Nitrogen-Doped Carbon Quantum Dots Enhance In Vitro Fertilization and Early Embryo Development by Improving Sperm Activation in Mice

Nitrogen-doped Carbon Quantum Dots (NCQDs) exhibit distinctive optical properties and potential bioactivity in mammalian systems. However, their effects on reproductive cells remain poorly understood. To clarify their role in gamete function and embryo development, the present study examined the influence of NCQDs on sperm activation, fertilization, and early embryo development in vitro using a mouse model. At a low concentration (10 µg/mL), NCQDs exposure markedly enhanced sperm motility, survival, and capacitation, as determined by computer-assisted sperm analysis (CASA). These functional improvements significantly increased fertilization rates and enhanced embryonic development up to the morula stage. In contrast, blastocyst formation was delayed, accompanied by reduced pluripotency (Oct4) and trophectoderm differentiation (Cdx2, Tead2). Elevated mRNA expression of endoplasmic reticulum (ER) stress markers (Atf6, Chop) in morula-stage embryos suggested that prolonged NCQD exposure induces cellular stress that may interfere with lineage specification. Collectively, these findings reveal a stage-specific, biphasic effect of NCQDs, promoting sperm activation and early cleavage while inhibiting later differentiation, highlighting the need for optimized dosing and exposure timing to safely harness their reproductive benefits.