Effects of ink characteristics and piezo-electric inkjetting parameters on lysozyme activity

Abstract

Inkjet printing of enzymes can facilitate many novel applications where a small amount of materials need to be deposited in a precise and flexible manner. However, maintaining the satisfactory activity of inkjet printed enzyme is a challenging task due to the requirements of ink rheology and printhead parameters. Thus to find optimum inkjetting conditions we studied the effects of several ink formulation and jetting parameters on lysozyme activity using a piezoelectric printhead. Within linear activity range of protein concentrations ink containing 50 µg/mL lysozyme showed a satisfactory activity retention of 85%. An acceptable activity of jetted ink was found at pH 6.2 and ionic strength of 0.06 molar. Glycerol was found to be an effective viscosity modifier (10–15 mPa.s), humectant and protein structure stabilizer for the prepared ink. A non-ionic surfactant when used just below critical micelle concentration was found to be favourable for the jetted inks. An increase in activity retention was observed for inks jetted after 24 hours of room temperature incubation. However, no additional activity was seen for inkjetting above the room temperature. Findings of this study would be useful for formulating other protein-based inks and setting their inkjet printing parameters without highly compromising the functionality.

Effective Pretreatment Routes of Polyethylene Terephthalate Fabric for Digital Inkjet Printing of Enzyme

“…Glycerol has been demonstrated to be an efficient viscosity modifier for lysozyme solution [ 36,37 ] and thus used in our study. However, compared to our previous work, [ 12 ] amount of glycerol was reduced in this study considering its humectant nature and thus minimizing post‐print drying duration to 1 h (at room temperature). This resulted in ink viscosity of 5.5 mPa.s at 25 °C printing temperature, which is slightly less than printhead manufacturer recommendation range (7–12 mPas).…”

“…Ink formulation containing enzyme requires careful consideration of rheology, ionic environment, and printhead parameters to ensure optimum activity of printed enzymes as demonstrated in our previous paper. [ 12 ] Considering rheology, viscosity, and surface tension are most necessary to adjust for ensuring proper ejection, drop formation, and spreading of ink on fabric. Glycerol has been demonstrated to be an efficient viscosity modifier for lysozyme solution [ 36,37 ] and thus used in our study.…”

“…[42] For the prepared ink, most suitable ionic strength was 0.05 m at pH 7, which is in line with our previous study. [12] At this range, maximum lysozyme coverage on fabric surface could be expected. [15] An appropriately high concentration of enzyme in the ink solution would ensure a constant rate of catalysis for maximum possible activity of printed fabric.…”

“…Ink Formulation and Printing: An optimization of ink formulation was conducted following the same strategies suggested in our previous work [12] by varying amount of phosphate buffer, glycerol (as viscosity modifier and humectant), Triton X-100 (surfactant), and lysozyme. The optimized ink vehicle had a buffer, glycerol, and surfactant ratio of 70: 29.90: 0.10 (w/w) with pH adjusted to 7.…”

“…[ 11 ] Optimization strategy of ink‐containing enzyme for rheological, ionic, and printhead parameters has been demonstrated in our previous work. [ 12 ] In this work, fabric surface characteristics necessary for efficient inkjet printing and retention of active enzymes are studied.…”