A pilot study investigating a novel particle-based growth factor delivery system for preimplantation embryo culture.

Study Question: Can vascular endothelial growth factor (VEGF)-loaded silica supraparticles (V-SPs) be used as a novel mode of delivering VEGF to the developing preimplantation embryo in vitro?

Summary Answer: Supplementation of embryo culture media with V-SPs promoted embryonic development in a manner equivalent to media supplemented with free VEGF.

What Is Known Already: VEGF is a maternally derived growth factor that promotes preimplantation embryonic development in vitro. However, its use in clinical media has limitations due to its low stability in solution.

Study Design, Size, Duration: This study was a laboratory-based analysis utilising a mouse model. V-SPs were prepared in vitro and supplemented to embryonic culture media. The bioactivity of V-SPs was determined by analysis of blastocyst developmental outcomes (blastocyst development rate and total cell number).

Participants/materials, Setting, Methods: SPs were loaded with fluorescently labelled VEGF and release kinetics were characterised. Bioactivity of unlabelled VEGF released from V-SPs was determined by analysis of embryo developmental outcomes (blastocyst developmental rate and total cell number) following individual mouse embryo culture in 20 µl of G1/G2 media at 5% oxygen, supplemented with 10 ng/ml recombinant mouse VEGF in solution or with V-SPs. The bioactivity of freeze-dried V-SPs was also assessed to determine the efficacy of cryostorage.

Main Results And The Role Of Chance: VEGF release kinetics were characterised by an initial burst of VEGF from loaded spheres followed by a consistent lower level of VEGF release over 48 h. VEGF released from V-SPs resulted in significant increases in total blastocyst cell number relative to the control (P < 0.001), replicating the effects of medium freely supplemented with fresh VEGF (P < 0.001). Similarly, freeze dried V-SPs exerted comparable effects on embryonic development (P < 0.05).

Large Scale Data: N/A.

Limitations, Reasons For Caution: In this proof of principle study, the effects of V-SPs on embryonic development were only analysed in a mouse model.

Wider Implications Of The Findings: These findings suggest that SPs represent a novel method by which a targeted dose of therapeutic agents (e.g. bioactive VEGF) can be delivered to the developing in vitro embryo to promote embryonic development, an approach that negates the breakdown of VEGF associated with storage in solution. As such, V-SPs may be an alternative and effective method of delivering bioactive VEGF to the developing in vitro embryo; however, the potential use of V-SPs in clinical IVF requires further investigation.

Study Funding/competing Interest(s): This work was funded by the University of Melbourne. The authors have no conflict of interest to declare.