Tripolyphosphate Cross-linked Chitosan Research Articles

Modeling and characterization of lenalidomide-loaded tripolyphosphate-crosslinked chitosan nanoparticles for anticancer drug delivery

Tripolyphosphate-crosslinked chitosan (TPPCS) nanoparticles were employed in the encapsulation of lenalidomide (LND) using a straightforward ionic cross-linking approach. The primary objectives of this technique were to enhance the bioavailability of LND and mitigate inadequate or overloading of hydrophobic and sparingly soluble drug towards cancer cells. In this context, a quantum chemical model was employed to elucidate the characteristics of TPPCS nanoparticles, aiming to assess the efficiency of these nanocarriers for the anticancer drug LND. Fifteen configurations of TPPCS and LND (TPPCS /LND1-15) were optimized using B3LYP density functional level of theory and PCM model (H2O). AIM analysis revealed that the high drug loading capacity of TPPCS can be attributed to hydrogen bonds, as supported by the average binding energy (168 kJ mol−1). The encouraging theoretical results prompted us to fabricate this drug delivery system and characterize it using advanced analytical techniques. The encapsulation efficiency of LND within the TPPCS was remarkably high, reaching approximately 87 %. Cytotoxicity studies showed that TPPCS/LND nanoparticles are more effective than the LND drug. To sum up, TPPCS/LND nanoparticles improved bioavailability of poorly soluble LND through cancerous cell membrane. In light of this accomplishment, the novel drug delivery route enhances efficiency, allowing for lower therapy doses.

Coating with tripolyphosphate-crosslinked chitosan as a novel approach for enhanced stability of emulsomes following oral administration: Rutin as a model drug with improved anti-hyperlipidemic effect in rats

The aim of the current study is to preserve the emulsomal vesicles against the harsh condition of gastrointestinal tract (GIT), after oral administration, employing tripolyphosphate (TPP)-crosslinked chitosan as a protective coating layer. Rutin was used as a model drug with evaluation of anti-hyperlipidemic activity in rats. The rutin loaded unmodified emulsomes were prepared using tripalmitin and soybean phosphatidylcholine (SPC), by thin film method. Drug loading for the prepared formulations ranged between 6.80 and 15.50 %. The selected formulation (RT-Emuls-6) comprised tripalmitin and SPC, molar ratio 1:1, and exhibited particle size (PS) and zeta potential (ZP) of 150.40 nm and −35.35 mV, respectively. RT-Emuls-6 was then modified by coating with either solely chitosan (RT-Emuls-6-Ch) or TPP-crosslinked chitosan (RT-Emuls-6-Ch-TPP-1). The latter exhibited PS and ZP values of 269.60 nm and 37.17 mV, respectively. Transmission electron microscopy of RT-Emuls-6-Ch-TPP-1 showed a dense pale greyish layer of a coating layer of chitosan crosslinked with TPP surrounding SPC bilayers. Fourier transform infrared spectroscopy analysis along with X-ray powder diffraction confirmed cross-linking between chitosan and TPP. Stability study in the simulated GIT fluids revealed that the order of rutin retained percentage was RT-Emuls-6-Ch-TPP-1 > RT-Emuls-6-Ch > RT-Emuls-6 (80.02, 50.66 and 44.41 %, respectively for simulated gastric fluid and 63.50, 55.66 and 24.00 %, respectively for simulated intestinal fluid, after 2 h incubation). Anti-hyperlipidemic activity of rutin loaded emulsomes was evaluated, after oral administration, in a high fat diet-induced hyperlipidemia in rats. The order of activity was as follows: RT-Emuls-6-Ch-TPP-1 > RT-Emuls-6-Ch > RT-Emuls-6 > free rutin. These findings revealed the potential of TPP-crosslinked chitosan as a protective coating layer for enhancing the stability of emulsomes against the harsh condition of GIT. RT-Emuls-6-Ch-TPP-1 had a potent anti-hyperlipidemic activity via regulation of lipids, oxidative stress, irisin and uncoupling protein 1.

Fabrication and investigation of novel monochloroacetic acid fortified, tripolyphosphate-crosslinked chitosan for highly efficient adsorption of uranyl ions from radioactive effluents

Chitosan crosslinked with potassium tripolyphosphate (CTPP) and monochloroacetic-acid-modified chitosan crosslinked with potassium tripolyphosphate (MCTPP) were synthesized for removing UO22+ from acidic radioactive effluents. The influential factors, operational requirements, and interactive mechanisms of the adsorption process were systematically investigated. The mesh-structured composites adsorbed UO22+ most effectively at pH 5.0. The maximum adsorption capacities for pure chitosan, CTPP, and MCTPP were 374.93, 780.89, and 1487.72 mg/g, respectively. Batch experiments indicated that the pH and adsorbent dose strongly influenced UO22+ adsorption. MCTPP could adsorb most UO22+ within 15 min, and equilibrium was reached by ~1 h. The adsorption isotherms indicated that UO22+ adsorption by MCTPP may be an endothermic single-layer adsorption process. Moreover, common metal ions in single-metal systems only slightly affected this process. The results of instrumental characterization and natural water application suggested that the highly developed pore structure and abundant tripolyphosphate groups in synthesized composites were dominant adsorption contributors besides amino and hydroxyl groups. Successful development of the novel material for efficiently adsorbing UO22+ and identification of the adsorption mechanism will provide valuable guidance to chitosan modification and further remediation practices of radioactive effluents.

Epichlorohydrin and tripolyphosphate-crosslinked chitosan–kaolin composite for Auramine O dye removal from aqueous solutions: Experimental study and DFT calculations

Chitosan (Ch, a natural polymer) and kaolin (K, a natural mineral) composite (Ch-K) was produced with the help of two crosslinkers, epichlorohydrin and tripolyphosphate, and then moulded into uniform beads in tripolyphosphate solution. The synthesis was proved by the analyses involving FT-IR and SEM-EDX. The beads were then used as the natural adsorbent for removal of the auramine O (AO), a frequently-used industrial dye, in aqueous solutions. Adsorbent performance of the Ch-K composite for AO dye molecules was optimized: 500 mg L−1 at pH 7.5 at 25 °C. The Langmuir model found 0.118 mol kg−1 for the maximum adsorption capacity of the Ch-K and the D-R isotherm model showed that the nature of the adsorption process was physical. Kinetics of the adsorption could be explained by using both IPD (intraparticle diffusion) and PSO (pseudo second order) models. Thermodynamic parameters demonstrated that the behaviour of the adsorption was an endothermic and spontaneous. The activity of the composite adsorbent was recovered (88%) after the five sequential adsorption/desorption cycles. Supported by experimental findings, the results obtained from in silico modeling at M06-2X/6–31+G (d,p) level helped hypothesise a mechanism for the formation of the Ch-K composite, and shed some light onto the adsorption behaviour of AO dye by assuming several favourable intermolecular interactions.

Synthesis, Characterization, Antioxidant Activity, and Toxicity Properties of Tripolyphosphate Crosslinked Chitosan

Chitosan is biopolymer obtained from chitin deacetylation reaction. Chitin is a constituent of shrimps’ outer shell. Chitosan modification using crosslinker agent could increase the active groups and stabilize the physical character. One of non-toxic crosslink agents was tripolyphosphate. This study aimed at synthesizing tripolyphosphate crosslinked chitosan (TPP-Cs) to test the antioxidant and toxicity. Synthesizing tripolyphosphate chitosan was conducted using ionic gelation method. The antioxidant activity test was studied from DPPH radicals scavenging and the ability to inhibit linoleic acid oxidation. The toxicity test was using BSLT (Brine Shrimp Lethality Test) method and Artemia salina leach nauplii. The study showed that TPP-Cs could be synthesized from pink shrimp and showed antioxidant activity. The activity was due to amino and hydroxyl groups. The BSLT method showed that TPP-Cs had the potential to be applied for antibacterial, antivirus, or anticancer products.

Characterization of cross-linked chitosan by ionic and covalent crosslinking agents as wall material of red ginger oleoresin microcapsules

The aim of this study was to determine the characterization of ionic and covalent interactions to form a crosslinking network with chitosan as a wall material of microcapsules. Red ginger oleoresin microcapsule was prepared by emulsion crosslinking method. Red ginger oleoresin was mixed and stirred with chitosan solution to form an emulsion, then added to corn oil and stirred again to form a second emulsion. Crosslinking agents of glutaraldehyde saturated toluene (GST) or sodium tripolyphosphate (TPP) solution was slowly added to the emulsion. When using a crosslinking agent of TPP solution was added glacial acetic acid to adjust pH. Red ginger oleoresin microcapsules were filtered and washed with petroleum ether followed by n-hexane and then dried in an oven. Microcapsules from chitosan that are cross-linked with GST produce higher yield and size of microcapsules compared to TPP. Whereas, the highest encapsulation efficiency produced from chitosan cross-linked with TPP was 91.63±0.02%. Meanwhile, the highest cumulative release was obtained from TPP cross-linked chitosan microcapsules of 63.71% and the lowest was 50.01% from chitosan microcapsules that cross-linked with GST. The conclusion of this study was the differences between ionic and covalent crosslinking agents produce different microcapsule characteristics. Microcapsules from chitosan cross-linked with GST generated more compact with a smoother surface than with TPP.

Chitosan and crosslinked chitosan nanoparticles: Synthesis, characterization and their role as Pickering emulsifiers

Chitosan has been modified in order to produce nanoparticles with promising characteristics in diverse food applications, e.g. Pickering emulsions. Chitosan deprotonation and ionic crosslinking with tripolyphosphate were assessed in this work. Chitosan nanoparticles produced by these two methods were characterized according to surface charge, particle size distribution, chemical structure, wettability and microstructure imaging. The nanoparticles’ performance in the formation of oil-in-water Pickering emulsions was studied by physicochemical and rheological assays. Chitosan nanoparticles produced by amino deprotonation were larger and resulted in emulsions with larger oil droplets, with rheological behavior of the emulsions being greatly affected by increasing concentration of chitosan, which formed a network structure in the continuous phase. On the contrary, the tripolyphosphate-crosslinked chitosan nanoparticles were smaller and produced emulsions with smaller droplets, which remained less viscous even when chitosan concentration was increased and showed evidences of Pickering stabilization when analyzed by microscopy techniques.

Study on the relationship between crosslinking degree and properties of TPP crosslinked chitosan nanoparticles

In order to reveal the relationship between the degree of crosslinking and the properties of chitosan nanoparticles, a potassium polyvinyl sulfate (PVSK) titration method was established for the determination of free amino group in chitosan, which showed that there was a window effect in the crosslinking degree and particle size of three kinds of molecular weight chitosan cross-linked by different content of tripolyphosphate (TPP), and the nanoparticles with moderate crosslinking degree were smaller. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) showed the moderate degree of cross-linking nanoparticles had strong antibacterial properties. IR analysis showed that the interaction between chitosan nanoparticles with different crosslinking degree and TPP were different. X-ray diffraction analysis showed that the cross-linked chitosan nanoparticles were amorphous. Above all, the crosslinking degree of TPP cross-linked chitosan nanoparticles was related to the particle size and antibacterial properties.

Removal of Cadmium (II) from aqueous solution using tripolyphosphate cross-linked chitosan

Finding an economical technique for Cadmium (Cd (II)) removal from aqueous solution through an environmentally friendly method has always been of great importance. To this aim, chitosan and sodium tripolyphosphate cross-linked chitosan beads were prepared for Cd (II) uptake from aqueous media. Chitosan with different cross-linking ratio was synthesized via changing the concentration of sodium tripolyphosphate solution (5, 10, and 15 % (w/v)). Fourier-transform infrared spectroscopy (FT-IR) and X-ray diffraction were then implemented to characterize chitosan and tripolyphosphate cross-linked chitosan beads. Investigating thermodynamic parameters proved the feasibility and spontaneity (ΔG0>0), endothermic nature (ΔH0>0) and randomness increase at solid/solution interface (ΔS0>0) of the adsorbents. The experimental adsorption data for cross-linked chitosan were fitted to isotherm models out of which the Langmuir model showed the best fit. Lastly, factors influencing Cd (II) adsorption onto adsorbents, including temperature and crosslinking extent, were studied in detail by employing Response Surface Methodology (RSM). The quadratic regression model was in good agreement with experimental data (R2 = 0.95). The designed model suggested that the maximum adsorption capacity of 99.87 (mg/g) is achievable at 55 ℃ and 2.92 % (w/v) crosslinking degree, which was higher than the frequent cross-linked chitosans investigated by other researchers.

Synthesis and characterization of chitosan nanoparticles containing teicoplanin using sol–gel

Chitosan, as a natural polysaccharide, has a unique structure and multi-functional properties. One of the most prominent specifications of chitosan is high biocompatibility, good biodegradability, low toxicity and antibacterial and antiallergenicity properties. Chitosan has a high potential for controlled drug delivery. Therefore, investigating the loading capacity and release rate of chitosan at different conditions is important. By reducing particle size, chitosan has shown a high ability of teicoplanin loading due to its cationic property, which is important in this research. The aim of this study was to investigate chitosan nanoparticle potential for use in biomedical devices for drug delivery systems. Nanoparticles were prepared by ionic gelation with tripolyphosphate (TPP) ion, and the factors that affected chitosan nanoparticle size were investigated. The prepared samples were characterized using DLS, FTIR, TGA, DSC and XRD techniques. It is found at best condition with CS/TPP ratio of 2:1 nanoparticles were obtained at an average size of about 100 nm. The results confirmed that the drug (teicoplanin) loaded on the TPP cross-linked chitosan nanoparticles causes an increase in nanochitosan size and there was no interaction between teicoplanin and chitosan. Also, it is observed that 28.2% of teicoplanin was released in the first 10 h and the release is continued gradually to receive 37.4% in 100 h. Thus, it seems that chitosan nanoparticles mitigate the drug release and are suitable for sustained drug release.

Permeability improvement of polyethersulfone-polietylene glycol (PEG-PES) flat sheet type membranes by tripolyphosphate-crosslinked chitosan (TPP-CS) coating

In this study, improvement of urea and creatinine permeability of polyethersulfone (PES) membrane by coating with synthesized tripolyphosphate-crosslinked chitosan (TPP-CS) has been conducted. Original and modified membranes, e.g. pristine PES, polyethersulfone-polyethylene glycol (PES-PEG) and PES-PEG/TPP-CS membranes were characterized using FTIR, DTG, SEM, AFM, water uptake, contact angles, porosity measurement, tensile strength test and permeation tests against urea and creatinine. The results show that the PES modification by TPP-CS coating has been successfully carried out. The water uptake ability, hydrophilicity and porosity of the modified membranes increase significantly to a greater degree. All modified membranes have good thermal stability and tensile strength and their permeation ability towards urea and creatinine increase with the increasing concentration of TPP-CS. PES membrane has urea clearance ability of 7.36 mg/dL and creatinine of 0.014 mg/dL; membrane PES-PEG shows urea clearance of 11.87 mg/dL and creatinine of 0.32 mg/dL; while PES-PEG/TPP-CS membrane gives urea clearance of 20.87–36.40 mg/dL and creatinine in the range of 0.52–0.78 mg/dL. These results suggest that the PES-PEG membrane coated with TPP-CS is superior and can be used as potential material for hemodialysis membrane.

Fabrication and in vitro biocompatibility of sodium tripolyphosphate-crosslinked chitosan–hydroxyapatite scaffolds for bone regeneration

The aims of this study were to fabricate a novel chitosan–hydroxyapatite (CHA) scaffold crosslinked with sodium tripolyphosphate (TPP) and evaluate its in vitro biocompatibility. CHA scaffolds were fabricated via direct blending and lyophilization and further crosslinked with different concentrations (0.1 M, 0.2 M and 0.4 M) of TPP. Microstructure of TPP-CHA scaffolds was examined by using field emission scanning electron microscope. Porosity and compressive modulus of composite scaffolds were analyzed. The biodegradability of TPP-crosslinked CHA scaffolds was studied for 30 days and in vitro biocompatibility and functionality were evaluated using osteoblast-like cells, MG63, in terms of cell viability, adhesion, proliferation and early differentiation. All scaffolds showed an interconnected honeycomb-like microstructure except 0.4 M TPP-CHA scaffolds, which demonstrated the most compact and least porous structure with pore sizes of 62–185 µm. In contrast, 0.1 M TPP-CHA scaffolds exhibited the highest porosity, measured as 58.6% and pore sizes of 74–207 µm. Besides, 0.1 M TPP-CHA scaffolds also showed the lowest compressive modulus of 2.54 kPa. All TPP-crosslinked CHA scaffolds degraded to a similar extent (1.93–5.03%). Current findings revealed that 0.1 M TPP-CHA scaffolds are the most biocompatible one by promoting good cell viability with the highest adhesion, proliferation and early differentiation activities on MG63 cells among the other scaffolds. In conclusion, 0.1 M TPP-CHA scaffolds exhibited the most promising physiochemical and biocompatible properties which can be used as an alternative regenerative material for bone tissue engineering.

Sodium tripolyphosphate cross-linked chitosan based sensor for enhacing sensing properties towards acetone

In this report, sensing properties of sodium tripolyphosphate (TPP) cross-linked chitosan based sensor has been successfully enhanced towards acetone. Chitosan solutions were cross-linked with sodium TPP in variation of 0.1%, 0.5%, 1% and 1.5% w/v, respectively. The sensors were fabricated in film form using an electrochemical deposition method. The sensing properties of the sensors were observed by exposing the pure chitosan and sodium TPP cross-linked chitosan sensors towards acetone concentrations of 5, 10, 50, 100 and 200 ppm. The measurement results revealed that the maximum response in output voltage value of pure chitosan sensor was 0.35 V while sodium TPP crosslinked chitosan sensors were above 0.35 V towards 5 ppm acetone concentration. When the sensors were exposed towards acetone concentration of 200 ppm, the maximum response of pure chitosan was 0.45 V while sodium TPP crosslinked chitosan sensors were above 0.45 V. Amongst the variation of sodium TPP, the maximum response of 1% sodium TPP was the highest since the maximum response was 0.4 V and 0.6 V towards 5 ppm and 200 ppm acetone concentration, respectively. While the maximum responses of other sodium TPP concentrations were under 0.4 V and 0.6 V towards 5 ppm and 200 ppm acetone concentration. Moreover, 1% sodium TPP cross-linked chitosan based sensor showed good reproducibility and outstanding lifetime. Therefore, 1% sodium TPP cross-linked chitosan based sensor has exhibited remarkable sensing properties as a novel acetone sensor.

Development and characterization of hydroxyapatite/β-TCP/chitosan composites for tissue engineering applications

Calcium phosphate ceramics that mimic bone composition provide interesting possibilities for the advancement in bone tissue engineering. The present study reports on a chitosan composite reinforced by hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) obtained from waste mussel shells and cross-linked using tripolyphosphate (TPP). The ratios of the ceramic components in composites were 20/10/70, 30/20/50 and 40/30/30 (HA/β-TCP/CH, w/w %). Biodegradation rate, structural properties and in-vitro degradation of the bone-like composite scaffolds were investigated. The optimum amount of TPP required for composite was 2.5% and glycerol was used as plasticizer at an optimized concentration of 1%. Tripolyphosphate cross-linked chitosan composites were developed by freezing and lyophilisation. The Young's modulus of the scaffolds was increased from 4kPa to 17kPa and the porosity of composites dropped from 85 to 68% by increasing the HA/β-TCP ratio. After 28days in physiological solution, bone-like composite scaffolds with a higher ratio of HA/β-TCP (e.g. 40/30/30) showed about 2% lower biodegradation in comparison to scaffolds with a lower ratio of HA/β-TCP (i.e. 20/10/70). The obtained data suggest that the chitosan based bone-like composites could be potential candidates for biomedical applications.

DESIGN AND IN VITRO EVALUATION OF MULTIPARTICULATE SYSTEM FOR THE CHRONOMODULATED DELIVERY OF LORNOXICAM

In view of chronobiological considerations of rheumatoid arthritis, the present study deals with the design and evaluation of multiparticulate system for the chronomodulated delivery of lornoxicam. The basic design is based on the Pulsincap technology and consisted of formaldehyde treated insoluble hard gelatin capsule body filled with tripolyphosphate cross-linked chitosan microspheres of lornoxicam and sealed with a hydrogel tablet plug. The entire device was enteric coated, so as to prevent the variable gastric emptying time. The microspheres were found to be discrete, nearly spherical with rough surface characteristics. Particle size, encapsulation efficiency and release rate of lornoxicam from the microspheres are dependent on the fabrication conditions of the microencapsulation. FT-IR, DSC and XRD studies revealed the compatibility of the drug with the excipients used. The exposure of hard gelatine capsule bodies with formaldehyde for a period of 12 hrs was found to be optimum in maintaining the intactness of the capsule bodies in the simulated GI fluids. The lag time of the designed delivery system varied from 4-8 hrs and depended on the nature and concentration of the plugging material. The ejection of the plug was delayed with increase in the polymer concentration. Among the two polymers studied as plugging materials, guar gum exhibited better control in maintaining the lag time compared to xanthan gum. From the study it can be concluded that, the lag time be efficiently tailored by varying the concentrations of the polymers in the hydrogel plug for the chronomodulated delivery of lornoxicam. Key Words: Rheumatoid arthritis; Lornoxicam; Microspheres; Chronomodulated delivery systems; Hydrogel plug; Lag time;

Physico-chemical/biological properties of tripolyphosphate cross-linked chitosan based nanofibers

In this study, chitosan-PEO blend, prepared in a 15M acetic acid, was electrospun into nanofibers (~78nm diameter) with bead free morphology. While investigating physico-chemical parameters of blend solutions, effect of yield stress on chitosan based nanofiber fabrication was clearly evidenced. Architectural stability of nanofiber mat in aqueous medium was achieved by ionotropic cross-linking of chitosan by tripolyphosphate (TPP) ions. The TPP cross-linked nanofiber mat showed swelling up to ~300% in 1h and ~40% degradation during 30 day study period. 3T3 fibroblast cells showed good attachment, proliferation and viability on TPP treated chitosan based nanofiber mats. The results indicate non-toxic nature of TPP cross-linked chitosan based nanofibers and their potential to be explored as a tissue engineering matrix.

Ionically cross-linked chitosan/tripolyphosphate microparticles for the controlled delivery of pyrimethamine

Chitosan ionically cross-linked with tripolyphosphate at regulated temperatures (25°C, 40°C, and 50°C) and varying cross-linking times (30 min, 2 h and 4 h respectively) was used to form microparticles employed in the encapsulation of pyrimethamine, an antiprotozoal drug. The yields, equilibrium moisture contents, percentage concentration, swelling characteristics, entrapment efficiency, release properties, infrared spectroscopy, and differential scanning calorimetry of the formulated microparticles were evaluated. The yield of microparticles produced ranged from 0.3515 to 0.7749 g per 100 ml of cross linking solution. The products possessed relatively little amounts of moisture (0.22 − 3.04 % w/v). The entrapment efficiencies ranged from 25.55 to 99 % with the product formed at ambient temperature and cross linking time of 30 min possessing the highest efficiency. The swelling kinetics on the microcapsules revealed that all the products swelled in the various pH media following mainly anomalous sorption mechanism with a few diffusion controlled mechanism. The greatest swellings however occurred at the swelling medium of pH 1 while the least swelling occurred at pH 7. Spectral and differential scanning calorimetric properties of the chitosan used in the study were consistent with those of standard chitosan. The infrared spectroscopy and differential scanning calorimetry of the products confirmed that encapsulation actually occurred with the spectral characters of the products differing from those of the parent constituents (chitosan, tripolyphosphate and pyrimethamine). Based on these factors, tripolyphosphate cross-linked chitosan microparticles present a suitable matrix for the controlled release of pyrimethamine.

Adsorptive removal of Cr(III) from aqueous solution using tripolyphosphate cross-linked chitosan beads

Chitosan tripolyphosphate (CTPP) beads were prepared at two different cross-linking densities and adsorption of Cr(III) onto it were studied as a function of different operational parameters such as solution pH, equilibration time and initial Cr(III) ion concentration. Higher cross-linked beads were found to have more adsorption capacity at all the experimental pH employed (pH = 3–5), whereas adsorption capacity is found to increase with increase in pH. Adsorption data were analyzed using Langmuir and Freundlich isotherm models. Langmuir model is found be more suitable to explain the experimental results with a monolayer adsorption capacity of 469.5 mg/g. Among the kinetic models used, pseudo-second order kinetic model could best describe the adsorption process. Competition experiments done in presence of Na(I), Mg(II), Ca(II), Al(III) and Fe(III) revealed that, except in the case of Al(III), adsorption of Cr(III) is not significantly affected by the presence of foreign cations. NaCl is found to be a suitable leaching agent for the desorption of adsorbed Cr(III) from CTPP beads. FTIR spectroscopic investigations confirmed that phosphate groups are the principal binding site responsible for the sorption of Cr(III) onto CTPP beads.

Evaluation of ultrasonic atomization as a new approach to prepare ionically cross-linked chitosan microparticles

Ultrasonic atomization was evaluated as a new approach for the preparation of ionically cross-linked controlled-release chitosan microparticles loaded with theophylline as the model drug, using tripolyphosphate (TPP) as counter-ion. It was possible to nebulize both 2% and 3% (w/v) chitosan solutions as a function of their viscosity, usually not processed by employing the conventional nebulizer. The results of the chitosan molecular characterization using the SEC-MALS analysis revealed that ultrasonic atomization caused a certain depolymerization, probably due to the main chain scission of the 1,4-glycosidic bond; however, Fourier transform-infrared spectroscopy revealed the absence of other chemical modifications. The ultrasonic atomization allowed preparation of TPP cross-linked chitosan microparticles mostly ranging between 50 and 200 mum. As regards manufacturing parameters, the linking time and washing medium were found to affect the properties of the microparticles, while the stirring rate of the TPP solution did not show any influence. The evaluation of the formulation variables revealed that chitosan concentration strongly affected both the feasibility of the ultrasonic atomization and the drug release. All the microparticles showed an encapsulation efficiency of > 50 % and, after an initial burst effect, a controlled release of drug for 48 h. In conclusion, the ultrasonic atomization could be proposed as a robust and innovative single-step procedure with scale-up potential to successfully prepare ionically cross-linked chitosan microparticles.

Study of sodium tripolyphosphate-crosslinked chitosan beads entrapped with Pseudomonas putida for phenol degradation

This study was aimed to investigate the efficiency of phenol degradation by Pseudomonas putida entrapped within the beads prepared by chitosan crosslinked with sodium tripolyphosphate. The efficiency of phenol degradation was optimized by changing various processing parameters, such as the amount of cells, beads washing medium as well as acclimatization strategy. These entrapped cells were found to be superior to the free suspended ones in terms of improving the toleration to the environmental loadings (e.g., high pH, low ionic strength and high phenol concentration) and repeating usage for an extended period. Diffusion coefficient calculation has indicated that phenol degradation by the entrapped cells varied from the intraparticle diffusion control to the reaction control as the beads were used repeatedly. In the bead-packed column test, with the addition of hydrogen peroxide to increase the dissolved oxygen level for cell metabolism, phenol in the influent was almost completely degraded.