Fig. 1: Smart sealant patch design.

a Envisaged application of the leak-detecting sealant hydrogel patches enabling non-invasive postoperative surveillance of anastomoses using port-able, pocket handheld ultrasound probes (cross denotes high mortality of developed sepsis). b Composition of the layered-leak detecting sealant hydrogel patch, composed of a non-adhesive backing (PNHEA), adhesive suture support layer (PAMPS), sensing elements (TurnOFF sens-ing elements comprising enzyme-digestible gas vesicles or TurnON elements comprising pH-reactive sodium bicarbonate) attached to tissue via the formation of a mutually interpenetrating network (mIPN). b-I Application of the as-prepared hydrogel patch, which is incubated in a 33 wt% NAGA monomer/water solution containing LAP initiator (b-II) and finally is attached to tissue using visible light to form an mIPN (lightning denotes light) (b-III). c As-prepared hy-drogels, manufactured in various shapes, exhibit discrete layers and compartments, namely adhesive support (light blue arrow), non-adhesive backing (dark blue arrow), TurnOFF Halo gas vesicles sensing elements (5 µL 20 vol%, orange arrow) and 2.5 mg/mL ZnO in PAAm an-tibacterial elements (green arrow). d Illustration showcasing gastrointestinal organs and the application of the hydrogel patches containing sensing elements (orange arrow) on the outer lining of porcine stomach, small intestine and colon, each closing a 4 mm defect (black arrow). Figure wide color coding: light blue—adhesive support, dark blue—non-adhesive backing, yellow—Turn-OFF sensing element, purple—TurnON sensing element, turquoise green—mIPN. Figure 1a, b, d has been created using biorender.com.