Influence of compression speed and deformation percentage on mechanical properties of calcium alginate particles

Abstract

Hydrogel particles are often used as carriers for the immobilization of enzymes, polyphenolic antioxidants, whole microbial, plant or mammalian cells. In many processes, the mechanical properties of alginate particles are essential due to their exposure to mechanical forces in production process. Determination and improvement of hydrogels mechanical properties is very important in prevention of the undesirable side effects during the manufacturing process and product application. The aim of this study was to define the mechanical properties of single particles submerged in water and in dry conditions using the compression method between two flat surfaces. The results indicated that the formulation of alginate beads and water loss during compression have significant influence on their mechanical behavior and stiffness. Calcium-alginate particles were produced using an electrostatic droplet extrusion technique, with an initial sodium alginate concentration of 1.5%, w/V, and calcium chloride (2.0%, w/V) as the gelling solution. The research findings were used to determine the influence of working conditions, sample deformation (10-50%) and different compression speeds (1-50 mm/min) on the mechanical strength of alginate beads. The Young's moduli and maximal forces for investigated deformation percentage of the alginate particles were determined from generated force-displacement and stress-strain curves during compression.

Hidrogel čestice su najčešće korišćeni nosači prilikom imobilizacije enzima, polifenolnih jedinjenja, biljnih i životinjskih ćelija. U mnogim procesima čestice hidrogela su izložene mehaničkim silama koje mogu izazvati deformaciju, čime se ograničava njihova praktična primena. Definisanje i unapređenje mehaničkih svojstava hidrogelova je veoma važno u cilju sprečavanja neželjenih efekata u toku samog proizvodnog procesa, kao i dalje primene proizvoda. Cilj ovog rada je bilo ispitivanje mehaničkih svojstava pojedinačnih čestica potopljenih u vodi, kao i na vazduhu (suvi uslovi) pomoću metode kompresije između dve ravne površine. Rezultati su ukazali da sastav alginatnih čestica i gubitak vode tokom procesa kompresije imaju značajan uticaj na njihove mehaničke karakteristike i čvrstoću. Kalcijum-alginatne čestice su dobijene postupkom elektrostatičke ekstruzije, potiskivanjem natrijum-alginata (1.5%) kroz špric pomoću infuzione pumpe u rastvor kalcijum-hlorida (2.0%). Dobijeni rezultati su iskorišćeni za ispitivanja uticaja radnih uslova, procenta deformacije (10-50%) i različitih vrednosti brzine sabijanja (1-50mm/min) uzorka na mehanička svojstva nosača. Modul elastičnosti kao i maksimalna sila za ispitivani procenat deformacije alginatnih čestica su određeni pomoću dobijenih eksperimentalnih krivih zavisnosti sile od pomeranja i napona od deformacije tokom procesa kompresije.