BACKGROUND: Fibrous capsules (Fb) in response to cardiovascular implantable electronic devices (CIEDs), including a pacemaker (P) system, can produce patient discomfort and difficulties in revision surgery due partially to their increased compressive strength, previously linked to elevated tissue fibers. OBJECTIVE: A preliminary study to quantify structural proteins, determine if biologic extracellular matrix-enveloped CIEDs (PECM) caused differential Fb properties, and to implement a realistic mechanical model. METHODS: Retrieved Fb (-P and -PECM) from minipigs were subjected to biomechanical (shear oscillation and uniaxial compression) and histological (collagen I and elastin) analyses. RESULTS: Fb-PECM showed significant decreases compared to Fb-P in: low strain-loss modulus (390 vs. 541 Pa) across angular frequencies, high strain-compressive elastic modulus (1043 vs. 2042 kPa), and elastic fiber content (1.92 vs. 3.15 μg/mg tissue). Decreases in elastin were particularly noted closer to the implant’s surface (Fb-PECM = 71% vs. Fb-P = 143% relative to dermal elastin at mid-tangential sections) and verified with a solid mechanics hyperelasticity with direction-dependent fiber viscoelasticity compression simulation (r2 ≥ 98.9%). CONCLUSIONS: The biologic envelope composed of decellularized porcine small intestine submucosa ECM for CIEDs promoted fibrous tissues with less elastic fibers. Novel compression modeling analyses directly correlated this singular reduction to more desirable subcutaneous tissue mechanics.

Controlled drug delivery systems such as the stimulation-based biomaterial scaffolds for sequestration and release of drugs offer safety and regulated therapeutic approach. In this study, the drug: para-aminobenzoic acid (PABA) was absorbed into a crosslinked chitosan and poly(caprolactone) (PCL) hydrogel and its release kinetics quantified under different conditions. It was experimentally-observed that the higher the pH (or the more basic the pH), the slower the PABA saturation release trended over time. At the acidic environment of pH 4, PABA was released the fastest, and enhanced by the degradation of chitosan-PCL gel. When a constant electric current of 0.6 mA as applied, PABA release was induced at pH 10. However, at pH 7, PABA was stably-bound to the chitosan-PCL matrix, with or without the external current. The selective sequestration of PABA at basic pH and its stimulated release via electric current application can be further explored for clinical translatability.