Considering occupational performance during recovery of distal radius fracture: A scoping review.

INTRODUCTION: Distal radius fracture (DRF) is one of the most common upper extremity fractures treated by hand therapists and can lead to chronic physical impairment and reduced occupational performance. This scoping review aimed to reveal what is currently known about occupational performance following DRF and to explore if and how occupational performance is defined and considered in the research. METHODS: This review was guided by the PRISMA-Scoping review and the Joanna Briggs Institute (JBI) guidelines. Relevant databases were searched, and studies that addressed occupation performance in adult participants following DRF were included. The findings were summarised according to the components of occupational performance (person, occupation, and environment), and quality was measured using the Mixed Methods Appraisal Tool. RESULTS: Forty-three articles met the eligibility criteria for inclusion. All of the studies discussed at least two components of occupational performance, while 25 recognised all three. The consideration of occupational performance was dominated by biomechanical issues associated with the person component (i.e. range of motion, strength). There was some acknowledgement of the psychosocial aspects of the person and, to a lesser extent, the environment, as well as the impact of both on return to occupational performance. CONCLUSION: Despite occupational performance being at the core of occupational therapy theory, its consideration within the context of research on DRF appears to be focussed on the person component of occupational performance and on biomechanical issues. Further research is recommended to determine how much this reflects current clinical practice and if a more comprehensive consideration of occupational performance will improve rates of recovery following DRF. CONSUMER AND COMMUNITY INVOLVEMENT: As part of the protocol development for this review, consumers and stakeholders were consulted. They provided feedback on clarity and importance of the research questions. PLAIN LANGUAGE SUMMARY: A distal radius fracture happens when you break the bone on the thumb side of your wrist. This type of injury often occurs when you fall and land on an outstretched hand. It is one of the more common injuries that hand therapists see in their practice. For some people, recovering from this fracture can take a long time and come with a lot of pain, difficulty moving, and emotional stress. These problems can make it hard to do everyday things like driving, cooking, or getting dressed. It can also affect both paid and unpaid work as well as leisure and social activities, making life more difficult for everyone involved. The findings from this review suggest that the current research usually focuses on how the body physically heals from this type of injury, but it does not pay as much attention to the emotional and social impact on healing. Also, it does not always discuss the activities that are important to the person, or the environment where they live, work, and socialise. This may show a gap in the research regarding our full comprehension of recovery from distal radius fractures. Taking a broader view and approach to recovery, considering a person's emotions, social life, environment, and daily activities, could help people recover fully and get back to their previous life routines and roles after this type of injury.

Accessible high-speed image-activated cell sorting.

Over the past six decades, fluorescence-activated cell sorting (FACS) has become an essential technology for basic and clinical research by enabling the isolation of cells of interest in high throughput. Recent technological advancements have started a new era of flow cytometry. By combining the spatial resolution of microscopy with high-speed cell sorting, new instruments allow cell sorting based on simple image-derived parameters or sophisticated image analysis algorithms, thereby greatly expanding the scope of applications. In this review, we discuss the systems that are commercially available or have been described in enough methodological and engineering detail to allow their replication. We summarize their strengths and limitations and highlight applications that have the potential to transform various fields in basic life science research and clinical settings.

A Qualitative Analysis of the Effects of COVID-19 on Home Visiting Service Provision.

Home visiting programs have been found to improve parenting practices and to reduce negative child outcomes. The 2019 coronavirus disease (COVID-19) resulted in an abrupt transition to telehealth services for many home visiting services. Limited research has examined the impacts of delivering home visiting services via telehealth, and the effects of this abrupt transition during COVID-19 is understudied as well. This study examined the impact of the abrupt transition to telehealth as a result of COVID-19 on home visiting service provision in one mid-sized midwestern community from the perspective of clients and providers. We conducted semi-structured interviews with both home visiting clients and providers (N = 26) in prevention-focused home visiting services. Although some benefits to telehealth were reported, providers discussed challenges with regard to engaging clients in services and difficulties in completing important home visiting tasks (i.e., assessment of child development, teaching parent-child interaction). Providers and clients also noted that they missed face-to-face interactions. Effective use of telehealth in home visiting requires provision of devices that allow for video-chatting as well as development of effective methods to engage in observation and teaching tasks.

Current clinical practice patterns and perspectives of Australian hand therapists during the treatment of adults with distal radius fracture: A national survey.

INTRODUCTION: Successful return to pre-injury occupational performance following distal radius fracture (DRF) may be influenced by person and environment factors such as pain, age, social support, and socioeconomic status. The primary aim of this study was to explore Australian hand therapists' current clinical practice and determine whether they consider these factors during the management of DRF. METHODS: A mixed methods online survey was distributed to members of the Australian Hand Therapy Association. Descriptive statistics were used to examine the quantitative data, and the qualitative data were analysed by content analysis. RESULTS: Of the 120 members who completed the survey, 68% were occupational therapists and 32% were physiotherapists with 74% in the private and 26% in the public health-care setting. Most factors perceived to influence recovery were consistent with person factors and a biomechanical approach. Other factors related to occupational performance, such as social and leisure skills, environment and culture were reported less often. When asked about defining occupational performance, the key categories identified through qualitative open responses were 'performing meaningful activities/occupations', 'performing work/employment', and 'completing activities/function'. CONCLUSION: The data suggest that hand therapists in Australia primarily identify person factors as key to recovery after DRF. Context and environmental factors that influence occupational performance did not appear to be considered as often during treatment or when defining occupational performance. Further research is needed to explore the contextual and environmental factors that influence hand therapy intervention and determine whether they play a role in the successful return to pre-injury occupational performance following DRF. CONSUMER AND COMMUNITY INVOLVEMENT: The survey was conceptualised by the research team, which included two experienced hand therapists and piloted with 10 consumers. Hand therapists (consumers) of various years of experience and discipline (i.e., occupational therapy and physiotherapy) provided feedback to improve the survey in terms of content, comprehensibility, and length. No clients/patients of hand therapists were involved in the development of the survey or the study, and the consumers of the study were considered hand therapists.

Clinical Pharmacokinetics of Ponesimod, a Selective S1P1 Receptor Modulator, in the Treatment of Multiple Sclerosis.

Ponesimod, a selective, rapidly reversible, and orally active, sphingosine-1 phosphate receptor (S1P) modulator, is indicated for the treatment of relapsing-remitting multiple sclerosis (RRMS). The clinical pharmacokinetics (PK) and pharmacodynamics (PD) of ponesimod was studied in 16 phase I, one phase II, and one phase III clinical studies. Ponesimod population PK was characterized by an open two-compartment disposition model with a terminal half-life of 33 h (accumulation factor of 2- to 2.6-fold), and fast and almost complete oral absorption (absolute oral bioavailability: 84%), reaching peak plasma and blood concentrations within 2-4 h. Ponesimod is highly metabolized, and the parent compound along with its two major (non-clinically active) metabolites are mainly excreted in the feces (recovery: 57.3-79.6%) and to a lesser extent in the urine (recovery: 10.3-18.4%). Additionally, the population PKPD model characterized the ponesimod effects on heart rate: a transient, dose-dependent decrease in heart rate in the first days of dosing, that is mitigated by administering the first doses of ponesimod treatment using a gradual up-titration schedule, before reaching the daily maintenance dose of 20 mg. This selected maintenance dose has been shown to be superior in reducing annualized relapse rate (ARR) when compared with teriflunomide in a pivotal phase III study. Furthermore, a dose-dependent reduction of peripheral lymphocyte counts that is sustained with continued daily oral dosing of ponesimod and is rapidly (4-7 days) reversible upon drug discontinuation has been characterized with an indirect response model.

Prehospital accuracy of (H)EMS pelvic ring injury assessment and the application of non-invasive pelvic binder devices.

BACKGROUND: Pre-hospital application of a non-invasive pelvic binder device (NIPBD) is essential to increase chances of survival by limiting blood loss in patients with an unstable pelvic ring injury. However, unstable pelvic ring injuries are often not recognized during prehospital assessment. We investigated the prehospital (helicopter) emergency medical services ((H)EMS)' accuracy of the assessment of unstable pelvic ring injuries and NIPBD application rate. METHODS: We performed a retrospective cohort study on all patients with a pelvic injury transported by (H)EMS to our level one trauma centre between 2012 and 2020. Pelvic ring injuries were included and radiographically categorized using the Young & Burgess classification system. Lateral Compression (LC) type II/III -, Anterior-Posterior (AP) type II/III - and Vertical Shear (VS) injuries were considered as unstable pelvic ring injuries. (H)EMS charts and in-hospital patient records were evaluated to determine the sensitivity, specificity and diagnostic accuracy of the prehospital assessment of unstable pelvic ring injuries and prehospital NIPBD application. RESULTS: A total of 634 patients with pelvic injuries were identified, of whom 392 (61.8%) had pelvic ring injuries and 143 (22.6%) had unstable pelvic ring injuries. (H)EMS personnel suspected a pelvic injury in 30.6% of the pelvic ring injuries and in 46.9% of the unstable pelvic ring injuries. An NIPBD was applied in 108 (27.6%) of the patients with a pelvic ring injury and in 63 (44.1%) of the patients with an unstable pelvic ring injury. (H)EMS prehospital diagnostic accuracy measured in pelvic ring injuries alone was 67.1% for identifying unstable pelvic ring injuries from stable pelvic ring injuries and 68.1% for NIPBD application. CONCLUSION: The (H)EMS prehospital sensitivity of unstable pelvic ring injury assessment and NIPBD application rate is low. (H)EMS did not suspect an unstable pelvic injury nor applied an NIPBD in roughly half of all unstable pelvic ring injuries. We advise future research on decision tools to aid the routine use of an NIPBD in any patient with a relevant mechanism of injury.

AM-879, a PPARy non-agonist and Ser273 phosphorylation blocker, promotes insulin sensitivity without adverse effects in mice.

Obesity is one of the main risk factors for type 2 diabetes, and peroxisome proliferator-activated receptor γ (PPARγ) is considered a promising pathway on insulin sensitivity and adipose tissue metabolism. The search for molecules acting as insulin sensitizers have increased, especially for molecules that block PPARγ-Ser273 phosphorylation, without reaching full agonism. We evaluated the in vivo effects of AM-879, a PPARγ non-agonist, and found that AM-879 exerts different effects in mice depending on the dose. At lower doses, this ligand decreased BAT, increased leptin and Crh expression. However, at a higher dose, it promoted improvement on insulin sensitivity, ameliorates expression of metabolism-related genes, decreased the expression of genes related to liver toxicity, maintaining body weight and adipocyte size. These results present a new lead molecule to ameliorates insulin resistance and confirm AM-879 as a PPARγ non-agonist which blocks Ser273 phosphorylation as a good strategy to modulate insulin sensitivity without developing the adverse effects promoted by PPARγ full agonists.

High-speed fluorescence image-enabled cell sorting.

Fast and selective isolation of single cells with unique spatial and morphological traits remains a technical challenge. Here, we address this by establishing high-speed image-enabled cell sorting (ICS), which records multicolor fluorescence images and sorts cells based on measurements from image data at speeds up to 15,000 events per second. We show that ICS quantifies cell morphology and localization of labeled proteins and increases the resolution of cell cycle analyses by separating mitotic stages. We combine ICS with CRISPR-pooled screens to identify regulators of the nuclear factor κB (NF-κB) pathway, enabling the completion of genome-wide image-based screens in about 9 hours of run time. By assessing complex cellular phenotypes, ICS substantially expands the phenotypic space accessible to cell-sorting applications and pooled genetic screening.

Correct dosage of X chromosome transcription is controlled by a nuclear pore component.

Dosage compensation in Drosophila melanogaster involves a 2-fold transcriptional upregulation of the male X chromosome, which relies on the X-chromosome-binding males-specific lethal (MSL) complex. However, how such 2-fold precision is accomplished remains unclear. Here, we show that a nuclear pore component, Mtor, is involved in setting the correct levels of transcription from the male X chromosome. Using larval tissues, we demonstrate that the depletion of Mtor results in selective upregulation at MSL targets of the male X, beyond the required 2-fold. Mtor and MSL components interact genetically, and depletion of Mtor can rescue the male lethality phenotype of MSL components. Using RNA fluorescence in situ hybridization (FISH) analysis and nascent transcript sequencing, we find that the effect of Mtor is not due to defects in mRNA export but occurs at the level of nascent transcription. These findings demonstrate a physiological role for Mtor in the process of dosage compensation, as a transcriptional attenuator of X chromosome gene expression.

Characteristics of helicopter emergency medical services (HEMS) dispatch cancellations during a six-year period in a Dutch HEMS region.

BACKGROUND: For decades, Helicopter Emergency Medical Services (HEMS) contribute greatly to prehospital patient care by performing advanced medical interventions on-scene. Unnecessary dispatches, resulting in cancellations, cause these vital resources to be temporarily unavailable and generate additional costs. A previous study showed a cancellation rate of 43.5% in our trauma region. However, little recent data about cancellation rates and reasons exist, despite revision of dispatch protocols. This study examines the current cancellation rate in our trauma region over a six-year period. Additionally, cancellation reasons are evaluated per type of dispatch and initial incident report, upon which HEMS is dispatched. METHODS: This retrospective study analyzed the data of the Dutch HEMS Lifeliner 1 (North-West region of the Netherlands, covering a population of 5 million inhabitants), analyzing all subsequent cases between April 1st 2013 and April 1st 2019. Patient characteristics, type of dispatch (primary; based on dispatcher criteria versus secondary, as judged by the first ambulance team on site), initial incident report received by the EMS dispatch center, and information regarding day- or nighttime dispatches were collected. In case of cancellation, cancel rate and reason per type of dispatch and initial incident report were assessed. RESULTS: In total, 18,638 dispatches were included. HEMS was canceled in 54.5% (95% CI 53.8-55.3%) of cases. The majority of canceled dispatches (76.1%) were canceled because respiratory, hemodynamic, and neurologic parameters were stable. Dispatches simultaneously activated with EMS (primary dispatch) were canceled in 58.3%, compared to 15.1% when HEMS assistance was requested by EMS based on their findings on-scene (secondary dispatch). A cancellation rate of 54.6% was found in trauma related dispatches (n = 12,148), compared to 52.2% in non-trauma related dispatches (n = 5378). Higher cancellation rates exceeding 60% were observed in the less common dispatch categories, e.g., anaphylaxis (66.3%), unknown incident report (66.0%), assault with a blunt object (64.1%), obstetrics (62.8%), and submersion (61.9%). CONCLUSION: HEMS cancellations are increased, compared to previous research in our region. Yet, the cancellations are acceptable as the effect on HEMS' unavailbility remains minimized. Focus should be on identifying the patient in need of HEMS care while maintaining overtriage rates low. Continuous evaluation of HEMS triage is important, and dispatch criteria should be adjusted if necessary.

A Soft Mechanical Phenotype of SH-SY5Y Neuroblastoma and Primary Human Neurons Is Resilient to Oligomeric Aß(1-42) Injury.

Aggregated amyloid beta (Aß) is widely reported to cause neuronal dystrophy and toxicity through multiple pathways: oxidative stress, disrupting calcium homeostasis, and cytoskeletal dysregulation. The neuro-cytoskeleton is a dynamic structure that reorganizes to maintain cell homeostasis in response to varying soluble and physical cues presented from the extracellular matrix (ECM). Due this relationship between cell health and the ECM, we hypothesize that amyloid toxicity may be directly influenced by physical changes to the ECM (stiffness and dimensionality) through mechanosensitive pathways, and while previous studies demonstrated that Aß can distort focal adhesion signaling with pathological consequences, these studies do not address the physical contribution from a physiologically relevant matrix. To test our hypothesis that physical cues can adjust Aß toxicity, SH-SY5Y human neuroblastoma and primary human cortical neurons were plated on soft and stiff, 2D polyacrylamide matrices or suspended in 3D collagen gels. Each cell culture was exposed to escalating concentrations of oligomeric or fibrillated Aß(1-42) with MTS viability and lactate dehydrogenase toxicity assessed. Actin restructuring was further monitored in live cells by atomic force microscopy nanoindentation, and our results demonstrate that increasing either matrix stiffness or exposure to oligomeric Aß promotes F-actin polymerization and cell stiffening, while mature Aß fibrils yielded no apparent cell stiffening and minor toxicity. Moreover, the rounded, softer mechanical phenotype displayed by cells plated onto a compliant matrix also demonstrated a resilience to oligomeric Aß as noted by a significant recovery of viability when compared to same-dosed cells plated on traditional tissue culture plastic. This recovery was reproduced pharmacologically through inhibiting actin polymerization with cytochalasin D prior to Aß exposure. These studies indicate that the cell-ECM interface can modify amyloid toxicity in neurons and the matrix-mediated pathways that promote this protection may offer unique targets in amyloid pathologies like Alzheimer's disease.

Stapled Diaphragmatic Plication: Is It Better Than Suture Plication?

Diaphragm dysfunction, which can be due to eventration or an abnormally high-positioned diaphragm, can cause respiratory compromise. Eventration is most commonly due to unilateral diaphragm paralysis, which reduces ventilatory function in adults by about 25%. Since the 1920s, this condition has been treated with diaphragm plication, which itself has evolved to include the use of several different techniques and materials. This review explores the relevant literature on diaphragm plication using sutures or staples for the treatment of eventration to determine if either provides a clinical benefit over the other.

Preparation of Drosophila Polytene Chromosomes, Followed by Immunofluorescence Analysis of Chromatin Structure by Multi-fluorescence Correlations.

Drosophila larval salivary gland polytene chromosome squashes have been used for decades to analyze genome-wide protein-binding patterns, transcriptional activation processes, and changes in chromatin structure at specific genetic loci. There have been many evolutions of the squashing protocol over the years, with sub-optimal reproducibility and low sample success rate as accepted caveats. However, low sample success rates are an obvious disadvantage when polytene chromosomes are used for more high-throughput approaches, such as genetic or antibody screens, or for experiments requiring high-quality chromosome structure preservation. Here we present an exceptionally reproducible squashing and fluorescence staining protocol, which generates high-quality fluorescence images on well-spread chromosomes. This is followed by our novel, semi-automated MATLAB analysis program used to determine correlations between fluorescence signals of interest at a single site on polytene chromosomes, in a pixel-by-pixel manner. In our case, we have used this approach to assess chromatin changes at genomic sites, ectopically targeted by nuclear pore proteins. The use of our analysis program increases the ability to make unbiased conclusions on changes in chromatin structure, or in protein recruitment to chromatin, regardless of sample variation in immunofluorescence staining. As it is simply based upon differences in fluorescence intensity at a defined location, the provided analysis program is not limited to analysis of polytene chromosome, and could be applied to many different contexts where correlation between fluorescent signals at any particular location is of interest.

The accuracy of an injection technique for Flexor hallucis longus tendon sheath: A cadaveric study.

BACKGROUND: Corticosteroid injections are used in the conservative treatment of Flexor hallucis longus (FHL) tendinopathy. Studies for imaging guided injection are done, however, the accuracy of blind injection has not yet been studied. PURPOSE: The aim of this study was to determine the accuracy of a blind injection technique into the FHL tendon sheath. HYPOTHESIS: We hypothesize that a blind injections technique into the FHL tendon sheath based on clinical examination has a high accuracy. STUDY DESIGN: Descriptive cadaveric study. METHODS: Ten ankles of human cadavers were blindly injected with radiologic contrast mixed with methylene blue into the FHL tendon sheath. After injection, a CT scan of each ankle was performed to evaluate the location of contrast material. CT scans were reviewed by an experienced musculoskeletal radiologist blinded to the procedure. Anatomic dissection was undertaken to assess the location of the injection fluid. RESULTS: In nine ankles the radiological contrast was injected in the FHL tendon sheath. In one cadaver there was a technical problem and was therefore excluded. CONCLUSION: This study shows that the FHL tendon sheath can be blindly injected based on only clinical examination with high accuracy. LEVEL OF EVIDENCE: Descriptive cadaveric study.

Diaphragmatic Pacing: Is There a Benefit?

The diaphragm is the primary muscle of respiration and its injury can cause diaphragm dysfunction and respiratory deficits. Respiratory compromise has historically been managed with mechanical ventilation, however, its use has also been shown to result in poor functional outcomes. Therefore, stimulation of the phrenic nerve, called diaphragm pacing, has been used to replace and/or delay the need for mechanical ventilation. This article will review the relevant literature on diaphragm pacing, discuss the physiology of diaphragm dysfunction in a variety of patient populations, and address whether diaphragm pacing is a valuable and effective option for treatment of respiratory failure.

Nuclear Pore Proteins in Regulation of Chromatin State.

Nuclear pore complexes (NPCs) are canonically known to regulate nucleocytoplasmic transport. However, research efforts over the last decade have demonstrated that NPCs and their constituent nucleoporins (Nups) also interact with the genome and perform important roles in regulation of gene expression. It has become increasingly clear that many Nups execute these roles specifically through regulation of chromatin state, whether through interactions with histone modifiers and downstream changes in post-translational histone modifications, or through relationships with chromatin-remodeling proteins that can result in physical changes in nucleosome occupancy and chromatin compaction. This review focuses on these findings, highlighting the functional connection between NPCs/Nups and regulation of chromatin structure, and how this connection can manifest in regulation of transcription.

Factors influencing the admission decision for Medical Psychiatry Units: A concept mapping approach.

OBJECTIVE: Medical Psychiatry Units (MPUs), also known as Complexity Intervention Units (CIUs), provide care for complex patients suffering from both psychiatric and physical disorders. Because there is no consensus on the indications for admission to an MPU, daily practice and effectiveness research are hampered. This study therefore used a concept mapping approach to investigate which organizational and medical factors determine the decision to admit a patient to an MPU. METHODS: The first step of the concept mapping approach was to create a list of factors determining MPU admission from literature. Secondly, clinical experts sorted and ranked these factors. The sorted and ranked data were then analyzed, and a draft conceptual framework was created. A final conceptual MPU admission framework was then drawn during an expert consensus meeting and recommendations for implementation were suggested. RESULTS: Thirteen clinical experts defined 90 factors from literature, which were sorted and ranked by 40 experts from 21 Dutch hospitals. This concept mapping approach resulted in a five-cluster solution for an MPU admission framework based on: 1. Staff competencies and organizational pre-requisites; 2. Patient context; 3. Patient characteristics; 4. Medical needs and capabilities; and 5. Psychiatric symptoms and behavioral problems. Furthermore, three inclusion and two exclusion criteria were formulated to help the clinicians decide whether or not to admit patients to an MPU. These criteria can be implemented in daily practice. CONCLUSION: Implementing the five criteria derived from this conceptual framework will help make the admission decision for complex patients with psychiatric and physical disorders to an MPU more correct, consistent, and transparent.

Chromatin targeting of nuclear pore proteins induces chromatin decondensation.

Nuclear pore complexes have emerged in recent years as chromatin-binding nuclear scaffolds, able to influence target gene expression. However, how nucleoporins (Nups) exert this control remains poorly understood. Here we show that ectopically tethering Drosophila Nups, especially Sec13, to chromatin is sufficient to induce chromatin decondensation. This decondensation is mediated through chromatin-remodeling complex PBAP, as PBAP is both robustly recruited by Sec13 and required for Sec13-induced decondensation. This phenomenon is not correlated with localization of the target locus to the nuclear periphery, but is correlated with robust recruitment of Nup Elys. Furthermore, we identified a biochemical interaction between endogenous Sec13 and Elys with PBAP, and a role for endogenous Elys in global as well as gene-specific chromatin decompaction. Together, these findings reveal a functional role and mechanism for specific nuclear pore components in promoting an open chromatin state.

Reduced Extracellular Matrix Stiffness Prompts SH-SY5Y Cell Softening and Actin Turnover To Selectively Increase Aß(1-42) Endocytosis.

Alzheimer's disease (AD), the most common neurodegenerative disorder, is characterized by the extracellular deposition of dense amyloid beta plaques. Emerging evidence suggests that the production of these plaques is initiated by the intracellular uptake and lysosomal preconcentration of the amyloid-beta (Aß) peptide. All previous endocytosis studies assess Aß uptake with cells plated on traditional tissue culture plastic; however, brain tissue is distinctly soft with a low-kPa stiffness. Use of an ultrastiff plastic/glass substrate prompts a mechanosensitive response (increased cell spreading, cell stiffness, and membrane tension) that potentially distorts a cell's endocytic behavior from that observed in vivo or in a more physiologically relevant mechanical environment. Our studies demonstrate substrate stiffness significantly modifies the behavior of undifferentiated SH-SY5Y neuroblastoma, where cells plated on soft (∼1 kPa) substrates display a rounded morphology, decreased actin polymerization, reduced adhesion (decreased ß1 integrin expression), and reduced cell stiffness compared to cells plated on tissue culture plastic. Moreover, these neuroblastoma on softer substrates display a preferential increase in the uptake of the Aß(1-42) compared to Aß(1-40), while both isoforms display a clear stiffness-dependent increase of uptake relative to cells plated on plastic. Considering the brain is a soft tissue that continues to soften with age, this mechanosensitive endocytosis of Aß has significant implications for understanding age-related neurodegeneration and the mechanism behind Aß uptake and fibril production. Overall, identifying these physical factors that contribute to the pathology of AD may offer novel avenues of therapeutic intervention.

Mechanosensitive Endocytosis of High-Stiffness, Submicron Microgels in Macrophage and Hepatocarcinoma Cell Lines.

The mechanical properties of submicron particles offer a unique design space for advanced drug-delivery particle engineering. However, the recognition of this potential is limited by a poor consensus about both the specificity and sensitivity of mechanosensitive endocytosis over a broad particle stiffness range. In this report, our model series of polystyrene-co-poly(N-isopropylacrylamide) (pS-co-NIPAM) microgels have been prepared with a nominally constant monomer composition (50 mol % styrene and 50 mol % NIPAM) with varied bis-acrylamide cross-linking densities to introduce a tuned spectrum of particle mechanics without significant variation in particle size and surface charge. While previous mechanosensitive studies use particles with moduli ranging from 15 kPa to 20 MPa, the pS-co-NIPAM particles have Young's moduli (E) ranging from 300 to 700 MPa, which is drastically stiffer than these previous studies as well as pure pNIPAM. Despite this elevated stiffness, particle uptake in RAW264.7 murine macrophages displays a clear stiffness dependence, with a significant increase in particle uptake for our softest microgels after a 4 h incubation. Preferential uptake of the softest microgel, pS-co-NIPAM-1 (E = 310 kPa), was similarly observed with nonphagocytic HepG2 hepatoma cells; however, the uptake kinetics were distinct relative to that observed for RAW264.7 cells. Pharmacological inhibitors, used to probe for specific routes of particle internalization, identify actin- and microtubule-dependent pathways in RAW264.7 cells as sensitive particle mechanics. For our pS-co-NIPAM particles at nominally 300-400 nm in size, this microtubule-dependent pathway was interpreted as a phagocytic route. For our high-stiffness microgel series, this study provides evidence of cell-specific, mechanosensitive endocytosis in a distinctly new stiffness regime that will further broaden the functional landscape of mechanics as a design space for particle engineering.