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The biomedical measurements such as electrocorticography and electromyography have been widely performed for medical monitoring, diagnosis, and treatment of the diseases. In particular, subdural electrodes directly placed on the surface of a brain have been developed for a treatment of epilepsy and surgery. Conventional subdural electrodes consisting of metal electrodes such as Pt and the silicone-based substrate has various problems; the silicone substrate is not able to completely adhere to the brain surface due to its hardness and hydrophobicity, and artifacts will be generated in MRI imaging due to metal electrodes. We have developed a total organic hydrogel-based subdural electrode by embedding carbon fabric (CF) modified with poly(3,4-ethylenedioxythiophene) (PEDOT) into a poly(vinyl alcohol) (PVA) hydrogel substrate. Their softness similar to the living tissue and conformability to the curved surface of brains enabled easy handling, and the total organic materials will contribute to clearer MRI images without image artifacts. Moreover, molecules can pass through the hydrogel substrate of the electrode. Currently, we are working on the development of a hydrogel salt bridge electrode that is more transparent than conventional and our reported electrodes and reduces adverse effect on the body by avoiding the electrode from the biotissue surface and embedding salt bridges in the hydrogel substrate (Figure 1a). Although silicone microchannel is needed for a separation between hydrogels for the salt bridge and substrate, the bonding strength of silicone and hydrogel is poor, which causes a slip of the electrodes from measuring points. Various techniques for chemical bonding of silicone and hydrogel have been reported [1] [2], however, some of the substances used in these techniques are toxic and not biocompatible. In this study, we employed a physical bonding method with protrusions which are placed on the silicone surface to reduce the sliding of silicone and hydrogel. A frustum structure was selected as the shape of the protrusion, as for avoiding an exfoliation of the PVA hydrogel substrate from the silicone microchannel (Figure 1a). In order to evaluate the bonding strength, we prepared micro-structured polydimethylsiloxane (PDMS) sheets with 3D printed molds. The various micro-structured PDMS sheets were designed as rectangular (2 mm in the width) and frustum protrusions (4 mm, 2 mm, 1 mm and 0.5 mm in width) (Figure 1b). PDMS sheets with protrusions were embedded in PVA gel (15wt%), which were cross-linked by repeating freezing and thawing cycles (10 min at -30 °C and 10 min at room temperature for three times). A digital force gauge and an electric stand were used to perform tensile tests. Tensile loads were applied to both ends of the specimens, and the tension was recorded until the PDMS sheet and PVA gel were completely separated. In order to apply to the electrocorticography, we prepared the salt bridge electrode combined with the protrusions. The electrode was fabricated by injecting PVA precursor (10wt%) into the PDMS channel with protrusions and embedding that in PVA gel (15wt%). Each PVA was cross-linked by repeating freezing and thawing cycles at the same condition the above experiment. Then the electrode was placed on the brain of a pig along with a conventional electrode, and the brain wave was measured by electrocorticography (ECoG). Among the prepared PDMS sheets, the bonding strength of specimens with frustrum protrusions (10.8 kPa for 2 mm) showed higher than that of specimens with rectangular protrusions (9.3 kPa) and without protrusions (8.0 kPa) (Figure 1c). The bonding strength increased with a decrease of the size (0.5 mm, 2 mm and 4 mm) of protrusions (Figure 1d). Only 1 mm of protrusions did not follow the manner, which was under discussing. These results show that the frustum protrusions contribute to the physical bonding. Finally, we measured the ECoG signal by using the prepared hydrogel electrode. The salt bridge electrode was highly flexible enough to closely contact with the surface of the brain. Moreover, the ECoG signal measured by the hydrogel electrode was followed to conventional electrodes (Figure 1e). In conclusion, we successfully fabricated a flexible and biocompatible subdural electrode. References [1] Q. Liu, G. Nian, C. Yang, S. Qu and Z. Suo, “Bonding dissimilar polymer networks in various manufacturing processes,” Nature Communications, vol. 9, (2018) [2] D. Wirthl, R. Pichler, M. Drack, G. Kettlguber, R. Moser, R. Gerstmayr, F. Hartmann, E. Bradt, R. Kaltseis, C. M. Siket, S. E. Schausberger, S. Hild, S. Bauer and M. Kalten, “Instant tough bonding of hydrogels for soft machines and electronics,” Science Advances, vol. 3, no. 6, (2017). Figure 1

Background Rupture is an important complication of breast implants. Before cohesive gel silicone implants, rupture rates of both saline and silicone breast implants were over 10%. Through an analysis of ruptured implants, we can determine the various factors related to ruptured implants. Methods We performed a retrospective review of 72 implants that were removed for implant rupture between 2005 and 2014 at a single institution. The following data were collected: type of implants (saline or silicone), duration of implantation, type of implant shell, degree of capsular contracture, associated symptoms, cause of rupture, diagnostic tools, and management. Results Forty-five Saline implants and 27 silicone implants were used. Rupture was diagnosed at a mean of 5.6 and 12 years after insertion of saline and silicone implants, respectively. There was no association between shell type and risk of rupture. Spontaneous was the most common reason for the rupture. Rupture management was implant change (39 case), microfat graft (2 case), removal only (14 case), and follow-up loss (17 case). Conclusions Saline implants have a shorter average duration of rupture, but diagnosis is easier and safer, leading to fewer complications. Previous-generation silicone implants required frequent follow-up observation, and it is recommended that they be changed to a cohesive gel implant before hidden rupture occurs.

Background: Two-year safety and efficacy data were presented to the Canadian Therapeutic Products Directorate Scientific Advisory Panel, in Ottawa, Ontario, Canada. Methods: The 955 women enrolled in the 10-year, multicenter, Mentor MemoryGel study were distributed into four cohorts: 572 augmentation patients, 123 revision-augmentation patients, 191 reconstruction patients, and 69 revision-reconstruction patients. The surgeons in the study received an intensive clinical educational program in addition to the protocol. Results: Mentor’s 2-year study results indicate that the risk of any complication or reoperation at some point through 2 years after implant surgery is 24.5 percent for primary augmentation patients, 30.2 percent for revision-augmentation patients, 42.9 percent for primary reconstruction patients, and 41.8 percent for revision-reconstruction patients. The rupture rates reported from the magnetic resonance imaging cohort were 0 percent for all groups. Patients reoperated on at least one time were as follows: 9.4 percent for primary augmentation, 12.8 percent for revision-augmentation, 27.3 percent for primary reconstruction, and 19.4 percent for revision-reconstruction. Also, 2.4 percent of primary augmentation patients, 7.3 percent of revision-augmentation patients, 8.9 percent of primary, and 11.6 percent of reconstruction patients had their implants removed, with patient choice and capsular contracture being the most common reasons. Conclusions: The data from the Mentor CPG Gel Study resulted in approval of these implants for general use on October 20, 2006. The educational program resulted in improved clinical outcomes and probably should be required for all surgeons using the devices.

Bioplastique, a biphasic polymer of textured dimetylpolysiloxane is reported to be useful in filling small soft tissue defects. The microparticles range in size from 100 to 600 p and are suspended in a hydrogel carier from the family of the plasdones. The bioexcretable gel component is rapidly phagocytized and replaced by fibrin-like matrix with in a few days. In this study it is aimed to observe the local and systemic effects of Bioplastique and gel silicone in comparison. Our study in rabbit ears has shown that Bioplastique caused severe foreign body reaction in injection site and showed no migration to lymph nodes. On the other hand, silicone gel caused fibrous encapsulation and showed migration to lymph nodes, and formation of granulomatous reaction.

An experimental study is recorded that compares the use of soft gel silicone implants with, and without, a silicone sheet Dacron felt spacer, using the scalp of the guinea pig as a test site. Capsular contractures were produced in 45 percent of the control animals without the spacer. This was documented histologically to be related to a migration of muscle fibroblasts and could be prevented by the fixation of the Dacron felt to the pocket floor peripheral to the implant.