Synthetic studies towards isomeric pyrazolopyrimidines as potential ATP synthesis inhibitors of Mycobacterium tuberculosis. Structural correction of reported N-(6-(2-(dimethylamino)ethoxy)-5-fluoropyridin-3-yl)-2-(4-fluorophenyl)-5-(trifluoromethyl)pyrazolo[1,5-α]pyrimidin-7-amine.

During our studies into preparing analogues of pyrazolopyrimidine as ATP synthesis inhibitors of Mycobacterium tuberculosis, a regiospecific condensation reaction between ethyl 4,4,4-trifluoroacetoacetate and 3-(4-fluorophenyl)-1H-pyrazol-5-amine was observed which was dependent on the specific reaction conditions employed. This work identifies optimized reaction conditions to access either the pyrazolo[3,4-ß]pyridine or the pyrazolo[1,5-α]pyrimidine scaffold. This has led to the structural confirmation of the previously reported pyrazolopyrimidine 17b which was reported as pyrazolo[1,5-α]pyrimidine structure 2 which was corrected to pyrazolo[3,4-ß]-pyrimidine 19.

Parallel discovery of selective and dual inhibitors of tryptophan dioxygenases IDO1 and TDO2 with a newly-modified enzymatic assay.

The expression of tryptophan catabolising enzyme indoleamine 2,3-dioxygenase 1 (IDO1) or tryptophan 2,3-dioxygenase 2 (TDO2) in cancers is associated with suppressed immunity and poor patient prognosis. Results from human clinical trials of IDO1 inhibitors have been disappointing. There is now a strong interest in the development of TDO2-selective or dual IDO1/TDO2 inhibitors that may surpass IDO1 inhibitors by providing broader efficacy and blocking constitutively-expressed hepatic TDO2. To expedite the discovery of novel TDO2-specific and dual inhibitors, an assay that enabled the efficient and accurate measurement of the inhibitory activity of compounds against both IDO1 and TDO2 enzymes, concurrently in the same experiment was established to screen 5,682 compounds that included the National Cancer Institute Diversity set 5, for inhibition of IDO1 and TDO2 activity. This screen identified 82 compounds that inhibited either IDO1, TDO2 or both enzymes > 50% at 20 µM. Thirty Pan Assay Interference compounds were removed from the list and the IC50 of the remaining 52 compounds against IDO1 and TDO2 was subsequently determined using the newly-developed concurrent assay. Ten compounds were confirmed as dual IDO1/TDO2 inhibitors having IC50 values under 50 µM against both enzymes and within 2-fold of each other. Six compounds with IC50 values between 1.39 and 8.41 µM were identified as potential TDO2-selective leads. The use of this concurrent protocol is anticipated to expedite the discovery of novel leads for dual and selective inhibitors against IDO1 and or TDO2 and speed the evaluation of novel analogues that will ensue.

Variations in the C-unit of bedaquiline provides analogues with improved biology and pharmacology.

Analogues of the anti-tuberculosis drug bedaquiline, bearing a 3,5-dimethoxy-4-pyridyl C-unit, retain high anti-bacterial potency yet exert less inhibition of the hERG potassium channel, in vitro, than the parent compound. Two of these analogues (TBAJ-587 and TBAJ-876) are now in preclinical development. The present study further explores structure-activity relationships across a range of related 3,5-disubstituted-4-pyridyl C-unit bedaquiline analogues of greatly varying lipophilicity (clogP from 8.16 to 1.89). This broader class shows similar properties to the 3,5-dimethoxy-4-pyridyl series, being substantially more potent in vitro and equally active in an in vivo (mouse) model than bedaquiline, while retaining a lower cardiovascular risk profile through greatly attenuated hERG inhibition.

Synthesis and structure-activity relationships for tetrahydroisoquinoline-based inhibitors of Mycobacterium tuberculosis.

A series of 5,8-disubstituted tetrahydroisoquinolines were shown to be effective inhibitors of M. tb in culture and modest inhibitors of M. tb ATP synthase. There was a broad general trend of improved potency with higher lipophilicity. Large substituents (e.g., Bn) at the tetrahydroquinoline 5-position were well-tolerated, while N-methylpiperazine was the preferred 8-substituent. Structure-activity relationships for 7-linked side chains showed that the nature of the 7-linking group was important; -CO- and -COCH2- linkers were less effective than -CH2- or -CONH- ones. This suggests that the positioning of a terminal aromatic ring is important for target binding. Selected compounds showed much faster rates of microsomal clearance than did the clinical ATP synthase inhibitor bedaquiline, and modest inhibition of mycobacterial ATP synthase.

Synthetic Studies to Help Elucidate the Metabolism of the Preclinical Candidate TBAJ-876-A Less Toxic and More Potent Analogue of Bedaquiline.

Bedaquiline is a novel drug approved in 2012 by the FDA for treatment of drug-resistant tuberculosis (TB). Although it shows high efficacy towards drug-resistant forms of TB, its use has been limited by the potential for significant side effects. In particular, bedaquiline is a very lipophilic compound with an associated long terminal half-life and shows potent inhibition of the cardiac potassium hERG channel, resulting in QTc interval prolongation in humans that may result in cardiac arrhythmia. To address these issues, we carried out a drug discovery programme to develop an improved second generation analogue of bedaquiline. From this medicinal chemistry program, a candidate (TBAJ-876) has been selected to undergo further preclinical evaluation. During this evaluation, three major metabolites arising from TBAJ-876 were observed in several preclinical animal models. We report here our synthetic efforts to unequivocally structurally characterize these three metabolites through their independent directed synthesis.

Structure-activity relationships for unit C pyridyl analogues of the tuberculosis drug bedaquiline.

The ATP-synthase inhibitor bedaquiline is effective against drug-resistant tuberculosis but is extremely lipophilic (clogP 7.25) with a very long plasma half-life. Additionally, inhibition of potassium current through the cardiac hERG channel by bedaquiline, is associated with prolongation of the QT interval, necessitating cardiovascular monitoring. Analogues were prepared where the naphthalene C-unit was replaced with substituted pyridines to produce compounds with reduced lipophilicity, anticipating a reduction in half-life. While there was a direct correlation between in vitro inhibitory activity against M. tuberculosis (MIC90) and compound lipophilicity, potency only fell off sharply below a clogP of about 4.0, providing a useful lower bound for analogue design. The bulk of the compounds remained potent inhibitors of the hERG potassium channel, with notable exceptions where IC50 values were at least 5-fold higher than that of bedaquiline. Many of the compounds had desirably higher rates of clearance than bedaquiline, but this was associated with lower plasma exposures in mice, and similar or higher MICs resulted in lower AUC/MIC ratios than bedaquiline for most compounds. The two compounds with lower potency against hERG exhibited similar clearance to bedaquiline and excellent efficacy in vivo, suggesting further exploration of C-ring pyridyls is worthwhile.

3,5-Dialkoxypyridine analogues of bedaquiline are potent antituberculosis agents with minimal inhibition of the hERG channel.

Bedaquiline is a new drug of the diarylquinoline class that has proven to be clinically effective against drug-resistant tuberculosis, but has a cardiac liability (prolongation of the QT interval) due to its potent inhibition of the cardiac potassium channel protein hERG. Bedaquiline is highly lipophilic and has an extremely long terminal half-life, so has the potential for more-than-desired accumulation in tissues during the relatively long treatment durations required to cure TB. The present work is part of a program that seeks to identify a diarylquinoline that is as potent as bedaquiline against Mycobacterium tuberculosis, with lower lipophilicity, higher clearance, and lower risk for QT prolongation. Previous work led to the identification of compounds with greatly-reduced lipophilicity compounds that retain good anti-tubercular activity in vitro and in mouse models of TB, but has not addressed the hERG blockade. We now present compounds where the C-unit naphthalene is replaced by a 3,5-dialkoxy-4-pyridyl, demonstrate more potent in vitro and in vivo anti-tubercular activity, with greatly attenuated hERG blockade. Two examples of this series are in preclinical development.

Multi-walled carbon nanotube oxidation dependent keratinocyte cytotoxicity and skin inflammation.

BACKGROUND: The effects of carbon nanotubes on skin toxicity have not been extensively studied; however, our lab has previously shown that a carboxylated multi-walled carbon nanotube (MWCNT) exacerbates the 2, 4-dinitrofluorobenzene induced contact hypersensitivity response in mice. Here we examine the role of carboxylation in MWCNT skin toxicity. RESULTS: MWCNTs were analyzed by transmission electron microscopy, zetasizer, and x-ray photoelectron spectroscopy to fully characterize the physical properties. Two MWCNTs with different levels of surface carboxylation were chosen for further testing. The MWCNTs with a high level of carboxylation displayed increased cytotoxicity in a HaCaT keratinocyte cell line, compared to the MWCNTs with intermediate levels of carboxylation. However, neither functionalized MWCNT increased the level of in vitro reactive oxygen species suggesting an alternative mechanism of cytotoxicity. Each MWCNT was tested in the contact hypersensitivity model, and only the MWCNTs with greater than 20% surface carboxylation exacerbated the ear swelling responses. Analysis of the skin after MWCNT exposure reveals that the same MWCNTs with a high level of carboxylation increase epidermal thickness, mast cell and basophil degranulation, and lead to increases in polymorphonuclear cell recruitment when co-administered with 2, 4-dinitrofluorobenzene. CONCLUSIONS: The data presented here suggest that acute, topical application of low doses of MWCNTs can induce keratinocyte cytotoxicity and exacerbation of allergic skin conditions in a carboxylation dependent manner.

A cross-sectional study of learning styles among continuing medical education participants.

PURPOSE: Experiential learning has been suggested as a framework for planning continuing medical education (CME). We aimed to (1) determine participants' learning styles at traditional CME courses and (2) explore associations between learning styles and participant characteristics. MATERIALS AND METHODS: Cross-sectional study of all participants (n = 393) at two Mayo Clinic CME courses who completed the Kolb Learning Style Inventory and provided demographic data. RESULTS: A total of 393 participants returned 241 surveys (response rate, 61.3%). Among the 143 participants (36.4%) who supplied complete demographic and Kolb data, Kolb learning styles included diverging (45; 31.5%), assimilating (56; 39.2%), converging (8; 5.6%), and accommodating (34; 23.8%). Associations existed between learning style and gender (p = 0.02). For most men, learning styles were diverging (23 of 63; 36.5%) and assimilating (30 of 63; 47.6%); for most women, diverging (22 of 80; 27.5%), assimilating (26 of 80; 32.5%), and accommodating (26 of 80; 32.5%). CONCLUSIONS: Internal medicine and psychiatry CME participants had diverse learning styles. Female participants had more variation in their learning styles than men. Teaching techniques must vary to appeal to all learners. The experiential learning theory sequentially moves a learner from Why? to What? to How? to If? to accommodate learning styles.

Effectiveness of Electroconvulsive Therapy in Patients With Major Depressive Disorder and Comorbid Borderline Personality Disorder.

OBJECTIVE: Previous research suggests that electroconvulsive therapy (ECT)-the criterion standard for the treatment of severe depression-is not as effective when the patient has comorbid borderline personality disorder (BPD). The ECT outcomes of patients with and without BPD were compared in a retrospective chart review to test this claim. METHODS: We enrolled 137 patients with a diagnosis of major depressive disorder who completed the McLean Screening Instrument for Borderline Personality Disorder. Twenty-nine patients had positive screening scores for BPD. The difference in Patient Health Questionnaire (PHQ-9) scores before and after ECT was compared between patients with and without BPD. Follow-up PHQ-9 scores determined after treatment were collected and analyzed. RESULTS: Electroconvulsive therapy equally improved symptoms of depression as measured by PHQ-9 score in both patients who screened positive and patients who screened negative for BPD. No difference in the increase in PHQ-9 scores between these 2 groups was noted 1 month after treatment (P = 0.19). CONCLUSIONS: These data showed that a positive BPD screen does not necessarily predict a poorer response to ECT, nor does it predict greater symptom recurrence after ECT. This does not suggest that ECT is necessarily an appropriate treatment for major depressive disorder in patients with a comorbid BPD, given the limitations of screening instruments.

Difficult Conversations: Training Medical Students to Assess, Educate, and Treat the Patient with Chronic Pain.

OBJECTIVE: Chronic pain, along with opioid abuse and misuse, continues to be a prevalent problem across the USA. Medical students have minimal training in biopsychosocial treatment of chronic pain and often lack the knowledge and skill necessary to address chronic pain with their patients. While there are a variety of treatment options available, research repeatedly has demonstrated that biopsychosocial treatment is the most effective option for chronic pain. Engaging patients in this type of treatment requires training and education. METHODS: The authors implemented a simulation workshop with standardized patients to educate medical students on the physical, psychological, and social aspects of chronic pain and also train students on the most effective ways to discuss chronic pain and educate their patients. Outcomes were measured by a pre- and post-test survey of knowledge, attitudes, and confidence in treating chronic pain, as well as satisfaction with the learning experience. RESULTS: Test and survey results indicated improvements in knowledge, attitudes, and confidence in treating chronic pain. Additionally, students were satisfied with the experience as evidenced by high post-workshop ratings. CONCLUSIONS: Chronic pain training during medical school is associated with students feeling more prepared to provide non-opioid biopsychosocial pain treatment. Additionally, training with standardized patients allows students to learn how to effectively educate their patients, reduce negative confrontations, and maintain a positive physician-patient relationship.

Effect of In-Class vs Online Education on Sexual Health Communication Skills in First-Year Medical Students: a Pilot Study.

OBJECTIVE: Online education is effective for knowledge acquisition, but its effect on clinical skill development is not well characterized. We aimed to compare communication skills of 50 first-year medical students who learned to assess and treat patients through an online learning module vs an in-class lecture. METHODS: Twenty-six students were randomized to learn about antidepressant-induced sexual dysfunction in class and 24 learned the same content through an online module. Students were individually observed conducting an interview with a standardized patient with antidepressant-induced sexual dysfunction. Students were assessed by faculty raters blinded to the student's learning mode. Standardized patients were asked about their willingness to have the student as their physician. RESULTS: More students who learned in class vs online demonstrated appropriate verbal empathy (18 [69%] vs 8 [33%]; P = 0.01), defined as completing each task in the "verbal empathy" assessment domain, as measured by a faculty rater. Other assessed variables were not significantly different. Standardized patients' willingness (vs unwillingness; P = 0.01) to have the student as their physician was associated with the demonstration (by faculty appraisal) of a number of basic skills: using open-ended questions, asking one question at a time, using gender-neutral terminology when asking about the patient's relationship, and using appropriate sexual-health terminology. CONCLUSIONS: This study, although limited by a single-site design and the small number of participants, offers preliminary evidence that, if confirmed, may suggest that in-class learning from a psychiatrist (vs from an online module) is associated with greater verbal empathy in the assessment of SSRI-related sexual dysfunction.

Antidepressant Use by Class: Association with Major Adverse Cardiac Events in Patients with Coronary Artery Disease.

BACKGROUND: To assess use of antidepressants by class in relation to cardiology practice recommendations, and the association of antidepressant use with the occurrence of major adverse cardiovascular events (MACE) including death. METHODS: This is a historical cohort study of all patients who completed cardiac rehabilitation (CR) between 2002 and 2012 in a major CR center. Participants completed the Patient Health Questionnaire (PHQ-9) at the start and end of the program. A linkage system enabled ascertainment of antidepressant use and MACE through 2014. RESULTS: There were 1,694 CR participants, 1,266 (74.7%) of whom completed the PHQ-9 after the program. Depressive symptoms decreased significantly from pre- (4.98 ± 5.20) to postprogram (3.57 ± 4.43) (p < 0.001). Overall, 433 (34.2%) participants were on antidepressants, most often selective serotonin reuptake inhibitors (SSRI; n = 299; 23.6%). The proportion of days covered was approximately 70% for all 4 major antidepressant classes; discontinuation rates ranged from 37.3% for tricyclics to 53.2% for serotonin-norepinephrine reuptake inhibitors (SNRI). Antidepressant use was significantly associated with lower depressive symptoms after CR (before, 7.33 ± 5.94 vs. after, 4.69 ± 4.87; p < 0.001). After a median follow-up of 4.7 years, 264 (20.9%) participants had a MACE. After propensity matching based on pre-CR depressive symptoms among other variables, participants taking tricyclics had significantly more MACE than those not taking tricyclics (HR = 2.46; 95% CI 1.37-4.42), as well as those taking atypicals versus not (HR = 1.59; 95% CI 1.05-2.41) and those on SSRI (HR = 1.45; 95% CI 1.07-1.97). There was no increased risk with use of SNRI (HR = 0.89; 95% CI 0.43-1.82). CONCLUSION: The use of antidepressants was associated with lower depression, but the use of all antidepressants except SNRI was associated with more adverse events.

PEG-Benzaldehyde-Hydrazone-Lipid Based PEG-Sheddable pH-Sensitive Liposomes: Abilities for Endosomal Escape and Long Circulation.

PURPOSE: To fabricate an acid-cleavable PEG polymer for the development of PEG-cleavable pH-sensitive liposomes (CL-pPSL), and to investigate their ability for endosomal escape and long circulation. METHODS: PEG-benzaldehyde-hydrazone-cholesteryl hemisuccinate (PEGB-Hz-CHEMS) containing hydrazone and ester bonds was synthesised and used to fabricate a dual pH-sensitive CL-pPSL. Non-cleavable PEGylated pH-sensitive liposome (pPSL) was used as a reference and gemcitabine as a model drug. The cell uptake and endosomal escape were investigated in pancreatic cancer Mia PaCa-2 cells and pharmacokinetics were studied in rats. RESULTS: The CL-pPSL showed accelerated drug release at endosomal pH 5.0 compared to pPSL. Compared to pPSL, CL-pPSL released their fluorescent payload to cytosol more efficiently and showed a 1.4-fold increase in intracellular gemcitabine concentration and higher cytotoxicity. In rats, injection of gemcitabine loaded CL-pPSL resulted in a slightly smaller Vd (149 ± 27 ml/kg; 170 ± 30 ml/kg) and shorter terminal T1/2 (5.4 ± 0.3 h; 5.8 ± 0.6 h) (both p > 0.05) but a significantly lower AUC (p < 0.01), than pPSL, due to the lower PEGylation degree (1.7 mol%) which means a 'mushroom' configuration of PEG. A five-time increase in the dose with CL-pPSL resulted in a 11-fold increase in AUC and a longer T1/2 (8.2 ± 0.5 h). CONCLUSION: The PEG-detachment from the CL-pPSL enhanced endosome escape efficiency compared with pPSL, without significantly compromising their stealth abilities.

Structure-activity relationships for analogs of the tuberculosis drug bedaquiline with the naphthalene unit replaced by bicyclic heterocycles.

Replacing the naphthalene C-unit of the anti-tuberculosis drug bedaquiline with a range of bicyclic heterocycles of widely differing lipophilicity gave analogs with a 4.5-fold range in clogP values. The biological results for these compounds indicate on average a lower clogP limit of about 5.0 in this series for retention of potent inhibitory activity (MIC90s) against M.tb in culture. Some of the compounds also showed a significant reduction in inhibition of hERG channel potassium current compared with bedaquiline, but there was no common structural feature that distinguished these.

Pain, psychiatric comorbidities, and psychosocial stressors associated with Klippel-Trenaunay syndrome.

BACKGROUND: Klippel-Trenaunay syndrome (KTS) is characterized by the triad of capillary malformation, venous malformation with or without lymphatic malformation, and limb overgrowth. Patients with KTS have lower scores in general in mental health, physical function, and quality of life than the general population. OBJECTIVE: To determine the prevalence of pain and psychiatric comorbidity in patients with KTS. METHODS: A retrospective review of 410 patients with KTS evaluated during 1976-2012 was conducted to identify the presence of pain, psychiatric comorbidities, and psychosocial stressors. RESULTS: Pain was reported by 260 patients (63.4%) and was associated with any KTS complication (P < .0001) and venous malformations of the lower extremities (P = .0008) and feet (P = .0007). Ninety-five patients had a diagnosed psychiatric condition (23.2%), most commonly depression (15.1%) and anxiety (5.1%). Pain (P = .0016), superficial thrombosis (P = .0269), deep embolic/thrombotic events (P = .0005), gastrointestinal complications (P = .0085), genitourinary complications (P = .0163), and capillary malformation of the hands (P = .0040) were associated with having a psychiatric diagnosis. LIMITATIONS: This is a retrospective study that relied on physician detection and reporting of variables. CONCLUSION: Pain and psychiatric conditions, particularly depression and anxiety, are common in patients with KTS. Awareness of the psychosocial impact of KTS and appropriate screening are important.

Validation of a Teaching Effectiveness Assessment in Psychiatry Continuing Medical Education.

OBJECTIVE: Little is known about factors associated with effective continuing medical education (CME) in psychiatry. The authors aimed to validate a method to assess psychiatry CME teaching effectiveness and to determine associations between teaching effectiveness scores and characteristics of presentations, presenters, and participants. METHODS: This cross-sectional study was conducted at the Mayo Clinic Psychiatry Clinical Reviews and Psychiatry in Medical Settings. Presentations were evaluated using an eight-item CME teaching effectiveness instrument, its content based on previously published instruments. Factor analysis, internal consistency and interrater reliabilities, and temporal stability reliability were calculated. Associations were determined between teaching effectiveness scores and characteristics of presentations, presenters, and participants. RESULTS: In total, 364 participants returned 246 completed surveys (response rate, 67.6%). Factor analysis revealed a unidimensional model of psychiatry CME teaching effectiveness. Cronbach α for the instrument was excellent at 0.94. Item mean score (SD) ranged from 4.33 (0.92) to 4.71 (0.59) on a 5-point scale. Overall interrater reliability was 0.84 (95% CI, 0.75-0.91), and temporal stability was 0.89 (95% CI, 0.77-0.97). No associations were found between teaching effectiveness scores and characteristics of presentations, presenters, and participants. CONCLUSIONS: This study provides a new, validated measure of CME teaching effectiveness that could be used to improve psychiatry CME. In contrast to prior research in other medical specialties, CME teaching effectiveness scores were not associated with use of case-based or interactive presentations. This outcome suggests the need for distinctive considerations regarding psychiatry CME; a singular approach to CME teaching may not apply to all medical specialties.

6-Nitro-2,3-dihydroimidazo[2,1-b][1,3]thiazoles: Facile synthesis and comparative appraisal against tuberculosis and neglected tropical diseases.

As part of a quest for backups to the antitubercular drug pretomanid (PA-824), we investigated the unexplored 6-nitro-2,3-dihydroimidazo[2,1-b][1,3]-thiazoles and related -oxazoles. The nitroimidazothiazoles were prepared in high yield from 2-bromo-4-nitroimidazole via heating with substituted thiiranes and diisopropylethylamine. Equivalent examples of these two structural classes provided broadly comparable MICs, with 2-methyl substitution and extended aryloxymethyl side chains preferred; albeit, S-oxidised thiazoles were ineffective for tuberculosis. Favourable microsomal stability data for a biaryl thiazole (45) led to its assessment in an acute Mycobacterium tuberculosis mouse model, alongside the corresponding oxazole (48), but the latter proved to be more efficacious. In vitro screening against kinetoplastid diseases revealed that nitroimidazothiazoles were inactive versus leishmaniasis but showed interesting activity, superior to that of the nitroimidazooxazoles, against Chagas disease. Overall, "thio-delamanid" (49) is regarded as the best lead.

Synthesis and evaluation of analogues of the tuberculosis drug bedaquiline containing heterocyclic B-ring units.

Analogues of bedaquiline where the phenyl B-unit was replaced with monocyclic heterocycles of widely differing lipophilicity (thiophenes, furans, pyridines) were synthesised and evaluated. While there was an expected broad positive correlation between lipophilicity and anti-TB activity, the 4-pyridyl derivatives appeared to have an additional contribution to antibacterial potency. The majority of the compounds were (desirably) more polar and had higher rates of clearance than bedaquiline, and showed acceptable oral bioavailability, but there was only limited (and unpredictable) improvement in their hERG liability.

In vivo quantification of quantum dot systemic transport in C57BL/6 hairless mice following skin application post-ultraviolet radiation.

BACKGROUND: Previous work has demonstrated size, surface charge and skin barrier dependent penetration of nanoparticles into the viable layers of mouse skin. The goal of this work was to characterize the tissue distribution and mechanism of transport of nanoparticles beyond skin, with and without Ultraviolet Radiation (UVR) induced skin barrier disruption. Atomic absorption spectroscopy (AAS), flow cytometry and confocal microscopy were used to examine the effect of UVR dose (180 and 360 mJ/cm2 UVB) on the skin penetration and systemic distribution of quantum dot (QD) nanoparticles topically applied at different time-points post UVR using a hairless C57BL/6 mouse model. RESULTS: Results indicate that QDs can penetrate mouse skin, regardless of UVR exposure, as evidenced by the increased cadmium in the local lymph nodes of all QD treated mice. The average % recovery for all treatment groups was 69.68% with ~66.84% of the applied dose recovered from the skin (both epicutaneous and intracutaneous). An average of 0.024% of the applied dose was recovered from the lymph nodes across various treatment groups. When QDs are applied 4 days post UV irradiation, at the peak of the skin barrier defect and LC migration to the local lymph node, there is an increased cellular presence of QD in the lymph node; however, AAS analysis of local lymph nodes display no difference in cadmium levels due to UVR treatment. CONCLUSIONS: Our data suggests that Langerhans cells (LCs) can engulf QDs in skin, but transport to the lymph node may occur by both cellular (dendritic and macrophage) and non-cellular mechanisms. It is interesting that these specific nanoparticles were retained in skin similarly regardless of UVR barrier disruption, but the observed skin immune cell interaction with nanoparticles suggest a potential for immunomodulation, which we are currently examining in a murine model of skin allergy.