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.

Enzymes immobilized on synthetic polyethylene terephthalate (PET) textile surface by resource‐efficient inkjet printing technology can promote developments for various novel applications. Synthetic fabrics often require adequate pretreatments to facilitate such printing process. This work discusses PET–woven fabric pretreatment routes to improve wettability by alkaline, enzymatic, and plasma processes for effective printing of lysozyme using an industrial piezoelectric printhead. Results indicate that all pretreated samples contain a similar amount of enzymes upon printing. Plasma treated fabrics show relatively more hydrophilic surface characteristics, better protein binding stability, and lower retained activity. Alkali and cutinase‐treated samples possess relatively higher activity due to the greater amount of enzyme desorption to substrate solution. Depending on respective enzyme‐binding stability, a combination of a well-pretreated surface and inkjet as preferential placement technology, the approach of this study can be used as a facile enzyme immobilization method for suitable applications, for example, controlled‐release and bio‐sensing.

Tyrosinase enzyme was digitally printed on plasma pretreated polyamide-6,6 fabric using several sustainable technologies. Ink containing carboxymethyl cellulose was found to be the most suitable viscosity modifier for this enzyme. Before and after being deposited on the fabric surface, the printed inks retained enzyme activity of 69% and 60%, respectively, compared to activity prior printing process. A good number of the printed enzyme was found to be strongly adsorbed on the fabric surface even after several rinsing cycles due to surface activation by plasma treatment. Rinsed out fabrics retained a maximum activity of 34% resulting from the well-adsorbed enzymes. The activity of tyrosinase on printed fabrics was more stable than ink solution for at least 60 days. Effects of pH, temperature and enzyme kinetics on ink solution and printed fabrics were assessed. Tyrosinase printed synthetic fabrics can be utilized for a range of applications from biosensing and wastewater treatment to cultural heritage works.

An ink containing tyrosinase catalyzes the tyrosine residues on lysozyme protein to bind it on a plasma-treated polyamide-6,6 (PA) fabric. Inkjet printing enables controlled and sequential deposition of two enzymes on PA which is necessary for proper binding. The effect of different printing sequences on crosslinking stability and enzymatic activity is presented. The lysozyme bound on the fabric shows satisfactory antimicrobial activity. The printed fabric retains about 68% of the ink activity when tyrosinase is printed before lysozyme. Further, this fabric retains about 24% of the initial activity up to four reuses. The fabric shows acceptable inhibition of bacterial growth and retains almost half of its initial activity when cold stored for a month. This work shows the potential of protein binding on textile surface using various means of sustainable technologies, namely enzyme, inkjet, and plasma.