Is YouTube a reliable source of health-related information? A systematic review

BACKGROUND

YouTube is a valuable source of health-related educational material which can have a profound impact on people's behaviors and decisions. However, YouTube contains a wide variety of unverified content that may promote unhealthy behaviors and activities. We aim in this systematic review to provide insight into the published literature concerning the quality of health information and educational videos found on YouTube.

METHODS

We searched Google Scholar, Medline (through PubMed), EMBASE, Scopus, Direct Science, Web of Science, and ProQuest databases to find all papers on the analysis of medical and health-related content published in English up to August 2020. Based on eligibility criteria, 202 papers were included in our study. We reviewed every article and extracted relevant data such as the number of videos and assessors, the number and type of quality categories, and the recommendations made by the authors. The extracted data from the papers were aggregated using different methods to compile the results.

RESULTS

The total number of videos assessed in the selected articles is 22,300 (median = 94, interquartile range = 50.5-133). The videos were evaluated by one or multiple assessors (median = 2, interquartile range = 1-3). The video quality was assessed by scoring, categorization, or based on creators' bias. Researchers commonly employed scoring systems that are either standardized (e.g., GQS, DISCERN, and JAMA) or based upon the guidelines and recommendations of professional associations. Results from the aggregation of scoring or categorization data indicate that health-related content on YouTube is of average to below-average quality. The compiled results from bias-based classification show that only 32% of the videos appear neutral toward the health content. Furthermore, the majority of the studies confirmed either negative or no correlation between the quality and popularity of the assessed videos.

CONCLUSIONS

YouTube is not a reliable source of medical and health-related information. YouTube's popularity-driven metrics such as the number of views and likes should not be considered quality indicators. YouTube should improve its ranking and recommender system to promote higher-quality content. One way is to consider expert reviews of medical and health-related videos and to include their assessment data in the ranking algorithm.

Homo sapiens systemic RNA interference-defective-1 transmembrane family member 1 (SIDT1) protein mediates contact-dependent small RNA transfer and microRNA-21-driven chemoresistance

Locally initiated RNA interference (RNAi) has the potential for spatial propagation, inducing posttranscriptional gene silencing in distant cells. In Caenorhabditis elegans, systemic RNAi requires a phylogenetically conserved transmembrane channel, SID-1. Here, we show that a human SID-1 orthologue, SIDT1, facilitates rapid, contact-dependent, bidirectional small RNA transfer between human cells, resulting in target-specific non-cell-autonomous RNAi. Intercellular small RNA transfer can be both homotypic and heterotypic. We show SIDT1-mediated intercellular transfer of microRNA-21 to be a driver of resistance to the nucleoside analog gemcitabine in human adenocarcinoma cells. Documentation of a SIDT1-dependent small RNA transfer mechanism and the associated phenotypic effects on chemoresistance in human cancer cells raises the possibility that conserved systemic RNAi pathways contribute to the acquisition of drug resistance. Mediators of non-cell-autonomous RNAi may be tractable targets for novel therapies aimed at improving the efficacy of current cytotoxic agents.

No-biopsy strategy for coeliac disease is applicable in adult patients: a 'real-world' Scottish experience

Objective

Emergency interim guidance from the British Society for Gastroenterology (BSG) states that a no-biopsy strategy is possible to diagnose coeliac disease (CD) in adults with elevated transglutaminase IgA antibody (TGA-IgA) levels. We aimed to determine if the suggested TGA-IgA ≥10× ULN is safe and robust in making the diagnosis in adult patients in Scotland. We also aimed to establish if any important co-diagnoses would be missed if no biopsy was performed.

Method

All positive coeliac serology results for patients aged >15 years in Scotland in 2016 (Grampian 2019) were accessed. Data were collected on demographics, TGA-IgA titres, D1 sampling, histology and macroscopic findings at upper and lower gastrointestinal (GI) endoscopy.

Results

1037/1429 patients with positive serology proceeded to biopsy, of which 796/1037 (76.8%) were diagnosed as CD. A total of 320/322 (99.37%) patients with TGA-IgA ≥10× ULN were diagnosed as CD giving the cut-off a positive predictive value of 99.38%. No significant co-pathology was found at endoscopy in these patients.

Conclusion

Our results show that a no-biopsy strategy using a cut-off of TGA-IgA ≥10× ULN is safe to diagnose CD and that no important pathology would be missed. The European Society for Paediatric Gastroenterology, Hepatology and Nutrition 2020 and BSG COVID-19 interim guidelines are applicable to adult patients in Scotland.

BJS commission on surgery and perioperative care post-COVID-19

BACKGROUND

Coronavirus disease 2019 (COVID-19) was declared a pandemic by the WHO on 11 March 2020 and global surgical practice was compromised. This Commission aimed to document and reflect on the changes seen in the surgical environment during the pandemic, by reviewing colleagues' experiences and published evidence.

METHODS

In late 2020, BJS contacted colleagues across the global surgical community and asked them to describe how severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) had affected their practice. In addition to this, the Commission undertook a literature review on the impact of COVID-19 on surgery and perioperative care. A thematic analysis was performed to identify the issues most frequently encountered by the correspondents, as well as the solutions and ideas suggested to address them.

RESULTS

BJS received communications for this Commission from leading clinicians and academics across a variety of surgical specialties in every inhabited continent. The responses from all over the world provided insights into multiple facets of surgical practice from a governmental level to individual clinical practice and training.

CONCLUSION

The COVID-19 pandemic has uncovered a variety of problems in healthcare systems, including negative impacts on surgical practice. Global surgical multidisciplinary teams are working collaboratively to address research questions about the future of surgery in the post-COVID-19 era. The COVID-19 pandemic is severely damaging surgical training. The establishment of a multidisciplinary ethics committee should be encouraged at all surgical oncology centres. Innovative leadership and collaboration is vital in the post-COVID-19 era.

Persistent Cortical Blindness Following Posterior Reversible Encephalopathy Syndrome (PRES) as a Complication of COVID-19 Pneumonia

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic emerged in China in December 2019. Since then, there have been growing reports of coronavirus disease 2019 (COVID-19) cases with neurological involvement. We present a case of a 54-year-old woman who presented with confirmed SARS-CoV-2 pneumonia, complicated by a prolonged intensive care stay and posterior reversible encephalopathy syndrome (PRES). This resulted in persistent cortical blindness (Anton's syndrome). PRES has only rarely been reported in relation to SARS-CoV-2 infection and no patients have developed persistent cortical blindness. We summarise the clinical presentation of the patient and review the current literature.

From Muscles to Wires: Report of Two Cases and Literature Review on COVID-19 Vaccination and Cardiac Conduction Disturbance

Since the end of 2020, several vaccines have become available as part of the global efforts to contain the adverse health outcomes of the coronavirus disease 2019 (COVID-19) pandemic. Although research has confirmed their safety on large scales, several post-marketing reports have revealed some rare cardiovascular side effects. Towards the end of the first half of 2021, multiple reports indicate possible links between COVID-19 vaccines (both mRNA-based vaccine and vector-based vaccines) and myopericarditis. Nevertheless, cardiac conduction disease in this context has only rarely been reported. In this report, we present two cases of probable vaccination-induced cardiac conduction disturbances along with a thorough literature review. In addition, we discuss probable pathophysiological mechanisms and insights into the suggested areas for future research. To our knowledge, these are the first published cases to result in permanent pacemaker implantation.

Screening and diagnostic testing protocols for HIV and Syphilis infections in health care setting in Qatar: Evaluation and recommendations

BACKGROUND

HIV and Syphilis are common STIs, which have become a concern and burden on healthcare systems, as many infections go untreated and lead to potentially serious complications. HIV is usually diagnosed with Western blot, PCR, and p24 antigen testing. Whereas, Syphilis is mainly diagnosed through clinical findings and serologic testing. The Medical Commission Department (MC) under MOPH is responsible for screening all newcomers to Qatar, aiming to keep the country free from serious infectious diseases.

OBJECTIVE

We aimed to evaluate the diagnostic efficiency of the protocols used in the MC for screening HIV and Syphilis infections.

METHODS

We conducted a retrospective study of samples analyzed by 4th Generation ARCHITECT® HIV Ag/Ab Combo and Rapid Plasma Reagin (RPR) between January to December 2019. ARCHITECT® HIV Ag/Ab Combo positive samples were confirmed by INNO-LIA™ HIVI/II and RT-PCR. RPR-reactive samples were confirmed by ARCHITECT® Syphilis Treponema pallidium Antibody (Syphilis TPA) assay.

RESULTS

For HIV, data were collected from 585,587 individuals, of which 595 (0.1%) were positive by the ARCHITECT® HIV Ag/Ab Combo (Analyzer A). When all initially positive sera were re-tested on newly collected blood samples using different ARCHITECT® HIV Ag/Ab Combo analyzer (analyzer B), 99.8% (594/595) of samples were also positive, suggesting high reproducibility. The positive predictive value (PPV) between ARCHITECT® HIV Ag/Ab Combo and the INNO-LIA™ HIVI/II confirmatory assay was 31.8%. The PPV between ARCHITECT® HIV Ag/Ab Combo and HIV-PCR assay was 26.8%. Retrospective data for Syphilis were collected from a total of 97,298 individuals who visited the MC, of which 198 (0.20%) were initially positive by RPR. The PPV between RPR and Syphilis TPA confirmatory assay was 36.6%.

CONCLUSION

Despite the high rate of false positivity using ARCHITECT® HIV Ag/Ab Combo and RPR screening assays, both assays have proven to be highly effective as screening testing methods.

1255 Crowdedness and Consequences of Long Waiting Time in Public and Private Health Centers Among Patients in Khartoum State, Sudan - 2016

Aim

Waiting time (WT) reflects quality of services delivered by Primary health care level. Long waiting time is due to various causes, among which crowdedness is a main cause. This prolonged time has negative impacts on PHC services utilization as well as patients’ outcomes. The aim of this study is to measure the total WT, assess the crowdedness in PHC centers, and to determine the possible consequences of this long waiting time.

Method

Descriptive cross sectional– health institution-based study done in 40 Health centres across Khartoum state using randomized multi-stage sampling. Patients, doctors and lab technicians were interviewed using three different pre-tested structured questionnaires.

Results

A total of 477 patients were included in the study. The average waiting time was found to be 168 minutes. Crowdedness was one of the main causes of delay in waiting time. The lab was the most perceived crowded service (74.4% of the respondents). This long WT had health consequences on patients, ranging from backache, joint pain, and headaches to hypoglycemic symptoms. These symptoms affected patients' willingness to return to the same center. 36.4% of the affected patients were unwilling to revisit the same center.

Conclusions

WT in this study is longer compared to studies from other countries. Crowdedness is one of the main causes of long WT. Due to this prolonged time, patients experienced physical symptoms. It also affected their future attitude regarding PHC centers utilization. There is a need to understand the underlying causes of this issue and address them appropriately.

Novel Hydrogels Based on the Nano-Emulsion Formulation Process: Development, Rheological Characterization, and Study as a Drug Delivery System

In this study, we present a new type of polymer-free hydrogel made only from nonionic surfactants, oil, and water. Such a system is produced by taking advantage of the physicochemical behavior and interactions between nonionic surfactants and oil and water phases, according to a process close to spontaneous emulsification used in the production of nano-emulsions. Contrary to the classical process of emulsion-based gel formulation, we propose a simple one-step approach. Beyond the originality of the concept, these nanoemulgels appear as very promising systems able to encapsulate and deliver various molecules with different solubilities. In the first section, we propose a comprehensive investigation of the gel formation process and its limits through oscillatory rheological characterization, characterization of the sol/gel transitions, and gel strength. The second section is focused on the follow-up of the release of an encapsulated model hydrophilic molecule and on the impact of the rheological gel properties on the release profiles.

Lipophilic molecular rotor to assess the viscosity of oil core in nano-emulsion droplets

Characterization of nanoscale formulations is a continuous challenge. Size, morphology and surface properties are the most common characterizations. However, physicochemical properties inside the nanoparticles, like viscosity, cannot be directly measured. Herein, we propose an original approach to measuring dynamic viscosity using a lipidic molecular rotor solubilized in the core of nano-formulations. These molecules undergo conformational changes in response to viscosity variations, leading to observable changes in fluorescence intensity and lifetime, able to sense the volume properties of dispersed nano-domains. The lipophilic molecular rotor (BOPIDY derivatives) was specifically synthesized and characterized as oil viscosity sensing in large volumes. A second part of the study compares these results with rBDP-Toco in nano-emulsions. The objective is to evaluate the impact of the formulation, droplet size and composition on the viscosity of the droplet's core. The lipophilic rotor showed a universal behavior whatever the oil composition, giving a master curve. Applied to nano-formulations, it reveals the viscosity inside the nano-emulsion droplets, enabling the detection of slight variations between reference oil samples and the nano-formulated ones. This new tool opens the way to the fine characterization of complex colloids and multi-domain nano and micro systems, potentially applied to hybrid materials and biomaterials.

Unusual Presentation of Non-Gestational Extragonadal Choriocarcinoma

Non-gestational choriocarcinoma is an extremely rare and highly aggressive malignant tumor that arises independent of gestational events, making less than 0.6% of all ovarian germ cell tumors. Unlike the more common gestational choriocarcinoma, which is associated with pregnancy, non-gestational choriocarcinoma originates from germ cells within the ovary. It accounts for a small fraction of ovarian malignancies and is often characterized by elevated levels of serum beta-human chorionic gonadotropin (β-HCG). The rarity and clinical overlap with other ovarian tumors pose significant diagnostic challenges, necessitating a thorough histopathological and immunohistochemical examination for accurate diagnosis. A 39-year-old female presented with a two-week history of right-sided migraine and general malaise, followed by a three-day onset of vision loss in the right eye. Initial evaluation in the emergency department included a chest X-ray, which revealed a 10 cm rounded opacity in the upper lobe of the left lung. A CT scan of the head showed a 4.5 cm rim-enhancing lesion in the left occipital lobe, along with a left middle cerebral artery (MCA) aneurysm. Notably, her serum β-HCG levels were significantly elevated at 5,642 mIU/mL despite the absence of intrauterine or extrauterine pregnancy on abdominal and pelvic ultrasound. Further workup included a CT thorax and MRI of the brain, which confirmed the isolated lung mass and left occipital lobe mass with no other sites of disease, leading to her transfer to the neurosurgery department. The patient underwent a left occipital craniotomy with tumor resection. Histopathological analysis confirmed the diagnosis of choriocarcinoma. Chromosomal analysis showed no evidence of the Y chromosome and confirmed the non-gestational origin of the choriocarcinoma. This case report discusses the non-specific presentation, radiological features, current treatment options, and potential safety strategies for managing this rare condition.

Solitary thyroid nodule in Khartoum

Ninety four patients with solitary and significantly dominant thyroid nodules were studied. Inadequate sampling was reported in 5 patients (5.9%). In the remaining 89 patients, 64 had simple goitre (72%), 12 follicular adenoma (13.5%), 12 were malignant nodules (6 follicular, 5 papillary and one anaplastic) (13.5%) and one patient had Hashimoto's thyroiditis. The incidence of malignancy in the clinically solitary nodules was 14% (10/70) compared to 10% (2/19) for the dominant nodules which increased to 16% (8/49) versus 10% (4/40) respectively after ultrasonography and histopathological confirmation of the nature of the gland. There is a low positive predictive value for follicular neoplasm with fine needle aspiration cytology (FNAC) (44%). This is due to the fact that reports of suspicious follicular pattern is agreed not to imply definite malignancy, however total lobectomy was done for those patients whereas terms like "not suspicious" and "highly suspicious" are considered to mean, benign and malignant respectively and in those latter groups the prediction was 100%. The study stresses the importance of FNAC techniques in reducing the surgical load with minimal false negative results, increasing the yield of carcinoma and projecting the importance of a significantly dominant nodule in endemic areas.

Hemi-Gastrocnemius Hemi-Soleus Bi-pedicled Muscle Flap and Bone Transport in Reconstruction of Bone and Soft Tissue Defects in an Open Fracture Tibia Gustilo Type IIIc

Soft tissue injury in open fracture of the lower extremity represents a challenging trauma that requires complex strategies to reconstruct both bony and soft tissue defects. Various options are available to cover the soft tissue defect in the lower extremities, from simple skin grafting to local fasciocutaneous and muscle flaps. However, when the injury is extensive and involves a large surface area, options for treatment of local flap coverage become limited. Vascular injury (Gustilo type IIIc) further increases the risk of complications and flap failure. Despite these complexities, meticulous planning and attention to detail can optimize patient outcomes. Herein, we present a case of an open lower extremity fracture involving a substantial soft tissue defect over the proximal and middle segments of the tibia complicated by a vascular injury (Gustilo type IIIc). A combination of the hemigastrocnemius and hemisoleus muscles was implemented to cover soft tissue defect over the proximal two-thirds of the tibia despite significant popliteal artery compromise. This case underscores the feasibility of using a combined local muscle flap approach involving the hemigastrocnemius and hemisoleus muscles in managing open fractures with concomitant vascular injuries.

A Rare Presentation of Encapsulated Left Ventricular Thrombus

Left ventricular thrombus formation is not an uncommon complication. There are a variety of reasons for this, for example, myocardial infarction, aneurysm formation and hypercoagulability. This usually has different fates; the most serious of which is propagation and embolization causing distal organ dysfunction. Thrombus formation appearance on echocardiography can sometimes give an idea of whether this is acute, subacute or chronic. In this article, we present a rare case in which large thrombi were noted on transthoracic echocardiography to be fully encapsulated within the left ventricle. It is unclear whether this phenomenon represents chronicity or whether this has consequential clinical impacts of significance. To our knowledge, this has only rarely been reported in the literature. We present an in-depth discussion of the presentation along with reported postulated mechanisms that might have a role in encapsulation per se.

Outcomes after surgery for children in Africa (ASOS-Paeds): a 14-day prospective observational cohort study

BACKGROUND

Safe anaesthesia and surgery are a public health imperative. There are few data describing outcomes for children undergoing anaesthesia and surgery in Africa. We aimed to get robust epidemiological data to describe patient care and outcomes for children undergoing anaesthesia and surgery in hospitals in Africa.

METHODS

This study was a 14-day, international, prospective, observational cohort study of children (aged <18 years) undergoing surgery in Africa. We recruited as many hospitals as possible across all levels of care (first, second, and third) providing surgical treatment. Each hospital recruited all eligible children for a 14-day period commencing on the date chosen by each participating hospital within the study recruitment period from Jan 15 to Dec 23, 2022. Data were collected prospectively for consecutive patients on paper case record forms. The primary outcome was in-hospital postoperative complications within 30 days of surgery and the secondary outcome was in-hospital mortality within 30 days after surgery. We also collected hospital-level data describing equipment, facilities, and protocols available. This study is registered with ClinicalTrials.gov, NCT05061407.

FINDINGS

We recruited 8625 children from 249 hospitals in 31 African countries. The mean age was 6·1 (SD 4·9) years, with 5675 (66·0%) of 8600 children being male. Most children (6110 [71·2%] of 8579 patients) were from category 1 of the American Society of Anesthesiologists Physical Status score undergoing elective surgery (5325 [61·9%] of 8604 patients). Postoperative complications occurred in 1532 (18·0%) of 8515 children, predominated by infections (971 [11·4%] of 8538 children). Deaths occurred in 199 (2·3%) of 8596 patients, 169 (84·9%) of 199 patients following emergency surgeries. Deaths following postoperative complications occurred in 166 (10·8%) of 1530 complications. Operating rooms were reported as safe for anaesthesia and surgery for neonates (121 [54·3%] of 223 hospitals), infants (147 [65·9%] of 223 hospitals), and children younger than 6 years (188 [84·3%] of 223 hospitals).

INTERPRETATION

Outcomes following anaesthesia and surgery for children in Africa are poor, with complication rates up to four-fold higher (18% vs 4·4-14%) and mortality rates 11-fold higher than high-income countries in a crude, unadjusted comparison (23·15 deaths vs 2·18 deaths per 1000 children). To improve surgical outcomes for children in Africa, we need health system strengthening, provision of safe environments for anaesthesia and surgery, and strategies to address the high rate of failure to rescue.

FUNDING

Jan Pretorius Research Fund of the South African Society of Anaesthesiologists and Association of Anesthesiologists of Uganda.

Abstract 5272: Multimodality interrogation of systemic RNA interference-defective-1 transmembrane family member 1 (SIDT1) identifies axon guidance protein interactions

Introduction

SIDT1 is an 11-transmembrane domain channel protein that conveys small double stranded RNA (dsRNA) molecules between cells. SIDT1 is highly expressed in human pancreatic stellate cells and disruption of SIDT1 function attenuates synthesis of components of the desmoplastic response that is typical of pancreatic cancer. We sought to identify the intra- and extracellular protein interaction partners of SIDT1 using an unbiased multimodality screening approach.

Methods

SIDT1 was used as ‘bait’ in a membrane-directed split ubiquitin yeast 2-hybrid (Y2H) screen. Candidate interacting partners identified in multiple biological replicates using a stringent selection approach were validated using immunoprecipiation and the functional effects of disrupting candidate interacting partner protein expression were determined using lentiviral short hairpin RNA-based RNA interference. Gene ontology (GO) term analysis was performed. A high-throughput flow cytometry-based assay was used to quantify the effects of depleting SIDT1 interacting partners on fluorescent dsRNA transfer mediated by SIDT1.

Potential SIDT1 ectodomain interactors were probed using cell surface phage display. SIDT1-tGFP transfected HEK293 cells were probed, with tGFP transfectants serving as a counter-selection control population. Phage display hits were deconvoluted using BLASTP. Fluorescently labeled peptides were synthesized and interactions assessed by epifluorescence microscopy using human pancreatic ductal adenocarcinoma cells. Enzymatic quantification of biotinylated synthetic peptide colocalisation was performed. Immunohistochemical and clincopathological correlation using resected pancreatic adenocarcinoma specimens was undertaken.

Results

The Y2H screen identified a shortlist of consistent SIDT1 interacting partners in which axon guidance proteins were significantly overrepresented, based on GO-term analysis. Disruption of Reticulon 4 expression resulted in impairment of SIDT1 intercellular small dsRNA transfer function.

Phage display identified a SIDT1-binding 12-mer with sequence homology to human Growth arrest-specific 6 (GAS6). 12-mer colocalisation with full length SIDT1 and the SIDT1 ectodomain was confirmed using controlled epifluorescence microscopy. Levels of SIDT1 protein expression correlate with the presence of perineural invasion in human resection specimens (P&lt;0.001).

Discussion

Using a multimodality screening approach we have identified novel SIDT1 binding partners. The role of SIDT1 and its interacting partners in heterotypic cellular interactions, e.g. with peritumoral neurons, warrants further investigation.

Citation Format: Mohamed O. Elhassan, Jennifer Christie, Marlieke Molendijk, Mark Duxbury. Multimodality interrogation of systemic RNA interference-defective-1 transmembrane family member 1 (SIDT1) identifies axon guidance protein interactions. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5272. doi:10.1158/1538-7445.AM2013-5272

Non-prescription pharmacy syringes sales to people who inject drugs (PWID) in Khartoum, Sudan: policy, practice, and perceptions

Background: People who inject drugs (PWID) are at high risk of contracting blood-borne infections. Many developed countries started a needle exchange program to provide PWID with sterile syringes. In Sudan, healthcare professionals are exposed to legal liability if they cooperate with people who use drugs; therefore, the accessibility to sterile syringes without prescription depends heavily on pharmacists' knowledge and attitude toward PWID.Objectives: Assessing policy, practice, and perceptions of pharmacists toward selling sterile syringes to PWID in Khartoum, Sudan.Methods: A self-administered questionnaire was given to 157 pharmacists (57 male, 100 female).Results: Out of 157 participating pharmacists, 86.6% reported selling syringes without a medical prescription, 53.5% inquired about the reason for buying syringes, and 87.9% refused to sell the syringes to a PWID. 43.3% of participating pharmacists were uncertain about the presence of law to regulate selling syringes without prescriptions. Although 47.7% of the participants agreed that selling empty syringes without a medical prescription to PWID will reduce harm, 68.5% will not sell them to PWID without a medical prescription even if it is encouraged by law due to their religious or moral beliefs.Conclusion: Pharmacists are the main providers of clean syringes for PWID in Khartoum, Sudan. With the majority of them reporting refusal to provide syringes to PWID, this may put PWID at higher risk of contracting blood-borne infections due syringe sharing. This is a challenge to overcome in planning for effective harm reduction programs in Khartoum.

Red-Emitting Pyrrolyl Squaraine Molecular Rotor Reports Variations of Plasma Membrane and Vesicular Viscosity in Fluorescence Lifetime Imaging

The viscosity that ensures the controlled diffusion of biomolecules in cells is a crucial biophysical parameter. Consequently, fluorescent probes capable of reporting viscosity variations are valuable tools in bioimaging. In this field, red-shifted probes are essential, as the widely used and gold standard probe remains green-emitting molecular rotors based on BODIPY. Here, we demonstrate that pyrrolyl squaraines, red-emissive fluorophores, exhibit high sensitivity over a wide viscosity range from 30 to 4890 mPa·s. Upon alkylation of the pyrrole moieties, the probes improve their sensitivity to viscosity through an enhanced twisted intramolecular charge transfer phenomenon. We utilized this scaffold to develop a plasma membrane probe, pSQ-PM, that efficiently stains the plasma membrane in a fluorogenic manner. Using fluorescence lifetime imaging, pSQ-PM enabled efficient sensing of viscosity variations in the plasma membrane under various conditions and in different cell lines (HeLa, U2OS, and NIH/3T3). Moreover, upon incubation, pSQ-PM stained the membrane of intracellular vesicles and suggested that the lysosomal membranes displayed enhanced fluidity.