Overwrapping Bivalved Casts: Does the Material Matter?

BACKGROUND: Circumferential integrity of bivalved casts (cut twice longitudinally) can be restored by overwrapping with different materials. This study compared the mechanical properties of solid casts and bivalved casts overwrapped with semirigid fiberglass (SF), elastic bandages (EB), and rigid fiberglass (RF) using an overwrapped-bivalved cast-bone fracture (OBCBF) model. METHODS: This study used an MTS Bionix Servohydraulic system to test properties of OBCBF models in 4 conditions: intact Control made of RF (not bivalved or overwrapped), a Rigid overwrapped model made of a Control bivalved and overwrapped with RF, a Semirigid overwrapped model made of a Control bivalved and overwrapped with SF, and an Elastic model made of a Control bivalved and overwrapped with EB. Constructs were tested in 4-point bending. Force-displacement curves (FDC) were generated to calculate load-at-critical-failure (LCF, angulation > 10 degrees = 6.6 mm vertical deformation) and stiffness. RESULTS: Five controls and 30 OBCBF models with 3 overwrapped cast types were tested, with each overwrapped cast type tested with 2 orientations of the initial cast bivalve axis, yielding 7 conditions (Control, Rigid 0 degrees, Rigid 90 degrees, Semirigid 0 degrees, Semirigid 90 degrees, Elastic 0 degrees, Elastic 90 degrees). Mean LCF was: Rigid 90 degrees > Rigid 0 degrees > Control > Semirigid 0 degrees > Semirigid 90 degrees > Elastic 90 degrees > Elastic 0 degrees (P<0.0001). Mean stiffness was: Rigid 0 degrees > Rigid 90 degrees > Control > Semirigid 90 degrees > Semirigid 0 degrees > Elastic 0 degrees > Elastic 90 degrees (P<0.0001). Multiple comparisons indicated no significant difference between LCF and stiffness for Semirigid 0 degrees/90 degrees casts compared with Controls. CONCLUSIONS: Mechanical properties of overwrapped bivalved casts change depending on the materials used to overwrap, with higher LCF and stiffness when overwrapping with RF > SF > EB; however, mean comparisons indicate that rigid bivalved casts overwrapped with SF did not have significantly different mean stiffness and LCF from controls and other cast models. CLINICAL RELEVANCE: This study compares the bending properties of a bivalved cast-construct overwrapped with different materials, providing basic science evidence for orthopaedic surgeons who have several choices of materials to overwrap bivalved casts.

NIR-II emissive donor-acceptor-donor fluorophores for dual fluorescence bioimaging and photothermal therapy applications.

Fluorescence bioimaging with near-infrared II (NIR-II) emissive organic fluorophores has proven to be a viable noninvasive diagnostic technique. However, there is still the need for the development of fluorophores that possess increased stability as well as functionalities that impart stimuli responsiveness. Through strategic design, we can synthesize fluorophores that possess not only NIR-II optical profiles but also pH-sensitivity and the ability to generate heat upon irradiation. In this work, we employ a donor-acceptor-donor (D-A-D) design to synthesize a series of NIR-II fluorophores. Here we use thienothiadiazole (TTD) as the acceptor, 3-hexylthiophene (HexT) as the π-spacer and vary the alkyl amine donor units: N,N-dimethylaniline (DMA), phenylpiperidine (Pip), and phenylmorpholine (Morp). Spectroscopic analysis shows that all three derivatives exhibit emission in the NIR-II region with λemimax ranging from 1030 to 1075 nm. Upon irradiation, the fluorophores exhibited noticeable heat generation through non-radiative processes. The ability to generate heat indicates that these fluorophores will act as theranostic (combination therapeutic and diagnostic) agents in which simultaneous visualization and treatment can be performed. Additionally, biosensing capabilities were supported by changes in the absorbance properties while under acidic conditions as a result of protonation of the alkyl amine donor units. The fluorophores also show minimal toxicity in a human mammary cell line and with murine red blood cells. Overall, initial results indicate viable NIR-II materials for multiple biomedical applications.

Smallest Clinically Meaningful Improvement in Amputation-Related Pain and Brief Pain Inventory Scores as Defined by Patient Reports of Global Improvement After Cryoneurolysis: a Retrospective Analysis of a Randomized, Controlled Clinical Trial.

BACKGROUND: The smallest meaningful improvement in pain scores (minimal clinically important difference [MCID]) after an analgesic intervention is essential information when both interpreting published data and designing a clinical trial. However, limited information is available for patients with chronic pain conditions, and what is published is derived from studies involving pharmacologic and psychological interventions. We here calculate these values based on data collected from 144 participants of a previously published multicenter clinical trial investigating the effects of a single treatment with percutaneous cryoneurolysis. METHODS: In the original trial, we enrolled patients with a lower-limb amputation and established phantom pain. Each received a single-injection femoral and sciatic nerve block with lidocaine and was subsequently randomized to receive either ultrasound-guided percutaneous cryoneurolysis or sham treatment at these same locations. Investigators, participants, and clinical staff were masked to treatment group assignment with the exception of the treating physician performing the cryoneurolysis, who had no subsequent participant interaction. At both baseline and 4 months (primary end point), participants rated their phantom limb pain based on a numeric rating scale (NRS) and their interference of pain on physical and emotional functioning as measured with the Brief Pain Inventory's interference subscale. They subsequently qualitatively defined the change using the 7-point ordinal Patient Global Impression of Change (PGIC). The smallest clinically meaningful improvements in phantom limb pain and Brief Pain Inventory scores were calculated using an anchor-based method based on the PGIC. RESULTS: The median (interquartile range [IQR]) phantom pain NRS (0-10) improvements at 4 months considered small, medium, and large were 1 [1-1], 3 [3-4], and 4 [3-6], respectively. The median improvements in the Brief Pain Inventory interference subscale (0-70) associated with a small, medium, and large analgesic changes were 16 [6-18], 24 [22-31], and 34 [22-46]. The proportions of patients that experienced PGIC ≥5 were 33% and 36% in the active and placebo groups, respectively. The relative risk of a patient experiencing PGIC ≥5 in the active group compared to the sham group with 95% confidence interval was 0.9 (0.6-1.4), P = .667. CONCLUSIONS: Amputees with phantom limb pain treated with percutaneous cryoneurolysis rate analgesic improvements as clinically meaningful similar to pharmacologic treatments, although their MCID for the Brief Pain Inventory was somewhat larger than previously published values. This information on patient-defined clinically meaningful improvements will facilitate interpretation of available studies and guide future trial design.

DNA-Diffusion: Leveraging Generative Models for Controlling Chromatin Accessibility and Gene Expression via Synthetic Regulatory Elements.

The challenge of systematically modifying and optimizing regulatory elements for precise gene expression control is central to modern genomics and synthetic biology. Advancements in generative AI have paved the way for designing synthetic sequences with the aim of safely and accurately modulating gene expression. We leverage diffusion models to design context-specific DNA regulatory sequences, which hold significant potential toward enabling novel therapeutic applications requiring precise modulation of gene expression. Our framework uses a cell type-specific diffusion model to generate synthetic 200 bp regulatory elements based on chromatin accessibility across different cell types. We evaluate the generated sequences based on key metrics to ensure they retain properties of endogenous sequences: transcription factor binding site composition, potential for cell type-specific chromatin accessibility, and capacity for sequences generated by DNA diffusion to activate gene expression in different cell contexts using state-of-the-art prediction models. Our results demonstrate the ability to robustly generate DNA sequences with cell type-specific regulatory potential. DNA-Diffusion paves the way for revolutionizing a regulatory modulation approach to mammalian synthetic biology and precision gene therapy.

Cortical acetylcholine dynamics are predicted by cholinergic axon activity and behavior state.

Even under spontaneous conditions and in the absence of changing environmental demands, awake animals alternate between increased or decreased periods of alertness. These changes in brain state can occur rapidly, on a timescale of seconds, and neuromodulators such as acetylcholine (ACh) are thought to play an important role in driving these spontaneous state transitions. Here, we perform the first simultaneous imaging of ACh sensors and GCaMP-expressing axons in vivo, to examine the spatiotemporal properties of cortical ACh activity and release during spontaneous changes in behavioral state. We observed a high correlation between simultaneously recorded basal forebrain axon activity and neuromodulator sensor fluorescence around periods of locomotion and pupil dilation. Consistent with volume transmission of ACh, increases in axon activity were accompanied by increases in local ACh levels that fell off with the distance from the nearest axon. GRAB-ACh fluorescence could be accurately predicted from axonal activity alone, providing the first validation that neuromodulator axon activity is a reliable proxy for nearby neuromodulator levels. Deconvolution of fluorescence traces allowed us to account for the kinetics of the GRAB-ACh sensor and emphasized the rapid clearance of ACh for smaller transients outside of running periods. Finally, we trained a predictive model of ACh fluctuations from the combination of pupil size and running speed; this model performed better than using either variable alone, and generalized well to unseen data. Overall, these results contribute to a growing understanding of the precise timing and spatial characteristics of cortical ACh during fast brain state transitions.

Truly Tiny Acoustic Biomolecules for Ultrasound Imaging and Therapy.

Nanotechnology offers significant advantages for medical imaging and therapy, including enhanced contrast and precision targeting. However, integrating these benefits into ultrasonography is challenging due to the size and stability constraints of conventional bubble-based agents. Here bicones, truly tiny acoustic contrast agents based on gas vesicles (GVs), a unique class of air-filled protein nanostructures naturally produced in buoyant microbes, are described. It is shown that these sub-80 nm particles can be effectively detected both in vitro and in vivo, infiltrate tumors via leaky vasculature, deliver potent mechanical effects through ultrasound-induced inertial cavitation, and are easily engineered for molecular targeting, prolonged circulation time, and payload conjugation.

Empirical guide to a safe thoracic paravertebral block based on dimensions of paravertebral space when ultrasound visualization is challenging.

Although ultrasound (US) guidance is the mainstay technique for performing thoracic paravertebral blocks, situations arise when US imaging is limited due to subcutaneous emphysema or extremely deep structures. A detailed understanding of the anatomical structures of the paravertebral space can be strategic to safely and accurately perform a landmark-based or US-assisted approach. As such, we aimed to provide an anatomic roadmap to assist physicians. We examined 50 chest CT scans, measuring the distances of the bony structures and soft-tissue surrounding the thoracic paravertebral block at the 2nd/3rd (upper), 5th/6th (middle), and 9th/10th (lower) thoracic vertebral levels. This review of radiology records controlled for individual differences in body mass index, gender, and thoracic level. Midline to the lateral aspect of the transverse process (TP), the anterior-to-posterior distance of TP to pleura, and rib thickness range widely based on gender and thoracic level. The mean thickness of the TP is 0.9±0.1 cm in women and 1.1±0.2 cm in men. The best target for initial needle insertion from the midline (mean length of TP minus 2 SDs) distance would be 2.5 cm (upper thoracic)/2.2 cm (middle thoracic)/1.8 cm (lower thoracic) for females and 2.7 cm (upper)/2.5 cm (middle)/2.0 cm (lower thoracic) for males, with consideration that the lower thoracic region allows for a lower margin of error in the lateral dimension because of shorter TP. There are different dimensions for the key bony landmarks of a thoracic paravertebral block between males and females, which have not been previously described. These differences warrant adjustment of landmark-based or US-assisted approach to thoracic paravertebral space block for male and female patients.

Refractory primary and secondary headache disorders that dramatically responded to combined treatment of ultrasound-guided percutaneous suprazygomatic pterygopalatine ganglion blocks and non-invasive vagus nerve stimulation: a case series.

In 1981, Devoghel achieved an 85.6% success rate in treating patients with treatment-refractory cluster headaches with alcoholization of the pterygopalatine ganglion (PPG) via the percutaneous suprazygomatic approach. Devoghel's study led to the theory that interrupting the parasympathetic pathway by blocking its transduction at the PPG could prevent or treat symptoms related to primary headache disorders (PHDs). Furthermore, non-invasive vagus nerve stimulation (nVNS) has proven to treat PHDs and has been approved by national regulatory bodies to treat, among others, cluster headaches and migraines.In this case series, nine desperate patients who presented with 11 longstanding treatment-refractory primary headache disorders and epidural blood patch-resistant postdural puncture headache (PDPH) received ultrasound-guided percutaneous suprazygomatic pterygopalatine ganglion blocks (PPGB), and seven also received nVNS. The patients were randomly selected and were not part of a research study. They experienced dramatic, immediate, satisfactory, and apparently lasting symptom resolution (at the time of the writing of this report). The report provides the case descriptions, briefly reviews the trigeminovascular and neurogenic inflammatory theories of the pathophysiology, outlines aspects of these PPGB and nVNS interventions, and argues for adopting this treatment regime as a first-line or second-line treatment rather than desperate last-line treatment of PDPH and PHDs.

A randomized controlled trial of the impact of support visits on self-isolation compliance: The Havering winter/spring support trial.

OBJECTIVES: Limited evidence exists on the policies to increase self-isolation compliance, with no experimental evidence. This trial aimed to evaluate the effect of a home visiting intervention in the London Borough of Havering on compliance with self-isolation guidance, relative to positive COVID-19 cases who received no home visits. DESIGN: Mixed method evaluation involving a two-arm randomized controlled trial (RCT) with an implementation and process evaluation. METHODS: A total of 3878 cases who tested positive for COVID-19 were randomly allocated with equal probability to receive home visits from Havering outreach team staff (n = 1946) or to a control group (n = 1932) who did not receive home visits. Randomization was implemented through a spreadsheet consisting of random numbers generated online that was used to randomly allocate cases to treatment and control. Check-in calls were conducted by a separate blinded contact tracing team on day six of isolation to measure successful self-isolation compliance. The primary intention-to-treat (ITT) analysis was conducted on 3860 cases as 18 patients were excluded from analysis because of the missing outcome data. For the implementation and process evaluation, qualitative, semi-structured, one-to-one interviews were conducted with trial participants in the treatment arm of the RCT (n = 15) and stakeholders within the London Borough of Havering's Adult Social Care and Health Team (n = 8). Qualitative data was analysed thematically using a framework approach. RESULTS: Positive cases who were allocated to receive the home visiting intervention (n = 1933) were more likely to report successful self-isolation compared to those allocated to the control group (n = 1927), an effect that was statistically significant (odds ratio 1.204 [95% CI: 1.052, 1.377]; absolute probability difference: 4.1 percentage points [95% CI: 1.2-6.9]). The implementation and process evaluation found that a key driver of compliance was altruistic motivation based on its perceived importance for protecting the community with some participants also reporting the potential of being caught not complying as a driving factor. Participants also reported that the intervention helped them 'feel supported', provided them with information about practical and financial support, and clarified their understanding or increased their awareness of self-isolation and COVID-19 guidance. No harms were reported from this trial. The trial was registered at the ISRCTN registry, number ISRCTN10030612. CONCLUSIONS: A home-visiting intervention conducted between January and March 2022 increased the self-isolation compliance of positive COVID-19 cases allocated to receive home visits. The implementation and process evaluation highlighted that the intervention increased individuals' motivation to comply with guidance, and addressed some barriers associated with opportunity and capability to comply. This trial provides much-needed evidence to inform the policy and intervention design to support public health and social measures in future outbreak scenarios.

Broad Elevation Projection Super-Resolution Ultrasound (BEP-SRUS) Imaging With a 1-D Unfocused Linear Array.

Super-resolution ultrasound (SRUS) through localizing spatially isolated microbubbles (MBs) has been demonstrated to overcome the wave diffraction limit and reveal the microvascular structure and flow information at the microscopic scale. However, 3-D SRUS imaging remains a challenge due to the fabrication and computational complexity of 2-D matrix array probes. Inspired by X-ray radiography which can present information within a volume in a single projection image with much simpler hardware than X-ray computerized tomography (CT), this study investigates the feasibility of broad elevation projection super-resolution (BEP-SR) ultrasound using a 1-D unfocused linear array. Both simulation and in vitro experiments were conducted on 3-D microvessel phantoms. In vivo demonstration was done on the Rabbit kidney. Data from a 1-D linear array with and without an elevational focus were synthesized by summing up row signals acquired from a 2-D matrix array with and without delays. A full 3-D reconstruction was also generated as the reference, using the same data of the 2-D matrix array but without summing row signals. Results show that using an unfocused 1-D array probe, BEP-SR can capture significantly more information within a volume in both vascular structure and flow velocity than the conventional 1-D elevational-focused probe. Compared with the 2-D projection image of the full 3-D SRUS results using the 2-D array probe with the same aperture size, the 2-D projection SRUS image of BEP-SR has similar volume coverage, using 32 folds fewer independent elements. This study demonstrates BEP-SR's ability of high-resolution imaging of microvascular structures and flow velocity within a 3-D volume at significantly reduced costs. The proposed BEP method could significantly benefit the clinical translation of the SRUS imaging technique by making it more affordable and repeatable.

Perceptual addition of continuous magnitudes in an 'artificial algebra'.

Although there is substantial evidence for an innate 'number sense' that scaffolds learning about mathematics, whether the underlying representations are based on discrete or continuous perceptual magnitudes has been controversial. Yet the nature of the computations supported by these representations has been neglected in this debate. While basic computation of discrete non-symbolic quantities has been reliably demonstrated in adults, infants, and non-humans, far less consideration has been given to the capacity for computation of continuous perceptual magnitudes. Here we used a novel experimental task to ask if humans can learn to add non-symbolic, continuous magnitudes in accord with the properties of an algebraic group, by feedback and without explicit instruction. Three pairs of experiments tested perceptual addition under the group properties of commutativity (Experiments 1a-b), identity and inverses (Experiments 2a-b) and associativity (Experiments 3a-b), with both line length and brightness modalities. Transfer designs were used in which participants responded on trials with feedback based on sums of magnitudes and later were tested with novel stimulus configurations. In all experiments, correlations of average responses with magnitude sums were high on trials with feedback. Responding on transfer trials was accurate and provided strong support for addition under all of the group axioms with line length, and for all except associativity with brightness. Our results confirm that adult human subjects can implicitly add continuous quantities in a manner consistent with symbolic addition over the integers, and that an 'artificial algebra' task can be used to study implicit computation.

Corrigendum: Analytical approaches for the evaluation of data deficient simulated leachable compounds in ENDS products: a case study.

[This corrects the article DOI: 10.3389/fchem.2023.1212744.].

Insulin concentrations following termination of high-dose insulin euglycemic therapy.

INTRODUCTION: High-dose insulin therapy is used in patients with calcium channel blocker and beta-adrenergic antagonist overdoses. The pharmacokinetics of insulin are scantly reported following high-dose insulin therapy. We present two cases of persistently elevated insulin concentrations following high-dose insulin therapy. CASE REPORTS: A 50-year-old woman and a 45-year-old man experienced hypotension after overdosing on amlodipine and atenolol. They were treated with high-dose insulin therapy for 54 hours at 2 units/kilogram/hour and 48 hours at 10 units/kilogram/hour, respectively. Following termination, serum insulin elimination was studied. Insulin concentrations remained greater than 1,000 µU/mL (fasting reference 2.6-24.9 µU/mL) for longer than 4 hours (case 1) and 11 hours (case 2) and greater than 300 µU/mL for longer than 8 hours and 21 hours, respectively. Insulin concentrations decreased with apparent first-order elimination half-lives of 13.0 hours and 6.0 hours. DISCUSSION: Following high-dose insulin therapy, insulin concentrations remained elevated for longer than expected based on normal pharmacokinetics in therapeutic dosing. Three previous cases reported insulin half-lives of between 2.2 hours and 18.7 hours. The current cases add to the existing data that insulin has a variable but prolonged half-life following high-dose insulin therapy. CONCLUSIONS: These findings suggest that patients are at prolonged risk of hypoglycemia following cessation of high-dose insulin infusions.

Pharmacotherapeutic Approaches to Treatment of Muscular Dystrophies.

Muscular dystrophies are a heterogeneous group of genetic muscle-wasting disorders that are subdivided based on the region of the body impacted by muscle weakness as well as the functional activity of the underlying genetic mutations. A common feature of the pathophysiology of muscular dystrophies is chronic inflammation associated with the replacement of muscle mass with fibrotic scarring. With the progression of these disorders, many patients suffer cardiomyopathies with fibrosis of the cardiac tissue. Anti-inflammatory glucocorticoids represent the standard of care for Duchenne muscular dystrophy, the most common muscular dystrophy worldwide; however, long-term exposure to glucocorticoids results in highly adverse side effects, limiting their use. Thus, it is important to develop new pharmacotherapeutic approaches to limit inflammation and fibrosis to reduce muscle damage and promote repair. Here, we examine the pathophysiology, genetic background, and emerging therapeutic strategies for muscular dystrophies.

Incidence of acute compartment syndrome with routine use of regional anesthesia for patients with long bone fractures: a large single-center retrospective review from a level I trauma tertiary academic institution.

INTRODUCTION: Traditionally, using peripheral nerve blocks (PNBs) in patients with long bone fractures has been limited due to concerns that it may interfere with the timely diagnosis of acute compartment syndrome (ACS). However, our large academic institution and level I trauma center have been using regional anesthesia routinely for pain management of patients with long bone fractures for more than a decade, with strict adherence to a comprehensive management protocol. The aim of this retrospective review is to present our experience with this practice. METHODS: Following Institutional Review Board approval, we performed a retrospective chart review of patients with long bone fractures and ACS over a 10-year period (2008-2018). RESULTS: 26 537 patients were included in the review. Approximately 20% of these patients required surgery, and 91.5% of surgically treated patients received regional anesthesia. The incidence of ACS in our cohort was 0.1% or 1.017 per 1000 patients with long bone fractures. CONCLUSION: Current recommendations on using PNBs in patients at risk for ACS have been mainly based on expert opinion and dated case reports. Due to the nature of the condition, prospective data are lacking. Our large observational dataset evaluated the risk of missing or delaying ACS diagnosis when PNBs were offered for trauma patients and demonstrated a relatively low incidence of ACS despite the routine use of PNBs under strictly protocolized conditions when patients were managed by a dedicated multidisciplinary care team.

A multi-laboratory preclinical trial in rodents to assess treatment candidates for acute ischemic stroke.

Human diseases may be modeled in animals to allow preclinical assessment of putative new clinical interventions. Recent, highly publicized failures of large clinical trials called into question the rigor, design, and value of preclinical assessment. We established the Stroke Preclinical Assessment Network (SPAN) to design and implement a randomized, controlled, blinded, multi-laboratory trial for the rigorous assessment of candidate stroke treatments combined with intravascular thrombectomy. Efficacy and futility boundaries in a multi-arm multi-stage statistical design aimed to exclude from further study highly effective or futile interventions after each of four sequential stages. Six independent research laboratories performed a standard focal cerebral ischemic insult in five animal models that included equal numbers of males and females: young mice, young rats, aging mice, mice with diet-induced obesity, and spontaneously hypertensive rats. The laboratories adhered to a common protocol and efficiently enrolled 2615 animals with full data completion and comprehensive animal tracking. SPAN successfully implemented treatment masking, randomization, prerandomization inclusion and exclusion criteria, and blinded assessment of outcomes. The SPAN design and infrastructure provide an effective approach that could be used in similar preclinical, multi-laboratory studies in other disease areas and should help improve reproducibility in translational science.

Remote control of mechanochemical reactions under physiological conditions using biocompatible focused ultrasound.

External control of chemical reactions in biological settings with spatial and temporal precision is a grand challenge for noninvasive diagnostic and therapeutic applications. While light is a conventional stimulus for remote chemical activation, its penetration is severely attenuated in tissues, which limits biological applicability. On the other hand, ultrasound is a biocompatible remote energy source that is highly penetrant and offers a wide range of functional tunability. Coupling ultrasound to the activation of specific chemical reactions under physiological conditions, however, remains a challenge. Here, we describe a synergistic platform that couples the selective mechanochemical activation of mechanophore-functionalized polymers with biocompatible focused ultrasound (FUS) by leveraging pressure-sensitive gas vesicles (GVs) as acousto-mechanical transducers. The power of this approach is illustrated through the mechanically triggered release of covalently bound fluorogenic and therapeutic cargo molecules from polymers containing a masked 2-furylcarbinol mechanophore. Molecular release occurs selectively in the presence of GVs upon exposure to FUS under physiological conditions. These results showcase the viability of this system for enabling remote control of specific mechanochemical reactions with spatiotemporal precision in biologically relevant settings and demonstrate the translational potential of polymer mechanochemistry.

Determination of chemical constituent yields in e-cigarette aerosol using partial and whole pod collections, a comparative analysis.

Literature reports the chemical constituent yields of electronic nicotine delivery systems (ENDS) aerosol collected using a range of aerosol collection strategies. The number of puffs to deplete an ENDS product varies widely, but collections often consist of data from the first 50-100 puffs. However, it is not clear whether these discrete puff blocks are representative of constituent yields over the life of a pod. We aimed to assess the effect of differing aerosol collection strategies on reported yields for select chemical constituents in the aerosol of closed pod-based ENDS products. Constituents analyzed were chosen to reflect important classes of compounds from the Final Premarket Tobacco Product Application Guidance. Yields were normalized to total device mass loss (DML). Collection strategies that consisted of partial pod collection were valid for determining yields of constituents whose DML normalized yields were consistent for the duration of pod life. These included primary aerosol constituents, such as propylene glycol, glycerol, and nicotine, and whole pod yields could be determined from initial puff blocks. However, changes were observed in the yields of some metals, some carbonyl compounds, and glycidol over pod life in a chemical constituent and product dependent manner. These results suggest that collection strategies consisting of initial puff block collections require validation per chemical constituent/product and are not appropriate for chemical constituents with variable yields over pod life. Whole pod collection increased sensitivity and accuracy in determining metal, carbonyl, and glycidol yields compared to puff block-based collection methodologies for all products tested.

Analytical approaches for the evaluation of data deficient simulated leachable compounds in ENDS products: a case study.

Leachable investigations are routinely undertaken across a range of sectors (e.g., pharmaceuticals, medical devices, etc.) to determine whether chemicals from a container closure system transfer into a product under normal conditions of use. For Electronic Nicotine Delivery Systems (ENDS) the container closure system includes all materials in contact with the e-liquid that is aerosolized and subsequently inhaled by the user. Currently, there is no guidance for conducting leachable studies for ENDS products, however, there are relevant guidance documents for orally inhaled drug products that can be applied to an ENDS container closure system. We present a case study of the analytical investigation of two leachable compounds identified in simulated leachable studies using aged JUULpods filled with unflavored e-liquid (PG/VG/nicotine/benzoic acid). Both compounds had limited toxicological information and were considered data deficient. A qualitative analysis of the aerosol collected from aged commercial JUULpods (Virginia Tobacco and Menthol), using a similar analytical method (LC-MS/MS) used in the simulated leachable studies, showed no trace or detectable levels of either leachable compound. Therefore, this qualitative analysis did not provide semi-quantitative values for the data-deficient leachable compounds necessary to support toxicological risk assessment. Further, no commercial authentic standards or reasonable synthetic route were available due to the molecular size and structural complexity of the compounds. Instead, method limits were established using an alternative approach to standard ICH guidelines. The experimentally determined method limit of quantitation, using spiked samples of simulated leachable e-liquid, provided conservative semi-quantitative values for each data deficient leachable compound in the aerosol that enabled a transfer efficiency from e-liquid to aerosol to be estimated. The transfer efficiency of each leachable compound was experimentally determined to be less than 2% based on the limit of quantitation, which then could be used to define a relevant exposure limit for the toxicological risk assessment. This work details a novel analytical approach for determining the transfer efficiency of data deficient leachable compounds from ENDS container closure systems into the ENDS aerosol to support toxicological health risk assessments.

Truly tiny acoustic biomolecules for ultrasound imaging and therapy.

Nanotechnology offers significant advantages for medical imaging and therapy, including enhanced contrast and precision targeting. However, integrating these benefits into ultrasonography has been challenging due to the size and stability constraints of conventional bubble-based agents. Here we describe bicones, truly tiny acoustic contrast agents based on gas vesicles, a unique class of air-filled protein nanostructures naturally produced in buoyant microbes. We show that these sub-80 nm particles can be effectively detected both in vitro and in vivo, infiltrate tumors via leaky vasculature, deliver potent mechanical effects through ultrasound-induced inertial cavitation, and are easily engineered for molecular targeting, prolonged circulation time, and payload conjugation.