration. These studies suggest that the compression-coated tablets with self-assembled PEC film as coating outer layer may be a promising strategy for peroral controlled release delivery system of water soluble drugs.

Cationic drug-based self-assembled polyelectrolyte complex micelles: Physicochemical, pharmacokinetic, and anticancer activity analysis

Nanofabrication of polymeric micelles through self-assembly of an ionic block copolymer and oppositely charged small molecules has recently emerged as a promising method of formulating delivery systems. The present study therefore aimed to investigate the interaction of cationic drugs doxorubicin (DOX) and mitoxantrone (MTX) with the anionic block polymer poly(ethylene oxide)-block-poly(acrylic acid) (PEO-b-PAA) and to study the influence of these interactions on the pharmacokinetic stability and antitumor potential of the formulated micelles in clinically relevant animal models. To this end, individual DOX and MTX-loaded polyelectrolyte complex micelles (PCM) were prepared, and their physicochemical properties and pH-responsive release profiles were studied. MTX-PCM and DOX-PCM exhibited a different release profile under all pH conditions tested. MTX-PCM exhibited a monophasic release profile with no initial burst, while DOX-PCM exhibited a biphasic release. DOX-PCM showed a higher cellular uptake than that shown by MTX-PCM in A-549 cancer cells. Furthermore, DOX-PCM induced higher apoptosis of cancer cells than that induced by MTX-PCM. Importantly, both MTX-PCM and DOX-PCM showed prolonged blood circulation. MTX-PCM improved the AUCall of MTX 4-fold compared to a 3-fold increase by DOX-PCM for DOX. While a definite difference in blood circulation was observed between MTX-PCM and DOX-PCM in the pharmacokinetic study, both MTX-PCM and DOX-PCM suppressed tumor growth to the same level as the respective free drugs, indicating the potential of PEGylated polymeric micelles as effective delivery systems. Taken together, our results show that the nature of interactions of cationic drugs with the polyionic copolymer can have a tremendous influence on the biological performance of a delivery system.

A humic acid-polyquaternium-10 stoichiometric self-assembled fibrilla polyelectrolyte complex: Effect of pH on synthesis, characterization, and drug release

ABSTRACTA polyelectrolyte complex (PEC) was produced and validated from humic acid and polyquaternium-10 using a solution-blend method. Humic acid was used based on its properties of encapsulating hydrophilic and hydrophobic drugs while polyquaternium-10 provided high swellability in aqueous media. PECs at varying pH values were prepared and characterized for their physicochemical properties. Efavirenz (model drug) was used to assess the performance of the PEC. Results revealed that drug-loading ranged between 11.9–23.91% and PEC formation was due to ionic reactions between the amino (polyquaternium-10) and carboxylic (humic acid) groups. This formed a fibrilla PEC complex that provided controlled release of efavirenz.

Goblet cell targeting nanoparticle containing drug-loaded micelle cores for oral delivery of insulin

Oral administration of insulin remains a challenge due to its poor enzymatic stability and inefficient permeation across epithelium. We herein developed a novel self-assembled polyelectrolyte complex nanoparticles by coating insulin-loaded dodecylamine-graft-γ-polyglutamic acid micelles with trimethyl chitosan (TMC). The TMC material was also conjugated with a goblet cell-targeting peptide to enhance the affinity of nanoparticles with epithelium. The developed nanoparticle possessed significantly enhanced colloid stability, drug protection ability and ameliorated drug release profile compared with graft copolymer micelles or ionic crosslinked TMC nanoparticles. For in vitro evaluation, Caco-2/HT29-MTX-E12 cell co-cultures, which composed of not only enterocyte-like cells but also mucus-secreting cells and secreted mucus layer, were applied to mimic the epithelium. Intracellular uptake and transcellular permeation of encapsulated drug were greatly enhanced for NPs as compared with free insulin or micelles. Goblet cell-targeting modification further increased the affinity of NPs with epithelium with changed cellular internalization mechanism. The influence of mucus on the cell uptake was also investigated. Ex vivo performed with rat mucosal tissue demonstrated that the nanoparticle could facilitate the permeation of encapsulated insulin across the intestinal epithelium. In vivo study preformed on diabetic rats showed that the orally administered nanoparticles elicited a prolonged hypoglycemic response with relative bioavailability of 7.05%.

Chondroitin-based nanoplexes as peptide delivery systems – Investigations into the self-assembly process, solid-state and extended release characteristics

A new type of self-assembled polyelectrolyte complex nanocarrier composed of chondroitin (CHON) and protamine (PROT) was designed and the ability of the carriers to bind salmon calcitonin (sCT) was examined. The response of sCT-loaded CHON/PROT NPs to a change in the properties of the liquid medium, e.g. its pH, composition or ionic strength was studied and in vitro peptide release was assessed. The biocompatibility of the NPs was evaluated in Caco-2 cells.CHON/PROT NPs were successfully obtained with properties that were dependent on the concentration of the polyelectrolytes and their mixing ratio. X-ray diffraction determined the amorphous nature of the negatively charged NPs, while those with the positive surface potential were semi-crystalline. sCT was efficiently associated with the nanocarriers (98–100%) and a notably high drug loading (13–38%) was achieved. The particles had negative zeta potential values and were homogenously dispersed with sizes between 60 and 250nm. CHON/PROT NPs released less than 10% of the total loaded peptide in the first hour of the in vitro release studies. The enthalpy of the decomposition exotherm correlated with the amount of sCT remaining in NPs after the release experiments. The composition of medium and its ionic strength was found to have a considerable influence on the release of sCT from CHON/PROT NPs. Complexation to CHON markedly reduced the toxic effects exerted by PROT and the NPs were compatible and well tolerated by Caco-2 cells.

Characterization of Self-Assembled Polyelectrolyte Complex Nanoparticles Formed from Chitosan and Pectin

Chronic wounds continue to be a global healthcare concern. Thus, the development of new nanoparticle-based therapies that treat multiple symptoms of these "non-healing" wounds without encouraging antibiotic resistance is imperative. One potential solution is to use chitosan, a naturally antimicrobial polycation, which can spontaneously form polyelectrolyte complexes when mixed with a polyanion in appropriate aqueous conditions. The requirement of at least two different polymers opens up the opportunity for us to form chitosan complexes with an additional functional polyanion. In this study, chitosan:pectin (CS:Pec) nanoparticles were synthesized using an aqueous spontaneous ionic gelation method. Systematically, a number of parameters, polymer concentration, addition order, mass ratio, and solution pH, were explored and their effect on nanoparticle formation was determined. The size and surface charge of the particles were characterized, as well as their morphology using transmission electron microscopy. The effect of polymer concentration and addition order on the nanoparticles was found to be similar to that of other chitosan:polyanion complexes. The mass ratio was tuned to create nanoparticles with a chitosan shell and a controllable positive zeta potential. The particles were stable in a pH range from 3.5 to 6.0 and lost stability after 14 days of storage in aqueous media. Due to the high positive surface charge of the particles, the innate properties of the polysaccharides used, and the harmless disassociation of the polyelectrolytes, we suggest that the development of these CS:Pec nanoparticles offers great promise as a chronic wound healing platform.

Sequestration of rhBMP-2 into Self-Assembled Polyelectrolyte Complexes Promotes Anatomic Localization of New Bone in a Porcine Model of Spinal Reconstructive Surgery

Efficient and therapeutically safe delivery of recombinant human bone morphogenetic protein 2 (rhBMP-2) continues to be a central issue in bone tissue engineering. Recent evidence indicates that layer-by-layer self-assembly of polyelectrolyte complexes (PECs) can be used to recreate synthetic matrix environments that would act as tuneable reservoirs for delicate biomolecules and cells. Although preliminary in vitro as well as small-animal in vivo studies support this premise, translation into clinically relevant bone defect volumes in larger animal models remains unreported. Here we explored the use of native heparin-based PEC, deposited on a hydrated alginate gel template, to load bioactive rhBMP-2 and to facilitate lumbar interbody spinal fusion in pigs. We observed that triple PEC deposits with the highest protein sequestration efficiency and immobilization capacity promoted higher volume of new bone formation when compared with single PEC with low sequestration efficiency and immobilization capacity. This also resulted in a significantly enhanced biomechanical stability of the fused spinal segment when compared with PEC carriers with relatively low protein sequestration and immobilization capacities (p<0.05). Most importantly, PEC carriers showed a more orderly pattern of new bone deposition and superior containment of bone tissue within implant site when compared to collagen sponge carriers. We conclude that this growth factor sequestration platform is effective in the healing of clinically relevant bone defect volume and could overcome some of the safety concerns and limitations currently associated with rhBMP-2 therapy such as excessive heterotopic ossification.