Our paper Ferritin-Nanocaged Aggregation-Induced Emission Nanoaggregates for NIR-II Fluorescence-Guided Noninvasive, Controllable Male Contraception is accepted by Materials Today Bio. 

Non-Invasive Male Contraceptive Strategy Uses Light-Activated Nanotechnology for Reversible or Permanent Effect

A study published in Materials Today Bio unveils a novel, non-invasive approach to male contraception that leverages light-activated nanotechnology. The research demonstrates the ability to achieve highly effective, temporary, or permanent contraception in male mice through a simple intravenous injection and subsequent application of near-infrared light, offering a promising solution for animal population control and potentially human reproductive health.

The study, titled "Ferritin-nanocaged aggregation-induced emission nanoaggregates for NIR-II fluorescence-guided noninvasive, controllable male contraception," utilizes a naturally occurring protein, human heavy-chain ferritin (HFn), as a nanocarrier to deliver light-sensitive molecules (AIEgens) specifically to the testes. This innovative system allows for precise control over the contraceptive effect, ranging from fully reversible to permanent, by simply adjusting the intensity of the applied light.

"This research represents a significant paradigm shift from conventional methods," said the senior author of the study. "We've moved away from invasive injections or permanent surgical procedures to a targeted, intravenous approach. The ability to visually guide the procedure and finely tune the outcome—temporary or permanent—is a powerful advancement in the field of contraception."

A Targeted and Visible Mechanism:
The core of this technology is the engineered HFn nanocage, which is loaded with special fluorescent molecules known as Aggregation-Induced Emission Luminogens (AIEgens). This construct, called HFn@BBT, is administered via a simple intravenous injection.

• Precise Targeting: The HFn nanocarrier naturally binds to transferrin receptor 1 (TfR1), which is highly expressed on cells of the blood-testis barrier and within the testes. This allows HFn@BBT to accumulate specifically in the testicular tissue, bypassing the need for direct injection.

• Fluorescence Guidance: The AIEgens fluoresce in the near-infrared-II (NIR-II) window, enabling researchers to use non-invasive imaging to track the nanocarrier's journey and confirm its successful accumulation in the testes before activating it.

• Controllable Photothermal Effect: Once accumulated, the testes are exposed to a safe 808 nm near-infrared laser. The HFn@BBT nanoparticles convert the light energy into heat, inducing mild hyperthermia within the testicular tissue.

Temporary or Permanent Effects, Dictated by Heat:
The study's most striking finding is the dose-dependent, controllable nature of the contraceptive effect:

• Reversible Contraception: When a lower laser power was used to raise testicular temperature to 40°C, it caused partial, temporary damage to the seminiferous tubules where sperm are produced. This resulted in a 100% reduction in fertility one week post-treatment. Crucially, the process was reversible, with fertility indices recovering to approximately 80% after 60 days, and no abnormalities were observed in subsequent offspring.

• Permanent Infertility: When a higher laser power was used to achieve a testicular temperature of 45°C, it led to complete and irreversible destruction of the testicular structure. This resulted in a total and permanent loss of fertility, which was maintained throughout the 60-day observation period.

Proven Safety and High Biocompatibility:
The platform demonstrated an excellent safety profile. The HFn protein is a natural, biodegradable carrier, and the AIEgens showed minimal toxicity. Comprehensive blood tests and histological analysis of major organs (heart, liver, spleen, lungs, kidneys) revealed no significant signs of systemic toxicity. The nanoparticles were also shown to be cleared from the body within approximately 60 hours.

"This non-invasive, image-guided strategy is a major step forward for managing animal populations in a humane and controlled manner," noted a lead researcher. "While demonstrated in animals, the underlying principle of targeted, controllable cellular therapy opens new avenues for future research in human reproductive health."

This research paves the way for the development of safe, effective, and patient-centric contraceptive technologies. By combining precise biological targeting with tunable physical activation, it offers a powerful and versatile platform that could one day transform family planning and wildlife management.

About Materials Today Bio
Materials Today Bio is a high-impact, peer-reviewed journal focused on the interface between biology and materials science, publishing cutting-edge research on advanced materials for therapeutic and diagnostic applications.