Theoretical and experimental studies of vesicle formation in surfactant mixtures

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1996.Includes bibliographical references (p. 197-214).by Pak K. Yuet.Ph.D

Chemical Tools for Temporally and Spatially Resolved Mass Spectrometry-Based Proteomics

Accurate measurements of the abundances, synthesis rates and degradation rates of cellular proteins are critical for understanding how cells and organisms respond to changes in their environments. Over the past two decades, there has been increasing interest in the use of mass spectrometry for proteomic analysis. In many systems, however, protein diversity as well as cell and tissue heterogeneity limit the usefulness of mass spectrometry-based proteomics. As a result, researchers have had difficulty in systematically identifying proteins expressed within specified time intervals, or low abundance proteins expressed in specific tissues or in a few cells in complex microbial systems. In this review, we present recently-developed tools and strategies that probe these two subsets of the proteome: proteins synthesized during well-defined time intervals—temporally resolved proteomics—and proteins expressed in predetermined cell types, cells or cellular compartments—spatially resolved proteomics—with a focus on chemical and biological mass spectrometry-based methodologies

Cell Surface Display Yields Evolvable, Clickable Antibody Fragments

Non-canonical amino acids (ncAAs) provide powerful tools for engineering the chemical and physical properties of proteins. However, introducing ncAAs into proteins can affect protein properties in unpredictable ways, thus necessitating screening efforts to identify mutants with desirable properties. In this work, we describe an Escherichia coli cell surface display platform for the directed evolution of clickable antibody fragments. This platform enabled isolation of antibody fragments with improved digoxigenin binding and modest affinity maturation in several different ncAA contexts. Azide-functionalized fragments exhibited improved binding kinetics relative to their methionine counterparts, facile chemical modification through azide–alkyne cycloaddition, and retention of binding properties after modification. The results described here suggest new possibilities for protein engineering, including modulation of molecular recognition events by ncAAs and direct screening of libraries of chemically modified proteins

An Intelligent Clinical Decision Support System for Assessing the Needs of a Long-Term Care Plan

With the global aging population, providing effective long-term care has been promoted and emphasized for reducing the hospitalizations of the elderly and the care burden to hospitals and governments. Under the scheme of Long-term Care Project 2.0 (LTCP 2.0), initiated in Taiwan, two types of long-term care services, i.e., institutional care and home care, are provided for the elderly with chronic diseases and disabilities, according to their personality, living environment and health situation. Due to the increasing emphasis on the quality of life in recent years, the elderly expect long-term care service providers (LCSP) to provide the best quality of care (QoC). Such healthcare must be safe, effective, timely, efficiently, diversified and up-to-date. Instead of supporting basic activities in daily living, LCSPs have changed their goals to formulate elderly-centered care plans in an accurate, time-efficient and cost-effective manner. In order to ensure the quality of the care services, an intelligent clinical decision support system (ICDSS) is proposed for care managers to improve their efficiency and effectiveness in assessing the long-term care needs of the elderly. In the ICDSS, artificial intelligence (AI) techniques are adopted to distinguish and formulate personalized long-term care plans by retrieving relevant knowledge from past similar records

Recycling in the management of solid waste : a study of the governance of Hong Kong's EcoPark

published_or_final_versionPolitics and Public AdministrationMasterMaster of Public Administratio

Split cGAL, an intersectional strategy using a split intein for refined spatiotemporal transgene control in Caenorhabditis elegans

Bipartite expression systems, such as the GAL4-UAS system, allow fine manipulation of gene expression and are powerful tools for interrogating gene function. Recently, we established cGAL, a GAL4-based bipartite expression system for transgene control in Caenorhabditis elegans, where a single promoter dictates the expression pattern of a cGAL driver, which then binds target upstream activation sequences to drive expression of a downstream effector gene. Here, we report a split strategy for cGAL using the split intein gp41-1 for intersectional control of transgene expression. Split inteins are protein domains that associate, self-excise, and covalently ligate their flanking peptides together. We split the DNA binding domain and transcriptional activation domain of cGAL and fused them to the N terminal of gp41-1-N-intein and the C terminal of gp41-1-C-intein, respectively. In cells where both halves of cGAL are expressed, a functional cGAL driver is reconstituted via intein-mediated protein splicing. This reconstitution allows expression of the driver to be dictated by two promoters for refined spatial control or spatiotemporal control of transgene expression. We apply the split cGAL system to genetically access the single pair of MC neurons (previously inaccessible with a single promoter), and reveal an important role of protein kinase A in rhythmic pharyngeal pumping in C. elegans. Thus, the split cGAL system gives researchers a greater degree of spatiotemporal control over transgene expression, and will be a valuable genetic tool in C. elegans for dissecting gene function with finer cell-specific resolution

Clinical and biomechanical outcome of minimal invasive and open repair of the Achilles tendon

Introduction: With evolutions in surgical techniques, minimally invasive surgical (MIS) repair with Achillon applicator has been introduced. However, there is still a lack of literature to investigate into the clinical merits of MIS over open surgery. This study aims to investigate the correlation between clinical outcome, gait analysis and biomechanical properties comparing both surgical methods.Materials and methods: A single centre retrospective review on all the consecutive operated patients between January 2004 and December 2008 was performed. Twenty-six patients (19 male and 7 female; age 40.4 ± 9.2 years) had experienced a complete Achilles tendon rupture with operative repair. Nineteen of the patients, 10 MIS versus 9 open repairs (13 men with a mean age of 40.54 ± 10.43 (range 23-62 yrs) and 6 women with a mean age of 45.33 ± 7.71 (range 35-57 yrs) were further invited to attend a thorough clinical assessment using Holz's scale and biomechanical evaluation at a mean of 25.3 months after operation. This study utilized the Cybex II isokinetic dynamometer to assess the isokinetic peak force of plantar-flexion and dorsiflexion of both ankles. The patients were also invited to return to our Gait Laboratory for analysis. The eight-infrared camera motion capture system (VICON, UK) was utilized for the acquisition of kinematic variables. Their anthropometric data was measured according to the Davis and coworkers' standard.Results: The mean operative time and length of hospital stay were shorter in the MIS group. The operative time was 54.55 ± 15.15 minutes versus 68.80 ± 18.23 minutes of the MIS group and Open group respectively (p = 0.045), whereas length of stay was 3.36 ± 1.21 days versus 6.40 ± 3.70 days respectively (p = 0.039). There is statistically significant decrease (p = 0.005) in incision length in MIS group than the open surgery group, 3.23 ± 1.10 cm versus 9.64 ± 2.55 cm respectively. Both groups attained similar Holz's scores, 11.70 ± 0.95 versus 12.0 ± 1.50 respectively (p = 0.262). The mean percentage stance time of the injured leg for MIS patient was 58.44% while the mean percentage stance time of the injured leg for patients with open repair was 56.57%. T-test has shown there were no significance differences between the results of the two groups of patients. The loss of peak torque and total work done with respect to the injured side were similar between the MIS and open group.Discussion and conclusion: MIS using Achillon method can achieve smaller incisions, shorter operative time and hospital stay. There is no statistical significance difference in clinical outcome, the stance time to strike time ratio and biomechanical properties on the leg receiving Achilles tendon repair using MIS method and open surgery. © 2011 Chan et al; licensee BioMed Central Ltd

Clinical and biomechanical outcome of minimal invasive and open repair of the Achilles tendon

Introduction: With evolutions in surgical techniques, minimally invasive surgical (MIS) repair with Achillon applicator has been introduced. However, there is still a lack of literature to investigate into the clinical merits of MIS over open surgery. This study aims to investigate the correlation between clinical outcome, gait analysis and biomechanical properties comparing both surgical methods.Materials and methods: A single centre retrospective review on all the consecutive operated patients between January 2004 and December 2008 was performed. Twenty-six patients (19 male and 7 female; age 40.4 ± 9.2 years) had experienced a complete Achilles tendon rupture with operative repair. Nineteen of the patients, 10 MIS versus 9 open repairs (13 men with a mean age of 40.54 ± 10.43 (range 23-62 yrs) and 6 women with a mean age of 45.33 ± 7.71 (range 35-57 yrs) were further invited to attend a thorough clinical assessment using Holz's scale and biomechanical evaluation at a mean of 25.3 months after operation. This study utilized the Cybex II isokinetic dynamometer to assess the isokinetic peak force of plantar-flexion and dorsiflexion of both ankles. The patients were also invited to return to our Gait Laboratory for analysis. The eight-infrared camera motion capture system (VICON, UK) was utilized for the acquisition of kinematic variables. Their anthropometric data was measured according to the Davis and coworkers' standard.Results: The mean operative time and length of hospital stay were shorter in the MIS group. The operative time was 54.55 ± 15.15 minutes versus 68.80 ± 18.23 minutes of the MIS group and Open group respectively (p = 0.045), whereas length of stay was 3.36 ± 1.21 days versus 6.40 ± 3.70 days respectively (p = 0.039). There is statistically significant decrease (p = 0.005) in incision length in MIS group than the open surgery group, 3.23 ± 1.10 cm versus 9.64 ± 2.55 cm respectively. Both groups attained similar Holz's scores, 11.70 ± 0.95 versus 12.0 ± 1.50 respectively (p = 0.262). The mean percentage stance time of the injured leg for MIS patient was 58.44% while the mean percentage stance time of the injured leg for patients with open repair was 56.57%. T-test has shown there were no significance differences between the results of the two groups of patients. The loss of peak torque and total work done with respect to the injured side were similar between the MIS and open group.Discussion and conclusion: MIS using Achillon method can achieve smaller incisions, shorter operative time and hospital stay. There is no statistical significance difference in clinical outcome, the stance time to strike time ratio and biomechanical properties on the leg receiving Achilles tendon repair using MIS method and open surgery. © 2011 Chan et al; licensee BioMed Central Ltd

ChemoRad nanoparticles: a novel multifunctional nanoparticle platform for targeted delivery of concurrent chemoradiation

Aim: The development of chemoradiation – the concurrent administration of chemotherapy and radiotherapy – has led to significant improvements in local tumor control and survival. However, it is limited by its high toxicity. In this study, we report the development of a novel NP (nanoparticle) therapeutic, ChemoRad NP, which can deliver biologically targeted chemoradiation. Method: A biodegradable and biocompatible lipid–polymer hybrid NP that is capable of delivering both chemotherapy and radiotherapy was formulated. Results: Using docetaxel, indium111 and yttrium90 as model drugs, we demonstrated that the ChemoRad NP can encapsulate chemotherapeutics (up to 9% of NP weight) and radiotherapeutics (100 mCi of radioisotope per gram of NP) efficiently and deliver both effectively. Using prostate cancer as a disease model, we demonstrated the targeted delivery of ChemoRad NPs and the higher therapeutic efficacy of ChemoRad NPs. Conclusion: We believe that the ChemoRad NP represents a new class of therapeutics that holds great potential to improve cancer treatment

Spatiotemporal controlled delivery of nanoparticles to injured vasculature

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2010.Cataloged from PDF version of thesis. Vita.Includes bibliographical references.Complex multimodal nanoparticles (NP) that target and deliver therapeutic agents to a site of disease are a promising direction in modem medicine. As a starting point for innovation, we designed a hybrid NP system combining the benefits of liposomes and polymeric NPs. These particles have a polymeric surface which displays targeting ligands while avoiding macrophage uptake. A liposome-like layer provides in vivo biocompatibility and a hydrophobic core allows for high-capacity small molecule drug delivery. Targeting ligands that bind injured vasculature were discovered and optimized by screening an M13 bacteriophage library (109 independent clones) against collagen IV, the major component of the basement membrane. Relative binding affinities using ELISA identified the lead targeting candidate, which bound with 900-fold greater relative affinity to collagen IV when compared with the unselected library. The selected peptide sequence was synthesized and tested for its ability to actively target the hybrid NP system. Paclitaxel, an anti-proliferative drug, was chosen as the delivered pharmaceutical. Drug release was modified through a slow-eluting paclitaxel conjugate using controlled ester hydrolysis (drug release -10-12 days in vitro). To test these targeted NPs, injured vasculature was approximated using an aortic smooth muscle culture embedded on a collagen IV matrix. In this setting, the hybrid NPs showed clear evidence of increased potency using the selected ligands. In experimental animal models of surgery-induced vascular injury, targeted NPs showed a four-fold improved retention at angioplastied aortas over intact aortas ex vivo. Targeted NPs were tested as intraarterially delivered therapy to angioplastied carotid arteries in vivo and showed a two-fold better localization at injury sites versus scrambled-peptide and non-targeted NPs. Targeted NPs were also tested using a systemic, intravenous infusion administered postprocedure on Day I and 6 and resulted in lower neointima-to-media (N/M) scores at two weeks compared to FDA-approved Taxol@ and injury-only groups (N/Msham= -249 + 0.046, vs. N/MTaxol=0.837 ± 0.087, N/MNP=0.749 ± 0.136 and N/MPep-NP=0.662 ± 0.169, all P < 0.01 vs. injury-only, mean ± SEM, n=5). These findings indicate that complex, multilayered NPs can functionally target and treat injured vasculature, a clinical problem of primary importance.by Juliana Maria Chan.Ph.D