Dicarboxylated hyaluronate: Synthesis of a new, highly functionalized and biocompatible derivative

Sequential periodate-chlorite oxidation of sodium hyaluronate to 2,3-dicarboxylated hyaluronate (DCH), a novel biocompatible and highly functionalized derivative bearing additional pair of COOH groups at C2 and C3 carbons of oxidized ᴅ-glucuronic acid units, is investigated. The impact of various reaction parameters (time, oxidizer concentration, and molar amount) on DCH's composition, molecular weight, degree of oxidation, and cytotoxicity are investigated to guide the synthesis of DCH derivatives of desired properties. Subsequently, fully (99%) and partially (70%) oxidized DCH derivatives were compared to untreated sodium hyaluronate in terms of anticancer drug cisplatin loading efficacy, carrier capacity, drug release rates, and cytotoxicity towards healthy and cancerous cell lines. DCH derivatives were found to be superior in every aspect, having nearly twice the carrier capacity, significantly slower release rates, and higher efficacy. DCH is thus a highly interesting hyaluronate derivative with an adjustable degree of oxidation, molecular weight, and great potential for further modifications.

Formulation of Magneto-Responsive Hydrogels from Dually Cross-Linked Polysaccharides: Synthesis, Tuning and Evaluation of Rheological Properties

Smart hydrogels based on natural polymers present an opportunity to fabricate responsive scaffolds that provide an immediate and reversible reaction to a given stimulus. Modulation of mechanical characteristics is especially interesting in myocyte cultivation, and can be achieved by magnetically controlled stiffening. Here, hyaluronan hydrogels with carbonyl iron particles as a magnetic filler are prepared in a low-toxicity process. Desired mechanical behaviour is achieved using a combination of two cross-linking routes—dynamic Schiff base linkages and ionic cross-linking. We found that gelation time is greatly affected by polymer chain conformation. This factor can surpass the influence of the number of reactive sites, shortening gelation from 5 h to 20 min. Ionic cross-linking efficiency increased with the number of carboxyl groups and led to the storage modulus reaching 103 Pa compared to 101 Pa–102 Pa for gels cross-linked with only Schiff bases. Furthermore, the ability of magnetic particles to induce significant stiffening of the hydrogel through the magnetorheological effect is confirmed, as a 103-times higher storage modulus is achieved in an external magnetic field of 842 kA·m−1. Finally, cytotoxicity testing confirms the ability to produce hydrogels that provide over 75% relative cell viability. Therefore, dual cross-linked hyaluronan-based magneto-responsive hydrogels present a potential material for on-demand mechanically tunable scaffolds usable in myocyte cultivation.

Enzyme-Catalyzed Polymerization Process: A Novel Approach to the Preparation of Polyaniline Colloidal Dispersions with an Immunomodulatory Effect

A green, nature-friendly synthesis of polyaniline colloidal particles based on enzyme-assisted oxidation of aniline with horseradish peroxidase and chitosan or poly(vinyl alcohol) as steric stabilizers was successfully employed. Physicochemical characterization revealed formation of particles containing the polyaniline emeraldine salt and demonstrated only a minor effect of polymer stabilizers on particle morphology. All tested colloidal particles showed in vitro antioxidation activity determined via scavenging of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals. In vitro, they were able to reduce oxidative stress and inhibit the production of reactive oxygen species by neutrophils and inflammatory cytokines by macrophages. The anti-inflammatory effect observed was related to their antioxidant activity, especially in the case of neutrophils. The particles can thus be especially advantageous as active components of biomaterials modulating the early stages of inflammation. In addition to the immunomodulatory effect, the presence of intrinsically conducting polyaniline can impart cell-instructive properties to the particles. The approach to particle synthesis that we employed─an original one using environmentally friendly and biocompatible horseradish peroxidase─represents a smart way of preparing conducting particles with unique properties, which can be further modified by the stabilizers used.

Comparison of dialdehyde polysaccharides as crosslinkers for hydrogels: The case of poly(vinyl alcohol)

A little is known about the link between the macromolecular architecture of dialdehyde polysaccharides (DAPs), their crosslinking capabilities, and the properties of resulting hydrogels. Here, DAPs based on cellulose, dextrin, dextran, and hyaluronate were compared as crosslinkers for poly(vinyl alcohol), PVA. The swelling, network parameters, viscoelastic properties, porosity, and cytotoxicity of PVA/DAP hydrogels were investigated concerning the crosslinker structure, molecular weight, aldehyde group density per macromolecule, and the size of spontaneously formed crosslinker nano-assemblies. Generally, crosslinkers based on linear polysaccharides (cellulose, hyaluronate) performed more reliably, while the presence of branching could be both beneficial (dextran) but also detrimental (dextrin) at lower crosslinker concentrations. For example, the hydrogel swelling differed by up to one-third (600 vs. 400%) and storage modulus even by up to one half (~7000 vs. ~3500 Pa) depending on crosslinker structure and properties. These differences were rationalized by variances in crosslinking modes derived based on obtained data.

Enhancing cisplatin anticancer effectivity and migrastatic potential by modulation of molecular weight of oxidized dextran carrier

The molecular weight (M_w) of dextran derivatives, such as regioselectively oxidized dicarboxydextran (DXA), is greatly influencing their faith in an organism, which could be possibly used to improve anticancer drug delivery. Here we present a modified method of sulfonation-induced chain scission allowing direct and accurate control over the M_w of DXA without increasing its polydispersity. Prepared DXA derivatives (M_w = 10-185 kDa) have been conjugated to cisplatin and the M_w of the carrier found to have a significant impact on cisplatin release rates, in vitro cytotoxicity, and migrastatic potential. Conjugates with the high-M_w DXA showed particularly increased anticancer efficacy. The best conjugate was four times more effective against malignant prostatic cell lines than free cisplatin and significantly inhibited the ovarian cancer cell migration. This was traced to the characteristics of spontaneously formed cisplatin-crosslinked DXA nanogels influenced by M_w of DXA and amount of loaded cisplatin.

Oxidized polysaccharides for anticancer-drug delivery: What is the role of structure?

Study provides an in-depth analysis of the structure-function relationship of polysaccharide anticancer drug carriers and points out benefits and potential drawbacks of differences in polysaccharide glycosidic bonding, branching and drug binding mode of the carriers. Cellulose, dextrin, dextran and hyaluronic acid have been regioselectively oxidized to respective dicarboxylated derivatives, allowing them to directly conjugate cisplatin, while preserving their major structural features intact. The structure of source polysaccharide has crucial impact on conjugation effectiveness, carrier capacity, drug release rates, in vitro cytotoxicity and cellular uptake. For example, while branched structure of dextrin-based carrier partially counter the undesirable initial burst release, it also attenuates the cellular uptake and the cytotoxicity of carried drug. Linear polysaccharides containing β-(1→4) glycosidic bonds and oxidized at C2 and C3 (cellulose and hyaluronate) have the best overall combination of structural features for improved drug delivery applications including potentiation of the cisplatin efficacy towards malignances.

Conducting composite films based on chitosan or sodium hyaluronate. Properties and cytocompatibility with human induced pluripotent stem cells

Novel composite films combining biocompatible polysaccharides with conducting polyaniline (PANI) were prepared via the in-situ polymerization of aniline hydrochloride in the presence of sodium hyaluronate (SH) or chitosan (CH). The composite films possess very good cytocompatibility in terms of adhesion and proliferation of two lines of human induced pluripotent stem cells (hiPSC). Moreover, the cardiomyogenesis and even formation of beating clusters were successfully induced on the films. The proportion of formed cardiomyocytes demonstrated excellent properties of composites for tissue engineering of stimuli-responsive tissues. The testing also demonstrated antibacterial activity of the films against E. coli and PANI-SH was able to reduce bacterial growth from 2 × 10⁵ to < 1 cfu cm^-2. Physicochemical characterization revealed that the presence of polysaccharides did not notably influence conductivities of the composites being ∼1 and ∼2 S cm^-1 for PANI-SH and PANI-CH respectively; however, in comparison with neat PANI, it modified their topography making the films smoother with mean surface roughness of 4 (PANI-SH) and 14 nm (PANI-CH). The combination of conductivity, antibacterial activity and mainly cytocompatibility with hiPSC opens wide application potential of these polysaccharide-based composites.

Self-crosslinked chitosan/dialdehyde xanthan gum blended hypromellose hydrogel for the controlled delivery of ampicillin, minocycline and rifampicin

The design of improved biopolymeric based hydrogel materials with high load-capacity to serve as biocompatible drug carriers is a challenging task with vital implications in health sciences. In this work, chitosan crosslinked dialdehyde xanthan gum interpenetrated hydroxypropyl methylcellulose gels were developed for the controlled delivery of different antibiotic drugs including ampicillin, minocycline and rifampicin. The prepared hydrogel scaffolds were characterized by rheology method, FTIR, SEM, TGA and compression analysis. In addition, gelation kinetics, swelling, in vitro degradation and drug release rate were studied under simulated gastrointestinal fluid conditions of pH 2.0 and 7.4 at 37 °C. Results demonstrated the gel composition and structure affected drug release kinetics. The release study showed more than 50% cumulative release within 24 h for all investigated antibiotic drugs. In vitro cell cytocompatibility using mouse embryonic fibroblast cell lines depicted ≥80% cell viability, indicating the gels are non-toxic. Finally, the antibacterial activity of loaded gels was evaluated against Gram-negative and positive bacteria (Escherichia coli, Staphylococcus aureus and Klebsiella pneumonia), which correlated well with swelling and drug release results. Overall, the present study demonstrated that the produced hydrogel scaffolds serves as promising material for controlled antibiotic delivery towards microbial growth inhibition.

Effect of Iron-Oxide Nanoparticles Impregnated Bacterial Cellulose on Overall Properties of Alginate/Casein Hydrogels: Potential Injectable Biomaterial for Wound Healing Applications

In this study we report the preparation of novel multicomponent hydrogels as potential biomaterials for injectable hydrogels comprised of alginate, casein and bacterial cellulose impregnated with iron nanoparticles (BCF). These hydrogels demonstrated amide cross-linking of alginate-casein, ionic cross-linking of alginate and supramolecular interaction due to incorporation of BCF. Incorporation of BCF into the hydrogels based on natural biopolymers was done to reinforce the hydrogels and impart magnetic properties critical for targeted drug delivery. This study aimed to improve overall properties of alginate/casein hydrogels by varying the BCF loading. The physico-chemical properties of gels were characterized via FTIR, XRD, DSC, TGA, VSM and mechanical compression. In addition, swelling, drug release, antibacterial activity and cytotoxicity studies were also conducted on these hydrogels. The results indicated that incorporation of BCF in alginate/casein hydrogels led to mechanically stronger gels with magnetic properties, increased porosity and hence increased swelling. A porous structure, which is essential for migration of cells and biomolecule transportation, was confirmed from microscopic analysis. The porous internal structure promoted cell viability, which was confirmed through MTT assay of fibroblasts. Moreover, a hydrogel can be useful for the delivery of essential drugs or biomolecules in a sustained manner for longer durations. These hydrogels are porous, cell viable and possess mechanical properties that match closely to the native tissue. Collectively, these hybrid alginate-casein hydrogels laden with BCF can be fabricated by a facile approach for potential wound healing applications.

Design of dialdehyde cellulose crosslinked poly(vinyl alcohol) hydrogels for transdermal drug delivery and wound dressings

2,3-Dialdehyde cellulose (DAC) was used as an efficient and low-toxicity crosslinker to prepare thin PVA/DAC hydrogel films designed for topical applications such as drug-loaded patches, wound dressings or cosmetic products. An optimization of hydrogel properties was achieved by the variation of two factors - the amount of crosslinker and the weight-average molecular weight (M_w) of the source PVA. The role of each factor to network parameters, mechanical, rheological and surface properties, hydrogel porosity and transdermal absorption is discussed. The best results were obtained for hydrogel films prepared using 0.25 wt% of DAC and PVA with M_w = 130 kDa, which had a high porosity and drug-loading capacity (high water content), mechanical properties allowing easy handling, best adherence to the skin from all tested samples and improved transdermal drug-delivery. Hydrogel films are biocompatible, show no cytotoxicity and have no negative impact on cell growth and morphology in their presence. Furthermore, hydrogels do not support cell migration and attachment to their surface, which should ensure easy removal of hydrogel patches even from wounded or damaged skin after use.

Antibacterial photodynamic activity of carbon quantum dots/polydimethylsiloxane nanocomposites against Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae

Despite great efforts, the design of antibacterial surfaces is still a challenge. In this work, results of structural, mechanical, cytotoxic and antibacterial activities of hydrophobic carbon quantum dots/polydimethylsiloxane surfaces are presented. Antibacterial action of this surface is based on the generation of reactive oxygen species which cause bacteria damage by oxidative stress. At the same time, this surface was not cytotoxic towards the NIH/3T3 cells. Swelling-encapsulation-shrink method is applied for encapsulation of hydrophobic carbon quantum dots in medical grade silicone-polydimethylsiloxane. XPS and photoluminescence spectroscopy analyses confirm that hydrophobic carbon quantum dots have been encapsulated successfully into polydimethylsiloxane polymer matrix. Based on stress-strain test the improvement of mechanical properties of these nanocomposites is established. It is shown by electron paramagnetic resonance spectroscopy and luminescence method that nanocomposite generates singlet oxygen initiated by 470 nm blue light irradiation. Antibacterial testing shows the nanocomposite in the form of foil kills Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae and is very effective after only a 15 min irradiation.

Exploring the Critical Factors Limiting Polyaniline Biocompatibility

Today, the application of polyaniline in biomedicine is widely discussed. However, information about impurities released from polyaniline and about the cytotoxicity of its precursors aniline, aniline hydrochloride, and ammonium persulfate are scarce. Therefore, cytotoxicity thresholds for the individual precursors and their combinations were determined (MTT assay) and the type of cell death caused by exposition to the precursors was identified using flow-cytometry. Tests on fibroblasts revealed higher cytotoxicity of ammonium persulfate than aniline hydrochloride. Thanks to the synergic effect, both monomers in combination enhanced their cytotoxicities compared with individual substances. Thereafter, cytotoxicity of polyaniline doped with different acids (sulfuric, nitric, phosphoric, hydrochloric, and methanesulfonic) was determined and correlated with impurities present in respective sample (HPLC). The lowest cytotoxicity showed polyaniline doped with phosphoric acid (followed by sulfuric, methanesulfonic, and nitric acid). Cytotoxicity of polyaniline was mainly attributed to the presence of residual ammonium persulfate and low-molecular-weight polar substances. This is crucial information with respect to the purification of polyaniline and production of its cytocompatible form.

The use of fractionated Kraft lignin to improve the mechanical and biological properties of PVA-based scaffolds

The mechanical properties of poly(vinyl alcohol) (PVA)-based scaffolds were successfully improved. The improvements in mechanical properties correlated with the amount of Kraft lignin in PVA matrices. The critical property for any scaffold is its capacity to allow cells to ingrow and survive within its internal structure. The ingrowth of cells was tested using bioreactors creating simulated in vivo conditions. In the context of all the mentioned parameters, the most advantageous properties were exhibited by the scaffold containing 99 wt% PVA and 1 wt% Kraft lignin. The composites with 1 wt% Kraft lignin exhibited sufficient mechanical stability, a lack of cytotoxicity, and mainly the ability to allow the ingrowth of cells into the scaffold in a rotation bioreactor.

The mechanical properties of poly(vinyl alcohol) (PVA)-based scaffolds were successfully improved.

Carbon Quantum Dots Modified Polyurethane Nanocomposite as Effective Photocatalytic and Antibacterial Agents

Development of new types of antibacterial coatings or nanocomposites is of great importance due to widespread multidrug-resistant infections including bacterial infections. Herein, we investigated biocompatibility as well as structural, photocatalytic, and antibacterial properties of photoactive hydrophobic carbon quantum dots/polyurethane nanocomposite. The swell-encapsulation-shrink method was applied for production of these nanocomposites. Hydrophobic carbon quantum dots/polyurethane nanocomposites were found to be highly effective generator of singlet oxygen upon irradiation by low-power blue light. Analysis of conducted antibacterial tests on Staphyloccocus aureus and Escherichia coli showed 5-log bactericidal effect of these nanocomposites within 60 min of irradiation. Very powerful degradation of dye (rose bengal) was observed within 180 min of blue light irradiation of the nanocomposites. Biocompatibility studies revealed that nanocomposites were not cytotoxic against mouse embryonic fibroblast cell line, whereas they showed moderate cytotoxicity toward adenocarcinomic human epithelial cell line. Minor hemolytic effect of these nanocomposites toward red blood cells was revealed.

The biocompatibility of polyaniline and polypyrrole: A comparative study of their cytotoxicity, embryotoxicity and impurity profile

Conducting polymers (CP), namely polyaniline (PANI) and polypyrrole (PPy), are promising materials applicable for the use as biointerfaces as they intrinsically combine electronic and ionic conductivity. Although a number of works have employed PANI or PPy in the preparation of copolymers, composites, and blends with other polymers, there is no systematic study dealing with the comparison of their fundamental biological properties. The present study, therefore, compares the biocompatibility of PANI and PPy in terms of cytotoxicity (using NIH/3T3 fibroblasts and embryonic stem cells) and embryotoxicity (their impact on erythropoiesis and cardiomyogenesis within embryonic bodies). The novelty of the study lies not only in the fact that embryotoxicity is presented for the first time for both studied polymers, but also in the elimination of inter-laboratory variations within the testing, such variation making the comparison of previously published works difficult. The results clearly show that there is a bigger difference between the biocompatibility of the respective polymers in their salt and base forms than between PANI and PPy as such. PANI and PPy can, therefore, be similarly applied in biomedicine when solely their biological properties are considered. Impurity content detected by mass spectroscopy is presented. These results can change the generally accepted opinion of the scientific community on better biocompatibility of PPy in comparison with PANI.

Cell-compatible conducting polyaniline films prepared in colloidal dispersion mode

Conducting polyaniline can be prepared and modified using several procedures, all of which can significantly influence its applicability in different fields of biomedicine or biotechnology. The modifications of surface properties are crucial with respect to the possible applications of this polymer in tissue engineering or as biosensors. Innovative technique for preparing polyaniline films via in-situ polymerization in colloidal dispersion mode using four stabilizers (poly-N-vinylpyrrolidone; sodium dodecylsulfate; Tween 20 and Pluronic F108) was developed. The surface energy, conductivity, spectroscopic features, and cell compatibility of thin polyaniline films were determined using contact-angle measurement, the van der Pauw method, Fourier-transform infrared spectroscopy, and assay conducted on mouse fibroblasts, respectively. The stabilizers significantly influenced not only the surface and electrical properties of the films but also their cell compatibility. Sodium dodecylsulfate seems preferentially to combine both the high conductivity and good cell compatibility. Moreover, the films with sodium dodecylsulfate were non-irritant for skin, which was confirmed by their in-vitro exposure to the 3D-reconstructed human tissue model.