Chemical and Structural Characterization of Several Mid-Term Explanted Breast Prostheses

Bioprinted Vascularized Mature Adipose Tissue with Collagen Microfibers for Soft Tissue Regeneration

The development of soft tissue regeneration has recently gained importance due to safety concerns about artificial breast implants. Current autologous fat graft implantations can result in up to 90% of volume loss in long-term outcomes due to their limited revascularization. Adipose tissue has a highly vascularized structure which enables its proper homeostasis as well as its endocrine function. Mature adipocytes surrounded by a dense vascular network are the specific features required for efficient regeneration of the adipose tissue to perform host anastomosis after its implantation. Recently, bioprinting has been introduced as a promising solution to recreate in vitro this architecture in large-scale tissues. However, the in vitro induction of both the angiogenesis and adipogenesis differentiations from stem cells yields limited maturation states for these two pathways. To overcome these issues, we report a novel method for obtaining a fully vascularized adipose tissue reconstruction using supporting bath bioprinting. For the first time, directly isolated mature adipocytes encapsulated in a bioink containing physiological collagen microfibers (CMF) were bioprinted in a gellan gum supporting bath. These multilayered bioprinted tissues retained high viability even after 7 days of culture. Moreover, the functionality was also confirmed by the maintenance of fatty acid uptake from mature adipocytes. Therefore, this method of constructing fully functional adipose tissue regeneration holds promise for future clinical applications.

Biomechanical analysis of intact versus ruptured Poly Implant Prothèse breast implants

Despite there being many studies that have evaluated breast implant rupture, there is no consensus about causes and incidence. Most studies lack a multifactorial analysis of what causes breast implants to rupture. To fill this gap, an experimental protocol was developed to compare ruptured and intact Poly Implant Prothèse (PIP) breast implants from the same woman. These conditions guarantee that the physical/biological variables are the same for each pair of ruptured and intact implants. A total of 1008 samples from 22 PIP explants (11 intact and 11 ruptured) and three control PIP implants were analysed. The mechanical properties (tensile strength) of the ruptured and intact implants were compared according to brand, lot, implantation time and demographic conditions. In general, statistically significant differences were found between the intact and ruptured PIP implants. Ruptured implants were thinner (0.73 ± 0.10 mm versus 0.91 ± 0.11 mm) and weaker (7.42 ± 2.65 MPa versus 9.59 ± 2.37 MPa) than intact implants. Intact and ruptured implants have shown distinct mechanical behaviours and variations in thickness. Our understanding is that these differences may be associated with the typical manufacturing process of breast implant shells. These results stress the importance of thorough control of the shell thickness. Given its relevance, shell thickness should be used as a quality control measure for homologation purposes. Thus, the homogeneity of the shell should be considered as a relevant parameter during the manufacturing process. This will translate into an improved quality of life for patients and will potentiate safer and longer lasting products.

Mechanical and surface chemical analysis of retrieved breast implants from a single centre

INTRODUCTION

Breast implants are associated with complications such as capsular contracture, implant rupture and leakage often necessitating further corrective surgery. Re-operation rates have been reported to occur in up to 15.4% of primary augmentation patients and up to 27% in primary reconstructions patients within the first three years (Cunningham, 2007). The aim of this study was to examine the mechanical and surface chemical properties as well as the fibroblast response of retrieved breast implants in our unit to determine the in vivo changes which occur over time.

METHODS

Ethical approval was obtained. 47 implants were retrieved. Implantation time ranged from 1 month to 388 months (Mean 106.1 months). Tensile strength, elongation, Young's modulus and tear strength properties were measured using Instron 5565 tensiometer on anterior and posterior aspects of the implant. Attenuated total reflectance-fourier transform infra-red spectroscopy (ATR-FTIR), wettability and scanning electron microscopy (SEM) analysis was performed on the shell surfaces. Bicinchoninic acid assay was performed to determine shell protein content. The fibroblast response was determined by seeding HDFa cells on the retrieved implants and cell metabolism measured using Alamar Blue™ assay.

RESULTS

Mechanical properties fall with increasing duration of implantation. There were no significant changes in ATR-FTIR spectra between ruptured and intact implants nor significant changes in wettability in implants grouped into 5 year categories. SEM imaging reveals surface degradation changes with increasing duration of implantation.

CONCLUSIONS

With increasing duration of implantation, mechanical properties of the breast implants fall. However this was not associated with surface chemical changes as determined by ATR-FTIR and wettability nor protein content of the shells. Thus the reduction in mechanical properties is associated with breast implant failure but further research is required to elucidate the mechanisms.

In vitro degradation of polydimethylsiloxanes in breast implant applications

BACKGROUND

The durability of breast implant material is associated with failure probability, increasing with time from implantation. The current study avoided the bias introduced by biological factors, to systematically investigate the degradation over time of shell materials. The same fundamental physical and chemical conditions were maintained (temperature and pH) throughout the study, to decouple biological aspects from the degradation process.

METHODS

Six virgin implants of 2 brands were submitted to the in vitro degradation process, mechanical testing of shell materials, surface change analysis (via scanning electron microscopy [SEM]) and chemical composition analysis by Fourier transform infrared (FTIR) spectroscopy.

RESULTS

FTIR results showed that the principal chemical bonds of the material remained intact after 12 weeks of degradation. Apparently the implants' shell structures remained unchanged. Despite this observation, there were statistically significant differences between strain at failure at different time points for the shells of both brands, translated into a stiffening of the material over time.

CONCLUSIONS

Material stiffening is reported as an indicator of material degradation. This altered mechanical behavior, added to the mechanical friction from tissue-tissue and tissue-implant contact and to the external mechanical loading (physical activity), may alter the material performance in women's bodies. Ultimately these changes may affect the implants' durability. Further work is needed to understand the biological aspects of the degradation process and their impact on implant durability.