Multifunctional Metal–Organic Framework Exoskeletons Protect Biohybrid Sperm Microrobots for Active Drug Delivery from the Surrounding Threats

Utilizing
spermatozoa as the engine unit of robotic systems at
a microscale has brought revolutionized inspirations and strategies
to the biomedical community. However, the motility of sperms is impaired
by the surrounding threats. For example, the antisperm antibody (AsA)
can specifically bind with surface antigens on the sperm membrane
and adversely affect their propulsion, hindering the operation of
sperm-based microrobots in practical environments. In the present
work, we report a biohybrid sperm microrobot by encapsulating sperm
cells within metal–organic frameworks (MOFs) and zeolitic imidazolate
framework-8 (ZIF-8) nanoparticles (NPs) (ZIFSpermbot), capable of
active drug delivery and cytoprotection from the biological threats
of AsA. ZIF-8 NPs can be facilely coated on the sperm membrane through
complexation with tannic acid. Such cell surface engineering has a
negligible impact on sperm motility under optimized conditions. The
selective permeability of the resulting porous ZIF-8 wrappings protects
ZIFSpermbots from the specific binding of AsA, enabling the preservation
of intrinsic propulsion of the sperm engine. Besides, ZIF-8 wrappings
sustainably release zinc ions and attenuate the oxidative damage generated
in sperm cells, allowing the maintenance of sperm movement. Combining
the effective protection of sperm propulsion with the drug-loading
capacity of ZIF-8 NPs provides new applicability to ZIFSpermbots in
risky surroundings with AsA, exhibiting rapid migration in a microfluidic
device for active drug delivery with enhanced therapeutic efficacy
due to their retained effective propulsion. Imparting bioengine-based
microrobots with multifunctional wrappings holds great promise for
designing adaptive cell robots that endure harsh environments toward
locally extended and diverse operations, facilitating their use in
practical and clinical applications.