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A surge in the prevalence of obesity and metabolic syndrome, which promote systemic inflammation, underlies an increase in cardiometabolic disease. Free fatty acid receptor 4 is a nutrient sensor for long-chain fatty acids, like ω3-polyunsaturated fatty acids (ω3-PUFAs), that attenuates metabolic disease and resolves inflammation. Clinical trials indicate ω3-PUFAs are cardioprotective, and this review discusses the mechanistic links between ω3-PUFAs, free fatty acid receptor 4, and attenuation of cardiometabolic disease.

The "job talk"is a standard element of faculty recruiting. How audiences treat candidates for faculty positions during job talks could have disparate impact on protected groups, including women. We annotated 156 job talks from five engineering and science departments for 13 categories of questions and comments. All departments were ranked in the top 10 by US News & World Report. We find that differences in the number, nature, and total duration of audience questions and comments are neither material nor statistically significant. For instance, the median difference (by gender) in the duration of questioning ranges from zero to less than two minutes in the five departments. Moreover, in some departments, candidates who were interrupted more often were more likely to be offered a position, challenging the premise that interruptions are necessarily prejudicial. These results are specific to the departments and years covered by the data, but they are broadly consistent with previous research, which found differences of comparable in magnitude. However, those studies concluded that the (small) differences were statistically significant. We present evidence that the nominal statistical significance is an artifact of using inappropriate hypothesis tests. We show that it is possible to calibrate those tests to obtain a proper P-value using randomization.

More than half of the current members of the US Congress served in their state legislature prior to holding federal office. We quantify the relationship between state legislative service and career progression to Congress. Using close elections for exogenous assignment of political experience across otherwise similar candidates, we show that serving in the state legislature more than doubles an individual's probability of eventually contesting a Congressional seat relative to a similar candidate who lost in a comparable election; it also doubles the individual politician's probability of eventually winning a Congressional seat. State legislatures thus create national politicians out of otherwise marginal political entrants. We then show that the effect of state legislative service on career progression is larger in more professionalized legislatures, highlighting the role of institutions in facilitating political career progression. Our results hold important implications for representation and accountability, and confirm that prevailing institutions can affect political selection via career progression.

Does increasing the number of women in career stages that precede high-level positions affect female representation at the top of the career ladder? State legislature elections narrowly won by female candidates in India are exploited to examine the effect of expanding the pipeline of women in local politics on subsequent female representation and success in national legislature elections. For each additional state legislature election won by a woman, there is a 34 percent increase in the number of female candidates contesting in the subsequent national election, and a 2.6 percentage-point increase in the average vote share won per female candidate. This relationship is driven by new female politicians and not by the progression of female state legislators nor by continued candidacy of previous female candidates for the national legislature.

Human articular cartilage has a poor ability to self-repair, meaning small injuries often lead to osteoarthritis, a painful and debilitating condition which is a major contributor to the global burden of disease. Existing clinical strategies generally do not regenerate hyaline type cartilage, motivating research toward tissue engineering solutions. Prospective cartilage tissue engineering therapies can be placed into two broad categories: i) Ex situ strategies, where cartilage tissue constructs are engineered in the lab prior to implantation and ii) in situ strategies, where cells and/or a bioscaffold are delivered to the defect site to stimulate chondral repair directly. While commonalities exist between these two approaches, the core point of distinction-whether chondrogenesis primarily occurs "within" or "without" (outside) the body-can dictate many aspects of the treatment. This difference influences decisions around cell selection, the biomaterials formulation and the surgical implantation procedure, the processes of tissue integration and maturation, as well as, the prospects for regulatory clearance and clinical translation. Here, ex situ and in situ cartilage engineering strategies are compared: Highlighting their respective challenges, opportunities, and prospects on their translational pathways toward long term human cartilage repair.

The natriuretic peptide receptors NPR1 and NPR2, also known as guanylyl cyclase A and guanylyl cyclase B, have critical functions in many signaling pathways, but much remains unknown about their localization and function in vivo. To facilitate studies of these proteins, we developed genetically modified mouse lines in which endogenous NPR1 and NPR2 were tagged with the HA epitope. To investigate the role of phosphorylation in regulating NPR1 and NPR2 guanylyl cyclase activity, we developed mouse lines in which regulatory serines and threonines were substituted with glutamates, to mimic the negative charge of the phosphorylated forms (NPR1-8E and NPR2-7E). Here we describe the generation and applications of these mice. We show that the HA-NPR1 and HA-NPR2 mice can be used to characterize the relative expression levels of these proteins in different tissues. We describe studies using the NPR2-7E mice that indicate that dephosphorylation of NPR2 transduces signaling pathways in ovary and bone, and studies using the NPR1-8E mice that indicate that the phosphorylation state of NPR1 is a regulator of heart, testis, and adrenal function.

Mechanical testing is a valuable tool for assessing intervertebral disc health, but the wide range of testing protocols makes it difficult to compare results from different studies. Normalizing mechanical properties by disc geometry allows for such comparisons, but there is little consistency in the methods by which disc geometry is measured. As such, we hypothesized that methods used to measure disc geometry would impact reported mechanical properties. Disc height and area were measured using computed tomography (CT), digital calipers, and ImageJ to yield three different measurements for disc height and six for disc area. Disc heights measured by digital calipers ex situ were >30% less than disc heights measured in situ by CT, and disc areas measured ex situ using ImageJ were >30% larger than those measured by CT. This significantly affected reported mechanical properties, leading to a 65% reduction in normalized compressive stiffness in the most extreme case. Though we cannot quantitatively correct between methods, results presented in this study suggest that disc geometry measurement methods have a significant impact on normalized mechanical properties and should be accounted for when comparing results.

The human tissues most sensitive to electrical activity such as neural and muscle tissues are relatively soft, and yet traditional conductive materials used to interface with them are typically stiffer by many orders of magnitude. Overcoming this mismatch, by creating both very soft and electroactive materials, is a major challenge in bioelectronics and biomaterials science. One strategy is to imbue soft materials, such as hydrogels, with electroactive properties by adding small amounts of highly conductive nanomaterials. However, electroactive hydrogels reported to date have required relatively large volume fractions (>1%) of added nanomaterial, have shown only modest electroactivity, and have not been processable via additive manufacturing to create 3D architectures. Here, we describe the development and characterization of improved biocompatible photo-cross-linkable soft hybrid electroactive hydrogels based on gelatin methacryloyol (GelMA) and large area graphene oxide (GO) flakes, which resolve each of these three limitations. The addition of very small amounts (less than a 0.07% volume fraction) of GO to a 5% w/v GelMA hydrogel resulted in a dramatic (∼35-fold) decrease in the impedance at 1 Hz compared with GelMA alone. The GelMA/GO coated indium tin oxide (ITO) electrode also showed a considerable reduction in the impedance at 1 kHz (down to 170 Ω compared with 340 Ω for the GelMA-coated ITO), while charge injection capacity increased more than 6-fold. We attribute this enhanced electroactivity to the increased electroactive surface area contributed by the GO. Despite this dramatic change in electroactivity, the GelMA/GO composite hydrogels' mechanical properties were only moderately affected. Mechanical properties increased by ∼2-fold, and therefore, the hydrogels' desired softness of

The leading cause of disability of all ages worldwide is severe lower back pain. To address this untreated epidemic, further investigation is needed into the leading cause of back pain, intervertebral disc degeneration. In particular, microphysiological systems modeling critical tissues in a degenerative disc, like the annulus fibrosus (AF), are needed to investigate the effects of complex multiaxial strains on AF cells. By replicating these mechanobiological effects unique to the AF that are not yet understood, we can advance therapies for early-stage degeneration at the cellular level. To this end, we designed, fabricated, and collected proof-of-concept data for a novel microphysiological device called the flexing annulus-on-a-chip (AoC). We used computational models and experimental measurements to characterize the device's ability to mimic complex physiologically relevant strains. As a result, these strains proved to be controllable, multi-directional, and uniformly distributed with magnitudes ranging from

Gale crater, the field site for NASA's Mars Science Laboratory Curiosity rover, contains a diverse and extensive record of aeolian deposition and erosion. This study focuses on a series of regularly spaced, curvilinear, and sometimes branching bedrock ridges that occur within the Glen Torridon region on the lower northwest flank of Aeolis Mons, the central mound within Gale crater. During Curiosity's exploration of Glen Torridon between sols ∼2300-3080, the rover drove through this field of ridges, providing the opportunity for in situ observation of these features. This study uses orbiter and rover data to characterize ridge morphology, spatial distribution, compositional and material properties, and association with other aeolian features in the area. Based on these observations, we find that the Glen Torridon ridges are consistent with an origin as wind-eroded bedrock ridges, carved during the exhumation of Mount Sharp. Erosional features like the Glen Torridon ridges observed elsewhere on Mars, termed periodic bedrock ridges (PBRs), have been interpreted to form transverse to the dominant wind direction. The size and morphology of the Glen Torridon PBRs are consistent with transverse formative winds, but the orientation of nearby aeolian bedforms and bedrock erosional features raise the possibility of PBR formation by a net northeasterly wind regime. Although several formation models for the Glen Torridon PBRs are still under consideration, and questions persist about the nature of PBR-forming paleowinds, the presence of PBRs at this site provides important constraints on the depositional and erosional history of Gale crater.

Background: Articular cartilage repair using implantable photocrosslinkable hydrogels laden with chondrogenic cells, represents a promising in situ cartilage engineering approach for surgical treatment. The development of a surgical procedure requires a minimal viable product optimized for the clinical scenario. In our previous work we demonstrated how gelatin based photocrosslinkable hydrogels in combination with infrapatellar derived stem cells allow the production of neocartilage in vitro. In this study, we aim to optimize the critical facets of the in situ cartilage engineering therapy: the cell source, the cell isolation methodology, the cell expansion protocol, the cell number, and the delivery approach. Methods: We evaluated the impact of the critical facets of the cell-laden hydrogel therapy in vitro to define an optimized protocol that was then used in a rabbit model of cartilage repair. We performed cells counting and immunophenotype analyses, chondrogenic potential evaluation via immunostaining and gene expression, extrusion test analysis of the photocrosslinkable hydrogel, and clinical assessment of cartilage repair using macroscopic and microscopic scores. Results: We identified the adipose derived stem cells as the most chondrogenic cells source within the knee joint. We then devised a minimally manipulated stem cell isolation procedure that allows a chondrogenic population to be obtained in only 85 minutes. We found that cell expansion prior to chondrogenesis can be reduced to 5 days after the isolation procedure. We characterized that at least 5 million of cells/ml is needed in the photocrosslinkable hydrogel to successfully trigger the production of neocartilage. The maximum repairable defect was calculated based on the correlation between the number of cells retrievable with the rapid isolation followed by 5-day non-passaged expansion phase, and the minimum chondrogenic concentration in photocrosslinkable hydrogel. We next optimized the delivery parameters of the cell-laden hydrogel therapy. Finally, using the optimized procedure for in situ tissue engineering, we scored superior cartilage repair when compared to the gold standard microfracture approach. CONCLUSION: This study demonstrates the possibility to repair a critical size articular cartilage defect by means of a surgical streamlined procedure with optimized conditions.

Hydrogel materials are promising candidates in cartilage tissue engineering as they provide a 3D porous environment for cell proliferation and the development of new cartilage tissue. Both the mechanical and transport properties of hydrogel scaffolds influence the ability of encapsulated cells to produce neocartilage. In photocrosslinkable hydrogels, both of these material properties can be tuned by changing the crosslinking density. However, the interdependent nature of the structural, physical and biological properties of photocrosslinkable hydrogels means that optimizing composition is typically a complicated process, involving sequential and/or iterative steps of physiochemical and biological characterization. The combinational nature of the variables indicates that an exhaustive analysis of all reasonable concentration ranges would be impractical. Herein, response surface methodology (RSM) was used to efficiently optimize the composition of a hybrid of gelatin-methacryloyl (GelMA) and hyaluronic acid methacryloyl (HAMA) with respect to both mechanical and transport properties. RSM was employed to investigate the effect of GelMA, HAMA, and photoinitiator concentration on the shear modulus and diffusion coefficient of the hydrogel membrane. Two mathematical models were fitted to the experimental data and used to predict the optimum hydrogel composition. Finally, the optimal composition was tested and compared with the predicted values.

While censorship within China has been a longstanding phenomenon, efforts to suppress information and to reshape perception of China abroad have become increasingly widespread and sophisticated. Re...

Aims Free fatty acid receptor 4 (Ffar4) is a G-protein-coupled receptor for endogenous medium-/long-chain fatty acids that attenuates metabolic disease and inflammation. However, the function of Ffar4 in the heart is unclear. Given its putative beneficial role, we hypothesized that Ffar4 would protect the heart from pathologic stress. Methods and results In mice lacking Ffar4 (Ffar4KO), we found that Ffar4 is required for an adaptive response to pressure overload induced by transverse aortic constriction (TAC), identifying a novel cardioprotective function for Ffar4. Following TAC, remodelling was worsened in Ffar4KO hearts, with greater hypertrophy and contractile dysfunction. Transcriptome analysis 3-day post-TAC identified transcriptional deficits in genes associated with cytoplasmic phospholipase A2α signalling and oxylipin synthesis and the reduction of oxidative stress in Ffar4KO myocytes. In cultured adult cardiac myocytes, Ffar4 induced the production of the eicosapentaenoic acid (EPA)-derived, pro-resolving oxylipin 18-hydroxyeicosapentaenoic acid (18-HEPE). Furthermore, the activation of Ffar4 attenuated cardiac myocyte death from oxidative stress, while 18-HEPE rescued Ffar4KO myocytes. Systemically, Ffar4 maintained pro-resolving oxylipins and attenuated autoxidation basally, and increased pro-inflammatory and pro-resolving oxylipins, including 18-HEPE, in high-density lipoproteins post-TAC. In humans, Ffar4 expression decreased in heart failure, while the signalling-deficient Ffar4 R270H polymorphism correlated with eccentric remodelling in a large clinical cohort paralleling changes observed in Ffar4KO mice post-TAC. Conclusion Our data indicate that Ffar4 in cardiac myocytes responds to endogenous fatty acids, reducing oxidative injury, and protecting the heart from pathologic stress, with significant translational implications for targeting Ffar4 in cardiovascular disease.

The challenge with engineering soft materials is to find a chemically functionalized material that can be easily fabricated into complex structures while providing a supportive cellular milieu. The current gold standard is gelatin methacryloyl (GelMA), a semi-synthetic collagen-derived biomaterial that has found widespread utility as a bioink for 3D bioprinting. Although a fundamental understanding of controlling the mechanical properties of GelMA exists, the nano- and cell-scale network topology needs to be investigated to produce controlled structures. Here, for the first time, small-angle X-ray scattering (SAXS) is used to elucidate how structural changes on the network level dictate the final properties within a GelMA hydrogel. Scaffold nanostructure was observed pre- and post-crosslinking, with emphasis on assessing structural changes in response to changes in Degree of Functionalization (DoF) and polymer concentration. Samples were modelled regarding local-polymer conformation (mass fractal dimension), distance between entanglements (correlation length), and mesh size. Importantly, DoF is observed to alter crosslinked polymer conformation and nanoscale mesh size. These results inform future design of GelMA-based bioinks, allowing researchers to further leverage the young and evolving bioprinting technology for broad-spectrum applications such as cell/stem cell printing, organoid-based tissue structure, building cell/organ-on-a-chip, through to the hierarchical engineering of multicellular living systems.

Accurate assignment of monoisotopic peaks is essential for the identification of peptides in bottom-up proteomics. Misassignment or inaccurate attribution of peptidic ions leads to lower sensitivity and fewer total peptide identifications. In the present work we present a performant, open-source, cross-platform algorithm, Monocle, for the rapid reassignment of instrument assigned precursor peaks to monoisotopic peptide assignments. We demonstrate that the present algorithm can be integrated into many common proteomics pipelines and provides rapid conversion from multiple data source types. Finally, we show that our monoisotopic peak assignment results in up to a two-fold increase in total peptide identifications compared to analyses lacking monoisotopic correction and a 44% improvement over previous monoisotopic peak correction algorithms.

Extracellular-matrix composition impacts mechanical performance in native and engineered tissues. Previous studies showed collagen type I-agarose blends increased cell-matrix interactions and extracellular matrix production. However, long-term impacts on protein production and mechanical properties of engineered cartilage are unknown. Our objective was to characterize the effect of collagen type I on the matrix production of chondrocytes embedded in agarose hydrogels. We hypothesized that the addition of collagen would improve long-term mechanical properties and matrix production (e.g. collagen and glycosaminoglycans) through increased bioactivity. Agarose hydrogels (2% w/v) were mixed with varying concentrations of collagen type I (0, 2 and 5 mg/ml). Juvenile bovine chondrocytes were added to the hydrogels to assess matrix production over 4 weeks through biochemical assays, and mechanical properties were assessed through unconfined compression. We observed a dose-dependent effect on cell bioactivity, where 2 mg/ml of collagen improved bioactivity, but 5 mg/ml had a negative impact on bioactivity. This resulted in a higher modulus for scaffolds supplemented with lower collagen concentration as compared to the higher collagen concentration, but not when compared to the control. In conclusion, the addition of collagen to agarose constructs provided a dose-dependent impact on improving glycosaminoglycan production but did not improve collagen production or compressive mechanics.

Free fatty acid receptor 4 (Ffar4) is a G-protein coupled receptor for long-chain fatty acids that improves metabolism and attenuates inflammation. Heart failure preserved ejection fraction (HFpEF) is a complex clinical syndrome, but a predominant subset of patients has meta-bolic syndrome (MetS). Mechanistically, systemic, non-resolving inflammation associated with MetS might promote HFpEF. Interestingly, we recently demonstrated that Ffar4 is cardioprotective in pressure overload. The beneficial effects of Ffar4 on metabolism/inflammation, the high incidence of MetS in HFpEF patients, and the cardioprotective effects of Ffar4 led us to hypothesize that loss of Ffar4 would worsen remodeling in HFpEF secondary to MetS (HFpEF-MetS). To test this, mice with systemic deletion of Ffar4 (Ffar4KO) were fed a high-fat/high-sucrose diet with L-NAME in their water (HFpEF-MetS diet) to induce HFpEF-MetS. In male Ffar4KO mice, the HFpEF-MetS diet induced similar metabolic deficits, but worsened diastolic function and microvascular rarefaction compared to wild-type mice. Conversely, in female Ffar4KO mice, the diet produced greater obesity but no worsening of HFpEF. Loss of Ffar4 in males altered the balance of inflammatory oxylipins in the heart, decreasing the eicosapentaenoic acid derived, pro-resolving oxylipin 18-hydroxyeicosapentaenoic acid (18-HEPE), while increasing the arachadonic acid derived, proinflammatory oxylipin 12-hydroxyeicosatetraenoic acid (12-HETE). This increased 12-HETE/18-HEPE ratio, reflecting a more proinflammatory state, was associated with increased macrophage numbers, which in turn correlated with worsened ventricular remodeling in male Ffar4KO hearts. In summary, our data suggest that Ffar4 controls the pro/anti-inflammatory oxylipin balance in the heart to modulate macrophage function and attenuate HFpEF remodeling.

The intervertebral disc is a complex structure that experiences multiaxial stresses regularly. Disc failure through herniation is a common cause of lower back pain, which causes reduced mobility and debilitating pain, resulting in heavy socioeconomic burdens. Unfortunately, herniation etiology is not well understood, partially due to challenges in replicating herniation in vitro. Previous studies suggest that flexion elevated risks of herniation. Thus, the objective of this study was to use a multiscale and multiphasic finite element model to evaluate the risk of failure under torque- or muscle-driven flexion. Models were developed to represent torque-driven flexion with the instantaneous center of rotation (ICR) located on the disc, and the more physiologically representative muscle-driven flexion with the ICR located anterior of the disc. Model predictions highlighted disparate disc mechanics regarding bulk deformation, stress-bearing mechanisms, and intradiscal stress–strain distributions. Specifically, failure was predicted to initiate at the bone-disc boundary under torque-driven flexion, which may explain why endplate junction failure, instead of herniation, has been the more common failure mode observed in vitro. By contrast, failure was predicted to initiate in the posterolateral annulus fibrosus under muscle-driven flexion, resulting in consistent herniation. Our findings also suggested that muscle-driven flexion combined with axial compression could be sufficient for provoking herniation in vitro and in silico. In conclusion, this study provided a computational framework for designing in vitro testing protocols that can advance the assessment of disc failure behavior and the performance of engineered disc implants.

Patients with well-controlled low-density lipoprotein cholesterol levels, but persistent high triglycerides, remain at increased risk for cardiovascular events as evidenced by multiple genetic and epidemiologic studies, as well as recent clinical outcome trials. While many trials of low-dose ω3-polyunsaturated fatty acids (ω3-PUFAs), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) have shown mixed results to reduce cardiovascular events, recent trials with high-dose ω3-PUFAs have reignited interest in ω3-PUFAs, particularly EPA, in cardiovascular disease (CVD). REDUCE-IT demonstrated that high-dose EPA (4 g/day icosapent-ethyl) reduced a composite of clinical events by 25% in statin-treated patients with established CVD or diabetes and other cardiovascular risk factors. Outcome trials in similar statin-treated patients using DHA-containing high-dose ω3 formulations have not yet shown the benefits of EPA alone. However, there are data to show that high-dose ω3-PUFAs in patients with acute myocardial infarction had reduced left ventricular remodelling, non-infarct myocardial fibrosis, and systemic inflammation. ω3-polyunsaturated fatty acids, along with their metabolites, such as oxylipins and other lipid mediators, have complex effects on the cardiovascular system. Together they target free fatty acid receptors and peroxisome proliferator-activated receptors in various tissues to modulate inflammation and lipid metabolism. Here, we review these multifactorial mechanisms of ω3-PUFAs in view of recent clinical findings. These findings indicate physico-chemical and biological diversity among ω3-PUFAs that influence tissue distributions as well as disparate effects on membrane organization, rates of lipid oxidation, as well as various receptor-mediated signal transduction pathways and effects on gene expression.

Author(s): Yang, Bo; Wendland, Michael F; O'Connell, Grace D | Abstract: BackgroundWater content is a key parameter for simulating tissue swelling and nutrient diffusion. Accurately measuring water content throughout the intervertebral disc (NP = nucleus pulposus; AF = annulus fibrosus) is important for developing patient-specific models. Water content is measured using destructive techniques, Quantitative MRI has been used to estimate water content and detect early degeneration, but it is dependent on scan parameters, concentration of free water molecules, and fiber architecture.PurposeTo directly measure disc-tissue water content using quantitative MRI and compare MRI-based measurements with biochemical assays, and to quantify changes in disc geometry due to compression.Study typeBasic science, controlled.SpecimenTwenty bone-disc-bone motion segments from skeletally mature bovines.Field strength/sequence7T/3D fast low angle shot (FLASH) pulse sequence and a T2 rapid imaging with refocused echoes (RARE) sequence.AssessmentDisc volumes, NP and AF volumetric water content, and T2 relaxation times were measured through MRI; NP and AF tissue gravimetric water content, mass density, and glycosaminoglycan content were measured through a biochemical assay.Statistical testsCorrelations between MRI-based measurement and biochemical composition were evaluated using Pearson's linear regression.ResultsMechanical dehydration resulted in a decrease in disc volume by up to 20% and a decrease in disc height by up to 35%. Direct water content measurements for the NP was achieved by normalizing MRI-based spin density by NP mass density (1.10 ± 0.03 g/cm3 ). However, the same approach underestimated water content in the AF by ~10%, which may be due to a higher concentration of collagen fibers and bound water molecules.Data conclusionSpin density or spin density normalized by mass density to estimate NP and AF water content was more accurate than correlations between water content and relaxation times. Mechanical dehydration decreased disc volume and disc height, and increased maximum cross-sectional area.Level of evidenceTECHNICAL EFFICACY STAGE: J. Magn. Reson. Imaging 2020;52:1152-1162.

Three‐dimensional biofabrication using photo‐crosslinkable hydrogel bioscaffolds has the potential to revolutionize the need for transplants and implants in joints, with articular cartilage being an early target tissue. However, to successfully translate these approaches to clinical practice, several barriers must be overcome. In particular, the photo‐crosslinking process may impact on cell viability and DNA integrity, and consequently on chondrogenic differentiation. In this review, we primarily explore the specific sources of cellular cytotoxicity and genotoxicity inherent to the photo‐crosslinking reaction, the methods to analyze cell death, cell metabolism, and DNA damage within the bioscaffolds, and the possible strategies to overcome these detrimental effects., Three‐dimensional biofabrication using photo‐crosslinkable hydrogel bioscaffolds has the potential to revolutionize articular cartilage treatment. The photo‐crosslinking process may impact on cell viability and DNA integrity, and consequently on chondrogenic differentiation. In this review, we explore cellular cytotoxicity and genotoxicity inherent to the photo‐cross‐linking reaction, the methods to analyze them, and the possible strategies to overcome these detrimental effects.