Insight into the mechanism and formation process of bioinspired poly(amino acid)/polyphenol capsules engineered with fast pH switchable permeability

Capsules have hollow cores and closed wall structures, and they have attracted considerable interest due to their wide applications and significance in life science. The engineering process of bioinspired capsules and related applications have earned heavy concerns. However, the mechanism of capsule formation is often ignored. Herein, based on polyornithine (POR) and tannic acid (TA), two facile strategies to engineer bioinspired capsules were proposed, and the formation mechanisms were deeply explored. We found that the oxidized state of TA had a profound influence not on the thickness or permeability of the formed capsule but on the mechanism and generation process. Compared to TA/POR capsules produced from TA without oxidization (TA/POR), capsules produced from TA with preoxidization (oTA/POR) had thicker shells with higher impermeability. The dominant construction mode in the shells of TA/POR capsules was electrostatic interactions but became Schiff base bonds in oTA/POR capsules. The permeability of oTA/POR displayed pH reversibility and strong pH dependence, with 100% permeability at lower pH and 100% impermeability at pH 7, completing loading/releasing kinetics in minutes at pH 4. We believe these findings contribute to knowledge of bioinspired capsules from engineering processes and formation mechanisms, extending their applications in various fields, such as in drug delivery, artificial cells, and sensors.

Evaluation of Safe Systemic Immunosuppression Created with Dexamethasone in Prevention of Capsular Contracture: A Glance to Distinct Perspectives with Toll-Like Receptors

PURPOSE

The toll-like receptors (TLRs) stand at the interface of innate immune activation. We hypothesize to decrease the response of innate immunity activated by TLR4 by a safe, short-term, systemic immunosuppression.

METHODS

Two silicone block implants were placed into two dorsal subcutaneous pockets in 32 rats that were subdivided into four groups: The two study groups were the IV DEX group (single intravenous injection of dexamethasone 1 h before surgery) and the IV DEX + IP DEX group (in addition to a single intravenous injection of dexamethasone 1 h before surgery, intraperitoneal dexamethasone was administered for 10 days after surgery), and the two control groups were the untreated control group and the saline-treated control group. After 10 weeks, all animals were killed to determine capsular thickness, inflammatory cell density, presence of pseudoepitheliomatous hyperplasia, edema, necrosis, vascularization, TLR4 expression and myofibroblast proliferation.

RESULTS

No significant difference was observed in any parameter between the untreated and saline-treated control groups (p > 0.05). Capsular thickness, myofibroblast proliferation, TLR4 expression density were statistically different among study groups compared to control (p < 0.05).

CONCLUSIONS

This study demonstrates the relationship between toll-like receptors and fibrous capsule after implant surgery. Decreasing the innate immunity by a safe, short-term perioperative systemic immunosuppression resulted in decreased TLR4 expression and myofibroblast differentiation which could be a new research field in profibrotic pathophysiology underlying breast capsule formation.

NO LEVEL ASSIGNED

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Acellular dermal matrix reduces capsule formation in two-stage breast reconstruction

Acellular dermal matrix (ADM) is commonly employed to create an inferior pocket for the tissue expander in two-stage breast reconstruction. The authors sought to determine whether placement of ADM during the first stage of reconstruction decreases the amount of capsule formation at implant exchange. Patients who underwent mastectomy and tissue expander reconstruction were included in this study. Two biopsies were obtained at the time of implant exchange, one from the pocket adjacent to the ADM and the other from the area adjacent to the pectoralis muscle. Pathology analysis was performed on each sample. Ten patients underwent immediate breast reconstruction with Alloderm during the 3-month study period. Capsule thickness was significantly greater in the areas where the expander was in direct contact with the pectoralis muscle (782 ± 194 µm) compared to those in contact with human acellular dermal matrix (hADM) (47·91 ± 110·82 µm; P < 0·05). Analysis of the sub-pectoral capsule demonstrated diffuse deposition of collagen, neutrophils, contractile myofibroblasts and synovia-like metaplasia, characteristic of a foreign body response. Conversely, within the inferior pocket where the hADM was in direct contact with the expander, we noted migration of host epithelial cells, fibroblasts, mesenchymal cells and angiogenesis, indicating host tissue regeneration. Acellular dermal matrix, when placed at the first stage of breast reconstruction, significantly reduces thickness and inflammatory character of the capsule in comparison to the patient's native tissue.