Enzymatic degradation of natural polymers at physiological conditions

U današnje vrijeme, prirodni polimeri se sve više istražuju zbog biorazgradivosti koja se temelji na hidrolitičkom ili enzimskom djelovanju na kemijskim vezama u polimerima. Materijali koji imaju svojstvo biokompatibilnosti koriste se za medicinsku primjenu kao nosači lijekova, u inženjerstvu tkiva i kože, pri izradi srčanih zalistaka, proteza krvnih žila itd. Do njihove razgradnje dolazi u kontaktu s tjelesnim fluidima i tkivima, a produkti ne smiju biti toksični. Najčešće korišteni biomaterijali su celuloza, kolagen, poli(ε-kaprolakton) i hidrogelovi. U ovom radu praćena je enzimska razgradnja poroznih struktura kitozana uz katalizator lizozim tijekom četiri tjedna inkubacije pri temperaturi od 37 °C. Enzimska razgradnja pratila se u fosfatom puferiranoj otopini soli (PBS, pH = 7,38) i u vodenom mediju. Porozne strukture karakterizirane su prije i nakon razgradnje instrumentalnim metodama rendgenske difrakcijske analize i infracrvene spektroskopije s Fourierovim transformacijama. Morfologija uzoraka istražena je pomoću pretražnog elektronskog mikroskopa. Dobiveni rezultati ukazuju na enzimsku biorazgradivost kitozana visokog stupnja deacetilacije (95 – 98 %) pri fiziološkim uvjetima, dok je aktivnost enzima u vodenom mediju izostala. Identifikacijska analiza potvrdila je zaostatak adsorbiranog lizozima koji utječe na konačni pad mase uzoraka tijekom razgradnje. Mikroskopska analiza ukazala je na promjenu mikrostrukture kitozanskih spužvi tijekom enzimske razgradnje, ali i na potencijalnu nehomogenost pripravljenih uzoraka.Nowadays, natural polymers are being more studied due to their biodegradability, which is based on hydrolytic or enzymatic actions on chemical bonds in polymers. Biocompatible materials are used in medical applications, such as drug delivery, tissue and skin engineering, manufacturing of heart valves, vascular prostheses etc. They degrade in contact with body fluids and tissue, and degradation products must not be toxic. The mostly used biomaterials are cellulose, collagen, poly(ε-caprolactone) and hydrogels. In this paper, enzymatic degradation of porous chitosan structures was monitored with lysozyme as a catalyst during four weeks of incubation at 37 °C. The enzymatic degradation was monitored in phosphate buffered saline (PBS, pH = 7.38), and water media. Scaffolds were analyzed before and after enzymatic degradation using X-ray diffraction analysis and infrared spectroscopy with Fourier transformations, while morphology of scaffolds was investigated by scanning electron microscopy. The results indicate enzymatic biodegradability of highly deacetylated chitosan (95 – 98%) at physiological conditions, while lysozyme showed the absence of its activity in aqueous medium. The scaffolds’ identification has confirmed the residues of absorbed lysozyme, which affects the final weight loss of the sample. Microscopic analysis has indicated changes in the microstructure of chitosan sponges during the enzymatic degradation, but also potential lack of homogeneity of prepared samples

Enzymatic degradation of natural polymers at physiological conditions

U današnje vrijeme, prirodni polimeri se sve više istražuju zbog biorazgradivosti koja se temelji na hidrolitičkom ili enzimskom djelovanju na kemijskim vezama u polimerima. Materijali koji imaju svojstvo biokompatibilnosti koriste se za medicinsku primjenu kao nosači lijekova, u inženjerstvu tkiva i kože, pri izradi srčanih zalistaka, proteza krvnih žila itd. Do njihove razgradnje dolazi u kontaktu s tjelesnim fluidima i tkivima, a produkti ne smiju biti toksični. Najčešće korišteni biomaterijali su celuloza, kolagen, poli(ε-kaprolakton) i hidrogelovi. U ovom radu praćena je enzimska razgradnja poroznih struktura kitozana uz katalizator lizozim tijekom četiri tjedna inkubacije pri temperaturi od 37 °C. Enzimska razgradnja pratila se u fosfatom puferiranoj otopini soli (PBS, pH = 7,38) i u vodenom mediju. Porozne strukture karakterizirane su prije i nakon razgradnje instrumentalnim metodama rendgenske difrakcijske analize i infracrvene spektroskopije s Fourierovim transformacijama. Morfologija uzoraka istražena je pomoću pretražnog elektronskog mikroskopa. Dobiveni rezultati ukazuju na enzimsku biorazgradivost kitozana visokog stupnja deacetilacije (95 – 98 %) pri fiziološkim uvjetima, dok je aktivnost enzima u vodenom mediju izostala. Identifikacijska analiza potvrdila je zaostatak adsorbiranog lizozima koji utječe na konačni pad mase uzoraka tijekom razgradnje. Mikroskopska analiza ukazala je na promjenu mikrostrukture kitozanskih spužvi tijekom enzimske razgradnje, ali i na potencijalnu nehomogenost pripravljenih uzoraka.Nowadays, natural polymers are being more studied due to their biodegradability, which is based on hydrolytic or enzymatic actions on chemical bonds in polymers. Biocompatible materials are used in medical applications, such as drug delivery, tissue and skin engineering, manufacturing of heart valves, vascular prostheses etc. They degrade in contact with body fluids and tissue, and degradation products must not be toxic. The mostly used biomaterials are cellulose, collagen, poly(ε-caprolactone) and hydrogels. In this paper, enzymatic degradation of porous chitosan structures was monitored with lysozyme as a catalyst during four weeks of incubation at 37 °C. The enzymatic degradation was monitored in phosphate buffered saline (PBS, pH = 7.38), and water media. Scaffolds were analyzed before and after enzymatic degradation using X-ray diffraction analysis and infrared spectroscopy with Fourier transformations, while morphology of scaffolds was investigated by scanning electron microscopy. The results indicate enzymatic biodegradability of highly deacetylated chitosan (95 – 98%) at physiological conditions, while lysozyme showed the absence of its activity in aqueous medium. The scaffolds’ identification has confirmed the residues of absorbed lysozyme, which affects the final weight loss of the sample. Microscopic analysis has indicated changes in the microstructure of chitosan sponges during the enzymatic degradation, but also potential lack of homogeneity of prepared samples

Preparation of chitosan-copper complex microspheres modified by bioactive glass

The aim of this work was to prepare composite microspheres with high sphericity and narrow size distribution based on chitosan-copper complex and bioactive glass (bioglass). The influence of the bioactive glass content on the size and morphology of chitosan-copper complex microspheres was investigated. The electrohydrodynamic atomization process was used to produce highly spherical particles of narrow size distribution and with defined surface morphology. The addition of bioglass particles caused the surface changes, from smooth to wrinkled surface by increasing the bioglass quantity. The size of the obtained microspheres was estimated to be between 40 and 100 μm, depending on the bioglass content

Properties of Waste Polyamide Powder and Titanium Dioxide Nanocomposites

Selektivno lasersko sinteriranje (SLS) jedan je od važnijih postupaka 3D ispisa koji se u današnje vrijeme sve više primjenjuju za dobivanje različitih modela. Najvažniji polimerni materijali koji se upotrebljavaju u tom procesu su poliamidi. Značajan nedostatak tog procesa je velika količina otpadnog polimernog praha. Stoga je cilj ovoga rada bio istražiti utjecaj dodatka nanočestica titanijeva dioksida (TiO2) na toplinska i mehanička svojstva otpadnog poliamidnog praha (PA 2200). U ovom radu pripremljeni su nanokompoziti PA/TiO2 u rasponu masenog udjela punila 1 – 5 %, postupkom zamješavanja punila u talinu polimera u gnjetilici Brabender. Aglomerati nanopunila vidljivi su na SEM mikrografiji 5 %-tnog PA/TiO2 nanokompozita. Rezultati diferencijalne pretražne kalorimetrije (DSC) ukazuju na djelovanje nanočestica TiO2 kao heterogenih nukleacijskih centara. Također, dodatak nanopunila pospješuje stvaranje stabilnijih i uređenijih kristalnih struktura poliamidne matrice. Termogravimetrijskom analizom (TGA) dokazano je da dodatak TiO2 nanopunila povećava temperaturu početka razgradnje PA matrice, to jest poboljšava toplinsku postojanost PA matrice i neznatno povećava vrijednosti toplinske vodljivosti nanokompozita u odnosu na čistu polimernu matricu. Ispitivanjem mehaničkih svojstava uzoraka uočeno je smanjenje vrijednosti sekantnog modula te neznatne promjene naprezanja i istezanja u točki popuštanja s povećanjem udjela punila u nanokompozitu. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.The PA 2200 waste powder generated during selective laser sintering (SLS) process is an important environmental and economic problem. In order to test and modify the properties of the waste powder, nanocomposites based on polyamide matrix and TiO2 nanoparticles were prepared in this work. Agglomerates of the TiO2 nanofiller are visible on the SEM micrographs for the nanocomposite with 5 wt. % of the nanofiller (Fig. 1). The DSC analysis indicates an increase in crystallization temperature (Tc) by the addition of filler to the polymer matrix and it can be concluded that the TiO2 nanoparticles represent the nucleation centres in the PA matrix (Fig. 2, Table 1). In systems with 4 and 5 wt. % TiO2 crystallization enthalpy (ΔHc) and melting enthalpy (ΔHm) are higher than the values for the polyamide matrix (Table 1), indicating that the nanoparticles promote crystallization of the PA matrix. The results of TG analysis imply a positive effect of the TiO2 nanoparticles on the onset of thermal decomposition, which is most pronounced in the system with 3 wt. % TiO2 (Fig. 3, Table 2). As thermal degradation progresses further, the positive effect of the addition of TiO2 nanoparticles becomes less pronounced and finally becomes negative in the final stages, i.e. TiO2 nanoparticles accelerate the degradation. The thermal conductivity values (λ) are slightly higher for the nanocomposites relative to the pure PA matrix (Fig. 4) due to the formation of a more ordered structure of the polymer matrix by the addition of TiO2 and/or the formation of so-called conductive pathway. The results of the mechanical test indicate that the addition of TiO2 nanofiller decreases the values of the secant modulus (E), while the values of the yield stress (σ2>y2>y2 nanoparticles to the PA 2200 waste powder represents a useful approach for its reuse, thus improving the economic and environmental sustainability of the SLS process. The main disadvantage of the studied systems is the inconsistent mechanical properties at break. In future studies, this problem will be solved with adequate surface modification of TiO2 nanoparticles. This work is licensed under a Creative Commons Attribution 4.0 International License

With food to health : proceedings of the 10th International scientific and professional conference

Proceedings contains 13 original scientific papers, 10 professional papers and 2 review papers which were presented at "10th International Scientific and Professional Conference WITH FOOD TO HEALTH", organised in following sections: Nutrition, Dietetics and diet therapy, Functional food and food supplemnents, Food safety, Food analysis, Production of safe food and food with added nutritional value

Chitosan based materials as chelating agents

Do sada, mali broj istraživanja posvećen je utjecaju dvovalentnih metalnih iona na strukturu i svojstva hidrogelova kitozana. S toga je cilj ovog rada pokazati kako se dodatkom dvovalentnih metalnih iona u dozvoljenim granicama toksičnosti može manipulirati strukturom, fizikalnim i biološkim svojstvima hidrogelova kitozana. Kitozan je netoksičan, biokompatibilan i biorazgradivi polimer koji se može koristiti kao nosač u području tkivnog inženjerstva. Ovisno o stupnju deacetilacije i molekulskoj masi polimera, dodatkom bakrovih i cinkovih iona (Cu2+ i Zn2+) dobivaju se hidrogelovi definirane strukture. Potencijalna metoda priprave hidrogelova kelata kitozan – metalni ion s točno određenom strukturom je proces keliranja. U eksperimentalnom dijelu rada, korištene su dvije vrste kitozana: srednje (C1) i visoke (C2) molekulske mase. Kao metalni prekursori korištene su soli acetata bakra i cinka, dok su koncentrirana otopina natrijevog hidroksida te zasićena atmosfera amonijaka služili kao neutralizirajući agensi. UV-Vis spektroskopska analiza otopina ukazala je na nastanak kelata kitozan – metalni ion. Pripremljeni hidrogelovi postupkom liofilizacije prevedeni su u nosače i kserogelove koji su okarakterizirani primjenom infracrvene spektroskopske analize s Fourierovim transformacijama (FTIR) i kvalitativnom rendgenskom difrakcijskom analizom (XRD). Morfologija i mikrostruktura uzoraka istražena je pomoću pretražnog elektronskog mikroskopa (SEM). Provedene analize ukazuju na interakcije Cu2+ i Zn2+ iona s amino i hidroksilnim skupinama polimera, kao i na nastanak anorganskih kristalnih faza kada je gelirajući agens otopina NaOH. Test citotoksičnosti pokazao je da su kelati kitozana s bakrovim(II) ionima koncentracije veće od 3 mmol dm^-3 citotoksični za Hek293 stanice, dok uzorci s cinkovim(II) ionima za sve istraživane koncentracije nisu pokazali citotoksična svojstva.Up till now, a small number of studies were focused on the influence of divalent metal ions on the structure and properties of chitosan hydrogels. The aim of this work was to manipulate the physical and biological properties of chitosan’s hydrogels by the addition of divalent metal ions at non-toxic concentrations. Chitosan is a non-toxic, biocompatible and biodegradable polymer which can be used as a scaffold in tissue engineering. Depending on the degree of deacetylation and molecular weight of polymer, hydrogels with specific structures can be produced by the addition of copper and zinc ions (Cu2+ and Zn2+). As a potential method, the chelation process can be used to prepare hydrogels of chelate chitosan – metal ion with defined structure. In the experimental part of this work, two types of chitosan were used: medium (C1) and high (C2) molecular weight. Copper and zinc acetate were used as metal precursors, while concentrated solution of sodium hydroxide and saturated ammonia atmosphere were used as the neutralisation agents. The UV-Vis spectrophotometric analysis of the chitosan–M2+ solutions indicated the formation of corresponding chelates. The prepared hydrogels were transformed into scaffolds and xerogels by the lyophilisation method and characterized by Fourier transform infrared spectroscopic analysis (FTIR) and qualitative X-ray diffraction analysis (XRD). The morphology and microstructure of the samples were investigated by scanning electron microscopy (SEM). The analyses indicated interactions of Cu2+ and Zn2+ ions with amino and hydroxyl groups of the polymer, as well as the formation of inorganic crystalline phases with the NaOH as gelling agent. The cytotoxicity test confirmed that chelates with the concentration of copper(II) ion higher than 3 mmol dm^-3 were cytotoxic for Hek293 cells, whereas chelates with zinc(II) ions of whole investigated concentration range did not show cytotoxic properties

Enzymatic degradation of natural polymers at physiological conditions

U današnje vrijeme, prirodni polimeri se sve više istražuju zbog biorazgradivosti koja se temelji na hidrolitičkom ili enzimskom djelovanju na kemijskim vezama u polimerima. Materijali koji imaju svojstvo biokompatibilnosti koriste se za medicinsku primjenu kao nosači lijekova, u inženjerstvu tkiva i kože, pri izradi srčanih zalistaka, proteza krvnih žila itd. Do njihove razgradnje dolazi u kontaktu s tjelesnim fluidima i tkivima, a produkti ne smiju biti toksični. Najčešće korišteni biomaterijali su celuloza, kolagen, poli(ε-kaprolakton) i hidrogelovi. U ovom radu praćena je enzimska razgradnja poroznih struktura kitozana uz katalizator lizozim tijekom četiri tjedna inkubacije pri temperaturi od 37 °C. Enzimska razgradnja pratila se u fosfatom puferiranoj otopini soli (PBS, pH = 7,38) i u vodenom mediju. Porozne strukture karakterizirane su prije i nakon razgradnje instrumentalnim metodama rendgenske difrakcijske analize i infracrvene spektroskopije s Fourierovim transformacijama. Morfologija uzoraka istražena je pomoću pretražnog elektronskog mikroskopa. Dobiveni rezultati ukazuju na enzimsku biorazgradivost kitozana visokog stupnja deacetilacije (95 – 98 %) pri fiziološkim uvjetima, dok je aktivnost enzima u vodenom mediju izostala. Identifikacijska analiza potvrdila je zaostatak adsorbiranog lizozima koji utječe na konačni pad mase uzoraka tijekom razgradnje. Mikroskopska analiza ukazala je na promjenu mikrostrukture kitozanskih spužvi tijekom enzimske razgradnje, ali i na potencijalnu nehomogenost pripravljenih uzoraka.Nowadays, natural polymers are being more studied due to their biodegradability, which is based on hydrolytic or enzymatic actions on chemical bonds in polymers. Biocompatible materials are used in medical applications, such as drug delivery, tissue and skin engineering, manufacturing of heart valves, vascular prostheses etc. They degrade in contact with body fluids and tissue, and degradation products must not be toxic. The mostly used biomaterials are cellulose, collagen, poly(ε-caprolactone) and hydrogels. In this paper, enzymatic degradation of porous chitosan structures was monitored with lysozyme as a catalyst during four weeks of incubation at 37 °C. The enzymatic degradation was monitored in phosphate buffered saline (PBS, pH = 7.38), and water media. Scaffolds were analyzed before and after enzymatic degradation using X-ray diffraction analysis and infrared spectroscopy with Fourier transformations, while morphology of scaffolds was investigated by scanning electron microscopy. The results indicate enzymatic biodegradability of highly deacetylated chitosan (95 – 98%) at physiological conditions, while lysozyme showed the absence of its activity in aqueous medium. The scaffolds’ identification has confirmed the residues of absorbed lysozyme, which affects the final weight loss of the sample. Microscopic analysis has indicated changes in the microstructure of chitosan sponges during the enzymatic degradation, but also potential lack of homogeneity of prepared samples

Chitosan based materials as chelating agents

Do sada, mali broj istraživanja posvećen je utjecaju dvovalentnih metalnih iona na strukturu i svojstva hidrogelova kitozana. S toga je cilj ovog rada pokazati kako se dodatkom dvovalentnih metalnih iona u dozvoljenim granicama toksičnosti može manipulirati strukturom, fizikalnim i biološkim svojstvima hidrogelova kitozana. Kitozan je netoksičan, biokompatibilan i biorazgradivi polimer koji se može koristiti kao nosač u području tkivnog inženjerstva. Ovisno o stupnju deacetilacije i molekulskoj masi polimera, dodatkom bakrovih i cinkovih iona (Cu2+ i Zn2+) dobivaju se hidrogelovi definirane strukture. Potencijalna metoda priprave hidrogelova kelata kitozan – metalni ion s točno određenom strukturom je proces keliranja. U eksperimentalnom dijelu rada, korištene su dvije vrste kitozana: srednje (C1) i visoke (C2) molekulske mase. Kao metalni prekursori korištene su soli acetata bakra i cinka, dok su koncentrirana otopina natrijevog hidroksida te zasićena atmosfera amonijaka služili kao neutralizirajući agensi. UV-Vis spektroskopska analiza otopina ukazala je na nastanak kelata kitozan – metalni ion. Pripremljeni hidrogelovi postupkom liofilizacije prevedeni su u nosače i kserogelove koji su okarakterizirani primjenom infracrvene spektroskopske analize s Fourierovim transformacijama (FTIR) i kvalitativnom rendgenskom difrakcijskom analizom (XRD). Morfologija i mikrostruktura uzoraka istražena je pomoću pretražnog elektronskog mikroskopa (SEM). Provedene analize ukazuju na interakcije Cu2+ i Zn2+ iona s amino i hidroksilnim skupinama polimera, kao i na nastanak anorganskih kristalnih faza kada je gelirajući agens otopina NaOH. Test citotoksičnosti pokazao je da su kelati kitozana s bakrovim(II) ionima koncentracije veće od 3 mmol dm^-3 citotoksični za Hek293 stanice, dok uzorci s cinkovim(II) ionima za sve istraživane koncentracije nisu pokazali citotoksična svojstva.Up till now, a small number of studies were focused on the influence of divalent metal ions on the structure and properties of chitosan hydrogels. The aim of this work was to manipulate the physical and biological properties of chitosan’s hydrogels by the addition of divalent metal ions at non-toxic concentrations. Chitosan is a non-toxic, biocompatible and biodegradable polymer which can be used as a scaffold in tissue engineering. Depending on the degree of deacetylation and molecular weight of polymer, hydrogels with specific structures can be produced by the addition of copper and zinc ions (Cu2+ and Zn2+). As a potential method, the chelation process can be used to prepare hydrogels of chelate chitosan – metal ion with defined structure. In the experimental part of this work, two types of chitosan were used: medium (C1) and high (C2) molecular weight. Copper and zinc acetate were used as metal precursors, while concentrated solution of sodium hydroxide and saturated ammonia atmosphere were used as the neutralisation agents. The UV-Vis spectrophotometric analysis of the chitosan–M2+ solutions indicated the formation of corresponding chelates. The prepared hydrogels were transformed into scaffolds and xerogels by the lyophilisation method and characterized by Fourier transform infrared spectroscopic analysis (FTIR) and qualitative X-ray diffraction analysis (XRD). The morphology and microstructure of the samples were investigated by scanning electron microscopy (SEM). The analyses indicated interactions of Cu2+ and Zn2+ ions with amino and hydroxyl groups of the polymer, as well as the formation of inorganic crystalline phases with the NaOH as gelling agent. The cytotoxicity test confirmed that chelates with the concentration of copper(II) ion higher than 3 mmol dm^-3 were cytotoxic for Hek293 cells, whereas chelates with zinc(II) ions of whole investigated concentration range did not show cytotoxic properties

Chitosan based materials as chelating agents

Do sada, mali broj istraživanja posvećen je utjecaju dvovalentnih metalnih iona na strukturu i svojstva hidrogelova kitozana. S toga je cilj ovog rada pokazati kako se dodatkom dvovalentnih metalnih iona u dozvoljenim granicama toksičnosti može manipulirati strukturom, fizikalnim i biološkim svojstvima hidrogelova kitozana. Kitozan je netoksičan, biokompatibilan i biorazgradivi polimer koji se može koristiti kao nosač u području tkivnog inženjerstva. Ovisno o stupnju deacetilacije i molekulskoj masi polimera, dodatkom bakrovih i cinkovih iona (Cu2+ i Zn2+) dobivaju se hidrogelovi definirane strukture. Potencijalna metoda priprave hidrogelova kelata kitozan – metalni ion s točno određenom strukturom je proces keliranja. U eksperimentalnom dijelu rada, korištene su dvije vrste kitozana: srednje (C1) i visoke (C2) molekulske mase. Kao metalni prekursori korištene su soli acetata bakra i cinka, dok su koncentrirana otopina natrijevog hidroksida te zasićena atmosfera amonijaka služili kao neutralizirajući agensi. UV-Vis spektroskopska analiza otopina ukazala je na nastanak kelata kitozan – metalni ion. Pripremljeni hidrogelovi postupkom liofilizacije prevedeni su u nosače i kserogelove koji su okarakterizirani primjenom infracrvene spektroskopske analize s Fourierovim transformacijama (FTIR) i kvalitativnom rendgenskom difrakcijskom analizom (XRD). Morfologija i mikrostruktura uzoraka istražena je pomoću pretražnog elektronskog mikroskopa (SEM). Provedene analize ukazuju na interakcije Cu2+ i Zn2+ iona s amino i hidroksilnim skupinama polimera, kao i na nastanak anorganskih kristalnih faza kada je gelirajući agens otopina NaOH. Test citotoksičnosti pokazao je da su kelati kitozana s bakrovim(II) ionima koncentracije veće od 3 mmol dm^-3 citotoksični za Hek293 stanice, dok uzorci s cinkovim(II) ionima za sve istraživane koncentracije nisu pokazali citotoksična svojstva.Up till now, a small number of studies were focused on the influence of divalent metal ions on the structure and properties of chitosan hydrogels. The aim of this work was to manipulate the physical and biological properties of chitosan’s hydrogels by the addition of divalent metal ions at non-toxic concentrations. Chitosan is a non-toxic, biocompatible and biodegradable polymer which can be used as a scaffold in tissue engineering. Depending on the degree of deacetylation and molecular weight of polymer, hydrogels with specific structures can be produced by the addition of copper and zinc ions (Cu2+ and Zn2+). As a potential method, the chelation process can be used to prepare hydrogels of chelate chitosan – metal ion with defined structure. In the experimental part of this work, two types of chitosan were used: medium (C1) and high (C2) molecular weight. Copper and zinc acetate were used as metal precursors, while concentrated solution of sodium hydroxide and saturated ammonia atmosphere were used as the neutralisation agents. The UV-Vis spectrophotometric analysis of the chitosan–M2+ solutions indicated the formation of corresponding chelates. The prepared hydrogels were transformed into scaffolds and xerogels by the lyophilisation method and characterized by Fourier transform infrared spectroscopic analysis (FTIR) and qualitative X-ray diffraction analysis (XRD). The morphology and microstructure of the samples were investigated by scanning electron microscopy (SEM). The analyses indicated interactions of Cu2+ and Zn2+ ions with amino and hydroxyl groups of the polymer, as well as the formation of inorganic crystalline phases with the NaOH as gelling agent. The cytotoxicity test confirmed that chelates with the concentration of copper(II) ion higher than 3 mmol dm^-3 were cytotoxic for Hek293 cells, whereas chelates with zinc(II) ions of whole investigated concentration range did not show cytotoxic properties

Electrosprayed Chitosan–Copper Complex Microspheres with Uniform Size

Chitosan-based nano- and microspheres have shown great potential in a broad range of applications, including drug delivery, bone tissue engineering, wastewater treatments, etc. The preparation of uniformly sized spheres with controlled morphology and microstructure is still a challenge. This work investigates the influence of cupric ions (Cu2+) on the size, shape, morphology and stability of electrosprayed chitosan–copper (CHT–Cu2+) complex microspheres, using chitosans with different degrees of deacetylation. The dynamic viscosity of CHT–Cu2+ solutions was measured by Höppler viscometer, while attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used for the identification of dried microspheres. The size, shape and morphology of microspheres were analyzed by light microscope and scanning electron microscopy (SEM), while stability of dried microspheres was evaluated in different buffer solutions. The volume ratio of wet and dry microspheres was assessed based on the estimated diameter of microspheres. The higher concentration of Cu2+ ions resulted in a decrease in viscosity of CHT–Cu2+ solutions and volume ratio of prepared microspheres. Changes in the intensities and wave numbers of absorption bands of amino and hydroxyl groups, amide I and amide II suggested that the nitrogen and oxygen atoms in chitosan are coordinating the cupric ions. Micrographs obtained by light microscope and SEM showed that all prepared samples are spherical. The increase of cupric ions concentration changed the topography of microspheres and decreased their size. These results indicated the successful electrospraying of CHT–Cu2+ microspheres with uniform size and good stability in aqueous medium