Chitosan Chloride Research Articles

Preparation of magnetic fluorescent nanoparticles with quaternary ammonium chitosan derivatives and its properties

To explore a novel solution to the challenges in constructing polymer coated magnetic fluorescent nanoparticles, HTCC/Fe3O4/CdTe magnetic fluorescent nanoparticles (MFCNPs) that can be well dispersed in water were prepared via the electrostatic interaction of the cationic N-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (HTCC) and the anion precoated water-soluble cadmium telluride (CdTe) quantum dots (QDs) and the sodium citrate-coated Fe3O4 (SC-Fe3O4) magnetic nanoparticles (MNPs), which overcame the performance defects of hydrophobic polymer for surface coating and the possible toxicity of cross-linking agent induced by the hydrophilic polymer coating materials. The structural characterizations by FTIR, XRD and XPS reveal that the surfaces of SC-Fe3O4 MNPs and CdTe QDs are coated with HTCC. TEM imaging suggests that the MFCNPs are spherical particles with the diameters of ∼15–20 nm. The MFCNPs exhibit good biocompatibility. Further investigation suggests that the UV-Vis and fluorescence spectral properties and surface electrical properties of HTCC/Fe3O4/CdTe MFCNPs are mainly affected by the relative ratios of SC-Fe3O4 MNPs, CdTe QDs and HTCC. The adsorption and release properties of the MFCNPs were studied using bovine serum albumin (BSA) as the model. The results indicate that the chitosan-based magnetic fluorescent composite is a promising delivery carrier candidate with excellent comprehensive properties for both magnetic response and fluorescence imaging.

Fabrication of antibacterial Janus bandages with high wound healing performances by facile single-side electrospray PDMS coating

Bandages are widely utilized to cover local wounds. However, most bandages have limited capacities to promote wound healing, which may occasionally cause serious wound infections. Accordingly, herein, we demonstrated a facile electrospray method to fabricate an antibacterial Janus bandage that could simultaneously remove wound bed exudate and prevent wound infection. The advanced bandage was only composed of an adhesive strip and an antibacterial Janus cotton fabric, whose single side was controllably electrospray-coated with a thin polydimethylsiloxane coating. The Janus cotton fabric exhibited a high one-way transport index (R = 1068%), suggesting its appropriate directional liquid moisture transport ability, and excellent air permeability. Furthermore, in vitro experiments demonstrated that the advanced bandage had adequate biocompatibility and exhibited sustained release of hydroxypropyltrimethyl ammonium chloride chitosan, which considerably enhanced the proliferation of fibroblasts. As a proof-of-concept, this bandage was employed to drain the exudate from Staphylococcus aureus (S. aureus)-infected mice wounds and kill S. aureus in these wounds, which significantly accelerated wound healing. The simple fabrication process of unique bandage reveals it has considerable potential as a next-generation bandage for healing local wounds clinically.

Protective Effect of Composite Hydrogel Based on Hydroxypropyl Trimethylammonium Chloride Chitosan on Skin Photodamage

Long-term or excessive exposure to UV light can lead to sunburn, erythema, melanin deposition, inflammation, and even skin cancer. This study used composite hydrogels with N-2-hydroxypropyl trimethylammonium chloride chitosan (N-2-HACC) and hyaluronic acid (HA) as carriers. In addition, ellagic acid (EA) and proanthocyanidins (PC) as functionalized materials were prepared. The infrared results show that the N-2-HACC/HA/EA/PC hydrogel is formed by N-2-HACC connecting with HA by electrostatic interaction, and HA forms hydrogen bonds between EA and PC. The in vitro antioxidant results show that EA and PC have different clearance efficiency of DPPH and superoxide anion radicals at different pH values. Thus, they have complementary effects on antioxidant properties. The cumulative release results demonstrate that the hydrogels had an excellent slow-release rate at different pHs. The animal experiments reveal that N-2-HACC/HA/EA/PC could restore the consumption of antioxidant enzymes induced by UVB irradiation and inhibit matrix metalloproteinase 1. N-2-HACC/HA/EA/PC can inhibit UVB-induced histological damage, such as epidermal thickening, collagen fiber, and elastic fiber destruction. N-2-HACC/HA/EA/PC has a significant photoprotective effect by protecting the activities of superoxide dismutase, catalase, and glutathione peroxidase and inhibiting the activity of inflammatory factors. N-2-HACC/HA/EA/PC composite hydrogel system shows comprehensive performance. Its ability to scavenge free radicals may act as an antioxidant to protect mice from skin cancer.

An injectable, self-healing composite hydrogel with enhanced near-infrared photo-antibacterial therapeutic effects for accelerated wound healing

Antibacterial hydrogels with injectable and self-healing properties have attracted much attention in the field of wound dressings because they not only can prevent bacterial infections, but also meet the basic needs for wound healing. However, how to achieve high antibacterial efficacy and low drug resistance for hydrogels is still a challenge. Herein, an injectable, self-healing, near-infrared (NIR) photosensitive antibacterial hydrogel composed of CuS-grafted-curcumin (CuS@C) and carboxymethyl cellulose modified with aldehyde groups and hydroxypropyl trimethyl ammonium chloride chitosan is prepared for wound dressings. The p-n junction formed between curcumin and CuS promotes separation of electron-hole pairs, enhances the mobility of photogenerated charges, and destroys the conjugated structure of curcumin simultaneously consequently increasing the photocatalytic activity. CuS@C is immobilized and distributed uniformly in the hydrogel via the π-π conjugation ring. The hybrid hydrogel exhibits excellent antibacterial activity after irradiation with 808 NIR light for 10 min due to the enhanced photodynamic and photothermal antibacterial effects. In addition, the hybrid structure improves the biocompatibility of CuS and expedites infected-wound healing at a mild temperature of 45 ℃. This organic/inorganic hybrid is shown to be an excellent wound dressing for the treatment of bacterial-infected wounds.

N‐2‐hydroxypropyl trimethyl ammonium chloride chitosan‐glycerol complex temperature‐sensitive hydrogel for wound dressing

AbstractWith the development of the times, it becomes difficult or even impossible for traditional wound dressings to meet people's needs for high‐quality wound repair and management. Therefore, there is an urgent need for new biomedical dressings that can accelerate wound healing in clinical practice. In this study, N‐2‐hydroxypropyl trimethylammonium chloride chitosan (N‐2‐HACC), a derivative of chitosan, was used as raw material to sprepare N‐2‐HACC temperature sensitive hydrogel. The structure, thermal stability and water content of N‐2‐HACC temperature sensitive hydrogel were analyzed by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. The safety of N‐2‐HACC temperature sensitive hydrogel was evaluated by in vitro cell assay and in vitro degradation assay, and the effect of N‐2‐HACC temperature sensitive hydrogel on wound healing was evaluated by wound healing experiment in SD rats. The results show that N‐2‐HACC hydrogel, as a wound dressing, has the characteristics of good biocompatibility, good biodegradation, non‐toxic, anti‐inflammatory and so on. It plays a barrier role in the process of wound healing, provides a moist environment for the wound and accelerates wound healing. Therefore, N‐2‐HACC hydrogel has a broad application prospect in promoting wound healing as a wound dressing.

Combination of natural polyanions and polycations based on interfacial complexation for multi-functionalization of wound dressings.

Multi-functionalization of wound dressings with natural polymers is meaningful and remains a challenge. The combination of natural polyanions and polycations appears to be a promising strategy. Still, its performances based on current layer-by-layer self-assembly or homogeneous complexation are mutable and limited. Herein, Ca2+-incorporated carboxymethyl cellulose (Ca/Na-CMC) and hydroxypropyltrimethyl ammonium chloride chitosan (HACC) are adopted as the model polyanion and polycation, respectively, to develop multi-functionalized dressings based on interfacial complexation. The dressings exhibit a multilayer structure composed of a polyanion layer (Ca/Na-CMC) for hemostasis and promotion of cell proliferation, a formed polyelectrolyte complex (PEC) layer for structural stability, and a polycation layer (HACC) for antibiosis. Compared to the dressing based on homogeneous complexation, the multilayer dressings show stronger moisture penetrability (around 1,150 g/m2/24 h), higher hemostatic activity, and higher antibacterial rate (up to 100%) and promoted effect on cell proliferation. An in vivo evaluation using a rat full-thickness skin defect model reveals that the multilayer dressings can accelerate wound healing in 2 weeks. Overall, owing to interfacial complexation resulting in separate layers, the performances of polyanions and polycations after combination are more predictable, and their biological functions can be effectively preserved. These findings not only support the extensive application of multilayer dressings but also offer an alternative strategy for multi-functionalizing wound dressings with natural polyanions and polycations.

Amoxicillin encapsulated in the N-2-hydroxypropyl trimethyl ammonium chloride chitosan and N,O-carboxymethyl chitosan nanoparticles: Preparation, characterization, and antibacterial activity

This is a report on the encapsulation amoxicillin (AMX) in the N-2-Hydroxypropyl trimethyl ammonium chloride chitosan (N-2-HACC) and N,O-carboxymethyl chitosan (CMCS) nanoparticles (NPs) for biomedical applications. The N-2-HACC/CMCS NPs have broad-spectrum antibacterial properties. In order to achieve sustained and slow drug release, improve drug transport efficiency and bioavailability, prolong drug residence time, and reduce pollution, we synthesized highly efficient, easily absorbed and rapidly degradable nano-formulation veterinary antibiotics in this study. The N-2-HACC/CMCS NPs were used for the encapsulation of AMX, and the cytocompatibility, in vitro release, in vivo drug release kinetics and antimicrobial activity of N-2-HACC/CMCS/AMX NPs were investigated. The NPs displayed a round shape and smooth surface, and the NPs allowed the sustained release of AMX at a much slower rate than that of non-coated AMX. The NPs exhibited excellent cytocompatibility and the antimicrobial activity against Escherichia coli, Acinetobacter baumannii, Streptococcus pneumoniae and Staphylococcus aureus. Moreover, the NPs could store at 4 °C, −20 °C and 25 ± 5 °C for 30 d. These results suggested that the N-2-HACC/CMCS NPs could be availed as a candidate for drug delivery carrier to achieve sustained and slow release, improve bioavailability, prolong residence time at the target site, and reduce the dosage of drug.

Hydroxypropyltrimethyl Ammonium Chloride Chitosan Nanoparticles Coatings for Reinforcement and Concomitant Inhibition of Anionic Water-Sensitive Dyes Migration on Fragile Paper Documents.

The fragile paper is treated to improve the stability and appearance of the paper artifact, such as washing, lining, deacidification, and reinforcement. During the above treatments, paper documents inevitably make contact with water directly, leading to the appearance change, stability decrease, and migration or fading of anionic water-sensitive dyes, which are seriously harmful to information security. Herein, Hydroxypropyltrimethyl ammonium chloride chitosan (HACC) nanoparticles were employed for the reinforcement and concomitant inhibition of anionic water-sensitive dye migration on fragile paper. HACC nanoparticles were prepared through physical ball grinding method and characterized via LPSA, SEM, TEM, XRD and FTIR. To evaluate the protective potential of HACC nanoparticles coating, the chemical and mechanical properties of coated and uncoated papers were evaluated after dry heat and hygrothermal accelerated aging. Additionally, good color stability of anionic water-sensitive dyes was observed on the paper coated with HACC nanoparticles after lining technology. Finally, the interaction mechanism between the anionic water-sensitive dyes and HACC nanoparticles was analyzed using an ultraviolet spectrophotometer and FTIR. The as-proposed technique can provide technical support to improve the mechanical properties of fragile paper and enhance the anionic water-sensitive dyes stability in the aqueous phase.

Dielectric properties of chitosan and two ionic derivatives: Effect of counter anions

We report herein the dielectric properties response of two ionic chitosan derivatives. More specifically, we report here chitosan derivatives bearing guanidinium groups, prepared through the reaction between chitosan and cyanamide when scandium (III) triflate is present. The anionic counter ions of the guanidinium groups could be changed by working either in acetic acid or hydrochloric acid. In this way, two chitosan derivatives, namely N-guanidinium chitosan acetate (GChAc) and N-guanidinium chitosan chloride (GChCl), were produced. The materials were investigated by 13C solid state NMR, FT-IR spectroscopy, SEM and TEM analysis and compared with the parent chitosan. Dielectric spectroscopy has been used to study the relaxation behavior of the parent chitosan and the new chitosan derivatives over wide ranges of temperature and frequency, indicating that local motion is affected by counter ions. Due to these features, these materials are interesting candidates as high-power electrical materials for green technological applications.

Tannic acid/polyvinyl alcohol/2-hydroxypropyl trimethyl ammonium chloride chitosan double-network hydrogel with adhesive, antibacterial and biocompatible properties

Hydrogels have great potential for biomedical applications. However, there are still significant challenges in preparing biomass-based hydrogels with excellent adhesive, antibacterial and biocompatible properties. In this study, pure physically cross-linked tannic acid (TA)/polyvinyl alcohol (PVA)/2-hydroxypropyltrimethyl ammonium chloride chitosan (HACC) double-network (PVA/HACC-TA) hydrogels are prepared by a combination approach of cyclic freeze-thaw and soaking method. The prepared PVA/HACC-TA hydrogels are formed by hydrogen bond cross-linking and do not use any toxic and harmful cross-linking agents. Meanwhile, the prepared PVA/HACC-TA hydrogels have excellent mechanical properties, the maximum tensile strength can reach 4.13 MPa and the maximum tensile strain can attain 830%. In addition, PVA/HACC-TA hydrogels display good adhesion to different materials. At the same time, the PVA/HACC-TA hydrogels also show favorable antibacterial activities. Therefore, the excellent mechanical, adhesive, antibacterial and cytocompatible biomass hydrogels showed promising potential applications in the biomedicine field, especially as the skin wound dressings.

Rhodojaponin III-Loaded Chitosan Derivatives-Modified Solid Lipid Nanoparticles for Multimodal Antinociceptive Effects in vivo.

BackgroundRhodojaponin III (RJ-III) is a bioactive diterpenoid, which is mainly found in Rhododendron molle G. Don (Ericaceae), a potent analgesia in traditional Chinese medicine with several years of clinical applications in the country. However, its clinical use is limited by its acute toxicity and poor pharmacokinetic profiles. To reduce such limitations, the current study incorporated RJ-III into the colloidal drug delivery system of hydroxypropyl trimethyl ammonium chloride chitosan (HACC)-modified solid lipid nanoparticles (SLNs) to improve its sustained release and antinociceptive effects in vivo for oral delivery.ResultsThe optimized RJ-III@HACC-SLNs were close to spherical, approximately 134 nm in size, and with a positive zeta potential. In vitro experiments showed that RJ-III@HACC-SLNs were stable in the simulated gastric fluid and had a prolonged release in PBS (pH = 6.8). Pharmacokinetic results showed that after intragastric administration in mice, the relative bioavailability of RJ-III@HACC-SLNs was 87.9%. Further, it was evident that the peak time, half-time, and mean retention time of RJ-III@HACC-SLNs were improved than RJ-III after the administration. In addition, pharmacodynamic studies revealed that RJ-III@HACC-SLNs markedly reduced the acetic acid, hot, and formalin-induced nociceptive responses in mice (P < 0.001), and notably increased the analgesic time (P < 0.01). Moreover, RJ-III@HACC-SLNs not only showed good biocompatibility with Caco-2 cells in vitro but its LD50 value was also increased by 1.8-fold as compared with that of RJ-III in vivo.ConclusionThese results demonstrated that RJ-III@HACC-SLNs improved the pharmacokinetic characteristics of the RJ-III, thereby exhibiting toxicity-attenuating potential and antinociceptive enhancing properties. Consequently, HACC-SLNs loaded with RJ-III could become a promising oral formulation for pain management that deserves further investigation in the future.

Mice immunized with trimethyl chitosan nanoparticles containing DENV-2 envelope domain III elicit neutralizing antibodies with undetectable antibody-dependent enhancement activity.

Dengue is a disease that poses a significant global public health concern. Although a tetravalent live-attenuated dengue vaccine has been licensed, its efficacy is still debated due to evidence of vaccine breakthrough infection. To avoid this issue, dengue vaccines should stimulate a high degree of serotype-specific response. Thus, envelope domain III (EDIII), which contains serotype-specific neutralizing epitopes, is an attractive target for dengue vaccine development. In this study, we investigated how EDIII encapsidated in N, N, N-trimethyl chitosan chloride nanoparticles (TMC NPs) stimulates a serotype-specific response and whether this response exerts a potential in vitro breakthrough infection. The immune response to DENV-2 elicited by EDIII TMC NP-immunized mice was monitored. We demonstrated that immunization with EDIII TMC NPs resulted in a high level of anti-EDIII antibody production. These antibodies included IgG, IgG1, and IgG2a subtypes. Importantly, antibodies from the immunized mice exerted efficient neutralizing activity with undetectable antibody dependent enhancement (ADE) activity. We also found that EDIII TMC NPs activated functional EDIII-specific CD4+ and CD8+ T cell responses. In conclusion, EDIII TMC NPs stimulated humoral immunity with a strong neutralizing antibody response, as well as a cellular immune response against DENV-2.

Fabrication of hygroscopic photothermal fibroin-based aerogels for dehumidification and solar-driven water harvesting

The high-humidity environment will make people uncomfortable and even easily causes inconvenience to people's health. Thus, various chemical or biological desiccants and air conditioners are applied for air dehumidification. However, how to recycle water resources in the process of efficient dehumidification is a meaningful problem to be solved. In the present work, solar-powered hygroscopic photothermal fibroin-based aerogels for indoor dehumidification and water harvesting were fabricated. Briefly, copper sulfide nanoparticles (CuSNPs) were synthesized using silk fibroin (SF) chains as templates, and the aerogel of SF/CuSNPs composite was obtained by freeze-drying. Subsequently, coating of hydrophilic carboxymethyl chitosan (CMCS) and calcium chloride on the photothermal aerogel was performed for moisture absorption and water recovery from the environment. The CMCS-Ca@SF aerogel exhibits encouraging water uptakes of 1.35 g/g at 90 % relative humidity (RH) for 12 h. Meanwhile, most of the absorbed water from the composite aerogel can be rapidly released within 1 h under 4-sun irradiation due to the photothermal effects of CuSNPs. The hygroscopic aerogel efficiently reduces the humidity in enclosed space and can potentially be applied for outdoor atmospheric water harvesting. Besides, the excellent antibacterial capacity endows the hygroscopic aerogel with long-term storage stability even in a high-humidity environment. This work provides an alternative to developing a convenient, effective hygroscopic aerogel for indoor dehumidification and atmospheric water harvesting.

Rational design of biocompatible IPNs hydrogels containing carboxymethyl starch and trimethyl chitosan chloride with high antibacterial activity

Rational design of biocompatible IPNs hydrogels containing carboxymethyl starch and trimethyl chitosan chloride with high antibacterial activity

Structural characteristics and rheological properties of hydroxypropyl trimethyl ammonium chloride chitosan

Hydroxypropyl trimethyl ammonium chloride chitosan (HACC) was synthesized by reacting chitosan with glycidyl trimethylammonium chloride. Atomic force microscopy showed that HACC exhibited disorderly coils in dilute solution and formed a three-dimensional network. Flow, thixotropy, and dynamic viscoelasticity tests were conducted using an MCR301 rheometer. The HACC solution was a non-Newtonian pseudoplastic fluid, and the shear behavior of different concentrations (2–6 %, w/v) was evaluated by the Williamson model fitting. Furthermore, the thixotropy was highly dependent on concentration changes: the high-concentration solution structure was difficult to recover in a short time. The dynamic viscoelasticity test indicated that the viscoelasticity of the HACC solution not only exhibited a viscous behavior similar to that of a fluid, but also exhibited elastic properties of weak gel. HACC exhibited high-strength solid-like gel characteristics at high temperature.

Preparation of carrageenan/ chitosan-based (N,N,N-trimeth(yl chitosan chloride) silver nanocomposites as pH sensitive carrier for effective controlled curcumin delivery in cancer cells

PurposeThis work aims to formulate a novel pH-sensitive biocompatible metallic nanocomposite as a carrier for hydrophobic drugs with efficient loading and controlled drug release. The proposed carrier consists of a polyelectrolyte complex of chitosan-based, N,N,N-trimethyl chitosan chloride (TMC), and carrageenan (CAR) biopolymers with different silver nanoparticles (AgNPs) molar ratios forming CAR/TMC-Ag nanocomposites that investigated to be used as a carrier for controlled gastro-intestinal tract (GIT) release of curcumin (CUR) as a model of lipophilic drugs. MethodsThe structure of nanocomposites was scrutinized via FTIR, TEM, SEM, XRD and EDX, whereas the potential cytotoxicity and antimicrobial efficacy of loaded nanocomposite with 3% AgNPs (NC-3% Ag) were probed, as well. ResultsSuccessful loading and release of CUR were detected from the prepared nanocomposites without change in its functionality with a higher releasing profile in pH 7.4 (simulated intestinal fluid) than pH 1.2 (simulated gastric fluid). In vitro release study of CUR loaded NC-3% Ag showed the favored sustained drug release reaching 98.9% ± 0.9 within 24 h in pH 7.4, following Korsmeyer−Peppas model. Additionally, successful release from loaded CAR/TMC nanocomposite with 3% AgNPs (NC-3% Ag), revealed high cytotoxic effect with apoptotic induction against human colon cancerous cells (Caco-2) through G2/M cell cycle arrest and antibacterial potency against different bacterial strains. Moreover, cell viability results of NC-3% Ag against human normal cells exhibited good biocompatibility. ConclusionAccordingly, we suggested NC-3% Ag as a promising controlled drug delivery vehicle for hydrophobic drugs with preferred intestinal targeting effectiveness.

Ultrasonic-Aided Co-Precipitation of Tannins and Chitosan Ammonium Salt on Cotton Fabric for Antimicrobial and Ultraviolet-Shielding Properties: An Efficient, Colourless, and Eco-Finishing Strategy.

Sustainable fabrication of protective cotton, using bio-extracts, is becoming increasingly attractive. However, many shortcomings—including the introduction of potentially hazardous mordants or modifiers to cotton, annoying colour changes after finishing, and low processing efficiency—require further melioration. Therefore, an efficient ultrasonic-assisted colourless finishing process was developed in this study, to fabricate ultraviolet-proof and antimicrobial cotton. A pair of oppositely charged bio-based substances, i.e., tannin acid (TA) and hydroxypropyltrimethyl ammonium chloride chitosan (HACC) were introduced during the ultrasonic process. The results reveal that cationic HACC significantly promotes the adsorption of TA to cotton. The apparent colour of the cotton remained almost unchanged after finishing. Based on Pesudo first-/second-order kinetic models, chemisorption was verified as the dominant mechanism. Efficiency under ultrasound was enhanced by 5.3% (70 °C) and 27% (90 °C), respectively. A mathematical modelling study established the factors to be in the following order of significance: concentration > pH > temperature. Under optimal conditions, a theoretical maximum UPF of 380.8 was achieved. TA (8 g/L)-treated cotton deactivated up to 98% of Escherichia coli, and also provided excellent UV-shielding performance. In general, the ultrasonic-assisted eco-dyeing and finishing process for cotton was explored in depth from practical and theoretical perspectives, which should push forward the development of the sustainable textile industry.

Flocculation of Chlorella vulgaris-induced algal blooms: critical conditions and mechanisms.

Algal blooms have posed great threats to livestocks and human health. Although flocculation is effective, its efficiency may hinder the direct application for algal blooms. In this study, critical (optimal) conditions and mechanisms for AlCl3, FeCl3, poly-aluminum chloride (PAC), chitosan, and polydimethyldiallylammonium chloride (PDADMAC)-induced flocculation of Chlorella vulgaris (C. vulgaris) were studied. Results identified the critical conditions which can cause flocculation efficiencies over 90% in 45 min for the five flocculants. Specifically, 4~10-mg/L doses of PDADMAC were proved to be appropriate for the treatment of C. vulgaris-induced algal blooms at pH 6.0~12.0. To probe the underlying mechanisms, functional groups involved in flocculation, zeta potential, and species distribution were analyzed during flocculation. FT-IR results indicated that N-H stretching in amine and C-H deformation in aliphatics were involved in algal flocculation with FeCl3, and C-H deformation played an important role with PDADMAC, PAC, and chitosan. For AlCl3, zeta potential and species distribution results suggested that charge neutralization and adsorption bridging were responsible for algal flocculation at pH 6~8. However, adsorption bridging and sweeping effects were the main mechanisms at pH >3 for FeCl3. The flocculation mechanisms for the rest of the three polymers were charge neutralization, adsorption bridging, and sweeping. Meanwhile, all the flocculation processes followed second-order kinetics. Strong linkages were found between the rate constant, fractal dimension, and flocculation efficiency (P < 0.05). The results of critical flocculation conditions and mechanisms indicated that PDADMAC was an excellent flocculant for C. vulgaris removing and recycling, especially in water bloom treatment.

Temporal and spatial variation in the efficiency of a Floc & Sink technique for controlling cyanobacterial blooms in a tropical reservoir

One of the main symptoms of eutrophication is the proliferation of phytoplankton biomass, including nuisance cyanobacteria. Reduction of the external nutrient load is essential to control eutrophication, and in-lake interventions are suggested for mitigating cyanobacterial blooms to accelerate ecosystem recovery. Floc & Sink (F&S) is one such intervention technique that consists of applying a low dose of coagulants in combination with ballasts for removing cyanobacteria biomass. It is especially suitable for deep lakes with an external nutrient load that is higher than the internal load and suffers from perennial cyanobacterial bloom events. Studies showing the efficacy of the F&S technique have been published, but those testing its variation in efficacy with changes in the environmental conditions are still scarce. Therefore, we evaluated the efficiency of the F&S technique to remove cyanobacteria from water samples collected monthly from two different sites in a deep tropical reservoir (Funil Reservoir, Brazil) in the laboratory. We tested the efficacy of two coagulants, chitosan (CHI) and poly-aluminum chloride (PAC), alone and in combination with lanthanum-modified bentonite (LMB) in settling phytoplankton biomass. We hypothesized that: ⅰ) the combined treatments are more effective in removing the algal biomass and ⅱ) the efficiency of F&S treatments varies spatially and monthly due to changes in environmental conditions. The combined treatments (PAC + LMB or CHI + LMB) removed up to seven times more biomass than single treatments (PAC, CHI, or LMB). Only the treatments CHI and LMB + CHI differed in efficiency between the sites, although all treatments showed significant variation in efficiency over the months at both the sampling sites. The combined treatments exhibited lower removal efficacy during the warm-rainy months (October–March) than during the mild-cold dry months (April–September). At high pH (pH > 10), the efficiency of the CHI and LMB + CHI treatments decreased. CHI had lower removal efficiency when single-cell cyanobacteria were abundant, while the combined treatments were equally efficient regardless of the morphology of the cyanobacteria. Hence, the combination of PAC as a coagulant with a ballast LMB is the most effective technique to precipitate cyanobacteria under the conditions that are encountered around the year in this tropical reservoir.

Eco-friendly and biodegradable sodium alginate/quaternized chitosan hydrogel for controlled release of urea and its antimicrobial activity

Hydrogels could be employed in agriculture for efficient management of water and controlled-release urea (CRU). This study aimed to synthesize a superabsorbent hydrogel for CRU by cross-linking sodium alginate (Alg) and N-(2-hydroxy-3-trimethyl ammonium) propyl chitosan chloride (HTACC). The hydrogel structure was characterized by various techniques, and the urea loading and releasing behaviors of the synthetic hydrogels were investigated. The results revealed that the maximum urea loading ranged between 107 and 200%, and that the urea loading kinetics fitted with Langmuir model followed by the Freundlich model. The urea release behavior reached equilibrium after 30 days and urea releasing kinetics fitted with the zero-order and Higuchi models. The synthesized hydrogels exerted significant antimicrobial activities and molecular docking showed their binding affinity toward glucosamine-6-phosphate synthase, β-lactamase II, TraR binding site and nucleoside diphosphate kinase. In conclusion, these Alg/HTACC hydrogels showed swelling, urea release, and antimicrobial properties suitable to meet the plant requirements and produce economic and environmental benefits.