Polylactic is a Sustainable, Low Absorption, Low Autofluorescence Alternative to Other Plastics for Microfluidic and Organ-on-Chip Applications.

Organ-on-chip (OOC) devices are miniaturized devices replacing animal models in drug discovery and toxicology studies. The majority of OOC devices are made from polydimethylsiloxane (PDMS), an elastomer widely used in microfluidic prototyping, but posing a number of challenges to experimentalists, including leaching of uncured oligomers and uncontrolled absorption of small compounds. Here we assess the suitability of polylactic acid (PLA) as a replacement material to PDMS for microfluidic cell culture and OOC applications. We changed the wettability of PLA substrates and demonstrated the functionalization method to be stable over a time period of at least 9 months. We successfully cultured human cells on PLA substrates and devices, without coating. We demonstrated that PLA does not absorb small molecules, is transparent (92% transparency), and has low autofluorescence. As a proof of concept of its manufacturability, biocompatibility, and transparency, we performed a cell tracking experiment of prostate cancer cells in a PLA device for advanced cell culture.

On the injectability of free-standing magnetic nanofilms.

Free-standing films with sub-micrometric thickness, composed of soft polymers and functional nanostructures are promising candidates for many potential applications in the biomedical field, such as reduced port abdominal surgery. In this work, freely suspended poly(L-lactic acid) nanofilms with controlled morphology embedding superparamagnetic iron oxide nanoparticles were fabricated by spin-coating deposition. The mechanical properties of magnetic nanofilms were investigated by Strain-Induced Elastic Buckling Instability for Mechanical Measurements (SIEBIMM) test. Our results show that these freely suspended nanocomposite nanofilms are highly flexible and deformable, with Young's moduli of few GPa. Since they can be handled in liquid with syringes, a quantitative description of the nanofilms behavior during the manipulation with clinically applicable needles has been also provided. These magnetic nanofilms, remotely controllable by external electromagnetic fields, have potential applications in minimally invasive surgery as injectable nanopatches on inner organs wall. Graphical abstract ᅟ.

Porous Polymeric Nanofilms for Recreating the Basement Membrane in an Endothelial Barrier-on-Chip.

Organs-on-chips (OoCs) support an organotypic human cell culture in vitro. Precise representation of basement membranes (BMs) is critical for mimicking physiological functions of tissue interfaces. Artificial membranes in polyester (PES) and polycarbonate (PC) commonly used in in vitro models and OoCs do not replicate the characteristics of the natural BMs, such as submicrometric thickness, selective permeability, and elasticity. This study introduces porous poly(d,l-lactic acid) (PDLLA) nanofilms for replicating BMs in in vitro models and demonstrates their integration into microfluidic chips. Using roll-to-roll gravure coating and polymer phase separation, we fabricated transparent ∼200 nm thick PDLLA films. These nanofilms are 60 times thinner and 27 times more elastic than PES membranes and show uniformly distributed pores of controlled diameter (0.4 to 1.6 µm), which favor cell compartmentalization and exchange of large water-soluble molecules. Human umbilical vein endothelial cells (HUVECs) on PDLLA nanofilms stretched across microchannels exhibited 97% viability, enhanced adhesion, and a higher proliferation rate compared to their performance on PES membranes and glass substrates. After 5 days of culture, HUVECs formed a functional barrier on suspended PDLLA nanofilms, confirmed by a more than 10-fold increase in transendothelial electrical resistance and blocked 150 kDa dextran diffusion. When integrated between two microfluidic channels and exposed to physiological shear stress, despite their ultrathin thickness, PDLLA nanofilms upheld their integrity and efficiently maintained separation of the channels. The successful formation of an adherent endothelium and the coculture of HUVECs and human astrocytes on either side of the suspended nanofilm validate it as an artificial BM for OoCs. Its submicrometric thickness guarantees intimate contact, a key feature to mimic the blood-brain barrier and to study paracrine signaling between the two cell types. In summary, porous PDLLA nanofilms hold the potential for improving the accuracy and physiological relevance of the OoC as in vitro models and drug discovery tools.

Leveraging bioengineering to assess cellular functions and communication within human fetal membranes.

The fetal membranes enclose the growing fetus and amniotic fluid. Preterm prelabor rupture of fetal membranes is a leading cause of preterm birth. Fetal membranes are composed of many different cell types, both structural and immune. These cells must coordinate functions for tensile strength and membrane integrity to contain the growing fetus and amniotic fluid. They must also balance immune responses to pathogens with maintaining maternal-fetal tolerance. Perturbation of this equilibrium can lead to preterm premature rupture of membranes without labor. In this review, we describe the formation of the fetal membranes to orient the reader, discuss some of the common forms of communication between the cell types of the fetal membranes, and delve into the methods used to tease apart this paracrine signaling within the membranes, including emerging technologies such as organ-on-chip models of membrane immunobiology.

Free-standing poly(L-lactic acid) nanofilms loaded with superparamagnetic nanoparticles.

Freely suspended nanocomposite thin films based on soft polymers and functional nanostructures have been widely investigated for their potential application as active elements in microdevices. However, most studies are focused on the preparation of nanofilms composed of polyelectrolytes and charged colloidal particles. Here, a new technique for the preparation of poly(l-lactic acid) free-standing nanofilms embeddidng superparamagnetic iron oxide nanoparticles is presented. The fabrication process, based on a spin-coating deposition approach, is described, and the influence of each production parameter on the morphology and magnetic properties of the final structure is investigated. Superparamagnetic free-standing nanofilms were obtained, as evidenced by a magnetization hysteresis measurement performed with a superconducting quantum interference device (SQUID). Nanofilm surface morphology and thickness were evaluated by atomic force microscopy (AFM), and the nanoparticle dispersion inside the composites was investigated by transmission electron microscopy (TEM). These nanofilms, composed of a biodegradable polyester and remotely controllable by external magnetic fields, are promising candidates for many potential applications in the biomedical field.

A pilot study on a new anchoring mechanism for surgical applications based on mucoadhesives.

In order to minimize the invasiveness of laparoscopic surgery, different techniques are emerging from research to clinical practice. Whether the incision is performed on the outside - as in Single Port Laparoscopy (SPL) - or on the inside - as in Natural Orifice Transluminal Endoscopic Surgery (NOTES) - of the patient's body, inserting and operating all the instruments from a single access site seems to be the next challenge in surgery. Magnetic guidance has been recently proposed for controlling surgical tools deployed from a single access. However, the exponential drop of magnetic field with distance makes this solution suitable only for the upper side of the abdominal cavity in nonobese patients. In the present paper we introduce a polymeric anchoring mechanism to lock surgical assistive tools inside the gastric cavity, based on the use of mucoadhesive films. Mucoadhesive properties of four formulations, with different chemical components and concentration, are evaluated by using both in vitro and ex vivo test benches on porcine stomach samples. Hydration of mucoadhesive films by contact with the aqueous mucous layer is analyzed by means of in vitro swelling tests, whereas optimal preloading conditions and adhesion performances, in terms of detachment force, supported weight and size are investigated ex vivo. Mucoadhesion is observed with all the four formulations. For a contact area of 113 mm(2), the maximum normal and shear detachment forces withstood by the adhesive film are 2,6 N and 1 N respectively. These values grow up to 12,14 N and 4,5 N when the contact area increases to 706 mm(2). Lifetime of the bonding on the inner side of the stomach wall was around two hours. Mucoadhesive anchoring represents a fully biocompatible and safe approach to deploy multiple assistive surgical tools on mucosal tissues by minimizing the number of access ports. This technique has been quantitatively assessed ex vivo for anchoring on the inner wall of the gastric cavity or in gastroscopic surgery. By properly varying the chemical formulation, this approach can be extended to other cavities of the human body.

Embracing Mechanobiology in Next Generation Organ-On-A-Chip Models of Bone Metastasis.

Bone metastasis in breast cancer is associated with high mortality. Biomechanical cues presented by the extracellular matrix play a vital role in driving cancer metastasis. The lack of in vitro models that recapitulate the mechanical aspects of the in vivo microenvironment hinders the development of novel targeted therapies. Organ-on-a-chip (OOAC) platforms have recently emerged as a new generation of in vitro models that can mimic cell-cell interactions, enable control over fluid flow and allow the introduction of mechanical cues. Biomaterials used within OOAC platforms can determine the physical microenvironment that cells reside in and affect their behavior, adhesion, and localization. Refining the design of OOAC platforms to recreate microenvironmental regulation of metastasis and probe cell-matrix interactions will advance our understanding of breast cancer metastasis and support the development of next-generation metastasis-on-a-chip platforms. In this mini-review, we discuss the role of mechanobiology on the behavior of breast cancer and bone-residing cells, summarize the current capabilities of OOAC platforms for modeling breast cancer metastasis to bone, and highlight design opportunities offered by the incorporation of mechanobiological cues in these platforms.

Metabolomic Analysis Evidences That Uterine Epithelial Cells Enhance Blastocyst Development in a Microfluidic Device.

Here we report the use of a microfluidic system to assess the differential metabolomics of murine embryos cultured with endometrial cells-conditioned media (CM). Groups of 10, 1-cell murine B6C3F1 × B6D2F1 embryos were cultured in the microfluidic device. To produce CM, mouse uterine epithelial cells were cultured in potassium simplex optimized medium (KSOM) for 24 h. Media samples were collected from devices after 5 days of culture with KSOM (control) and CM, analyzed by reverse phase liquid chromatography and untargeted positive ion mode mass spectrometry analysis. Blastocyst rates were significantly higher (p < 0.05) in CM (71.8%) compared to control media (54.6%). We observed significant upregulation of 341 compounds and downregulation of 214 compounds in spent media from CM devices when compared to control. Out of these, 353 compounds were identified showing a significant increased abundance of metabolites involved in key metabolic pathways (e.g., arginine, proline and pyrimidine metabolism) in the CM group, suggesting a beneficial effect of CM on embryo development. The metabolomic study carried out in a microfluidic environment confirms our hypothesis on the potential of uterine epithelial cells to enhance blastocyst development. Further investigations are required to highlight specific pathways involved in embryo development and implantation.

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

Assisted reproduction technologies for clinical and research purposes rely on a brief in vitro embryo culture which, despite decades of progress, remain suboptimal in comparison to the physiological environment. One promising tool to improve this technique is the development of bespoke microfluidic chambers. Here we present and validate a new microfluidic device in polydimethylsiloxane (PDMS) for the culture of early mouse embryos. Device material and design resulted embryo compatible and elicit minimal stress. Blastocyst formation, hatching, attachment and outgrowth formation on fibronectin-coated devices were similar to traditional microdrop methods. Total blastocyst cell number and allocation to the trophectoderm and inner cell mass lineages were unaffected. The devices were designed for culture of 10-12 embryos. Development rates, mitochondrial polarization and metabolic turnover of key energy substrates glucose, pyruvate and lactate were consistent with groups of 10 embryos in microdrop controls. Increasing group size to 40 embryos per device was associated with increased variation in development rates and altered metabolism. Device culture did not perturb blastocyst gene expression but did elicit changes in embryo metabolome, which can be ascribed to substrate leaching from PDMS and warrant further investigation.

Adhesion and proliferation of skeletal muscle cells on single layer poly(lactic acid) ultra-thin films.

An increasing interest in bio-hybrid systems and cell-material interactions is evident in the last years. This leads towards the development of new nano-structured devices and the assessment of their biocompatibility. In the present study, the development of free-standing single layer poly(lactic acid) (PLA) ultra-thin films is described, together with the analysis of topography and roughness properties. The biocompatibility of the PLA films has been tested in vitro, by seeding C2C12 skeletal muscle cells, and thus assessing cells shape, density and viability after 24, 48 and 72 h. The results show that free-standing flexible PLA nanofilms represent a good matrix for C2C12 cells adhesion, spreading and proliferation. Early differentiation into myotubes is also allowed. The biocompatibility of the novel ultra-thin films as substrates for cell growth promotes their application in the fields of regenerative medicine, muscle tissue engineering, drug delivery, and-in general-in the field of bio-hybrid devices.

Translational Roadmap for the Organs-on-a-Chip Industry toward Broad Adoption.

Organs-on-a-Chip (OOAC) is a disruptive technology with widely recognized potential to change the efficiency, effectiveness, and costs of the drug discovery process; to advance insights into human biology; to enable clinical research where human trials are not feasible. However, further development is needed for the successful adoption and acceptance of this technology. Areas for improvement include technological maturity, more robust validation of translational and predictive in vivo-like biology, and requirements of tighter quality standards for commercial viability. In this review, we reported on the consensus around existing challenges and necessary performance benchmarks that are required toward the broader adoption of OOACs in the next five years, and we defined a potential roadmap for future translational development of OOAC technology. We provided a clear snapshot of the current developmental stage of OOAC commercialization, including existing platforms, ancillary technologies, and tools required for the use of OOAC devices, and analyze their technology readiness levels. Using data gathered from OOAC developers and end-users, we identified prevalent challenges faced by the community, strategic trends and requirements driving OOAC technology development, and existing technological bottlenecks that could be outsourced or leveraged by active collaborations with academia.

Organs-On-Chip Models of the Female Reproductive System.

Microfluidic-based technology attracts great interest in cell biology and medicine, in virtue of the ability to better mimic the in vivo cell microenvironment compared to conventional macroscale cell culture platforms. Recent Organs-on-chip (OoC) models allow to reproduce in vitro tissue and organ-level functions of living organs and systems. These models have been applied for the study of specific functions of the female reproductive tract, which is composed of several organs interconnected through intricate endocrine pathways and communication mechanisms. To date, a disease and toxicology study of this system has been difficult to perform. Thus, there is a compelling need to develop innovative platforms for the generation of disease model and for performing drug toxicity/screening in vitro studies. This review is focused on the analysis of recently published OoC models that recreate pathological and physiological characteristics of the female reproductive organs and tissues. These models aim to be used to assess changes in metabolic activity of the specific cell types and the effect of exposure to hormonal treatment or chemical substances on some aspects of reproduction and fertility. We examined these models in terms of device specifications, operating procedures, accuracy for studying the biochemical and functional activity of living tissues and the paracrine signalling that occurs within the different tissues. These models represent a powerful tool for understanding important diseases and syndromes affecting women all around the world. Immediate adoption of these models will allow to clarify diseases, causes and adverse events occurring during pregnancy such as pre-eclampsia, infertility or preterm birth, endometriosis and infertility.

Remote heart rate monitoring - Assessment of the Facereader rPPg by Noldus.

Remote photoplethysmography (rPPG) allows contactless monitoring of human cardiac activity through a video camera. In this study, we assessed the accuracy and precision for heart rate measurements of the only consumer product available on the market, namely the FacereaderTM rPPG by Noldus, with respect to a gold standard electrocardiograph. Twenty-four healthy participants were asked to sit in front of a computer screen and alternate two periods of rest with two stress tests (i.e. Go/No-Go task), while their heart rate was simultaneously acquired for 20 minutes using the ECG criterion measure and the FacereaderTM rPPG. Results show that the FacereaderTM rPPG tends to overestimate lower heart rates and underestimate higher heart rates compared to the ECG. The Facereader™ rPPG revealed a mean bias of 9.8 bpm, the 95% limits of agreement (LoA) ranged from almost -30 up to +50 bpm. These results suggest that whilst the rPPG FacereaderTM technology has potential for contactless heart rate monitoring, its predictions are inaccurate for higher heart rates, with unacceptable precision across the entire range, rendering its estimates unreliable for monitoring individuals.

Potential of Manuka Honey as a Natural Polyelectrolyte to Develop Biomimetic Nanostructured Meshes With Antimicrobial Properties.

The use of antibiotics has been the cornerstone to prevent bacterial infections; however, the emergency of antibiotic-resistant bacteria is still an open challenge. This work aimed to develop a delivery system for treating soft tissue infections for: (1) reducing the released antimicrobial amount, preventing drug-related systemic side effects; (2) rediscovering the beneficial effects of naturally derived agents; and (3) preserving the substrate functional properties. For the first time, Manuka honey (MH) was proposed as polyelectrolyte within the layer-by-layer assembly. Biomimetic electrospun poly(ε-caprolactone) meshes were treated via layer-by-layer assembly to obtain a multilayered nanocoating, consisting of MH as polyanion and poly-(allylamine-hydrochloride) as polycation. Physicochemical characterization demonstrated the successful nanocoating formation. Different cell lines (human immortalized and primary skin fibroblasts, and primary endothelial cells) confirmed positively the membranes cytocompatibility, while bacterial tests using Gram-negative and Gram-positive bacteria demonstrated that the antimicrobial MH activity was dependent on the concentration used and strains tested.

Assessment of the Fitbit Charge 2 for monitoring heart rate.

Fitness trackers are devices or applications for monitoring and tracking fitness-related metrics such as distance walked or run, calorie consumption, quality of sleep and heart rate. Since accurate heart rate monitoring is essential in fitness training, the objective of this study was to assess the accuracy and precision of the Fitbit Charge 2 for measuring heart rate with respect to a gold standard electrocardiograph. Fifteen healthy participants were asked to ride a stationary bike for 10 minutes and their heart rate was simultaneously recorded from each device. Results showed that the Fitbit Charge 2 underestimates the heart rate. Although the mean bias in measuring heart rate was a modest -5.9 bpm (95% CI: -6.1 to -5.6 bpm), the limits of agreement, which indicate the precision of individual measurements, between the Fitbit Charge 2 and criterion measure were wide (+16.8 to -28.5 bpm) indicating that an individual heart rate measure could plausibly be underestimated by almost 30 bpm.

Instrumenting a Fetal Membrane on a Chip as Emerging Technology for Preterm Birth Research.

Preterm birth (PTB) is clinically defined as process of giving birth before 37 weeks of gestation and is a leading cause of death among neonates and children under the age of five. Prematurity remains a critical issue in developed countries, yet our understanding of the pathophysiology of PTB remains largely unknown. Among pregnancy complications, subclinical infections such as chorioamnionitis (CAM) are implicated in up to 70% of PTB cases. Specifically, CAM is characterized by the infection of the fetal membranes that surround the developing fetus and extend from the placenta, and is often associated with preterm, premature rupture of the fetal membranes (PPROM). The fetal membrane plays a key structural role in maintaining the fetal and maternal compartments of the gravid uterus. However, our understanding of the mechanisms of PPROM and the spatio-temporal progress of CAM remains vastly unknown. A lack of human-derived models have hindered our understanding of the mechanism that govern spontaneous PTB. Thus, in this short review, we discuss the emerging microfabrication technologies, specifically, organ-on-chip (OoCs) models, that seek to recapitulate the cellular and molecular context of the gestational membranes in vitro. These models show promise to facilitate the investigation of pathologic mechanisms that drive these disease conditions by mimicking the interactive contribution of the major cell types that make up the microenvironment of the fetal membrane and enable high throughput screening. Herein, we histologically characterize the microenvironment of the fetal membrane as a metric for scaling to recapitulate the functional components of the human fetal membrane. We review the current OoC models of the gravid uterus and conceptualize an "Instrumented Fetal Membrane on a Chip" (IFMOC) design as a prototype for PPROM and CAM research. Lastly, we discuss further applications of these OoC models for toxicological or pharmacological screening and personalized medicine. Fetal membrane OoCs offer an innovative and valuable platform to explore complex interactions between multiple drug types, toxic substances, and/or pathogenic microbes and their potential impacts on pregnancy outcomes. Further work will be required by integrating technological and analytical capabilities in order to characterize the fetal membrane microenvironment for preterm birth research.

Exposure to the environmental endocrine disruptor TCDD and human reproductive dysfunction: Translating lessons from murine models.

Humans and other animals are exposed to a wide array of man-made toxicants, many of which act as endocrine disruptors that exhibit differential effects across the lifespan. In humans, while the impact of adult exposure is known for some compounds, the potential consequences of developmental exposure to endocrine disrupting chemicals (EDCs) is more difficult to ascertain. Animal studies have revealed that exposure to EDCs prior to puberty can lead to adult reproductive disease and dysfunction. Specifically, in adult female mice with an early life exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), we demonstrated a transgenerational occurrence of several reproductive diseases that have been linked to endometriosis in women. Herein, we review the evidence for TCDD-associated development of adult reproductive disease as well as known epigenetic alterations associated with TCDD and/or endometriosis. We will also introduce new "Organ-on-Chip" models which, combined with our established murine model, are expected to further enhance our ability to examine alterations in gene-environment interactions that lead to heritable disease.

Compartmentalized Culture of Perivascular Stroma and Endothelial Cells in a Microfluidic Model of the Human Endometrium.

The endometrium is the inner lining of the uterus. Following specific cyclic hormonal stimulation, endometrial stromal fibroblasts (stroma) and vascular endothelial cells exhibit morphological and biochemical changes to support embryo implantation and regulate vascular function, respectively. Herein, we integrated a resin-based porous membrane in a dual chamber microfluidic device in polydimethylsiloxane that allows long term in vitro co-culture of human endometrial stromal and endothelial cells. This transparent, 2-µm porous membrane separates the two chambers, allows for the diffusion of small molecules and enables high resolution bright field and fluorescent imaging. Within our primary human co-culture model of stromal and endothelial cells, we simulated the temporal hormone changes occurring during an idealized 28-day menstrual cycle. We observed the successful differentiation of stroma into functional decidual cells, determined by morphology as well as biochemically as measured by increased production of prolactin. By controlling the microfluidic properties of the device, we additionally found that shear stress forces promoted cytoskeleton alignment and tight junction formation in the endothelial layer. Finally, we demonstrated that the endometrial perivascular stroma model was sustainable for up to 4 weeks, remained sensitive to steroids and is suitable for quantitative biochemical analysis. Future utilization of this device will allow the direct evaluation of paracrine and endocrine crosstalk between these two cell types as well as studies of immunological events associated with normal vs. disease-related endometrial microenvironments.

Ultrathin Polymer Membranes with Patterned, Micrometric Pores for Organs-on-Chips.

The basal lamina or basement membrane (BM) is a key physiological system that participates in physicochemical signaling between tissue types. Its formation and function are essential in tissue maintenance, growth, angiogenesis, disease progression, and immunology. In vitro models of the BM (e.g., Boyden and transwell chambers) are common in cell biology and lab-on-a-chip devices where cells require apical and basolateral polarization. Extravasation, intravasation, membrane transport of chemokines, cytokines, chemotaxis of cells, and other key functions are routinely studied in these models. The goal of the present study was to integrate a semipermeable ultrathin polymer membrane with precisely positioned pores of 2 µm diameter in a microfluidic device with apical and basolateral chambers. We selected poly(l-lactic acid) (PLLA), a transparent biocompatible polymer, to prepare the semipermeable ultrathin membranes. The pores were generated by pattern transfer using a three-step method coupling femtosecond laser machining, polymer replication, and spin coating. Each step of the fabrication process was characterized by scanning electron microscopy to investigate reliability of the process and fidelity of pattern transfer. In order to evaluate the compatibility of the fabrication method with organs-on-a-chip technology, porous PLLA membranes were embedded in polydimethylsiloxane (PDMS) microfluidic devices and used to grow human umbilical vein endothelial cells (HUVECS) on top of the membrane with perfusion through the basolateral chamber. Viability of cells, optical transparency of membranes and strong adhesion of PLLA to PDMS were observed, thus confirming the suitability of the prepared membranes for use in organs-on-a-chip devices.

Repairing Fetal Membranes with a Self-adhesive Ultrathin Polymeric Film: Evaluation in Mid-gestational Rabbit Model.

Preterm premature rupture of membranes causes 40% of all preterm births, affecting 150000 women each year in the United States. Prenatal diagnostic procedures and surgical interventions increase incidence of adverse events, leading to iatrogenic membrane rupture after a fetoscopic procedure in 45% of cases. We propose an ultrathin, self-adherent, poly-L-lactic acid patch ("nanofilm") as a reparative wound closure after endoscopic/fetoscopic procedures. These nanofilms are compatible with application in wet conditions and with minimally invasive instrumentation. Ex vivo studies to evaluate the nanofilm were conducted using human chorion-amnion (CA) membranes. A custom-built inflation device was used for mechanical characterization of CA membranes and for assessment of nanofilm adhesion and sealing of membrane defects up to 3 mm in size. These ex vivo tests demonstrated the ability of the nanofilm to seal human CA defects ranging in size from 1 to 3 mm in diameter. In vivo survival studies were conducted in 25 mid-gestational rabbits, defects were created by perforating the uterus and the CA membranes and subsequently using the nanofilm to seal these wounds. These in vivo studies confirmed the successful sealing of defects smaller than 3 mm observed ex vivo. Histological analysis of whole harvested uteri 7 days after surgery showed intact uterine walls in 59% of the nanofilm repaired fetuses, along with increased uterine size and intrauterine development in 63% of the cases. In summary, we have developed an ultrathin, self-adhesive nanofilm for repair of uterine membrane defects.