Overlapping Hepatotoxicity and Colitis Associated with Immune Checkpoint Inhibitors.

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.

EUS-guided versus percutaneous liver biopsy: A prospective randomized clinical trial.

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.

Respiratory Syncytial Virus Associated Hepatitis in Pregnancy.

Respiratory syncytial virus (RSV) predominantly affects children and typically manifests as an upper respiratory tract infection. Primary RSV infection in immunosuppressed adults may increase risks of disseminated infection manifesting as RSV hepatitis. A 29-year-old pregnant woman of 10 weeks gestation presented with mild right upper quadrant abdominal pain, intractable nausea, and vomiting, requiring hospitalization. Due to initial lab work showing significantly elevated liver transaminases, she underwent a thorough workup to evaluate for causes of hepatitis. Common viral and autoimmune etiologies of hepatitis were excluded with appropriate serologies. A respiratory viral molecular panel (RVP) was obtained to evaluate for SARS-CoV-2/coronavirus disease 2019 (COVID-19) infection, despite lack of typical respiratory symptoms. No structural pathologies were detected on abdominal imaging with ultrasound and magnetic resonance imaging. No other etiologies for the patient's hepatitis were detected other than RSV infection detected on RVP. The patient's care required close coordination between multiple different subspecialties. Her condition improved due to the early detection of RSV infection and prompt initiation of supportive care. This case highlights the need for providers to consider obtaining an RVP early in workup of hepatitis to evaluate for RSV infection, even when patients have minimal respiratory symptoms. A high index of suspicion is required for early identification of RSV hepatitis as timely supportive care may prevent progression to acute liver failure.

International external validation of a stratification tool to identify branch-duct intraductal papillary mucinous neoplasms at lowest risk of progression.

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.

Peroral endoscopic myotomy for management of cricopharyngeal bars (CP-POEM): a retrospective evaluation.

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.

Zenker's peroral endoscopic myotomy, or flexible or rigid septotomy for Zenker's diverticulum: a multicenter retrospective comparison.

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.

Comorbidities Drive the Majority of Overall Mortality in Low-Risk Mucinous Pancreatic Cysts Under Surveillance.

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.

Syphilitic Aortic Aneurysm: A Rare Entity in the Era of Antibiotics.

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.

An Unusual Initial Presentation of Elderly-Onset Crohn's Disease.

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.

Vanishing Lung Syndrome: An Idiopathic Bullous Emphysema Mimicking Pneumothorax.

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.

Prevalence of Transfusion Transmissible Infections in Beta-Thalassemia Major Patients in Pakistan: A Systematic Review.

ß-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.

Glycogenic Hepatopathy: A Reversible Complication of Uncontrolled Diabetes Mellitus.

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.

Biloma: A Rare Manifestation of Spontaneous Bile Leak.

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.

The Pathophysiology of Gastrointestinal and Hepatic Manifestations of COVID-19.

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.

A leukocyte activation test identifies food items which induce release of DNA by innate immune peripheral blood leucocytes.

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.

Bio-Orthogonal Mediated Nucleic Acid Transfection of Cells via Cell Surface Engineering.

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.

General Dialdehyde Click Chemistry for Amine Bioconjugation.

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.

Scaffold Free Bio-orthogonal Assembly of 3-Dimensional Cardiac Tissue via Cell Surface Engineering.

There has been tremendous interest in constructing in vitro cardiac tissue for a range of fundamental studies of cardiac development and disease and as a commercial system to evaluate therapeutic drug discovery prioritization and toxicity. Although there has been progress towards studying 2-dimensional cardiac function in vitro, there remain challenging obstacles to generate rapid and efficient scaffold-free 3-dimensional multiple cell type co-culture cardiac tissue models. Herein, we develop a programmed rapid self-assembly strategy to induce specific and stable cell-cell contacts among multiple cell types found in heart tissue 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 scaffold free and stable self assembled 3 cell line co-culture 3D cardiac tissue model by assembling cardiomyocytes, endothelial cells and cardiac fibroblast cells via a rapid inter-cell click ligation process. We compare and analyze the function of the 3D cardiac tissue chips with 2D co-culture monolayers by assessing cardiac specific markers, electromechanical cell coupling, beating rates and evaluating drug toxicity.

Generation of a Scaffold-Free Three-Dimensional Liver Tissue via a Rapid Cell-to-Cell Click Assembly Process.

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.

Rewiring Gram-Negative Bacteria Cell Surfaces with Bio-Orthogonal Chemistry via Liposome Fusion.

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.