Probing morphological, genetic and metabolomic changes of in vitro embryo development in a microfluidic device

Culture conditions in the IVF laboratory: state of the ART and possible new directions

In the last four decades, the assisted reproductive technology (ART) field has witnessed advances, resulting in improving pregnancy rates and diminishing complications, in particular reduced incidence of multiple births. These improvements are secondary to advanced knowledge on embryonic physiology and metabolism, resulting in the ability to design new and improved culture conditions. Indeed, the incubator represents only a surrogate of the oviduct and uterus, and the culture conditions are only imitating the physiological environment of the female reproductive tract. In vivo, the embryo travels through a dynamic and changing environment from the oviduct to the uterus, while in vitro, the embryo is cultured in a static fashion. Importantly, while culture media play a critical role in optimising embryo development, a large host of additional factors are equally important. Additional potential variables, including but not limited to pH, temperature, osmolality, gas concentrations and light exposure need to be carefully controlled to prevent stress and permit optimal implantation potential. This manuscript will provide an overview of how different current culture conditions may affect oocyte and embryo viability with particular focus on human literature.

Nano-liter perfusion microfluidic device made entirely by two-photon polymerization for dynamic cell culture with easy cell recovery

Polydimethylsiloxane (PDMS) has been the material of choice for microfluidic applications in cell biology for many years, with recent advances encompassing nano-scaffolds and surface modifications to enhance cell-surface interactions at nano-scale. However, PDMS has not previously been amenable to applications which require complex geometries in three dimensions for cell culture device fabrication in the absence of additional components. Further, PDMS microfluidic devices have limited capacity for cell retrieval following culture without severely compromising cell health. This study presents a designed and entirely 3D-printed microfluidic chip (8.8 mm × 8.2 mm × 3.6 mm) using two-photon polymerization (2PP). The 'nest' chip is composed of ten channels that deliver sub-microliter volume flowrates (to ~ 600 nL/min per channel) to 10 individual retrievable cell sample 'cradles' that interlock with the nest to create the microfluidic device. Computational fluid dynamics modelling predicted medium flow in the device, which was accurately validated by real-time microbead tracking. Functional capability of the device was assessed, and demonstrated the capability to deliver culture medium, dyes, and biological molecules to support cell growth, staining and cell phenotype changes, respectively. Therefore, 2PP 3D-printing provides the precision needed for nanoliter fluidic devices constructed from multiple interlocking parts for cell culture application.

Surface functionalization of poly(dimethylsiloxane) substrates facilitates culture of pre-implantation mouse embryos by blocking non-selective adsorption

Poly(dimethylsiloxane) (PDMS) is widely used in biomedical settings such as microfluidics for its optical transparency, castability, gas permeability and relative biocompatibility. While PDMS devices with certain modifications or treatments have been used for mammalian pre-implantation embryo culture, it is unclear why native PDMS leads to significant embryo death. In this study, we employ Nile Red as a model hydrophobic small molecule to demonstrate that significant hydrophobic sequestration occurs on native PDMS substrates even with a bovine serum albumin-containing KSOM pre-equilibration. Our results suggest that this small molecule sequestration has detrimental effects on mouse embryo development in PDMS static culture wells, with 0% blastocyst development rates from embryos cultured on native PDMS. We found that prior saturation of the PDMS culture well with water vapour only rescues about 10% of blastocyst development rates, indicating osmolality alone is not responsible for the high rates of embryo arrest. We also present a safe and simple Pluronic F127 pretreatment for PDMS substrates that successfully circumvented the harmful effects of native PDMS, achieving a blastocyst and implantation rate akin to that of our polystyrene controls. Our results call into question how researchers and clinicians can account for the alterations in medium composition and embryo secretions when using hydrophobic substrates, especially in the mammalian embryo culture setting where minimum effective concentrations of peptides and amino acids are commonplace.