Biogenic Polymer based Patches for Congenital Cardiac Surgery: Future Development of Implants

Emma Richert ^1,2 Linda Grefen ² Alexandra Zorin ^1,2 Julian Hubrich ^1,2 Stefan Simon ² Christian P Sommerhoff ³ Christian Hagl ² Christopher Herz ² Dominik Obrist ⁴ Jurgen Horer ¹ Thierry Carrel ⁵ Maximilian Grab ² Paul Philipp Heinisch ^1*

• ¹ Department of Congenital Heart Defect Surgery and Paediatric Cardiac Surgery, German Heart Centre Munich, Technical University Munich, Munich, Germany
• ² Department of Cardiac Surgery Clinic and Polyclinic, LMU Munich University Hospital, Munich, Bavaria, Germany
• ³ Institute of Laboratory Medicine, LMU Munich University Hospital, Munich, Bavaria, Germany
• ⁴ ARTORG Center for Biomedical Engineering Research, Faculty of Medicine, University of Bern, Bern, Bern, Switzerland
• ⁵ Department of Cardiac Surgery, University Hospital Zürich, Zurich, Switzerland

Objective: Despite advancements in surgical techniques, many patients born with congenital heart defects (CHD) require repeated reinterventions due to the limitations of materials used in congenital cardiac surgery (CCS). Traditional biogenic polymers, such as bovine or equine pericardium, are prone to calcification, have limited durability, and fail to adapt to the growth of infants. This study aims to address these challenges by investigating bacterial cellulose (BC) as a promising material for CCS.Methods: Variability in patch quality from previous studies was addressed by refining the production protocol taking advantage of Ooptical Ddensity (OD) measurements. After a 72hour incubation, patches were harvested and tested mechanically with burst pressure and uniaxial strain testing. BC's biomechanical properties were further explored by modifying nutrient concentrations, creating different media groups (N10, N30, N50). Hybrid patches combining BC with electrospun polyurethane (ESP-PU) were developed using a specially designed 3D-printed flask to ensure uniform coating and integration.The initial bacterial concentration significantly influenced cellulose yield and growth rate, with static cultures outperforming shaken ones. Nutrient-enriched media (N10, N30, N50) produced cellulose with greater elasticity and strength compared to standard C-Medium, with stiffness correlating to nutrient concentration. Inflation tests showed that N10 and N30 samples withstood higher pressures, while N50 samples, though stiffer, performed less well under rapid inflation stress, yet all samples maintained pressures above physiological levels Inflation tests showed that N10 and N30 samples withstood higher pressures than N50, which, despite being stiffer, performed worse under rapid inflation. All samples, however, maintained pressures above physiological levels. Scanning electron microscopy analysis confirmed effective BCbacterial cellulose coating of PU fibres without altering BC fibre orientation or bacterial activity.