Abstract
Study question
Which fertilisation technique offers better embryo development results in patients without severe male factor?
Summary answer
Conventional IVF offers better results regarding ...embryo development than ICSI in patients without male factor when applying both techniques in the same cohort of oocytes.
What is known already
ICSI was originally indicated for severe male factor. Nevertheless, it is currently used for many other indications so that it has become the most used technique. One of the reasons for the use of ICSI is the fear of a fertilisation failure when using conventional IVF (cIVF).
We have to consider that ICSI is more expensive and invasive. For this reason, it is important to know whether there is a justification to use it in these cases.
Study design, size, duration
It is a randomized prospective study where 68 IVF/ICSI cycles were analysed. The study comprised 812 oocytes and 469 embryos and was conducted from January to December 2022 in the Assisted Reproduction Unit of a tertiary hospital.
In each cycle, we performed a mixed technique using cIVF and ICSI in the same cohort of oocytes.
MII rate, fertilisation rate and embryo development were analysed.
Participants/materials, setting, methods
All consecutive cycles with at least 6 fresh oocytes and semen parameters suitable for cIVF were offered to participate.
In each cycle, oocytes were divided into two groups in order of collection and the fertilisation technique (cIVF or ICSI) was randomly assigned for each group.
All the embryos were cultured to blastocyst stage.
Data of maturity, fertilisation and embryo development were individually registered for every oocyte.
Data were statistically analysed by applying multilevel regression models.
Main results and the role of chance
The patients average age was 36.3±3.0 (28 to 40) and the number of oocytes per cycle was 11.9±5.1 (6 to 26).
396 oocytes (48.8%) were allocated to cIVF group and 416 (51.2%) to ICSI group.
The percentage of mature oocytes was significantly higher in cIVF group than in ICSI group (88.9% vs 81.5%, p = 0.017), which is consistent with the later assessment of maturity in cIVF.
There were no statistically significant differences between cIVF and ICSI groups in terms of fertilisation rate (59.6% vs 56.0%) and high-quality blastocyst rate (A+B) (9.3% vs 8.7%) when analysed per oocyte.
We observed clinical but not statistical differences in blastocyst rate per oocyte (30.6% cIVF vs 23.6% ICSI, p = 0.09). However, blastocyst rate per fertilised oocyte showed statistically significant differences (51.3% cIVF vs 41.6% ICSI, p = 0.047).
Additionally, we found statistically significant differences between cIVF and ICSI in the rate of usable blastocysts (transferred or cryopreserved) per oocyte (26.3% vs 18.3%, p < 0.01) and per fertilised oocyte (44.1% vs 32.2%, p < 0.01).
In 57.8% of the cycles, the best blastocyst was obtained by cIVF and in 42.2% by ICSI.
Fertilisation failure was observed in 3 patients with cIVF and 1 patient with ICSI. All of them had ≤4 mature eggs.
Limitations, reasons for caution
This study includes the 68 patients who met the recruitment requirements until this moment. It is a part of a wider work, which will analyse a higher number of oocytes and pregnancy and perinatal outcomes. For this reason, the sample size is a limitation to the interpretation of the results.
Wider implications of the findings
Our findings encourage the use of cIVF when there is no severe male factor. Considering that cIVF is cheaper and less invasive than ICSI, the exclusive use of ICSI in these patients does not seem to be justified according to our results.
Trial registration number
not applicable
For the thermal management of high watt density circuit layers, it is common to use a filled epoxy system to provide an electrically insulating but thermally conducting bond to a metal substrate. An ...epoxy-thiol system filled with boron nitride (BN), in the form of 2, 30 and 180 µm platelets, has been investigated with a view to achieving enhanced thermal conductivity. The effect of BN content on the cure reaction kinetics has been studied by differential scanning calorimetry and the thermal conductivity of the cured samples has been measured by the Transient Hot Bridge method. The heat of reaction and the glass transition temperature of the fully cured samples are both independent of the BN content, but the cure reaction kinetics is systematically affected by both BN content and particle size. These results can be correlated with the thermal conductivity of the cured systems, which is found to increase with both BN content and particle size. For a given BN content, the thermal conductivity found here is significantly higher than most others reported in the literature; this effect is attributed to a Lewis acid-base interaction between filler and matrix.
Two different commercial hyperbranched poly(ethyleneimine)s (HBPEI), with molecular weights (MW) of 800 and 25,000 g/mol, and denoted as PEI800 and PEI25000, respectively, as well as the mixtures ...with a Diglycidyl Ether of Bisphenol-A (DGEBA) epoxy resin, have been studied using thermal analysis techniques (DSC, TGA), dielectric relaxation spectroscopy (DRS), and dynamic mechanical analysis (DMA). Only a single glass transition is observed in these mixtures by DSC. DRS of the HBPEIs shows three dipolar relaxations: γ, β, and α. The average activation energy for the γ-relaxation is similar for all HBPEIs and is associated with the motion of the terminal groups. The β-relaxation has the same average activation energy for both PEI800 and PEI25000; this relaxation is attributed to the mobility of the branches. The α-relaxation peak for all the HBPEIs is an asymmetric peak with a shoulder on the high temperature side. This shoulder suggests the existence of ionic charge trapped in the PEI. For the mixtures, the γ- and β-relaxations follow the behaviour of the epoxy resin alone, indicating that the epoxy resin dominates the molecular mobility. The α-relaxation by DRS is observed only as a shoulder, as a consequence of an overlap with conductivity effects, whereas by DMA, it is a clear peak.
Thermally conducting and electrically insulating materials have been prepared by filling an epoxy–thiol system with boron nitride (BN) particles of different shapes (platelets and agglomerates) and ...sizes (from 2 to 180 μm), and hence with different specific surface areas. The cure kinetics has been studied by differential scanning calorimetry in both non-isothermal and isothermal modes, and it has been shown that there is a systematic dependence of the cure kinetics on the BN content, the cure reaction generally being retarded by the addition of the BN particles. For filler loadings greater than about 30 vol%, the retardation of the cure, in both isothermal and non-isothermal mode, appears also to decrease as the specific surface area decreases. For the smallest (2 μm) platelets, which have a significantly higher specific surface area (10 m
2
g
−1
), the retardation is particularly pronounced, and this aspect is rationalized in terms of the activation energy and frequency factor of the reaction. The thermal conductivity of the cured epoxy–thiol–BN composites has been measured using the transient hot bridge method and is found to increase in the usual way with increasing BN content for all the particle types and sizes. For the platelets, the thermal conductivity increases with increasing particle size, mirroring the effect of BN content on the cure kinetics. The agglomerates, though, give the highest values of thermal conductivity, contrary to what might be expected in the light of their specific surface areas. Scanning electron microscopy of the fracture surfaces of the cured composites has been used to show that the interface between epoxy matrix and filler particles is better for the agglomerates. This, together with the reduced interfacial area, explains their higher thermal conductivity.
This work demonstrates that the application of even moderate pressures during cure can result in a remarkable enhancement of the thermal conductivity of composites of epoxy and boron nitride (BN). ...Two systems have been used: epoxy-thiol and epoxy-diamine composites, filled with BN particles of different sizes and types: 2, 30 and 180 μm platelets and 120 μm agglomerates. Using measurements of density and thermal conductivity, samples cured under pressures of 175 kPa and 2 MPa are compared with the same compositions cured at ambient pressure. The thermal conductivity increases for all samples cured under pressure, but the mechanism responsible depends on the composite system: For epoxy-diamine composites, the increase results principally from a reduction in the void content; for the epoxy-thiol system with BN platelets, the increase results from an improved matrix-particle interface; for the epoxy-thiol system with BN agglomerates, which has a thermal conductivity greater than 10 W/mK at 44.7 vol.% filler content, the agglomerates are deformed to give a significantly increased area of contact. These results indicate that curing under pressure is an effective means of achieving high conductivity in epoxy-BN composites.
The molecular mobility related to the glass transition and secondary relaxations in a hyperbranched polyethyleneimine, HBPEI, and its relaxation behaviour when incorporated into an epoxy resin matrix ...are investigated by dielectric relaxation spectroscopy (DRS) and dynamic mechanical analysis (DMA). Three systems are analysed: HBPEI, epoxy and an epoxy/HBPEI mixture, denoted ELP. The DRS behaviour is monitored in the ELP system in three stages: prior to curing, during curing, and in the fully cured system. In the stage prior to curing, DRS measurements show three dipolar relaxations: γ, β and α, for all systems (HBPEI, epoxy and ELP). The α-relaxation for the ELP system deviates significantly from that for HBPEI, but superposes on that for the epoxy resin. The fully cured thermoset displays both β- and α-relaxations. In DMA measurements, both α- and β-relaxations are observed in all systems and in both the uncured and fully cured systems, similar to the behaviour identified by DRS.
When an amorphous polymer is cooled under pressure from above its glass transition temperature to room temperature, and then the pressure is released, this results in a densified state of the glass. ...This procedure applied to an epoxy composite system filled with boron nitride (BN) particles has been shown to increase the density of the composite, reduce its enthalpy, and, most importantly, significantly enhance its thermal conductivity. An epoxy-BN composite with 58 wt% BN platelets of average size 30 µm has been densified by curing under pressures of up to 2.0 MPa and then cooling the cured sample to room temperature before releasing the pressure. It is found that the thermal conductivity is increased from approximately 3 W/mK for a sample cured at ambient pressure to approximately 7 W/mK; in parallel, the density increases from 1.55 to 1.72 ± 0.01 g/cm
. This densification process is much more effective in enhancing the thermal conductivity than is either simply applying pressure to consolidate the epoxy composite mixture before curing or applying pressure during cure but then removing the pressure before cooling to room temperature; this last procedure results in a thermal conductivity of approximately 5 W/mK. Furthermore, it has been shown that the densification and corresponding effect on the thermal conductivity is reversible; it can be removed by heating above the glass transition temperature and then cooling without pressure and can be reinstated by again heating above the glass transition temperature and then cooling under pressure. This implies that a densified state and an enhanced thermal conductivity can be induced even in a composite prepared without the use of pressure.
Multiarm star polymers, denoted PEI
-PLA
and containing a hyperbranched poly(ethyleneimine) (PEI) core of different molecular weights
and poly(lactide) (PLA) arms with
ratio of lactide repeat units ...to N links were used in this work. Samples were preconditioned to remove the moisture content and then characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy (DRS). The glass transition temperature,
, is between 48 and 50 °C for all the PEI
-PLA
samples. The dielectric curves show four dipolar relaxations: γ, β, α, and α' in order of increasing temperature. The temperatures at which these relaxations appear, together with their dependence on the frequency, allows relaxation maps to be drawn, from which the activation energies of the sub-
γ- and β-relaxations and the Vogel-Fulcher-Tammann parameters of the α-relaxation glass transition are obtained. The dependence of the characteristic features of these relaxations on the molecular weight of the PEI core and on the ratio of lactide repeat units to N links permits the assignation of molecular motions to each relaxation. The γ-relaxation is associated with local motions of the -OH groups of the poly(lactide) chains, the β-relaxation with motions of the main chain of poly(lactide), the α-relaxation with global motions of the complete assembly of PEI core and PLA arms, and the α'-relaxation is related to the normal mode relaxation due to fluctuations of the end-to-end vector in the PLA arms, without excluding the possibility that it could be a Maxwell-Wagner-Sillars type ionic peak because the material may have nano-regions of different conductivity.
The effect of three different organically modified layered silicate clays (Nanomer I.30E, Cloisite 30B and Nanofil SE 3000) on the exfoliation process and on the thermal properties and nanostructure ...of cured trifunctional epoxy resin based nanocomposites was studied. Optical microscopy showed that the best and poorest qualities of clay distribution in the epoxy matrix were obtained with Nanofil SE 3000 and Nanomer I.30E, respectively. However, the isothermal differential scanning calorimetry scans show that, of the three systems, it is only the Nanomer clay that promotes intra-gallery reaction due to homopolymerisation, appearing as an initial rapid peak prior to the cross-linking reaction. This rapid intra-gallery reaction is not present in the curing curve for the Cloisite and Nanofil systems. This fact implies that the fully cured nanostructure of the Cloisite and Nanofil system is poorly exfoliated, which is confirmed by small angle X-ray scattering which shows a scattering peak for these systems at around 2.53°, corresponding to about 3.5 nm d-spacing.
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