Chitosan-based thin films were assembled using the layer-by-layer technique, and the axial composition was accessed using X-ray photoelectron spectroscopy with depth profiling. Chitosan (CHI) samples ...possessing different degrees of acetylation ( D A ̅ ) and molecular weight ( M v ̅ ) produced via the ultrasound-assisted deacetylation reaction were used in this study along with two different polyanions, namely, sodium polystyrenesulfonate (PSS) and carboxymethylcellulose (CMC). When chitosan, a positively charged polymer in aqueous acid medium, was combined with a strong polyanion (PSS), the total positive charge of chitosan, directly related to its D A ̅ , was the key factor affecting the film formation. However, for CMC/CHI films, the pH of the medium and M v ̅ of chitosan strongly affected the film structure and composition. Consequently, the structure and the axial composition of chitosan-based films can be finely adjusted by choosing the polyanion and defining the chitosan to be used according to its DA and M v ̅ for the desired application, as demonstrated by the antibacterial tests.
Recently the squid pens, a rich source of β-chitin containing low contents of inorganic compounds, have become available in considerable amounts as a refuse of the fishery industries in Brazil. Thus, ...the aim of this work is to use squid pens from
Loligo sanpaulensis and
Loligo plei, species found in the Brazilian coast, as the raw material for the extraction of β-chitin. The squid pens were submitted to the usual sequence of treatments used for chitin extraction – demineralization and deproteinization – but due to its low content of inorganic compounds a two-step alkaline treatment was enough to produce β-chitin with low contents of ash (⩽0.7%). Indeed, the low contents of ash and metals, such as Ca (⩽10.4
ppm), Mg (⩽2.5
ppm), Mn (⩽3.1
ppm) and Fe (⩽1.8
ppm), are lower than those reported in most of the papers found in the literature. Also, the β-chitin extracted by employing only the alkaline treatment was more acetylated than the other samples prepared in this work. Regardless of the treatment employed for the extraction of the β-chitin from the squid pens, its infrared spectra and X-ray diffraction pattern presented only minor differences, however they were clearly distinguished from commercial α-chitin.
Langmuir monolayers are used to simulate the biological membrane environment, acting as a mimetic system of the outer or the inner membrane leaflet. Herein, we analyze the interaction of membrane ...models with a partially N-acetylated chitosan (Ch35%) possessing a quasi-ideal random pattern of acetylation, full water solubility up to pH ≈ 8.5 and unusually high weight average molecular weight. Lipid monolayers containing dipalmitoyl phosphatidyl choline (DPPC), dipalmitoyl phosphatidyl ethalonamine (DPPE), dipalmitoyl phosphatidyl glycerol (DPPG) or E. coli total lipid extract were spread onto subphases buffered at pH 4.5 or 7.4. The incorporation of Ch35% chitosan caused monolayer expansion and a general trend of decreasing monolayer rigidity with Ch35% concentration. Due to its relatively high content of N-acetylglucosamine (GlcNAc) units, Ch35% interactions with negatively charged monolayers and with E. coli extract were weaker than those involving zwitterionic monolayers or lipid rafts. While the smaller interaction with negatively charged lipids was unexpected, this finding can be attributed to the degree of acetylation (35%) which imparts a small number of charged groups for Ch35% to interact. Chitosan properties are therefore determinant for interactions with model cell membranes, which explains the variability in chitosan bactericide activity in the literature. This is the first study on the effects from chitosans on realistic models of bacterial membranes under physiological pH.
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•Chitosan interacts with bacterial lipid monolayers at physiological pH.•Effects of chitosan included monolayer expansion and change in fluidity.•Monolayers with charged lipids were less affected by chitosan.•Acetylation degree impacts interactions and applicability of chitosans.
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•The effects from chitosans on Langmuir monolayers with lipid raft compositions than with neat phospholipids.•Interactions were studied for chitosans soluble at physiological ...pH.•Changes in membrane packing and fluidity were observed at much lower concentrations at acid and physiological media.
Langmuir monolayers have been used as cell membrane models, where lipid composition is normally varied to mimic distinct types of membranes. For eukaryotic membranes, for instance, rather than using only zwitterionic phospholipids there is now a trend to employ mixtures to simulate the lipid rafts known to be relevant for various cellular processes. In this study, we demonstrate that effects from chitosans on Langmuir monolayers are considerably higher if lipid raft compositions (ternary mixtures of dipalmitoyl phosphatidyl choline (DPPC), sphingomyelin (SM) and cholesterol) are used. Significantly, measurable effects on the surface pressure isotherms start at 10-6 mg mL-1 for chitosans in lipid rafts, to be compared with 10-2 mg mL-1 for neat dipalmitoyl phosphatidylcholine (DPPC). This applies to both a commercial chitosan and chitosans soluble at physiological pH. Incorporation of these chitosans in the raft monolayers was confirmed in polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) experiments, where both the tail groups and headgroups were found to interact with chitosan. Since the effects on membrane models may be observed at such small concentrations for chitosans and probably other molecules, some studies may have to be revisited where neat phospholipids should be replaced by lipid raft compositions.
Low molecular weight chitosan has a stronger effect on phospholipid membrane models which represent mammalian (DPPC) and bacterial (DPPG) membranes.
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•The model explaining interaction ...between chitosan and DMPA is also valid for DPPC and DPPG monolayers.•Low molecular weight chitosans interact more strongly with DPPC and DPPG monolayers.•Penetration into the hydrophobic chains was confirmed with PM-IRRAS and SFG data.•Chitosan-rich and lipid-rich condensed domains are formed with chitosan incorporation.•Rh for LMWChi is smaller than for Chi which explains its easier access to hydrophobic tails.
The interaction between chitosans and Langmuir monolayers mimicking cell membranes has been explained with an empirical scheme based on electrostatic and hydrophobic forces, but so far this has been tested only for dimyristoyl phosphatidic acid (DMPA). In this paper, we show that the mode of action in such a scheme is also valid for dipalmitoyl phosphatidyl choline (DPPC) and dipalmitoyl phosphatidyl glycerol (DPPG), whose monolayers were expanded and their compressibility modulus decreased by interacting with chitosans. In general, the effects were stronger for the negatively charged DPPG in comparison to DPPC, and for the low molecular weight chitosan (LMWChi) which was better able to penetrate into the hydrophobic chains than the high molecular weight chitosan (Chi). Penetration into the hydrophobic chains was confirmed with polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) and sum frequency generation (SFG) spectroscopy. A slight reduction in conformational order of the lipid chains induced by the chitosans was quantitatively estimated by measuring the ratio between the intensities of the methyl (r+) and methylene (d+) peaks in the SFG spectra for DPPG. The ratio decreased from 35.6 for the closely packed DPPG monolayer to 7.0 and 6.6 for monolayers containing Chi and LMWChi, respectively. Since in both cases there was a significant phospholipid monolayer expansion, the incorporation of chitosans led to chitosan-rich and lipid-rich condensed domains, which mantained conformational order for their hydrophobic tails. The stronger effects from LMWChi are ascribed to an easier access to the hydrophobic tails, as corroborated by measuring aggregation in solution with dynamic light scattering, where the hydrodynamic radius for LMWChi was close to half of that for Chi. Taken together, the results presented here confirm that the same mode of action applies to different phospholipids that are important constituents of mammalian (DPPC) and bacterial (DPPG) cell membranes.
•3,6-O,O’-dimyristoyl chitosan (DMCh) micelles exhibits a great capacity of CPT solubilization and encapsulation.•DMCh micelles present a sustained release under gastrointestinal conditions.•CPT ...encapsulation into DMCh micelles decreases the drug toxicity.•Micelles enable the increase of CPT permeability across intestinal barrier.
The aim of this work was to investigate the potential of a new 3,6-O,O’-dimyristoyl derivative amphiphilic chitosan (DMCh), in improving the solubility of camptothecin (CPT), a hydrophobic anticancer drug, and its potential oral delivery. FTIR, 1H NMR and solid-state 13C NMR spectroscopy were used to characterize DMCh and to determine its average degree of substitution (DS¯=6.8%). DMCh/CPT micelles size ranged from (281–357nm), zeta potential (+32–50mV) of encapsulation efficiency of 42–100%. The in vitro cell viability showed that DMCh/CPT micelles were able to reduce the toxicity of CPT. The in vitro permeability of CPT through Caco-2 and Caco-2/HT29-MTX intestinal models was increased up to ten fold when formulated into DMCh micelles, underlining the mucoadhesive properties of the nanocarrier. DMCh/CPT micelles are able to enhance CPT solubility and bioavailability while reduce its cytotoxicity, showing the great potential for intestinal delivery of hydrophobic drugs.
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•A new 3,6-O,O’- dimyristoyl chitosan (DMC) derivative was synthesized and characterized.•DMC micelles were obtained and promoted PTX solubilization.•The derivative polymer and DMC ...micelles presented good biocompatibility in cytotoxicity studies.•The drug in vitro permeability was evaluated in different cell models.
The aim of the present study was to investigate the potential application of 3,6-O,O’- dimyristoyl chitosan DMCh, an amphiphilic derivative of chitosan, for improving the oral bioavailability of paclitaxel (PTX), a water insoluble anticancer drug. The O-acylation of chitosan with myristoyl chloride was carried out by employing high (≈13.3) or low (2.0) molar excess of chitosan to result in samples DMCh07 and DMCh12, respectively. The successful O-acylation of chitosan was confirmed by FTIR and 1H NMR spectroscopy, the latter allowing also the determination of average degree of substitution (DS). The critical aggregation concentration (CAC) of samples DMCh07 (DS≈6.8%) and DMCh12 (DS≈12.0%) were 8.9×10−3mg/mL and 13.2×103mg/mL, respectively. It was observed by TEM that the DMCh micelles showed spherical shape while DLS measurements allowed the determination of their average size (287nm–490nm) and zeta potential (+32mV to +44mV). Such DMCh micelles were able to encapsulate paclitaxel with high drug encapsulation efficiency (EE), as confirmed by HPLC analyses. Studies on the cytotoxicity of DMCh07 micelles toward Caco-2 and HT29-MTX cells showed that, regardless the PTX loaded, DMCh07 micelles slightly decreased cellular viability at low micelles concentration (≤1μg/mL) while at high concentration (>10μg/mL) PTX-loaded DMCh07 micelles were less toxic toward Caco-2 cells when compared to free PTX. The PTX permeation across Caco-2 monoculture and Caco-2/HT29-MTX co-culture model confirmed the potential of DMCh micelles in improving the intestinal absorption of PTX. These results suggest that DMCh micelles may be a promising carrier to encapsulate PTX aiming cancer therapy.
An amphiphilic derivative of chitosan containing quaternary ammonium and myristoyl groups, herein named as ammonium myristoyl chitosan (DMCat), was synthesized by reacting glycidyltrimethylammonium ...chloride (GTMAC) and myristoyl chitosan (DMCh). The success of the modification was confirmed using Fourier-transform infrared spectroscopy (FTIR) and ¹H nuclear magnetic resonance (NMR) spectroscopy. The average degrees of alkylation and quaternization ( D Q ¯ ) were determined by using ¹H NMR and conductometric titration. The zeta potential of the micelles was higher than 28 mV while its average size and encapsulation efficiency ranged from 280 nm to 375 nm and 68% to 100%, respectively. The in vitro cytotoxicity of the unloaded and curcumin (CUR)-loaded micelles was tested against Caco-2 and HT29-MTX intestinal epithelial cell lines. The results showed no cytotoxic effect from loaded and unloaded micelles as compared to free CUR. In the permeability test, it was observed that both types of micelles, i.e., DMCh and DMCat, improved CUR permeability. Additionally, higher permeability was verified for both systems in Caco-2/HT29-MTX:Raji B because of the mucoadhesive character of chitosan and its ability to open tight junctions. The results indicated that DMCat micelles, due to the physico-chemical, improved characteristics may be a promising carrier to encapsulate CUR aiming cancer therapy.
The development and application of a functionalized carbon nanotubes paste electrode (CNPE) modified with crosslinked chitosan for determination of Cu(II) in industrial wastewater, natural water and ...human urine samples by linear scan anodic stripping voltammetry (LSASV) are described. Different electrodes were constructed using chitosan and chitosan crosslinked with glutaraldehyde (CTS-GA) and epichlorohydrin (CTS-ECH). The best voltammetric response for Cu(II) was obtained with a paste composition of 65% (m/m) of functionalized carbon nanotubes, 15% (m/m) of CTS-ECH, and 20% (m/m) of mineral oil using a solution of 0.05
mol
L
−1 KNO
3 with pH adjusted to 2.25 with HNO
3, an accumulation potential of −0.3
V
vs. Ag/AgCl (3.0
mol
L
−1 KCl) for 300
s and a scan rate of 100
mV
s
−1. Under these optimal experimental conditions, the voltammetric response was linearly dependent on the Cu(II) concentration in the range from 7.90
×
10
−8 to 1.60
×
10
−5
mol
L
−1 with a detection limit of 1.00
×
10
−8
mol
L
−1. The samples analyses were evaluated using the proposed sensor and a good recovery of Cu(II) was obtained with results in the range from 98.0% to 104%. The analysis of industrial wastewater, natural water and human urine samples obtained using the proposed CNPE modified with CTS-ECH electrode and those obtained using a comparative method are in agreement at the 95% confidence level.
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