Molecular Weight Chitosan Research Articles

SiRNA Delivery with Chitosan: Influence of Chitosan Molecular Weight, Degree of Deacetylation, and Amine to Phosphate Ratio on in Vitro Silencing Efficiency, Hemocompatibility, Biodistribution, and in Vivo Efficacy.

Chitosan (CS) shows in vitro and in vivo efficacy for siRNA delivery but with contradictory findings for incompletely characterized systems. For understanding which parameters produce effective delivery, a library of precisely characterized chitosans was produced at different degrees of deacetylation (DDAs) and average molecular weights (Mn). Encapsulation and transfection efficiencies were characterized in vitro. Formulations were selected to examine the influence of Mn and N:P ratio on nanoparticle uptake, metabolic activity, genotoxicity, and in vitro transfection. Hemocompatibility and in vivo biodistribution were then investigated for different Mn, N:P ratios, and doses. Nanoparticle uptake and gene silencing correlated with increased surface charge, which was obtained at high DDA and high Mn. A minimum polymer length of ∼60-70 monomers (∼10 kDa) was required for stability and knockdown. In vitro knockdown was equivalent to lipid control with no metabolic or genotoxicity. An inhibitory effect of serum on biological performance was dependent on DDA, Mn, and N:P. In vivo biodistribution in mice show accumulation of nanoparticles in kidney with 40-50% functional knockdown.

Biomassa e extração de quitina e quitosana a partir de isolados de Cunninghamella sp.

O estudo objetivou avaliar a produção de biomassa de nove isolados de Cunninghamella sp. e da cepa referência de Cunninghamella elegans (CBMAI 0843) e estabelecer a capacidade de produção de quitina e quitosana por estas cepas. Assim como, caracterizar a quitosana fúngica obtida por parâmetros como massa molar, grau de desacetilação e distribuição dos grupos funcionais ao longo da cadeia polimérica. Para a maioria das cepas avaliadas, o período de maior crescimento foi em 48 horas de cultivo, sendo que, neste período, o isolado UFT Ce08 apresentou a maior quantidade de biomassa, 20,17 g L-1. Os rendimentos de quitina ficaram entre 15,64 a 30,33% e os rendimentos de quitosana entre 0,94 a 7,43%. A cepa UFT Ce11 apresentou o melhor quantitativo de quitina e a cepa UFT Ce09, mesmo apresentando o segundo menor quantitativo de biomassa, 9,34 g L-1, teve o melhor rendimento de quitosana. Sete cepas isoladas no presente estudo apresentaram maior rendimento de quitosana comparada à cepa referência. O grau médio de desacetilação foi de 83,7% para quitosana obtida do isolado UFT Ce09 e 80,5% para quitosana obtida da cepa referência. As massas molares para a quitosana do isolado UFT Ce09 e da cepa referência foram de 43,031 e 19,215 g mol-1, respetivamente. A espectrometria de infravermelho apresentou bandas com comprimentos de onda e grupos funcionais coincidentes com a literatura e com a quitosana comercial. A quitosana fúngica deste estudo apresentou propriedades que atestam sua qualidade e características de interesse biotecnológico e comercial.

Effects of chitosan molecular weight on its antioxidant and antimutagenic properties

Chitosan (300.0kDa) was enzymatically degraded to obtain six degraded chitosans with molecular weights (MWs) of 156.0, 72.1, 29.2, 7.1, 3.3, and 2.2kDa. The antioxidant and antimutagenic properties of all seven chitosan samples were evaluated in vitro. The antioxidant scavenging activities of chitosans on hydrogen peroxide and 2, 2-diphenyl-1-picryl hydrazyl radical, and on chelating ferrous ion were significantly increased with chitosan’s decreasing MW, with 2.2-kDa chitosan have the highest impact. All seven chitosan samples exhibited strong anitmutagenic effects against direct (4- nitroquinoline 1-oxide) and indirect (benzo[α]pyrene) mutagens in the presence of rat liver enzyme S9 mix in Salmonella typhimurium TA 98 and TA 100. The effect of MW on antimutagenicity was similar to that on antioxidant activity. The underlying mechanism for chitosan antimutagenicity proved to be its desmutagenic effect on mutagens.

Aging Study of Gold Nanoparticles Functionalized with Chitosan in Aqueous Solutions

We studied the way in which stability and physicochemical properties of gold (Au) nanoparticles (NP) coated with chitosan are influenced by the molecular weight of chitosan and Au precursor concentration when samples are subjected to aging. Pharmaceutical use of AuNPs coated with chitosan is closely related to stability and physicochemical properties in relation to storage conditions and processing. For this purpose, series of AuNPs of different sizes were prepared by aqueous chemical reduction method using chitosan with various molecular weights as template. The physicochemical properties and stability at room temperature of AuNPs in aqueous solutions of chitosan have been investigated by following the temporal evolution of surface plasmon absorbance, Zeta potential, average dimension, and Au-chitosan interaction, after synthesis and through a period of 24 months. In our experiment, during the observed aging period, the AuNPs coated with chitosan presented a better colloidal stability, while using chitosan with medium molecular weight and medium concentration of Au precursor.

Comparative assessment of poly (D,L-lactide-co-glycolide) nanoparticles modified by either cetyltrimethylammonium bromide or chitosan for plasmid DNA adsorption

Purpose: To evaluate poly (D,L-lactide-co-glycolide) PLGA nanoparticles modified by cetyltrimethyl ammonium bromide (CTAB) or chitosan for plasmid DNA adsorption.Methods: PLGA nanoparticles were prepared by solvent diffusion method and modified by including CTAB in the aqueous (F1) or oil phase (F2), or by including low (F3) or medium (F4) molecular weight chitosan. The nanoparticles were characterised by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR), as well as for cell toxicity, cell uptake and transfection.Results: CTAB failed to confer positive charge on the nanoparticles. CTAB desorbed easily from F1 surface. This resulted in negative zeta potential, increased cytotoxicity as well as decreased cell uptake and transfection. In F2, CTAB was located mainly in PLGA matrix, resulting in negative charge with decreased cytotoxicity, and increased cell uptake and transfection compared to F1. On the other hand, chitosan-modified nanoparticles (F3 and F4) showed stronger interaction between chitosan and PLGA, leading to positively-charged particles, decreased cytotoxicity, as well as increased cell uptake and transfection. Amongst the four formulations, F4 exhibited the highest transfection.Conclusion: These results should aid in understanding how PLGA nanoparticles are modified by CTAB and chitosan. Modification with chitosan yields PLGA nanoparticles with higher DNA adsorption and transfection with lower cytotoxicity.Keywords: Chitosan, cetyltrimethyl ammonium bromide (CTAB), Nanoparticle, Poly (D,L-lactide-coglycolide) PLGA, Plasmid DNA adsorption, Gene therapy

Development and characterization of chitosan/gelatin electrosprayed microparticles as food grade delivery vehicles for anthocyanin extracts

This work reports on the development of electrosprayed chitosan/gelatin microparticles for encapsulation purposes. Initially, the effects of the chitosan molecular weight (Mw), biopolymers and solvent composition on solution properties and capsule formation were investigated. Results demonstrated that the sprayability of the blend solutions was mainly determined by a critical range of solids content, which was needed for chain entanglement and subsequent capsule formation, and by their rheological properties. SAXS experiments from selected electrospraying solutions showed that clustered networks between both biopolymers were formed due to the electrostatic interactions between the positively charged amino groups in chitosan and negatively charged amino acid residues in gelatin. As a model bioactive extract, an anthocyanin-rich black carrot extract (BCE) was loaded into selected chitosan/gelatin electrosprayed structures and the encapsulation efficiency and release into two food simulants (ethanol 10% and acetic acid 3%) was evaluated. Faster and greater release was observed in the acetic acid medium as expected and the results showed that the main factor affecting the bioactive release was the blend composition, i.e. increasing the chitosan content of the formulations limited BCE release.

Modeling the Inhibition of Vibrio cholerae Non-01 in Trypticase Soy Broth by Chitosan of Low and High Molecular Weight

Chitosan has proved to have antimicrobial properties, which can be used to protect seafood from contamination and growth of pathogens such as Vibrio cholerae. The aim of this study was to model the inhibition of Vibrio cholerae Non-01 by low and high molecular weight chitosan. Chitosan of low (LMWC) and high (HMWC) molecular weight (15 and 32 KDa respectively) was used at final concentrations of 600 and 1,000 mg/L and antimicrobial assays were carried out at temperatures of 5 and 35°C. Data were fitted to the Weibull distribution and b and n values were used to plot resistance frequency curves. Inhibition curves showed that the four treatments were effective at 5oC, with 5.5 log reduction after 312 h with the highest chitosan concentration tested, while the effect of the 600 mg/L chitosan concentration was bacteriostatic rather than bactericidal (3.5 log reduction at 388 h). The 1,000 mg/L chitosan concentration was bactericidal at 35°C (6 log reduction) at a shorter time (12 h). No differences were observed by the different molecular weight of the chitosan used. Weibull model fit adequately (R2>0.8908) with experimental data, the highest cellular damage occurs significantly (p<0.05) with high chitosan concentrations regardless of molecular weight and treatment temperature. Resistance frequency plots showed a greater resistance of LMWC, with the maximum values of V. cholerae Non-01 resistance presented in the first minutes of the treatments regardless of the temperature.

In vitro gene silencing effect of chitosan/shRNA PDGF-D nanoparticles in breast cancer

Breast cancer is the most common cancer worldwide in women and it is highly malignant and fatal. PDGF-D plays role in regulation of many cellular processes such as angiogenesis. PDGF-D is overexpressed in many types of cancers and promote tumor growth and metastasis. Silencing of PDGF-D gene by using shRNA with an appropriate carrier system may decrease tumor growth and metastasis. In our study, we prepared chitosan nanoparticles loaded with five different shRNA plasmids targeting different exons of PDGF-D gene. Then, nanoparticles were characterized in vitro and transfection efficiency of these nanoparticles were investigated in breast cancer cell lines (MCF- 7, MDA-MB-231 and MDA-MB-435). The effects of single and multiple shRNA sequences, molecular weight of chitosan (150 kDa and 400 kDa) and the amount of shRNA (100 and 500 μg) on the characterization and transfection efficiencies of nanoparticles have been studied. Size of nanoparticles changed between 200-400 nm and approximately 95-100% encapsulation efficiency were obtained. Release of shRNA changed with the molecular weight of chitosan. It was obtained that formulation containing shRNA plasmid targeting PDGF-D exon 6 (NP1) has the highest silencing efficiency in MDA-MB-231 cell line. It was also evaluated that chitosan can be a suitable gene delivery system for shRNA targeting PDGF-D.

A systematic approach of chitosan nanoparticle preparation via emulsion crosslinking as potential adsorbent in wastewater treatment

This study investigates the impact of glutaraldehyde (glut) concentration and molecular weight (MW) of six commercially available, highly deacetylated chitosans (Chi) on nanoparticle (Chi-NP) formation by emulsion crosslinking technique and their use as potential adsorber for diclofenac (DCL) and carbamazepine (CBZ). With a glut:primary amine ratio of 1:1 and NaCl as a hydrophile, it was possible to reproducibly synthesize narrowly distributed, spherical Chi-NPs over a broad range of chitosan MW with a high yield. Increasing Chi MW resulted in larger particle sizes ranging from 109.9nm, for lowest MW, up to 200.3nm for the highest MW, measured by DLS. To evaluate the static adsorption behavior of the Chi-NPs, CBZ and DCL were used in single point adsorption experiments. An adsorption capacity of up to 351.8mgg−1 DCL for low MW Chi-NPs was observed and all Chi-NPs showed superior adsorptions when compared to untreated Chi.

Chitosan pretreatment for cotton dyeing with black tea

Chitosan is used in a wide range of applications due to its intrinsic properties. Chitosan is a biopolymer obtained from chitin and among their most important aspects highlights its bonding with cotton and its antibacterial properties. In this study two different molecular weight chitosan are used in the dyeing process of cotton with black tea to evaluate its influence. In order to evaluate the effect of the pretreatment with chitosan, DSC and reflection spectrophotometer analysis are performed. The curing temperature is evaluated by the DSC analysis of cotton fabric treated with 15 g/L of chitosan, whilst the enhancement of the dyeing is evaluated by the colorimetric coordinates and the K/S value obtained spectrophotometrically. This study shows the extent of improvement of the pretreatment with chitosan in dyeing with natural products as black tea.

Preperation of nanochitosan from radiation degraded oligochitosan for shelf life extension of strawberry

Oligochitosans (OCT) were prepared from chitosan (CTS) by gamma irradiation technique. The parameters affecting to the chitosan degradation were studied. And then, OCT nanoparticles wereformed using the method of tripolyphosphate (TPP) cross-linking. Effect of concentration and molecular weight of OCT, concentration of TPP on particle size of the formed OCT nanoparticles were also studied. The formation of OCT nanoparticles was verified by Fourier transform infrared (FT-IR) spectrometer and differential scanning calorimeter (DSC), the morphology was observed using scanning electron microscope (SEM), and the characteristics (particle size and zeta potential) of OCT nanoparticles were also studied. The effect of OCT nanoparticles on strawberry presevation was carried out using the coating method. Results showed that an increase in radiation dose resulted in a decrease of chitosan molecular weight. The OCT with molecular weight of approximately 7.7 kDa was obtained by the synergistic effect of hydrogen peroxide (5 %, v/v) and gamma ray at dose of 30 kGy. The smaller OCT nanoparticles was obtained with a lower molecular weight of OCT. The results of FTIR, DSC indicated the success in the formation of OCT nanoparticles with the particle size approximately 129.9 nm, with the spherical shape. The application of OCT nanoparticles on strawberry has prolonged the preservation times approximately 2.5 times higher comp

Effects of chitosan molecular weight on the physical and dissolution characteristics of amorphous curcumin–chitosan nanoparticle complex

Objective: To investigate the effects of varying molecular weight (MW) of chitosan (CHI) used in the complexation with curcumin (CUR) on the physical and dissolution characteristics of the amorphous CUR–CHI nanoparticle complex produced.Significance: Amorphous CUR–CHI nanoparticle complex (or CUR nanoplex in short) recently emerged as a promising bioavailability enhancement strategy of CUR attributed to its fast dissolution, supersaturation generation capability, and simple preparation. Existing CUR nanoplex prepared using low MW CHI, however, exhibited poor colloidal stability during storage. Herein we hypothesized that the colloidal stability could be improved by using CHI of higher MW. The effects of this approach on the nanoplex’s other characteristics were simultaneously investigated.Methods: The CUR nanoplex was prepared by electrostatically driven self-assembled complexation between CUR and oppositely charged CHI of three different MWs (i.e. low, medium, and high). Besides colloidal stability, the effects of MW variation were investigated for the nanoplex’s (1) other physical characteristics (i.e. size, zeta potential, CUR payload, amorphous state stability), (2) preparation efficiency (i.e. CUR utilization rate, yield), and (3) dissolutions under sink condition and supersaturation generation.Results: CUR nanoplex prepared using CHI of high MW exhibited improved colloidal stability, larger size, superior morphology, and prolonged supersaturation generation. On the other hand, the effects of MW variation on the payload, amorphous state stability, preparation efficiency, and dissolution under sink condition were found to be insignificant.Conclusions: Varying MW of CHI used was an effective means to improve certain aspects of the CUR nanoplex characteristics with minimal adverse effects on the others.

One pot synthesis of gold nanoparticles using chitosan with varying degree of deacetylation and molecular weight

Gold nanoparticles (AuNPs) were synthesized in one-step by reducing gold salt using nontoxic and biodegradable chitosan as dual roles of reducing agent and stabilizer. The obtained AuNPs were characterized with UV–vis spectroscopy and transmission electron microscopy. The results indicated that control over the size and shape of AuNPs is achieved through the careful selection of experimental conditions, such as reaction temperature, reaction time, concentration of gold salt and chitosan, and chitosan molecular parameters, i.e., degree of deacetylation (DD) and molecular weight (MW). At low chitosan concentration (0.005% and 0.01% (w/v)), individual spherical AuNPs with average particle size around 10nm were obtained regardless of chitosan DD and MW, while anisotropic AuNPs were obtained at concentration above 0.05% (w/v) for all investigated chitosan at the optimum condition (1mL of 1mmol/L HAuCl4 added to 3mL of chitosan solution reacted for 120min at 70°C). The growth of larger polygonal AuNPs was promoted as the higher concentration and lower DD chitosan was used as reducing agent and stabilizer. Au nanoplate was synthesized by water-soluble chitosan (Mv 566kDa, DD 53%) at concentration above 0.15% (w/v). Chitooligomers (Mv 2.4kDa, DD 94%) showed the highest reduction ability for Au3+ and the synthesized AuNPs exhibited aggregation on morphology. It was considered that chitosan DD and concentration played a more important role than MW in the size and shape of AuNPs.

Aptamer-Based Single-Step Assay by the Fluorescence Enhancement on Electroless Plated Nano Au Substrate.

A new single-step aptamer-based surface-enhanced fluorescent optical sensor is built, by combining an aptamer–target interaction for target recognition and a fluorophore interaction for signal enhancement. The developed aptasensor is simple, sensitive, specific and stable for the detection of thrombin. A new nanometallic Au structure in the range of 100 nm was constructed through effective electroless plating method on a Cu thin film. Cu+ ions act as sacrificial seeds for the reduction of Au2+/3+ ions to form Au nanolawns. In order to utilize the structure for a fluorescence-based sensor, aptamer conjugated with Cy3 was immobilized on the nanogold substrate through electrostatic attraction. The Au substrate was coated with chitosan (molecular weight 1000 Da). Thrombin binding aptamer (TBA) was applied as a model system demonstrating the aptamer-based fluorescence assay on nanogold substrates. Thrice-enhanced fluorescence emission was achieved with Cy3-conjugated TBA stably immobilized on the chitosan-coated Au substrate. The intensity change was proportional to the concentration of thrombin from 10 μM to 10 pM, whereas the intensity change was ignorable for other proteins such as human serum albumin (HSA). Aptamer-based assay benefited from simple immobilization of receptors and Au nanostructure contributed in building an effective surface enhancing/positively charged substrate was proved. Such an aptasensor holding high utilities for point-of-care devices by incorporating simplicity, sensitivity and selectivity in detection, low-cost for test, small sample volumes has been developed.

Production of chitin and chitosan from the exoskeleton of adult two‐spotted field crickets (Gryllus bimaculatus)

AbstractChitin and chitosan were extracted from all specimens of Type I and II two‐spotted field crickets (Gryllus bimaculatus) following chemical treatment with an acid and alkali. For chitin extraction, 2 N HCl and 1.25 N NaOH solutions were used to achieve demineralization and deproteinization, respectively. For chitosan extraction, 50 % NaOH (w/v) and 50 % NaOH (w/w) solutions were used to achieve deacetylation. Chitosan yielded from adult exoskeletons of G. bimaculatus in Test A of Type I was 1.76 and 8.40 % on a fresh weight (FW) and dry weight (DW) basis, respectively, after treatment with 50 % NaOH (w/v) at 95°C for 3 h. Furthermore, the chitosan yielded in Test D of Type II was 1.79 and 7.06 % on FW and DW basis, respectively, after treatment with 50 % NaOH (w/w) at 105°C for 3 h. The average yield of chitin and chitosan was 2.42 and 1.65 % on a FW basis, and 10.91 and 7.50 % on DW basis, respectively. The deacetylation (%) of chitosan extracted from adult exoskeletons in Tests A, B, C1, C2, D1, and D2 were 81.2 %, 14.5 %, 19.6 %, 90.7 %, 17.1 %, and 95.5 %, respectively. The viscosities of the chitosans extracted from adult exoskeletons in Tests A, C2, and D2 were 32.0, 21.6, and 62.4 cP (centi Poise), respectively. The molecular weight of chitosan from adult exoskeletons of G. bimaculatus was 308.3 kDa. Our results indicate that adult exoskeletons of G. bimaculatus could be used as a source of chitin and chitosan for use as functional additives in industrial animal feeds.

Electrochemical Characterization of Chitosan Films As Proton-Conducting Layers for Bioprotonic Devices

We describe the lithographic fabrication, electrochemical characterization, and modeling of bioprotonic conduction channels, using a proof-of-concept material, chitosan, as a proton-conducting film deposited onto palladium electrodes. Linear sweep voltammetry (LSV) has been used to probe both the electrochemical generation of protons from H2 feed gas and the conduction of those protons through channels fabricated with different molecular weights of chitosan. Higher MW chitosan produces channels with significantly higher proton conductivity. Additionally, rigorous evaluation of the LSV data by both standard electroanalytical expressions and by digital simulation reveal that proton generation at the PdHx electrodes varies substantially between devices of different geometries. Multiple hydrogen oxidation reaction (HOR) pathways are operational at some devices, while at others a single pathway dominates. The analyses reveal the sensitivity of proton-generation kinetics on the chitosan/PdHxinterface, and furthermore, to the geometry of the device itself. Simulations of the proton conductivity in the chitosan membrane, however, yields excellent agreement between devices. Direct measurement of proton conductivity using electrochemical impedance spectroscopy further corroborates this agreement, yielding proton conductivity values nearly identical to those determined by analysis of the LSV results. This work is supported by the Office of Naval Research.

Conditioning of Synthetic Sludge and Anaerobically Digested Sludge Using Chitosan, Organic Polyelectrolytes and Inorganic Metal Cations to Enhance Sludge Dewaterability

Anaerobic digestion (AD) and dewatering are the most common and widely applied sludge treatment methods in wastewater treatment plants (WWTPs). However, sludge dewatering has been recognised as one of the most expensive and least understood processes. Therefore, this study investigated the dewatering performance of synthetic sludge in comparison with anaerobically digested sludge when conditioned with chitosan, organic polyelectrolytes and inorganic metal cations. Capillary suction time (CST), turbidity, electrical conductivity, zeta potential, cake solids content and particle size were used to assess sludge dewatering performance and to determine the optimum conditioner dose. The effectiveness of sludge conditioning was evaluated by batch experiments using a series of 250-mL jar test beakers. Both synthetic sludge and AD sludge exhibited similar trend but little different extent of dewaterability when conditioned with low molecular weight (MW) chitosan. The low MW and medium MW chitosans, commercial cationic polyelectrolytes and trivalent metal cations (Al3+, Fe3+) demonstrated as effective conditioning agents with good sludge dewaterability. When assessing the dewaterability measurement parameters using synthetic sludge, the optimal dosage was found at the range of 15 to 20 g-chitosan/kg-dry sludge where the values of CST, turbidity and cake solids content were attained between 6.6 and 11.0 s, 35.4–40.6 NTU, and 24.3–25.3%, respectively. The application of cationic polyelectrolytes and trivalent metal cations generally improved the sludge dewaterability via charge neutralisation and polymer bridging. This study also demonstrated that less complex chemically controlled synthetic sludge can be used for studying the final properties of complex real digested sludge.

Stability and binding affinity of DNA/chitosan complexes by polyanion competition

The stability of DNA/chitosan complexes upon exposure to hyaluronic acid, chondroitin sulfate, and heparin, was assessed by fluorescence spectroscopy to quantify DNA release. Only the highly charged heparin was found to release DNA from the complexes. Complex stability upon exposure to heparin increased with the degree of deacetylation and molecular weight of chitosan and with the ratio of chitosan amino groups to DNA phosphate groups (N/P ratio) in the complexes. Isothermal titration microcalorimetry revealed that among polyanions tested, only heparin has a binding affinity to chitosan approaching that of DNA and can therefore release DNA from the complexes. These results also indicate that anionic components with sufficiently high charge density can induce extracellular or intracellular release of DNA, the former negatively affecting delivery efficiency while the latter is required for gene transfer to occur. Our findings also suggest that increased N/P ratio of the complexes can play an important role in preventing premature dissociation of DNA/polycation complexes upon interaction with anionic components in extracellular milieu.

Chitosans inhibit the growth and the adhesion of Klebsiella pneumoniae and Escherichia coli clinical isolates on urinary catheters

ObjectiveThe aim of this study was to determine the antimicrobial activity of different chitosans (CS) against typical colonizing pathogens of the urinary tract and to assess their efficacy against bacterial adhesion and the subsequent biofilm formation on urinary catheters. MethodsThe antimicrobial activity of high and low molecular weight CS (50 and 150 kDa) at pH 5.0 and 6.0 was tested against Klebsiella pneumoniae and Escherichia coli clinical isolates by time–kill studies. The anti-adhesion assays on Foley urinary catheters were performed in Artificial Urine Medium (AUM) with the addition of each CS (AUM-CS) at the same pH values. Finally, the efficacy over time of chitosan treatments on bacterial adhesion on urinary catheters was determined. ResultsA viability reduction of K. pneumoniae and E. coli isolates, regardless of pH value, was evidenced in time–kill studies, in particular in the presence of CS 50 kDa. As regards the anti-adhesion efficacy on urinary catheters, high and low molecular weight CS evidenced a higher efficacy to reduce bacterial adhesion at pH 5.0. A low number of viable K. pneumoniae and E. coli cells were recovered from catheters after CS treatments, highlighting a promising efficacy over time. ConclusionOur data show the potential of chitosans to reduce or prevent not only the adhesion of well-known human uropathogens on urinary catheters but also the re-growth ability of the uropathogens.

Effective flocculation of Chlorella vulgaris using chitosan with zeta potential measurement

Microalgae are considered as one promising source of third-generation biofuels due to their fast growth rates, potentially higher yield rates and wide ranges of growth conditions. However, the extremely low biomass concentration in microalgae cultures presents a great challenge to the harvesting of microalgae because a large volume of water needs to be removed to obtain dry microalgal cells for the subsequent oil extraction process. In this study, the fresh water microalgae Chlorella vulgaris (C. vulgaris) was effectively harvested using both low molecular weight (MW) and high MW chitosan flocculants. The flocculation efficiency was evaluated by physical appearance, supernatant absorbance, zeta potential and solids content after centrifugal dewatering. High flocculation efficiency of 98.0-99.0% was achieved at the optimal dosage of 30-40 mg/g with formation of large microalgae flocs. This study suggests that the polymer bridging mechanism was governing the flocculation behaviour of C. vulgaris using high MW chitosan. Besides, charge patch neutralisation mechanism prevailed at low MW chitosan where lower dosage was sufficient to reach near-zero zeta potential compared with the high MW chitosan. The amount of chitosan polymer present in the culture may also affect the mechanism of flocculation.