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Overlapping Hepatotoxicity and Colitis Associated with Immune Checkpoint Inhibitors. J Community Hosp Intern Med Perspect 2023; 13:75-78. [PMID: 37877043 PMCID: PMC10593176 DOI: 10.55729/2000-9666.1172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 01/26/2023] [Accepted: 01/27/2023] [Indexed: 10/26/2023] Open
Abstract
Immune checkpoint inhibitors (ICIs) are monoclonal antibodies that are widely used for the management of many solid-organ and hematologic cancers. These agents work by inhibition of cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4), programmed cell death-1 (PD-1), and PD ligand 1 (PD-L1). Hyperactivation of immune system results in ICI-associated adverse events. Simultaneous hepatotoxicity and colitis associated with ICIs is rare and potentially overlooked, as clinical symptoms are often nonspecific. A 73-year-old man with metastatic squamous cell carcinoma presented six weeks after starting pembrolizumab with abdominal discomfort and diarrhea. Pembrolizumab therapy was held, and supportive therapy with antidiarrheals provided partial relief. After initial workup, ICI-associated hepatitis (ICIH) and ICI-related colitis (ICIC) were diagnosed. Colitis resolution required corticosteroids. This case illustrates the importance of high index of clinical suspensions for gastrointestinal and hepatic adverse events associated with ICIs, which may be overlooked and result in severe complications. While isolated ICIH and ICIC are well known adverse events, overlapping ICIH and ICIC is rare. Prompt recognition, cessation of the inciting agent, and initiation of early supportive therapy are essential. Treatment may require corticosteroids or mycophenolate mofetil.
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EUS-guided versus percutaneous liver biopsy: A prospective randomized clinical trial. Endosc Ultrasound 2023; 12:334-341. [PMID: 37693114 PMCID: PMC10437149 DOI: 10.1097/eus.0000000000000010] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Accepted: 04/12/2023] [Indexed: 09/12/2023] Open
Abstract
Background and Objectives Prospective studies comparing EUS-guided liver biopsy (EUS-LB) to percutaneous LB (PC-LB) are scarce. We compared the efficacy and safety of EUS-LB with those of PC-LB in a prospective randomized clinical trial. Methods Between 2020 and 2021, patients were enrolled and randomized (1:1 ratio). The primary outcome was defined as the proportion of patients with ≥11 complete portal tracts (CPTs). The sample size (n = 80) was calculated based on the assumption that 60% of those in the EUS-LB and 90% of those in the PC-LB group will have LB with ≥11 CPTs. The secondary outcomes included proportion of patients in whom a diagnosis was established, number of CPTs, pain severity (Numeric Rating Scale-Pain Intensity), duration of hospital stay, and adverse events. Results Eighty patients were enrolled (median age, 53 years); 67.5% were female. Sixty percent of those in the EUS-LB and 75.0% of those in the PC-LB group met the primary outcome (P = 0.232). The median number of CPTs was higher in the PC-LB (17 vs 13; P = 0.031). The proportion of patients in whom a diagnosis was established was similar between the groups (92.5% [EUS-LB] vs 95.0% [PC-LB]; P = 1.0). Patients in the EUS-LB group had less pain severity (median Numeric Rating Scale-Pain Intensity, 2.0 vs 3.0; P = 0.003) and shorter hospital stay (2.0 vs 4.0 hours; P < 0.0001) compared with the PC-LB group. No patient experienced a serious adverse event. Conclusions EUS-guided liver biopsy was safe, effective, better tolerated, and associated with a shorter hospital stay.
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Peroral endoscopic myotomy for management of cricopharyngeal bars (CP-POEM): a retrospective evaluation. Endoscopy 2022; 54:498-502. [PMID: 34710910 DOI: 10.1055/a-1646-1151] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND Cricopharyngeal bars (CPBs) are a unique etiology of oropharyngeal dysphagia. Symptomatic patients are managed with endoscopic dilation or surgical myotomy. Cricopharyngeal peroral endoscopic myotomy (CP-POEM) is an emerging technique for the management of dysphagia due to CPBs. This study evaluated technical success, clinical success, adverse events, and long-term recurrence following CP-POEM. METHODS Consecutive patients who underwent POEM for management of CPBs between May 2015 and December 2020 at four tertiary care centers were included. Primary outcome was clinical success (defined as improvement of dysphagia score to ≤ 1). Secondary outcomes were technical success, rate and severity of adverse events, procedure duration, and symptom recurrence. RESULTS 27 patients (mean age 69 years; 10 female) underwent CP-POEM during the study period. The most common presenting symptoms at the time of index procedure were dysphagia (26; 96.3 %) and regurgitation (20; 74.1 %). Clinical and technical success were achieved in all patients. Mild/moderate adverse events occurred in two patients (7.4 %). CP-POEM significantly reduced the median dysphagia score. CONCLUSIONS CP-POEM was a safe and effective treatment for symptomatic CPBs. Although symptom recurrence was low, long-term outcome data are needed. CP-POEM should be considered as a management option for symptomatic CPBs at centers with POEM expertise.
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Zenker's peroral endoscopic myotomy, or flexible or rigid septotomy for Zenker's diverticulum: a multicenter retrospective comparison. Endoscopy 2022; 54:345-351. [PMID: 34198355 DOI: 10.1055/a-1518-7223] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND Treatment of Zenker's diverticulum has evolved from open surgery to endoscopic techniques, including flexible and rigid endoscopic septotomy, and more recently, peroral endoscopic myotomy (Z-POEM). This study compared the effectiveness of flexible and rigid endoscopic septotomy with that of Z-POEM. METHODS Consecutive patients who underwent endoscopic septotomy (flexible/rigid) or Z-POEM for Zenker's diverticulum between 1/2016 and 9/2019 were included. Primary outcomes were clinical success (decrease in Dakkak and Bennett dysphagia score to ≤ 1), clinical failure, and clinical recurrence. Secondary outcomes included technical success and rate/severity of adverse events. RESULTS 245 patients (110 females, mean age 72.63 years, standard deviation [SD] 12.37 years) from 12 centers were included. Z-POEM was the most common management modality (n = 119), followed by flexible (n = 86) and rigid (n = 40) endoscopic septotomy. Clinical success was 92.7 % for Z-POEM, 89.2 % for rigid septotomy, and 86.7 % for flexible septotomy (P = 0.26). Symptoms recurred in 24 patients (15 Z-POEM during a mean follow-up of 282.04 [SD 300.48] days, 6 flexible, 3 rigid [P = 0.47]). Adverse events occurred in 30.0 % rigid septotomy patients, 16.8 % Z-POEM patients, and 2.3 % flexible septotomy patients (P < 0.05). CONCLUSIONS There was no difference in outcomes between the three treatment approaches for symptomatic Zenker's diverticulum. Rigid endoscopic septotomy was associated with the highest rate of complications, while flexible endoscopic septotomy appeared to be the safest. Recurrence following Z-POEM was similar to flexible and rigid endoscopic septotomy. Prospective studies with long-term follow-up are required.
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Comorbidities Drive the Majority of Overall Mortality in Low-Risk Mucinous Pancreatic Cysts Under Surveillance. Clin Gastroenterol Hepatol 2022; 20:631-640.e1. [PMID: 33309984 DOI: 10.1016/j.cgh.2020.12.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 10/31/2020] [Accepted: 12/06/2020] [Indexed: 02/07/2023]
Abstract
BACKGROUND & AIMS The Charlson Comorbidity Index (CACI) has been suggested as a tool to determine comorbidity burden and guide management for patients with mucinous pancreatic cysts (Intrapapillary Mucinous Neoplasms and Mucinous Cystic Neoplasms), but has not been studied well among "low-risk" mucinous pancreatic cysts i.e. without worrisome features (WF) and high-risk stigmata (HRS). This study sought to determine the comorbidity burden among surveillance population of low-risk pancreatic cysts and provide their follow-up mortality outcomes. METHODS A single center study retrospectively reviewed a prospective pancreatic cyst database and included individuals with low-risk cysts undergoing serial imaging during 2016. Electronic medical records were reviewed to determine their baseline age-adjusted CACI (age-CACI). After 4 years, their progression to WF, disease specific (pancreatic malignancy-related, DSM), extra-pancreatic (EPM), and overall mortalities (OM) were determined using Kaplan-Meir Survival Analysis. RESULTS 502 individuals underwent prospective surveillance. The study included 440 individuals with low-risk suspected or presumed mucinous cysts and excluded 50 and 12 individuals with WF and HRS respectively. Over a median follow-up of 56 months, 12 WF progressions, 2 DSMs, 42 EPMs, and 44 OMs were observed. Baseline age-CACI had good predictive capacity for 4-year EPM (Area-Under Curve: 0.87; p< .0001). The median age-CACI of 4 enabled cohort stratification into Low (age-CACI <4) and High CACI (age-CACI ≥4) groups. A significantly higher OM (p< .001) was observed among the High CACI group as compared to the Low CACI group. CONCLUSION Through real-time application of CACI to patient outcomes, our analysis supports incorporation of this comorbidity assessment tool in making shared surveillance decisions among low-risk pancreatic cyst population.
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International external validation of a stratification tool to identify branch-duct intraductal papillary mucinous neoplasms at lowest risk of progression. United European Gastroenterol J 2022; 10:169-178. [PMID: 35199484 PMCID: PMC8911544 DOI: 10.1002/ueg2.12207] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Accepted: 01/20/2022] [Indexed: 12/28/2022] Open
Abstract
Background Identifying branch‐duct intraductal papillary mucinous neoplasms (BD‐IPMNs) at lowest risk of progression may allow for a reduced intensity of surveillance. Objective We aimed to externally validate the previously developed Dutch‐American Risk stratification Tool (DART‐1; https://rtools.mayo.edu/DART/), which identifies cysts at low risk of developing worrisome features (WFs) or high‐risk stigmata (HRS). Methods Three prospective cohorts of individuals under surveillance for BD‐IPMNs were combined, independent from the original development cohort. We assessed the performance (discrimination and calibration) of DART‐1, a multivariable Cox‐proportional logistic regression model with five predictors for the development of WFs or HRS. Results Of 832 individuals (mean age 77 years, SD 11.5) under surveillance for a median of 40 months (IQR 44), 163 (20%) developed WFs or HRS. DART‐1's discriminative ability (C‐statistic 0.68) was similar to that in the development cohort (0.64–0.72) and showed moderate calibration. DART‐1 adequately estimated the risk for patients in the middle risk quintile, and slightly underestimated it in the lowest quintiles. Their range of predicted versus observed 3‐year risk was 0%–0% versus 0%–3.7% for Q1; 0.3%–0.4% versus 3%–11% for Q2; and 2.6%–3% versus 2.4%–9.8% for Q3. The development of WFs or HRS was associated with pancreatic cancer (p < 0.001). Vice versa, in absence of WFs or HRS, the risk of malignancy was low (0.3%). Conclusions The performance of DART‐1 to predict the development of WFs or HRS in BD‐IPMN was validated in an external international cohort, with a discriminative ability equal as in the development cohort. Risk estimations were most accurate for patients with BD‐IPMNs in the middle risk quintile and slightly underestimated in the lowest quintiles.
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Syphilitic Aortic Aneurysm: A Rare Entity in the Era of Antibiotics. Cureus 2021; 13:e13647. [PMID: 33824800 PMCID: PMC8012739 DOI: 10.7759/cureus.13647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
A thoracic aortic aneurysm is a rare entity of tertiary syphilis in the era of antibiotics. The diagnosis of the aortic aneurysm due to tertiary syphilis may be challenging due to deceptive clinical presentation and rarity of the disease in the western world. We report the case of a 59-year-old man, who presents with worsening shortness of breath and was found to have a large ascending aortic aneurysm on computed tomography angiogram (CTA) of the chest. Further workup demonstrated a positive syphilis test. Untreated earlier stages of syphilis attribute to the development of the ascending aortic aneurysm. The patient was medically treated with IV penicillin and underwent surgical repair of the aortic aneurysm. Histopathology confirmed the diagnosis of syphilitic aortitis. Tertiary syphilis often presents several years after initial infection and usually after a latent phase, making it difficult to diagnose. Syphilitic aortic aneurysms may result in a high mortality rate in untreated patients. Therefore, a high index of suspicion is required for the early recognition of a syphilitic aortic aneurysm. Early treatment with antibiotic therapy and surgical repair of syphilitic aortic aneurysms can prevent life-threatening complications.
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Abstract
Coronavirus disease 2019 (COVID-19), also known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is the sixth international public health emergency. While COVID-19 classically manifests as a respiratory illness, SARS-CoV-2 may infect multiple organ systems and cause a wide array of presentations. The gastrointestinal tract has become increasingly recognized as a site of SARS-CoV-2 infection with reports of diarrhea, nausea, and liver failure, with or without concomitant respiratory involvement. In this case series and literature review, we report three cases of SARS-CoV-2 infected patients that presented with predominantly gastrointestinal symptoms or laboratory abnormalities such as diarrhea, anorexia, and transaminitis. The receptor for SARS-CoV-2, angiotensin-converting enzyme 2 (ACE2), as well as the necessary protease to facilitate viral entry, transmembrane protease serine-2 (TMPRSS2), and to a lesser extent, cathepsins, have been demonstrated to be present throughout the gastrointestinal tract, thus facilitating viral entry and pathogenesis. Furthermore, multiple reports have demonstrated evidence of viral shedding outside the nasopharynx, including the stool, for prolonged time periods even in the absence of detection of viral RNA in the nasopharynx. As such, testing for SARS-CoV-2 in stool samples with reverse transcription polymerase chain reaction (RT-PCR) assays for detection of viral RNA could aid in identifying patients that lack classic respiratory symptoms, present with atypical symptoms, or in those with a high index of suspicion (e.g. elevated inflammatory markers), but test negative on the classic nasopharyngeal swab. Furthermore, this underscores the potential for atypical transmission, with a focus on fecal-oral transmission and the need for strict hand hygiene.
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An Unusual Initial Presentation of Elderly-Onset Crohn's Disease. Cureus 2020; 12:e10173. [PMID: 33029453 PMCID: PMC7529485 DOI: 10.7759/cureus.10173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Crohn’s disease affects individuals across all age groups. However, given that it is more prevalent in younger adults, less attention is typically paid to elderly-onset Crohn’s disease. The incidence of late-onset inflammatory bowel disease is around 8 per 100,00 patients per year in the United States. The hallmark symptoms of Crohn’s, such as abdominal pain, diarrhea, and weight loss, may be absent in elderly patients, therefore making it more challenging to reach a diagnosis and initiate treatment in a timely manner. Crohn’s disease can lead to multiple complications, including abdominal abscess, enteroenteric or perianal fistulas, and bowel obstruction. Nevertheless, it is highly uncommon to have bowel obstruction as the initial sign of the disease.
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Prevalence of Transfusion Transmissible Infections in Beta-Thalassemia Major Patients in Pakistan: A Systematic Review. Cureus 2020; 12:e10070. [PMID: 32874814 PMCID: PMC7455379 DOI: 10.7759/cureus.10070] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
β-thalassemia major (TM) is one of the most prevalent inherited hemoglobinopathies in Pakistan. It has one of the highest prevalence of transfusion-dependent TM patients globally, with an estimated greater than 100,000 active cases. Blood transfusions (BT) are essential in the management of severe TM; it is critical to have a safe BT to reduce the risk of transfusion transmissible infections (TTIs). Frequent blood transfusions in these patients increase their risk of acquiring TTIs compared to the general population. We performed a systematic literature search to identify studies related to the TTIs and transfusion-related infections in Pakistan from January 1, 2010, to January 31, 2020. The search was conducted using PubMed and PakMediNet, with initial search retrieved 981 studies. Among these, 166 studies met the inclusion criteria, and only 14 studies met the final criteria for qualitative synthesis. Analysis of 14 studies (n = 3786) showed the seroprevalence of hepatitis B virus (HBV) of 3.13% (0.66% to 7.4%) and hepatitis C virus (HCV) of 26% (5.56% to 68.2%). There were only two studies that reported HIV seroprevalence of 0% and 0.5% (n = 6). The rate of seropositivity for HBV and HCV was directly related to the number of transfusions, higher ferritin levels, and older age groups. There was an increase in the HCV rate with the increasing age of patients. Thalassemia patients, who were older than ten years of age, had an HCV rate of 22% compared to only 8.4% in patients younger than ten years of age. A comparison of HCV in healthy donors vs. thalassemia patients showed a rate of 1.9% vs. 13.1% for TM patients. The majority of the patients were males (51% to 88%). The seroprevalence of TTIs was higher in males than in females (73.4% vs. 26.6%). On average, a single TM patient is exposed to at least 17 different donors annually, requiring 1-2 transfusions every month. Our study highlights that the prevalence of transfusion-transmitted infections, especially HCV, is alarmingly higher (26%) in the TM population than in the general population. There is limited data regarding the prevalence of HIV, syphilis, and malaria in this population. This is mainly due to a fragmented system of blood transfusion, weak regulations, and lower rates of voluntary blood donations. These findings warrant better health measures to improve the blood donation system and specialized care for TM patients.
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Abstract
Vanishing lung syndrome (VLS) is also referred to as idiopathic giant bullous emphysema and is a rare manifestation of chronic obstructive pulmonary disease (COPD). Middle-aged tobacco smokers, younger marijuana users, and those with alpha-1-antitrypsin deficiency may especially be affected. The clinical and radiographic findings of VLS may initially be misinterpreted as spontaneous pneumothorax. High-resolution CT is the diagnostic imaging modality of choice in these patients and can help to differentiate VLS from pneumothorax. Such imaging also helps guide appropriate management. Management of VLS ranges from a conservative to a surgical approach depending upon patients' comorbidities and candidacy for surgical resection. We present a case of a 64-year-old man with frequent hospitalizations for COPD exacerbation admitted with worsening shortness of breath and was found to have giant bullae mimicking a pneumothorax on the initial presentation.
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Abstract
Glycogenic hepatopathy (GH) is a rare complication of long-standing uncontrolled type I diabetes mellitus (TIDM) resulting in liver dysfunction and hepatomegaly due to intrahepatic deposition of glycogen. Herein we present a 19-year-old male with a history of TIDM and multiple prior hospitalizations with diabetic ketoacidosis (DKA) who presented with nausea, vomiting, right upper quadrant pain, and massive hepatomegaly. Laboratory workup was consistent with DKA and revealed a greater than 10-fold increase in liver enzymes. Despite the resolution of DKA, his liver function was worsening, and further workup was indicated. Ultimately, he underwent a liver biopsy that showed swollen hepatocytes overloaded with intracytoplasmic glycogen consistent with glycogenic hepatopathy. It is an underestimated entity and physicians should have a high index of suspicion for GH in individuals presenting with liver dysfunction, hepatomegaly, and poor glycemic control in TIDM. Strict glycemic control may result in complete resolution of disease.
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Abstract
A biloma is an intrahepatic or extrahepatic encapsulated collection of bile outside of the biliary tree and within the abdominal cavity. Hepatobiliary interventions and laparoscopic cholecystectomy are the most common etiologies of biloma followed by abdominal trauma, choledocholithiasis, and biliary dilation secondary to biliary stricture. We report a case of a 91-year-old female who presented to the emergency room with an acute onset of epigastric and right upper quadrant sharp pain for one day that radiated to the back, and was associated with two to three episodes of vomiting. Initial abdominal imaging including CT scan, ultrasound and magnetic resonance cholangiopancreatography (MRCP) of the abdomen and pelvis revealed a distended gallbladder with wall thickening, but without evidence of pancreatitis or gallstones. Hepatobiliary iminodiacetic acid (HIDA) scan findings were consistent with extrahepatic biliary leakage into the peritoneum. A cholangiogram demonstrated a perihepatic biloma. A combined approach using fluoroscopic-guided biloma drainage and endoscopic retrograde cholangiopancreatography (ERCP)-guided biliary stent placement across the site of the biliary leak resulted in the complete resolution of symptoms. Biloma should be included in the differential diagnosis of right upper quadrant abdominal pain. A high index of clinical suspicion is required for early diagnosis and treatment.
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A leukocyte activation test identifies food items which induce release of DNA by innate immune peripheral blood leucocytes. Nutr Metab (Lond) 2018; 15:26. [PMID: 29651299 PMCID: PMC5896029 DOI: 10.1186/s12986-018-0260-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 03/22/2018] [Indexed: 12/30/2022] Open
Abstract
Background Leukocyte activation (LA) testing identifies food items that induce a patient specific cellular response in the immune system, and has recently been shown in a randomized double blinded prospective study to reduce symptoms in patients with irritable bowel syndrome (IBS). We hypothesized that test reactivity to particular food items, and the systemic immune response initiated by these food items, is due to the release of cellular DNA from blood immune cells. Methods We tested this by quantifying total DNA concentration in the cellular supernatant of immune cells exposed to positive and negative foods from 20 healthy volunteers. To establish if the DNA release by positive samples is a specific phenomenon, we quantified myeloperoxidase (MPO) in cellular supernatants. We further assessed if a particular immune cell population (neutrophils, eosinophils, and basophils) was activated by the positive food items by flow cytometry analysis. To identify the signaling pathways that are required for DNA release we tested if specific inhibitors of key signaling pathways could block DNA release. Results Foods with a positive LA test result gave a higher supernatant DNA content when compared to foods with a negative result. This was specific as MPO levels were not increased by foods with a positive LA test. Protein kinase C (PKC) inhibitors resulted in inhibition of positive food stimulated DNA release. Positive foods resulted in CD63 levels greater than negative foods in eosinophils in 76.5% of tests. Conclusion LA test identifies food items that result in release of DNA and activation of peripheral blood innate immune cells in a PKC dependent manner, suggesting that this LA test identifies food items that result in release of inflammatory markers and activation of innate immune cells. This may be the basis for the improvement in symptoms in IBS patients who followed an LA test guided diet.
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Cartilage in the bulbus arteriosus of farmed Atlantic salmon (Salmo salar L.). JOURNAL OF FISH DISEASES 2017; 40:1249-1252. [PMID: 28105678 DOI: 10.1111/jfd.12600] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 11/16/2016] [Accepted: 11/17/2016] [Indexed: 06/06/2023]
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Bio-Orthogonal Mediated Nucleic Acid Transfection of Cells via Cell Surface Engineering. ACS CENTRAL SCIENCE 2017; 3:489-500. [PMID: 28573212 PMCID: PMC5445537 DOI: 10.1021/acscentsci.7b00132] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Indexed: 05/03/2023]
Abstract
The efficient delivery of foreign nucleic acids (transfection) into cells is a critical tool for fundamental biomedical research and a pillar of several biotechnology industries. There are currently three main strategies for transfection including reagent, instrument, and viral based methods. Each technology has significantly advanced cell transfection; however, reagent based methods have captured the majority of the transfection market due to their relatively low cost and ease of use. This general method relies on the efficient packaging of a reagent with nucleic acids to form a stable complex that is subsequently associated and delivered to cells via nonspecific electrostatic targeting. Reagent transfection methods generally use various polyamine cationic type molecules to condense with negatively charged nucleic acids into a highly positively charged complex, which is subsequently delivered to negatively charged cells in culture for association, internalization, release, and expression. Although this appears to be a straightforward procedure, there are several major issues including toxicity, low efficiency, sorting of viable transfected from nontransfected cells, and limited scope of transfectable cell types. Herein, we report a new strategy (SnapFect) for nucleic acid transfection to cells that does not rely on electrostatic interactions but instead uses an integrated approach combining bio-orthogonal liposome fusion, click chemistry, and cell surface engineering. We show that a target cell population is rapidly and efficiently engineered to present a bio-orthogonal functional group on its cell surface through nanoparticle liposome delivery and fusion. A complementary bio-orthogonal nucleic acid complex is then formed and delivered to which chemoselective click chemistry induced transfection occurs to the primed cell. This new strategy requires minimal time, steps, and reagents and leads to superior transfection results for a broad range of cell types. Moreover the transfection is efficient with high cell viability and does not require a postsorting step to separate transfected from nontransfected cells in the cell population. We also show for the first time a precision transfection strategy where a single cell type in a coculture is target transfected via bio-orthogonal click chemistry.
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Abstract
The development of methods for conjugating a range of molecules to primary amine functional groups has revolutionized the fields of chemistry, biology, and material science. The primary amine is a key functional group and one of the most important nucleophiles and bases used in all of synthetic chemistry. Therefore, tremendous interest in the synthesis of molecules containing primary amines and strategies to devise chemical reactions to react with primary amines has been at the core of chemical research. In particular, primary amines are a ubiquitous functional group found in biological systems as free amino acids, as key side chain lysines in proteins, and in signaling molecules and metabolites and are also present in many natural product classes. Due to its abundance, the primary amine is the most convenient functional group handle in molecules for ligation to other molecules for a broad range of applications that impact all scientific fields. Because of the primary amine's central importance in synthetic chemistry, acid-base chemistry, redox chemistry, and biology, many methods have been developed to efficiently react with primary amines, including activated carboxylic acids, isothiocyanates, Michael addition type systems, and reaction with ketones or aldehydes followed by in situ reductive amination. Herein, we introduce a new traceless, high-yield, fast click-chemistry method based on the rapid and efficient trapping of amine groups via a functionalized dialdehyde group. The click reaction occurs in mild conditions in organic solvents or aqueous media and proceeds in high yield, and the starting dialdehyde reagent and resulting dialdehyde click conjugates are stable. Moreover, no catalyst or dialdehyde-activating group is required, and the only byproduct is water. The initial dialdehyde and the resulting conjugate are both straightforward to characterize, and the reaction proceeds with high atom economy. To demonstrate the broad scope of this new click-conjugation strategy, we designed a straightforward scheme to synthesize a suite of dialdehyde reagents. The dialdehyde molecules were used for applications in cell-surface engineering and for tailoring surfaces for material science applications. We anticipate the broad utility of the general dialdehyde click chemistry to primary amines in all areas of chemical research, ranging from polymers and bioconjugation to material science and nanoscience.
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Generation of a Scaffold-Free Three-Dimensional Liver Tissue via a Rapid Cell-to-Cell Click Assembly Process. Bioconjug Chem 2016; 27:1991-8. [PMID: 27508505 DOI: 10.1021/acs.bioconjchem.6b00187] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
There has been tremendous interest in constructing in vitro liver organ models for a range of fundamental studies of cell signaling, metabolism, and infectious diseases, and as a commercial system to evaluate therapeutic drug discovery prioritization and toxicity. Although there has been progress toward studying two-dimensional hepatic function in vitro, there remain challenging obstacles to generate rapid and efficient scaffold-free three-dimensional multiple cell line coculture tissue models of liver. Herein, we develop and employ a strategy to induce specific and stable cell-cell contacts among multiple hepatic cell lines to generate 3D tissues through cell-surface engineering based on liposome delivery and fusion to display bio-orthogonal functional groups from cell membranes. We generate, for the first time, a three cell line coculture 3D liver tissue model by assembling hepatocytes, hepatic endothelial cells, and hepatic stellate cells via a rapid intercell click ligation process. We compare and analyze the function of the superior 3D liver tissue chips with 2D coculture monolayer by assessing mitochondrial metabolic activity and evaluating drug toxicity.
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Rewiring Gram-Negative Bacteria Cell Surfaces with Bio-Orthogonal Chemistry via Liposome Fusion. Bioconjug Chem 2016; 27:1082-9. [PMID: 27019118 DOI: 10.1021/acs.bioconjchem.6b00073] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The ability to tailor bacteria cell surfaces with non-native molecules is critical to advance the study of bacteria communication, cell behavior, and for next-generation therapeutics to improve livestock and human health. Such modifications would allow for novel control over cell behavior, cell-cell interactions, biofilm formation, adjuvant conjugation, and imaging. Current methods to engineer bacteria surfaces have made major advances but rely on complicated, slow, and often expensive molecular biology and metabolic manipulation methods with limited scope on the type of molecules installed onto the surface. In this report, we introduce a new straightforward method based on liposome fusion to engineer Gram-negative bacteria cells with bio-orthogonal groups that can subsequently be conjugated to a range of molecules (biomolecules, small molecules, probes, proteins, nucleic acids, ligands, and radiolabels) for further studies and programmed behavior of bacteria. This method is fast, efficient, inexpensive, and useful for installing a broad scope of ligands and biomolecules to Gram-negative bacteria surfaces.
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Abstract
The rapid development of new small molecule drugs, nanomaterials, and genetic tools to modulate cellular function through cell surface manipulation has revolutionized the diagnosis, study, and treatment of disorders in human health. Since the cell membrane is a selective gateway barrier that serves as the first line of defense/offense and communication to its environment, new approaches that molecularly engineer or tailor cell membrane surfaces would allow for a new era in therapeutic design, therapeutic delivery, complex coculture tissue construction, and in situ imaging probe tracking technologies. In order to develop the next generation of multimodal therapies, cell behavior studies, and biotechnologies that focus on cell membrane biology, new tools that intersect the fields of chemistry, biology, and engineering are required. Herein, we develop a liposome fusion and delivery strategy to present a novel dual receptor and reporter system at cell surfaces without the use of molecular biology or metabolic biosynthesis. The cell surface receptor is based on bio-orthogonal functional groups that can conjugate a range of ligands while simultaneously reporting the conjugation through the emission of fluorescence. We demonstrate this dual receptor and reporter system by conjugating and tracking various cell surface ligands for temporal control of cell fluorescent signaling, cell-cell interaction, and tissue assembly construction.
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Developing chemoselective and biodegradable polyester elastomers for bioscaffold application. J Mater Chem B 2015; 3:1405-1414. [PMID: 32264491 DOI: 10.1039/c4tb01481b] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Thermal polyesterification has emerged as a successful method for synthesizing polyesters for biomedical applications. However, to date, no general functionalization strategy has been incorporated into materials designed by the thermal polycondensation of polyacids and polyols. Herein, we report the design of several elastomers based on the thermal polycondensation of 4-ketopimelic acid, citric acid, and one of two diols: 1,6-hexanediol or 1,4-cyclohexanedimethanol. By varying the diol and the curing conditions, several elastomers were designed with a range of physical and mechanical properties. Poly(diol 4-ketopimelate-co-diol citrate) achieved Young's modulus, ultimate tensile stress, and rupture strain values of 0.39-1.13 MPa, 0.27-1.04 MPa, and 108-426%, respectively. Additionally, the incorporation of the ketone from 4-ketopimelic acid gave these materials two advantageous characteristics: a site for covalent functionalization through oxime formation and the ability to covalently bond to the surrounding tissue through imine linkages. Biocompatibility was studied both in vitro and in vivo in order to gain a complete understanding as to how biological systems respond to these novel materials. Based on preliminary results, we believe that poly(diol 4-ketopimelate-co-diol citrate) polyketoesters are excellent candidates for biomaterials.
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In situ modulation of cell behavior via smart dual-ligand surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:13656-66. [PMID: 25373713 PMCID: PMC4334223 DOI: 10.1021/la503521x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Due to the highly complex nature of the extracellular matrix (ECM), the design and implementation of dynamic, stimuli-responsive surfaces that present well-defined ligands and serve as model ECM substrates have been of tremendous interest to biomaterials, biosensor, and cell biology communities. Such tools provide strategies for identifying specific ligand-receptor interactions that induce vital biological consequences. Herein, we report a novel dual-ligand-presenting surface methodology that modulates dynamic ECM properties to investigate various cell behaviors. Peptides PHSRN, cRGD, and KKKTTK, which mimic the cell- and heparan sulfate-binding domains of fibronectin, and carbohydrates Gal and Man were combined with cell adhesive RGD to survey possible synergistic or antagonist ligand effects on cell adhesion, spreading, growth, and migration. Soluble molecule and enzymatic inhibition assays were also performed, and the levels of focal adhesion kinase in cells subjected to different ligand combinations were quantified. A redox-responsive trigger was incorporated into this surface strategy to spontaneously release ligands in the presence of adhered cells, and cell spreading, growth, and migration responses were measured and compared. The identity and nature of the dual-ligand combination directly influenced cell behavior.
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Remote control of tissue interactions via engineered photo-switchable cell surfaces. Sci Rep 2014; 4:6313. [PMID: 25204325 PMCID: PMC4159631 DOI: 10.1038/srep06313] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Accepted: 08/01/2014] [Indexed: 01/08/2023] Open
Abstract
We report a general cell surface molecular engineering strategy via liposome fusion delivery to create a dual photo-active and bio-orthogonal cell surface for remote controlled spatial and temporal manipulation of microtissue assembly and disassembly. Cell surface tailoring of chemoselective functional groups was achieved by a liposome fusion delivery method and quantified by flow cytometry and characterized by a new cell surface lipid pull down mass spectrometry strategy. Dynamic co-culture spheroid tissue assembly in solution and co-culture tissue multilayer assembly on materials was demonstrated by an intercellular photo-oxime ligation that could be remotely cleaved and disassembled on demand. Spatial and temporal control of microtissue structures containing multiple cell types was demonstrated by the generation of patterned multilayers for controlling stem cell differentiation. Remote control of cell interactions via cell surface engineering that allows for real-time manipulation of tissue dynamics may provide tools with the scope to answer fundamental questions of cell communication and initiate new biotechnologies ranging from imaging probes to drug delivery vehicles to regenerative medicine, inexpensive bioreactor technology and tissue engineering therapies.
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Abstract
We report the use of fluid lipid bilayer membrane as a model platform to study the influence of the bilayer microenvironment and composition on the enzymology in membrane. As a model system we determined the enzyme kinetics on membranes for the transformation of bilayers containing phosphoinositol(4,5)-bisphosphate (PI(4,5)P2) to phosphoinositol(3,4,5)-trisphosphate (PI(3,4,5)P3) by the enzyme phosphoinositol-3-kinase (PI3K) using radiolabeled ATP. The activity of the enzyme was monitored as a function of the radioactivity incorporated within the bilayer. The transformation of PI(4,5)P2 to PI(3,4,5)P3 was determined using a mass strip assay. The fluidity of the bilayer was confirmed by Fluorescence Recovery After Photobleaching (FRAP) experiments. Kinetic simulations were performed based on Langmuir adsorption and Michaelis-Menton kinetics equations to generate the rate constants for the enzymatic reaction. The effect of cholesterol on the enzyme kinetics was studied by doping the bilayer with 1% cholesterol. This leads to significant reduction in reaction rate due to change in membrane microenvironment. This strategy provides a method to study the enzymology of various kinases and phosphatases occurring at the membrane and also how these reactions are affected by the membrane composition and surface microenvironment.
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Cell division orientation on biospecific peptide gradients. ACS APPLIED MATERIALS & INTERFACES 2014; 6:11523-11528. [PMID: 25007410 DOI: 10.1021/am502209k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
An assay was developed for determining cell division orientation on gradients. The methodology is based on permeating microfluidic devices with alkanethiols and subsequent printing of cell adhesive peptide gradient self-assembled monolayers (SAMs) for examining oriented cell divisions. To our knowledge, there has been no study examining the correlation between cell division orientations based on an underlying ligand gradient. These results implicate an important role for how the extracellular matrix may control cell division. These surfaces would allow for a range of cell behavior (polarization, migration, division, differentiation) studies on tailored biospecific gradients and as a potential biotechnological platform to assess small molecule perturbations of cell function.
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Cell-Surface Engineering by a Conjugation-and-Release Approach Based on the Formation and Cleavage of Oxime Linkages upon Mild Electrochemical Oxidation and Reduction. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201404099] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Cell-surface engineering by a conjugation-and-release approach based on the formation and cleavage of oxime linkages upon mild electrochemical oxidation and reduction. Angew Chem Int Ed Engl 2014; 53:9487-92. [PMID: 25045145 DOI: 10.1002/anie.201404099] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Indexed: 12/22/2022]
Abstract
We report a strategy to rewire cell surfaces for the dynamic control of ligand composition on cell membranes and the modulation of cell-cell interactions to generate three-dimensional (3D) tissue structures applied to stem-cell differentiation, cell-surface tailoring, and tissue engineering. We tailored cell surfaces with bioorthogonal chemical groups on the basis of a liposome-fusion and -delivery method to create dynamic, electroactive, and switchable cell-tissue assemblies through chemistry involving chemoselective conjugation and release. Each step to modify the cell surface: activation, conjugation, release, and regeneration, can be monitored and modulated by noninvasive, label-free analytical techniques. We demonstrate the utility of this methodology by the conjugation and release of small molecules to and from cell surfaces and by the generation of 3D coculture spheroids and multilayered cell tissues that can be programmed to undergo assembly and disassembly on demand.
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Abstract
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We
report a switchable redox click and cleave reaction strategy for conjugating
and releasing a range of molecules on demand. This chemoselective
redox-responsive ligation (CRRL) and release strategy is based on
a redox switchable oxime linkage that is controlled by mild chemical
or electrochemical redox signals and can be performed at physiological
conditions without the use of a catalyst. Both conjugation and release
reactions are kinetically well behaved and quantitative. The CRRL
strategy is synthetically modular and easily monitored and characterized
by routine analytical techniques. We demonstrate how the CRRL strategy
can be used for the dynamic generation of cyclic peptides and the
ligation of two different peptides that are stable but can be selectively
cleaved upon changes in the redox environment. We also demonstrate
a new redox based delivery of cargoes to live cells strategy via the
CRRL methodology by synthesizing a FRET redox-responsive probe that
is selectively activated within a cellular environment. We believe
the ease of the CRRL strategy should find wide use in a range of applications
in biology, tissue engineering, nanoscience, synthetic chemistry,
and material science and will expand the suite of current conjugation
and release strategies.
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Ligand slope, density and affinity direct cell polarity and migration on molecular gradient surfaces. RSC Adv 2014. [DOI: 10.1039/c4ra03795b] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A patterned peptide gradient with control of slope and density is created for studies of directed cell polarization and migration.
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Localization of natriuretic peptides in the cardiac pacemaker of Atlantic salmon (Salmo salar L.). Acta Histochem 2012; 114:819-26. [PMID: 22385580 DOI: 10.1016/j.acthis.2012.02.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2012] [Revised: 02/04/2012] [Accepted: 02/06/2012] [Indexed: 01/18/2023]
Abstract
This study describes the location of the primary pacemaker at the sino-atrial (SA) junction and the localization of salmon cardiac peptide (sCP) and ventricular natriuretic peptide (VNP) in Atlantic salmon (Salmo salar L.). The pacemaker tissue appeared lightly stained and composed of: (1) wavy nerve bundles with oval elongated wavy appearing nuclei with pointed ends, (2) ganglion cells (12-22 μm) with granular cytoplasm and (3) wide muscle fibers with large nuclei (modified cardiomyocytes) clearly distinguishing them from the other myocardial cells. Pacemaker tissue was further evaluated using immunohistochemical staining. Immunoreactivity of natriuretic peptides (sCP and VNP) antisera showed specific staining in pacemaker ganglion cells in addition to the cardiomyocytes. Positive staining with anti-CD3ɛ antisera in the pacemaker ganglion cells is a novel finding in teleosts and is consistent with observations in mammals. In conclusion, the Atlantic salmon pacemaker was shown to be located at the SA node and to harbor sCP and VNP peptides, suggesting a possible neuromodulatory and/or neurotransmitter role for these cardiac hormones within the teleost heart.
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Biomolecular modification of carbon nanotubes for studies of cell adhesion and migration. NANOTECHNOLOGY 2011; 22:494019. [PMID: 22101926 DOI: 10.1088/0957-4484/22/49/494019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We report a strategy for tailoring and patterning carbon nanotubes (CNTs) for biospecific cell studies. We synthesized a new electroactive hydroquinone terminated pyrene molecule to tailor CNTs. These modified CNTs can be oxidized and chemoselectively reacted with oxyamine tethered ligands to generate various ligand tethered CNTs. A cell adhesive Arg-Gly-Asp peptide (RGD) is immobilized to the CNTs and a new microfluidic patterning method is employed to generate multiplex patterned surfaces for biospecific cell adhesion and migration studies. This work demonstrates the integration of a new functionalization strategy to immobilize a variety of ligands to CNTs for a range of potential drug delivery, tissue imaging and cellular behavior studies and a microfluidic patterning strategy for generating complex high-throughput surfaces for biotechnological and cell based assay applications.
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Abstract
In this study, we have rewired cell surfaces with ketone and oxyamine molecules based on liposome fusion for applications in cell-surface engineering. Lipid vesicles, functionalized with ketone and oxyamine molecules, display complementary chemistry and undergo recognition, docking, and subsequent fusion upon covalent oxime bond formation. Liposome fusion was characterized by several techniques including matrix-assisted laser-desorption/ionization mass spectrometry (MALDI-MS), light scattering, fluorescence resonance energy transfer (FRET), and transmission electron microscopy (TEM). When cultured with cells, ketone- and oxyamine-containing liposomes undergo spontaneous membrane fusion to present the respective molecules from cell surfaces. Ketone-functionalized cell surfaces serve as sites for chemoselective ligation with oxyamine-conjugated molecules. We tailored and fluorescently labeled cell surfaces with an oxyamine-conjugated rhodamine dye. As an application of this cell-surface engineering strategy, ketone- and oxyamine-functionalized cells were patterned on oxyamine- and ketone-presenting surfaces, respectively. Cells adhered, spread, and proliferated in the patterned regions via interfacial oxime linkage. The number of ketone molecules on the cell surface was also quantified by flow cytometry.
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Abstract
In this report, we develop smart surfaces for the spatial and temporal control of mammalian cell behavior. We integrate a bioactive surface strategy with a photo-electroactive surface strategy to generate dynamic ligand surface gradients for controlling cell adhesion, tissue shape morphing, and cell tissue migration.
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Abstract
A general surface chemistry strategy is described for the development of a new switchable material. The method modulates a surface-immobilized-molecules structure by using two orthogonal "click" reactions based on Huisgen cycloaddition and oxime chemistry, where the oxime linkage is redox active and switchable. We demonstrate this strategy by developing a noninvasive, biocompatible, in situ surface chemistry that is able to modulate the affinity of a cell-adhesive peptide to cell integrin receptors to study dynamic cell adhesion and cell migration in real time and as a new hide-and-reveal strategy for application in new types of smart biofouling biomaterials.
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Synthetic Chemoselective Rewiring of Cell Surfaces: Generation of Three-Dimensional Tissue Structures. J Am Chem Soc 2011; 133:8704-13. [DOI: 10.1021/ja2022569] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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38
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A renewable, chemoselective, and quantitative ligand density microarray for the study of biospecific interactions. Chem Commun (Camb) 2011; 47:523-5. [DOI: 10.1039/c0cc01509a] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Fabrication of dynamic self-assembled monolayers for cell migration and adhesion studies. Methods Mol Biol 2011; 751:421-36. [PMID: 21674346 DOI: 10.1007/978-1-61779-151-2_26] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
How cells interact with the extracellular matrix (ECM) is important for a number of fundamental -processes in cell biology. However, the ECM is highly complex and in order to simplify the matrix for cell biological studies, it has been modeled with self-assembled monolayers (SAMs) of alkanethiolates on gold substrates. In this chapter, we outline procedures to create dynamic surfaces by functionalizing SAMs. SAMs based on quinone, oxyamine, and alcohol-terminated thiols were used to immobilize cell adhesive peptides with spatial control. Cells were seeded to these surfaces to provide cell co-culture -patterns suitable for biological studies.
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Microfluidic permeation printing of self-assembled monolayer gradients on surfaces for chemoselective ligand immobilization applied to cell adhesion and polarization. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:12817-12823. [PMID: 20586451 DOI: 10.1021/la1022642] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
To study complex cell behavior on model surfaces requires biospecific interactions between the interfacing cell and material. Developing strategies to pattern well-defined molecular gradients on surfaces is difficult but critical for studying cell adhesion, polarization, and directed cell migration. We introduce a new strategy, microfluidic SPREAD (Solute PeRmeation Enhancement And Diffusion) for inking poly(dimethylsiloxane) (PDMS) microfluidic cassettes with a gradient of alkanethiol. Using SPREAD, an oxyamine-terminated alkanethiol is able to permeate into a PDMS microfluidic cassette, creating a chemical gradient, which can subsequently be transfer printed onto a gold surface to form the corresponding chemoselective gradient of oxyamine-alkanethiol self-assembled monolayer (SAM). By first patterning regions of the gold surface with a protective SAM using microfluidic lithography, directional gradients can be stamped exclusively onto unprotected bare gold regions to form single cell gradient microarrays. The microfluidic SPREAD strategy can also be extended to print micrometer-sized islands of radial SAM gradients with excellent geometric resolution. The immobilization of a cell adhesive Arg-Gly-Asp (RGD)-ketone peptide to the SPREAD stamped oxyamine-alkanethiol SAMs provides a stable interfacial oxime linkage for biospecific studies of cell adhesion, polarity, and migration.
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42
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Surface chemistry and cell biological tools for the analysis of cell adhesion and migration. Chembiochem 2010; 11:745-53, 730. [PMID: 20198673 DOI: 10.1002/cbic.200900787] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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43
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Selective tethering of ligands and proteins to a microfluidically patterned electroactive fluid lipid bilayer array. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:9835-9841. [PMID: 20131880 DOI: 10.1021/la1001545] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We report a new, quantitative methodology to pattern and present ligands from planar, supported, fluid lipid bilayers. By combining microfluidic lithography (microFL) with an electroactive, chemoselective interfacial reaction strategy, a number of ligands as well as protein concanavalin A were immobilized in lipid microarrays. Electroactive vesicles were generated after the spontaneous insertion of hydroquinone-tethered alkane (H(2)Q) into egg palmitoyl-oleoyl phosphatidylcholine (egg-POPC), followed by subsequent fusion to a siloxane-terminated self-assembled monolayer (SAM) on gold. An advantage of the H(2)Q system is that it can be electrochemically oxidized to the corresponding quinone (Q), followed by rapid chemoselective conjugation with oxyamine-functionalized (RONH(2)) ligands. The oxime product is also electroactive, and the reaction can be monitored and the amount of ligand bound can be quantified by electrochemistry. The bilayers were characterized by electrochemistry, fluorescence microscopy, and ellipsometry and were determined to be fluid by fluorescence recovery after photobleaching (FRAP). This strategy provides a synergistic method to pattern and present a number of ligands or biomolecules from the bilayer surface for the evaluation of enzyme or protein binding to biomembranes.
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Tailored electroactive and quantitative ligand density microarrays applied to stem cell differentiation. J Am Chem Soc 2010; 132:2614-21. [PMID: 20131824 DOI: 10.1021/ja907187f] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The ability to precisely control the interactions between materials and mammalian cells at the molecular level is crucial to understanding the fundamental chemical nature of how the local environment influences cellular behavior as well as for developing new biomaterials for a range of biotechnological and tissue engineering applications. In this report, we develop and apply for the first time a quantitative electroactive microarray strategy that can present a variety of ligands with precise control over ligand density to study human mesenchymal stem cell (hMSC) differentiation on transparent surfaces with a new method to quantitate adipogenic differentiation. We found that both the ligand composition and ligand density influence the rate of adipogenic differentiation from hMSC's. Furthermore, this new analytical biotechnology method is compatible with other biointerfacial characterization technologies (surface plasmon resonance, mass spectrometry) and can also be applied to investigate a range of protein-ligand or cell-material interactions for a variety of systems biology studies or cell behavior based assays.
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Inside Cover: Surface Chemistry and Cell Biological Tools for the Analysis of Cell Adhesion and Migration (ChemBioChem 6/2010). Chembiochem 2010. [DOI: 10.1002/cbic.201090021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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46
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Tandem surface microfluidic lithography and activation to generate patch pattern biospecific ligand and cell arrays. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:4130-4135. [PMID: 19839568 DOI: 10.1021/la903297d] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We report a rapid, inexpensive, and flexible methodology that combines microfluidic lithography and oxidative activation to pattern and chemically alter selective regions of SAMs on gold for subsequent chemoselective ligand immobilization. We demonstrate that PCC, a mild oxidant, can be used to convert hydroxyl-terminated SAMs to aldehydes and decorated with a variety of oxyamine-containing molecules. This strategy is compatible with cell culture and was employed to create a biospecific ligand platform for peptide-mediated, cell adhesion arrays. By using a number of different ligands and characterization tools, we showed that the generation of both cell patterning and ligand microarray patterning can be achieved. SAM formation, activation, ligand immobilization, and biospecific cell patterning are characterized by contact angle, cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS) (Supporting Information), scanning electron microscopy (SEM), and fluorescence microscopy.
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Role of surface chemistry and topology of chemoselectively tailored embossed films on shear adhesion. ACTA ACUST UNITED AC 2010. [DOI: 10.1039/b918084b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Model substrates for studies of cell mobility. Curr Opin Chem Biol 2009; 13:697-704. [DOI: 10.1016/j.cbpa.2009.10.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2009] [Revised: 10/01/2009] [Accepted: 10/02/2009] [Indexed: 11/28/2022]
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50
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Design and applications of biodegradable polyester tissue scaffolds based on endogenous monomers found in human metabolism. Molecules 2009; 14:4022-50. [PMID: 19924045 PMCID: PMC6255442 DOI: 10.3390/molecules14104022] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Revised: 09/22/2009] [Accepted: 09/28/2009] [Indexed: 11/17/2022] Open
Abstract
Synthetic polyesters have deeply impacted various biomedical and engineering fields, such as tissue scaffolding and therapeutic delivery. Currently, many applications involving polyesters are being explored with polymers derived from monomers that are endogenous to the human metabolism. Examples of these monomers include glycerol, xylitol, sorbitol, and lactic, sebacic, citric, succinic, alpha-ketoglutaric, and fumaric acids. In terms of mechanical versatility, crystallinity, hydrophobicity, and biocompatibility, polyesters synthesized partially or completely from these monomers can display a wide range of properties. The flexibility in these macromolecular properties allows for materials to be tailored according to the needs of a particular application. Along with the presence of natural monomers that allows for a high probability of biocompatibility, there is also an added benefit that this class of polyesters is more environmentally friendly than many other materials used in biomedical engineering. While the selection of monomers may be limited by nature, these polymers have produced or have the potential to produce an enormous number of successes in vitro and in vivo.
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