A liposomal Gd contrast agent does not cross the mouse placental barrier

Nanotechnological approaches for the treatment of placental dysfunction: recent trends and future perspectives

The transitory placenta develops during pregnancy and mediates the blood flow between the mother and the developing baby. Placental dysfunction, including but not limited to placenta accreta spectrum, fetal growth restriction, preeclampsia and gestational trophoblastic disease, arises from abnormal placental development and can result in significant adverse maternal and fetal health outcomes. Unfortunately, there is a lack of treatment alternatives for these disorders. Nanocarriers offer versatility, including extended circulation, organ-specific targeting and intracellular transport, finely tuning therapeutic placental interactions. This thorough review explores nanotechnological strategies for addressing placental disorders, encompassing dysfunction insights, potential drug-delivery targets and recent strides in placenta-targeted nanoparticle (NP) therapies, instilling hope for effective placental malfunction treatment.

Nanomedicine for Maternal and Fetal Health

Conception, pregnancy, and childbirth are complex processes that affect both mother and fetus. Thus, it is perhaps not surprising that in the United States alone, roughly 11% of women struggle with infertility and 16% of pregnancies involve some sort of complication. This presents a clear need to develop safe and effective treatment options, though the development of therapeutics for use in women's health and particularly in pregnancy is relatively limited. Physiological and biological changes during the menstrual cycle and pregnancy impact biodistribution, pharmacokinetics, and efficacy, further complicating the process of administration and delivery of therapeutics. In addition to the complex pharmacodynamics, there is also the challenge of overcoming physiological barriers that impact various routes of local and systemic administration, including the blood-follicle barrier and the placenta. Nanomedicine presents a unique opportunity to target and sustain drug delivery to the reproductive tract and other relevant organs in the mother and fetus, as well as improve the safety profile and minimize side effects. Nanomedicine-based approaches have the potential to improve the management and treatment of infertility, obstetric complications, and fetal conditions.

Nanomedicines for Improved Management of Ectopic Pregnancy: A Narrative Review

Ectopic pregnancy (EP) - the implantation of an embryo outside of the endometrial cavity, often in the fallopian tube - is a significant contributor to maternal morbidity and leading cause of maternal death due to hemorrhage in first trimester. Current diagnostic modalities including human chorionic gonadotropin (hCG) quantification and ultrasonography are effective, but may still misdiagnose EP at initial examination in many cases. Depending on the patient's hemodynamic stability and gestational duration of the pregnancy, as assessed by history, hCG measurement and ultrasonography, management strategies may include expectant management, chemotherapeutic treatment using methotrexate (MTX), or surgical intervention. While these strategies are largely successful, expectant management may result in tubal rupture if the pregnancy does not resolve spontaneously; MTX administration is not always successful and may induce significant side effects; and surgical intervention may result in loss of the already-damaged fallopian tube, further hampering the patient's subsequent attempts to conceive. Nanomaterial-based technologies offer the potential to enhance delivery of diagnostic imaging contrast and therapeutic agents to more effectively and safely manage EP. The purpose of this narrative review is to summarize the current state of nanomedicine technology dedicated to its potential to improve both the diagnosis and treatment of EP.

Nanoparticle Contrast-enhanced MRI for Visualization of Retroplacental Clear Space Disruption in a Mouse Model of Placental Accreta Spectrum (PAS)

INTRODUCTION

Prior preclinical studies established the utility of liposomal nanoparticle blood-pool contrast agents in visualizing the retroplacental clear space (RPCS), a marker of normal placentation, while sparing fetuses from exposure because the agent does not cross the placental barrier. In this work, we characterized RPCS disruption in a mouse model of placenta accreta spectrum (PAS) using these agents.

MATERIALS AND METHODS

Contrast-enhanced MRI (CE-MRI) and computed tomography (CE-CT) using liposomal nanoparticles bearing gadolinium (liposomal-Gd) and iodine were performed in pregnant Gab3-/- and wild type (WT) mice at day 16 of gestation. CE-MRI was performed on a 1T scanner using a 2D T1-weighted sequence (100×100×600 µm3 voxels) and CE-CT was performed at a higher resolution (70×70×70 µm3 voxels). Animals were euthanized post-imaging and feto-placental units (FPUs) were harvested for histological examination. RPCS conspicuity was scored through blinded assessment of images.

RESULTS

Pregnant Gab3-/- mice showed elevated rates of complicated pregnancy. Contrast-enhanced imaging demonstrated frank infiltration of the RPCS of Gab3-/- FPUs. RPCS in Gab3-/- FPUs was smaller in volume, demonstrated a heterogeneous signal profile, and received lower conspicuity scores than WT FPUs. Histology confirmed in vivo findings and demonstrated staining consistent with a thinner RPCS in Gab3-/- FPUs.

DISCUSSION

Imaging of the Gab3-/- mouse model at late gestation with liposomal contrast agents enabled in vivo characterization of morphological differences in the RPCS that could cause the observed pregnancy complications. An MRI-based method for visualizing the RPCS would be valuable for early detection of invasive placentation.

Rational Design of Nanomedicine for Placental Disorders: Birthing a New Era in Women's Reproductive Health

The placenta is a transient organ that forms during pregnancy and acts as a biological barrier, mediating exchange between maternal and fetal circulation. Placental disorders, such as preeclampsia, fetal growth restriction, placenta accreta spectrum, and gestational trophoblastic disease, originate in dysfunctional placental development during pregnancy and can lead to severe complications for both the mother and fetus. Unfortunately, treatment options for these disorders are severely lacking. Challenges in designing therapeutics for use during pregnancy involve selectively delivering payloads to the placenta while protecting the fetus from potential toxic side effects. Nanomedicine holds great promise in overcoming these barriers; the versatile and modular nature of nanocarriers, including prolonged circulation times, intracellular delivery, and organ-specific targeting, can control how therapeutics interact with the placenta. In this review, nanomedicine strategies are discussed to treat and diagnose placental disorders with an emphasis on understanding the unique pathophysiology behind each of these diseases. Finally, prior study of the pathophysiologic mechanisms underlying these placental disorders has revealed novel disease targets. These targets are highlighted here to motivate the rational design of precision nanocarriers to improve therapeutic options for placental disorders.

Rapid In Vitro Quantification of a Sensitized Gadolinium Chelate via Photoinduced Triplet Harvesting

Gadolinium (Gd) based contrast agents (GBCAs) are widely used in magnetic resonance imaging (MRI) and are paramount to cancer diagnostics and tumor pharmacokinetic analysis. Accurate quantification of gadolinium concentration is essential to monitoring the biodistribution, clearance, and pharmacodynamics of GBCAs. However, current methods of quantifying gadolinium in blood or plasma (biological media) are both low throughput and clinically unavailable. Here, we have demonstrated the use of a sensitized gadolinium chelate, Gd[DTPA-cs124], as an MRI contrast agent that can be used to measure the concentration of gadolinium via luminescence quantification in biological media following transmetalation with a terbium salt. Gd[DTPA-cs124] was synthesized by conjugating carbostyril-124 (cs124) to diethylenetriaminepentaacetic acid (DTPA) and chelating to gadolinium. We report increases in both stability and relaxivity compared to the clinically approved analog Gd[DTPA] (gadopentetic acid or Magnevist). In vivo MRI experiments were conducted using C57BL6 mice in order to further illustrate the performance of Gd[DTPA-cs124] as an MRI contrast agent in comparison to Magnevist. Our results indicate that similar chemical modification to existing clinically approved GBCA may likewise provide favorable property changes, with the ability to be used in a gadolinium quantification assay. Furthermore, our assay provides a straightforward and high-throughput method of measuring gadolinium in biological media using a standard laboratory plate reader.

Nanotechnologies in Obstetrics and Cancer during Pregnancy: A Narrative Review

Nanotechnology, the art of engineering structures on a molecular level, offers the opportunity to implement new strategies for the diagnosis and management of pregnancy-related disorders. This review aims to summarize the current state of nanotechnology in obstetrics and cancer in pregnancy, focusing on existing and potential applications, and provides insights on safety and future directions. A systematic and comprehensive literature assessment was performed, querying the following databases: PubMed/Medline, Scopus, and Endbase. The databases were searched from their inception to 22 March 2022. Five independent reviewers screened the items and extracted those which were more pertinent within the scope of this review. Although nanotechnology has been on the bench for many years, most of the studies in obstetrics are preclinical. Ongoing research spans from the development of diagnostic tools, including optimized strategies to selectively confine contrast agents in the maternal bloodstream and approaches to improve diagnostics tests to be used in obstetrics, to the synthesis of innovative delivery nanosystems for therapeutic interventions. Using nanotechnology to achieve spatial and temporal control over the delivery of therapeutic agents (e.g., commonly used drugs, more recently defined formulations, or gene therapy-based approaches) offers significant advantages, including the possibility to target specific cells/tissues of interest (e.g., the maternal bloodstream, uterus wall, or fetal compartment). This characteristic of nanotechnology-driven therapy reduces side effects and the amount of therapeutic agent used. However, nanotoxicology appears to be a significant obstacle to adopting these technologies in clinical therapeutic praxis. Further research is needed in order to improve these techniques, as they have tremendous potential to improve the accuracy of the tests applied in clinical praxis. This review showed the increasing interest in nanotechnology applications in obstetrics disorders and pregnancy-related pathologies to improve the diagnostic algorithms, monitor pregnancy-related diseases, and implement new treatment strategies.

Estimation of Contrast Agent Concentration in DCE-MRI Using 2 Flip Angles

PURPOSE

The aim of this study was to investigate the feasibility of using 2 flip angles (FAs) with an ultrashort echo time during dynamic contrast-enhanced (DCE)-magnetic resonance imaging (MRI) for estimation of plasma gadolinium (Gd) concentration without using a precontrast longitudinal relaxation time T1 (T10) measurement.

METHODS

T1-weighted DCE-MRI experiments were carried out with C57BL/6J mice using the scan protocol with 2 FAs over 3 sequential segments during 1 scan. The data with 2 FAs were used to estimate T10 (T1T) during conversion of a time-intensity curve to the time-concentration curve. Three dosages of gadolinium-based contrast agent were used to achieve a wide range of variability in Gd concentrations when measured at 10 minutes postinjection: 0.05 mmol/kg (n = 6), 0.1 mmol/kg (n = 11), and 0.15 mmol/kg (n = 7). For comparison, the signal-to-concentration conversion was also conducted using the T10 measured from the precontrast scan (T1M) as well as a constant T10 (2.1 seconds) from the literature (T1C). The Gd concentrations ([Gd]) estimated using DCE-MRI data for the time of retro-orbital blood collection ([Gd]T1T, [Gd]T1M, and [Gd]T1C, respectively) were compared against the [Gd] of the blood samples measured by inductively coupled plasma mass spectrometry ([Gd]MS). In addition, contrast kinetic model analysis was conducted on mice with GL261 brain tumors (n = 5) using the 3 different methods for T10.

RESULTS

T1T strongly correlated with T1M (r = 0.81). [Gd]T1M and [Gd]T1T were significantly different from [Gd]T1C. [Gd]T1M and [Gd]T1T were in good agreement with [Gd]MS with strong correlations (mean percentage error ± standard deviation) of r = 0.70 (16% ± 56%) and r = 0.85 (15% ± 44%), respectively. In contrast, [Gd]T1C had a weak correlation of r = 0.52 with larger errors of 33% ± 24%. The contrast kinetic model parameters of GL261 brain tumors using T1T were not significantly different from those using T1M.

CONCLUSIONS

This study substantiates the feasibility of using the 2-FA approach during DCE-MRI scan to estimate [Gd] in the plasma without using an extra scan to perform precontrast T1 measurements.

Placental Models for Evaluation of Nanocarriers as Drug Delivery Systems for Pregnancy Associated Disorders

Pregnancy-associated disorders affect around 20% of pregnancies each year around the world. The risk associated with pregnancy therapeutic management categorizes pregnant women as “drug orphan” patients. In the last few decades, nanocarriers have demonstrated relevant properties for controlled drug delivery, which have been studied for pregnancy-associated disorders. To develop new drug dosage forms it is mandatory to have access to the right evaluation models to ensure their usage safety and efficacy. This review exposes the various placental-based models suitable for nanocarrier evaluation for pregnancy-associated therapies. We first review the current knowledge about nanocarriers as drug delivery systems and how placenta can be used as an evaluation model. Models are divided into three categories: in vivo, in vitro, and ex vivo placental models. We then examine the recent studies using those models to evaluate nanocarriers behavior towards the placental barrier and which information can be gathered from these results. Finally, we propose a flow chart on the usage and the combination of models regarding the nanocarriers and nanoparticles studied and the intended therapeutic strategy.

How Could Nanomedicine Improve the Safety of Contrast Agents for MRI during Pregnancy?

Pregnancy is a delicate state, during which timely investigation of possible physiological anomalies is essential to reduce the risk of maternal and fetal complications. Medical imaging encompasses different technologies to image the human body for the diagnosis, course of treatment management, and follow-up of diseases. Ultrasound (US) is currently the imaging system of choice for pregnant patients. However, sonographic evaluations can be non-effective or give ambiguous results. Therefore, magnetic resonance imaging (MRI), due to its excellent tissue penetration, the possibility of acquisition of three-dimensional anatomical information, and its high spatial resolution, is considered a valid diagnostical alternative. Nevertheless, currently employed contrast agents to improve the MRI image quality are harmful to the fetus. Because of their ability to cross the placenta, their use on pregnant patients is avoided. This review will firstly recapitulate the most common non-obstetrical, obstetrical, and fetal indications for magnetic resonance imaging on pregnant women. Fetal safety risks, due to the use of strong magnetic fields and exogenous contrast agents, will be presented. Then, possible advantages of nanostructured contrast agents compared to current molecular ones are explored. Nanosystems’ characteristics affecting contrast efficiency, and their potential for improving contrast-enhanced MRI’s safety in pregnant women, are discussed. Lastly, promising examples of nanoparticles as safer alternatives to current MRI contrast agents in pregnancy are discussed.

MRI in Pregnancy and Precision Medicine: A Review from Literature

Magnetic resonance imaging (MRI) offers excellent spatial and contrast resolution for evaluating a wide variety of pathologies, without exposing patients to ionizing radiations. Additionally, MRI offers reproducible diagnostic imaging results that are not operator-dependent, a major advantage over ultrasound. MRI is commonly used in pregnant women to evaluate, most frequently, acute abdominal and pelvic pain or placental abnormalities, as well as neurological or fetal abnormalities, infections, or neoplasms. However, to date, our knowledge about MRI safety during pregnancy, especially about the administration of gadolinium-based contrast agents, which are able to cross the placental barrier, is still limited, raising concerns about possible negative effects on both the mother and the health of the fetus. Contrast agents that are unable to cross the placenta in a way that is safe for the fetus are desirable. In recent years, some preclinical studies, carried out in rodent models, have evaluated the role of long circulating liposomal nanoparticle-based blood-pool gadolinium contrast agents that do not penetrate the placental barrier due to their size and therefore do not expose the fetus to the contrast agent during pregnancy, preserving it from any hypothetical risks. Hence, we performed a literature review focusing on contrast and non-contrast MRI use during pregnancy.

Targeted drug delivery for maternal and perinatal health: Challenges and opportunities

Pre-existing conditions at reproductive age, and complications arising during pregnancy can be detrimental to maternal and fetal health. Current therapies to combat obstetric disorders are limited due to the inherent complexity of pregnancy, and can have harmful effects on developing fetus. Emerging research shows intricate signaling between the cells from mother and fetus at maternal-fetal interface, providing unique opportunities for interventions specifically targeted to the mother, fetus, or placenta. Advancements in nanotechnology, stem-cell biology and gene therapy have resulted in target-specific treatments with promising results in pre-clinical maternal and fetal disorder models. Comprehensive understanding of the effect of physicochemical properties of delivery systems on their uptake, retention and accumulation across placenta will help in the better diagnosis and treatment of perinatal disorders. This review describes the factors leading to obstetric complications along with their effect on pregnancy outcomes, and discusses key targeted therapeutic strategies for addressing conditions related to maternal and fetal health.

Dynamic contrast enhanced magnetic resonance imaging: A review of its application in the assessment of placental function

It is important to develop a better understanding of placental insufficiency given its role in common maternofetal complications such as preeclampsia and fetal growth restriction. Functional magnetic resonance imaging offers unprecedented techniques for exploring the placenta under both normal and pathological physiological conditions. Dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) is an established and very robust method to investigate the microcirculatory parameters of an organ and more specifically its perfusion. It is currently a gold standard in the physiological and circulatory evaluation of an organ. Its application to the human placenta could enable to access many microcirculatory parameters relevant to the placental function such as organ blood flow, fractional blood volume, and permeability surface area, by the acquisition of serial images, before, during, and after administration of an intravenous contrast agent. Widely used in animal models with gadolinium-based contrast agents, its application to the human placenta could be possible if the safety of contrast agents in pregnancy is established or they are confirmed to not cross the placenta.

Human placental perfusion measured using dynamic contrast enhancement MRI

Objectives

To evaluate the feasibility of dynamic contrast enhanced magnetic resonance imaging (DCE MRI) and measure values of in vivo placental perfusion in women.

Methods

This study was part of the Placentimage trial (NCT01092949). Gadolinium-chelate (Gd) enhanced dynamic MRI was performed two days before termination of pregnancies at 16 to 34 weeks gestational age (GA). Quantitative analysis was performed using one-compartment intravascular modeling. DCE perfusion parameters were analyzed across GA and were compared in IUGR and AGA fetuses.

Results

134 patients were enrolled. After quality control check, 62 DCE MRI were analyzed including 48 and 14 pregnancies with normal and abnormal karyotypes, respectively. Mean placental blood flow was 129±61 mL/min/100ml in cases with normal karyotypes. Fetuses affected by IUGR (n = 13) showed significantly lower total placental blood flow values than AGA fetuses (n = 35) (F _total = 122±88 mL/min versus 259±34 mL/min, p = 0.002). DCE perfusion parameters showed a linear correlation with GA.

Conclusions

Measuring placental perfusion in vivo is possible using DCE MRI. Although this study has many limitations it gives us the first DCE MRI values that provide a potential standard for future research into placental perfusion methods and suggests that placental functional parameters are altered in IUGR pregnancies.

Dynamic placenta-on-a-chip model for fetal risk assessment of nanoparticles intended to treat pregnancy-associated diseases

Pregnant women often have to take medication either for pregnancy-related diseases or for previously existing medical conditions. Current maternal medications pose fetal risks due to off target accumulation in the fetus. Nanoparticles, engineered particles in the nanometer scale, have been used for targeted drug delivery to the site of action without off-target effects. This has opened new avenues for treatment of pregnancy-associated diseases while minimizing risks on the fetus. It is therefore instrumental to study the potential transfer of nanoparticles from the mother to the fetus. Due to limitations of in vivo and ex vivo models, an in vitro model mimicking the in vivo situation is essential. Placenta-on-a-chip provides a microphysiological recapitulation of the human placenta. Here, we reviewed the fetal risks associated with current therapeutic approaches during pregnancy, analyzed the advantages and limitations of current models used for nanoparticle assessment, and highlighted the current need for using dynamic placenta-on-a-chip models for assessing the safety of novel nanoparticle-based therapies during pregnancy.

Diseases and conditions that impact maternal and fetal health and the potential for nanomedicine therapies

Maternal mortality rates in the United States have steadily increased since 1987 to the current rate of over 16 deaths per 100,000 live births. Whereas most of these deaths are related to an underlying condition, such as cardiovascular disease, many pregnant women die from diseases that emerge as a consequence of pregnancy. Both pre-existing and emergent diseases and conditions are difficult to treat in pregnant women because of the potential harmful effects of the treatment on the developing fetus. Often the health of the woman and the health of the baby are at odds and must be weighed against each other when medical treatment is needed, frequently leading to iatrogenic preterm birth. However, the use of engineered nanomedicines has the potential to fill the treatment gap for pregnant women. This review describes several conditions that may afflict pregnant women and fetuses and introduces how engineered nanomedicines may be used to treat these illnesses. Although the field of maternal-fetal nanomedicine is in its infancy, with additional research and development, engineered nanotherapeutics may greatly improve outcomes for pregnant women and their offspring in the future.

Nanoparticle Contrast-enhanced T1-Mapping Enables Estimation of Placental Fractional Blood Volume in a Pregnant Mouse Model

Non-invasive methods for estimating placental fractional blood volume (FBV) are of great interest for characterization of vascular perfusion in placentae during pregnancy to identify placental insufficiency that may be indicative of local ischemia or fetal growth restriction (FGR). Nanoparticle contrast-enhanced magnetic resonance imaging (CE-MRI) may enable direct placental FBV estimation and may provide a reliable, 3D alternative to assess maternal-side placental perfusion. In this pre-clinical study, we investigated if placental FBV at 14, 16, and 18 days of gestation could be estimated through contrast-enhanced MRI using a long circulating blood-pool liposomal gadolinium contrast agent that does not penetrate the placental barrier. Placental FBV estimates of 0.47 ± 0.06 (E14.5), 0.50 ± 0.04 (E16.5), and 0.52 ± 0.04 (E18.5) were found through fitting pre-contrast and post-contrast T1 values in placental tissue using a variable flip angle method. MRI-derived placental FBV was validated against nanoparticle contrast-enhanced computed tomography (CE-CT) derived placental FBV, where signal is directly proportional to the concentration of iodine contrast agent. The results demonstrate successful estimation of the placental FBV, with values statistically indistinguishable from the CT derived values.

Perfusion of the placenta assessed using arterial spin labeling and ferumoxytol dynamic contrast enhanced magnetic resonance imaging in the rhesus macaque

PURPOSE

To investigate the correspondence between arterial spin labeling (ASL) flow-sensitive alternating inversion recovery (FAIR) and ferumoxytol DCE MRI for the assessment of placental intervillous perfusion.

METHODS

Ten pregnant macaques in late second trimester were imaged at 3 T using a 2D ASL FAIR, with and without outer-volume saturation pulses used to control the bolus width, and a 3D ferumoxytol DCE-MRI acquisition. The ASL tagged/control pairs were averaged, subtracted, and normalized to create perfusion ratio maps. Contrast arrival time and uptake slope were estimated by fitting the DCE data to a sigmoid function. Macaques (N = 4) received interleukin-1β to induce inflammation and disrupt perfusion.

RESULTS

The FAIR tag modification with outer-volume saturation reduced the median ASL ratio percentage compared with conventional FAIR (0.64% ± 1.42% versus 0.71% ± 2.00%; P < .05). Extended ferumoxytol arrival times (34 ± 25 seconds) were observed across the placenta. No significant DCE signal change was measured in fetal tissue ( - 0.6% ± 3.0%; P = .52) or amniotic fluid (1.9% ± 8.8%; P = .59). High ASL ratio was significantly correlated with early arrival time and high uptake slope (P < .05), but ASL signal was not above noise in late-DCE-enhancing regions. No significant differences were observed in perfusion measurements between the interleukin-1β and controls (P > .05).

CONCLUSION

The ASL-FAIR and ferumoxytol DCE-MRI methods are feasible to detect early blood delivery to the macaque placenta. Outer volume saturation reduced the high macrovascular ASL signal. Interleukin-1β exposure did not alter placental intervillous perfusion. An endogenous-labeling perfusion technique is limited due to extended transit times for flow within the placenta beyond the immediate vicinity of the maternal spiral arteries.

Pre-clinical magnetic resonance imaging of retroplacental clear space throughout gestation

INTRODUCTION

Visualization of the retroplacental clear space (RPCS) may provide critical insight into the development of abnormally invasive placenta (AIP). In this pre-clinical study, we characterized the appearance of the RPCS on magnetic resonance imaging (MRI) during the second half of gestation using a liposomal gadolinium contrast agent (liposomal-Gd).

MATERIALS AND METHODS

Studies were performed in fifteen pregnant C57BL/6 mice at 10, 12, 14, 16, and 18 days of gestation. MRI was performed on a 1T permanent magnet scanner. Pre-contrast and post-contrast images were acquired using T1-weighted gradient-recalled echo (T1w-GRE) and T2-weighted fast spin echo (T2w-FSE) sequences. Animals were euthanized after imaging and feto-placental units harvested for histological examination. Visualization of the RPCS was scored by a maternal-fetal radiologist and quantified by measuring the contrast-to-noise ratio (CNR) on T1w images. Feto-placental features were segmented for analysis of volumetric changes during gestation.

RESULTS

Contrast-enhanced T1w images enabled the visualization of structural changes in placental development between days 10-18 of gestation. Although the placental margin on the fetal side was clearly visible at all time points, the RPCS was partially visible at day 10 of gestation, and clearly visible by day 12. Hematoxylin and eosin (H&E) staining of the placental tissue corroborated MRI findings of structural and morphological changes in the placenta.

CONCLUSIONS

Contrast-enhanced MR imaging using liposomal-Gd enabled adequate visualization of the retroplacental clear space starting at day 12 of gestation. The agent also enabled characterization of placental structure and morphological changes through gestation.

Nanosized Gadolinium and Uranium-Two Representatives of High-Reactivity Lanthanide and Actinide Metal Nanoparticles

Gadolinium (Gd⁰) and uranium (U⁰) nanoparticles are prepared via lithium naphthalenide ([LiNaph])-driven reduction in tetrahydrofuran (THF) using GdCl₃ and UCl₄, respectively, as low-cost starting materials. The as-prepared Gd⁰ and U⁰ suspensions are colloidally stable and contain metal nanoparticles with diameters of 2.5 ± 0.7 nm (Gd⁰) and 2.0 ± 0.5 nm (U⁰). Whereas THF suspensions are chemically stable under inert conditions (Ar and vacuum), nanoparticulate powder samples show high reactivity in contact with, for example, oxygen, moisture, alcohols, or halogens. Such small and highly reactive Gd⁰ and U⁰ nanoparticles are first prepared via a dependable liquid-phase synthesis and stand as representatives for further nanosized lanthanides and actinides.

A preliminary study on fetal lung injury in a rat model of acute pancreatitis in pregnancy

Acute pancreatitis in pregnancy (APIP), which was thought to be rare, is becoming more frequent. In addition, high perinatal mortality among fetuses has been reported. Our research aimed to investigate and assess fetal lung injury in a rat model of APIP and its possible mechanisms. The APIP model was induced by sodium taurocholate in Sprague-Dawley rats during the third trimester. Sham-operated (SO) rats in late gestation were used as controls, and dynamic observation and detection in the SO and acute pancreatitis (AP) groups were performed at 3 time-points. Histological changes in the fetal lungs, as well as the maternal pancreas and placenta were assessed. The levels of serum amylase, lipase, TNF-α and IL-1β were detected in maternal rats, and the expression of surfactant proteins A, B, C and D as well as their mRNA were determined. In this study, fetal lung injury as well as maternal pancreas and placenta injuries occurred in a time-dependent manner. The levels of serum amylase, lipase and TNF-α were markedly increased in maternal rats, and the levels of surfactant proteins A, B, C and D in fetal lungs were significantly decreased in the fetal lungs of the AP group. Ultrastructure injuries and the dysregulated synthesis and secretion of pulmonary surfactant proteins were observed in the AP group. Our research suggests that fetal lung injury is involved in the rat model of APIP and that the dysregulated synthesis and secretion of pulmonary surfactant proteins play a critical role in fetal lung injury during APIP.

Hydrodenticity to enhance relaxivity of gadolinium-DTPA within crosslinked hyaluronic acid nanoparticles

AIM

The efficacy of gadolinium (Gd) chelates as contrast agents for magnetic resonance imaging remains limited owing to poor relaxivity and toxic effects. Here, the effect of the hydration of the hydrogel structure on the relaxometric properties of Gd-DTPA is explained for the first time and called Hydrodenticity.

RESULTS

The ability to tune the hydrogel structure is proved through a microfluidic flow-focusing approach able to produce crosslinked hyaluronic acid nanoparticles, analyzed regarding the crosslink density and mesh size, and connected to the characteristic correlation times of the Gd-DTPA.

CONCLUSION

Hydrodenticity explains the boosting (12-times) of the Gd-DTPA relaxivity by tuning hydrogel structural parameters, potentially enabling the reduction of the administration dosage as approved for clinical use. [Formula: see text].