An Ultrasound-Induced Self-Clearance Hydrogel for Male Reversible Contraception

Abstract

Nearly half of pregnancies worldwide are unintended mainly due to failure of contraception, resulting in negative effects on women's health. Male contraception techniques, primarily condoms and vasectomy, play a crucial role in birth control, but cannot be both highly effective and reversible at the same time. Herein, an ultrasound (US)induced self-clearance hydrogel capable of real-time monitoring is utilized for in situ injection into the vas deferens, enabling effective contraception and noninvasive recanalization whenever needed. The hydrogel is composed of (i) sodium alginate (SA) conjugated with reactive oxygen species (ROS)-cleavable thioketal (SA-tK), (ii) titanium dioxide (TiO 2 ), which can generate a specific level of ROS after US treatment, and (iii) calcium chloride (CaCl 2 ), which triggers the formation of the hydrogel. For contraception, the above mixture agents are onetime injected into the vas deferens, which can transform from liquid to hydrogel within 160 s, thereby significantly physically blocking the vas deferens and inhibiting movability of sperm. When fertility is needed, a noninvasive remedial ultrasound can make TiO 2 generate ROS, which cleaves SA-tK to destroy the network of the hydrogel. Owing to the recanalization, the refertility rate is restored to 100%. Meanwhile, diagnostic ultrasound (D-US, 22 MHz) can monitor the occlusion and recanalization process in real-time. In summary, the proposed hydrogel contraception can be a reliable, safe, and reversible male contraceptive strategy that addresses an unmet need for men to control their fertility.

Advances in Bioresorbable Triboelectric Nanogenerators

“…The ability to determine the end point of an active operation while possessing the benefits of passive systems is highly advantageous. ,,, First, an active system reduces patient burden by eliminating residual devices in the body. The passive system still has discomfort because it requires follow-up for monitoring degradation and, potentially, surgical device removal if the device lifetime exceeds the time frame of a relevant process, thus hindering its commercial viability. ,, In contrast, implants based on active operations can be immediately dissolved if no longer needed, simplifying the planning and execution of the medical process.…”

“…(E) Self-clearance mechanism of an alginate hydrogel-TiO 2 NPs composite. Reproduced with permission from ref . Copyright 2022 American Chemical Society.…”

“…Wang et al reported a self-clearance hydrogel composite that can be dissolved by ultrasonic triggering events (Figure E) . The researchers prepared a hydrogel composite comprised of a sodium alginate hydrogel and titanium dioxide nanoparticles (TiO 2 NPs).…”

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“…Women suffer tremendous negative consequences from unintended pregnancies due to inadequate or no family planning. , Despite great advances in contraceptive technology in recent years, contraceptive failure remains a major factor in unwanted pregnancies worldwide. We summarized in Figure the currently available contraceptives in clinic and the contraceptive developed in laboratories for females and illustrated the contraceptive mechanisms.…”

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