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Sedaghat S, Krishnakumar A, Selvamani V, Barnard JP, Nejati S, Wang H, Detwiler DA, Seleem MN, Rahimi R. Laser-assisted surface alloying of titanium with silver to enhance antibacterial and bone-cell mineralization properties of orthopedic implants. J Mater Chem B 2024; 12:4489-4501. [PMID: 38644661 PMCID: PMC11078329 DOI: 10.1039/d3tb02481d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Accepted: 03/13/2024] [Indexed: 04/23/2024]
Abstract
Orthopedic device-related infection (ODRI) poses a significant threat to patients with titanium-based implants. The challenge lies in developing antibacterial surfaces that preserve the bulk mechanical properties of titanium implants while exhibiting characteristics similar to bone tissue. In response, we present a two-step approach: silver nanoparticle (AgNP) coating followed by selective laser-assisted surface alloying on commonly used titanium alumina vanadium (TiAl6V4) implant surfaces. This process imparts antibacterial properties without compromising the bulk mechanical characteristics of the titanium alloy. Systematic optimization of laser beam power (8-40 W) resulted in an optimized surface (32 W) with uniform TiAg alloy formation. This surface displayed a distinctive hierarchical mesoporous textured surface, featuring cauliflower-like nanostructures measuring between 5-10 nm uniformly covering spatial line periods of 25 μm while demonstrating homogenous elemental distribution of silver throughout the laser processed surface. The optimized laser processed surface exhibited prolonged superhydrophilicity (40 days) and antibacterial efficacy (12 days) against Staphylococcus aureus and Escherichia coli. Additionally, there was a significant twofold increase in bone mineralization compared to the pristine Ti6Al4V surface (p < 0.05). Rockwell hardness tests confirmed minimal (<1%) change in bulk mechanical properties compared to the pristine surface. This innovative laser-assisted approach, with its precisely tailored surface morphology, holds promise for providing enduring antibacterial and osteointegration properties, rendering it an optimal choice for modifying load-bearing implant devices without altering material bulk characteristics.
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Affiliation(s)
- Sotoudeh Sedaghat
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA.
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA
| | - Akshay Krishnakumar
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47907, USA
| | - Vidhya Selvamani
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA.
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA
| | - James P Barnard
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA.
| | - Sina Nejati
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA.
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA
| | - Haiyan Wang
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA.
| | - David A Detwiler
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA
- Nanovis, West Lafayette, West Lafayette, IN 47907, USA
| | - Mohamed N Seleem
- Department of Biomedical Sciences and Pathobiology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
| | - Rahim Rahimi
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA.
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47907, USA
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Björkelund C, Petersson EL, Svenningsson I, Saxvik A, Wiegner L, Hensing G, Jonsdottir IH, Larsson M, Wikberg C, Ariai N, Nejati S, Hange D. Effects of adding early cooperation and a work-place dialogue meeting to primary care management for sick-listed patients with stress-related disorders: CO-WORK-CARE-Stress - a pragmatic cluster randomised controlled trial. Scand J Prim Health Care 2024:1-15. [PMID: 38555865 DOI: 10.1080/02813432.2024.2329212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Accepted: 03/06/2024] [Indexed: 04/02/2024] Open
Abstract
OBJECTIVES To investigate whether intensified cooperation between general practitioner (GP), care manager and rehabilitation coordinator (RC) for patients sick-listed for stress-related mental disorder, combined with a person-centred dialogue meeting with employer, could reduce sick-leave days compared with usual care manager contact. DESIGN Pragmatic cluster-randomised controlled trial, randomisation at primary care centre (PCC) level. SETTING PCCs in Region Västra Götaland, Sweden, with care manager organisation. PARTICIPANTS Of 30 invited PCCs, 28 (93%) accepted the invitation and recruited 258 patients newly sick-listed due to stress-related mental disorder (n = 142 intervention, n = 116 control PCCs). INTERVENTION Cooperation between GP, care manager and rehabilitation coordinator from start of illness notification plus a person-centred dialogue meeting between patient and employer within 3 months. Regular contact with care manager was continued at the control PCCs. MAIN OUTCOME MEASURES 12-months net and gross number of sick-leave days. Secondary outcomes: Symptoms of stress, depression, anxiety; work ability and health related quality of life (EQ-5D) over 12 months. RESULTS There were no significant differences between intervention and control groups after 12 months: days on sick-leave (12-months net sick-leave days, intervention, mean = 110.7 days (95% confidence interval (CI) 82.6 - 138.8); control, mean = 99.1 days (95% CI 73.9 - 124.3)), stress, depression, or anxiety symptoms, work ability or EQ-5D. There were no significant differences between intervention and control groups concerning proportion on sick-leave after 3, 6, 12 months. At 3 months 64.8% were on sick-leave in intervention group vs 54.3% in control group; 6 months 38% vs 32.8%, and12 months 16.9% vs 15.5%. CONCLUSION Increased cooperation at the PCC between GP, care manager and RC for stress-related mental disorder coupled with an early workplace contact in the form of a person-centred dialogue meeting does not reduce days of sick-leave or speed up rehabilitation.Trial registration: ClinicalTrials.gov Identifier: NCT03250026 https://clinicaltrials.gov/study/NCT03250026?tab=results#publicationsCO-WORK-CAREFirst Posted: August 15, 2017. Recruitment of PCCs: September 2017. Inclusion of patients from December 2017.
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Affiliation(s)
- C Björkelund
- Primary Health Care/Department of Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Development & Innovation, Primary Health Care, Västra Götaland, Sweden
| | - E-L Petersson
- Primary Health Care/Department of Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Development & Innovation, Primary Health Care, Västra Götaland, Sweden
| | - I Svenningsson
- Primary Health Care/Department of Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Development & Innovation, Primary Health Care, Västra Götaland, Sweden
| | - A Saxvik
- Primary Health Care/Department of Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - L Wiegner
- Primary Health Care/Department of Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Institute of Stress Medicine, Västra Götaland, Sweden
| | - G Hensing
- Social Medicine/Department of Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - I H Jonsdottir
- Institute of Stress Medicine, Västra Götaland, Sweden
- Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - M Larsson
- Development & Innovation, Primary Health Care, Västra Götaland, Sweden
- Unit of Physiotherapy/Department of Health and Rehabilitation, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - C Wikberg
- Primary Health Care/Department of Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Development & Innovation, Primary Health Care, Västra Götaland, Sweden
| | - N Ariai
- Primary Health Care/Department of Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Development & Innovation, Primary Health Care, Västra Götaland, Sweden
| | - S Nejati
- Primary Health Care/Department of Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Development & Innovation, Primary Health Care, Västra Götaland, Sweden
| | - D Hange
- Primary Health Care/Department of Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Development & Innovation, Primary Health Care, Västra Götaland, Sweden
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Gopalakrishnan S, Thomas R, Sedaghat S, Krishnakumar A, Khan S, Meyer T, Ajieren H, Nejati S, Wang J, Verma MS, Irazoqui P, Rahimi R. Smart capsule for monitoring inflammation profile throughout the gastrointestinal tract. Biosens Bioelectron X 2023; 14:100380. [PMID: 37799507 PMCID: PMC10552446 DOI: 10.1016/j.biosx.2023.100380] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/07/2023]
Abstract
Inflammatory bowel disease (IBD) has become alarmingly prevalent in the last two decades affecting 6.8 million people worldwide with a starkly high relapse rate of 40% within 1 year of remission. Existing visual endoscopy techniques rely on subjective assessment of images that are error-prone and insufficient indicators of early-stage IBD, rendering them unsuitable for frequent and quantitative monitoring of gastrointestinal health necessary for detecting regular relapses in IBD patients. To address these limitations, we have implemented a miniaturized smart capsule (2.2 cm × 11 mm) that allows monitoring reactive oxygen species (ROS) levels as a biomarker of inflammation for quantitative and frequent profiling of inflammatory lesions throughout the gastrointestinal tract. The capsule is composed of a pH and oxidation reduction potential (ORP) sensor to track the capsule's location and ROS levels throughout the gastrointestinal tract, respectively, and an optimized electronic interface for wireless sensing and data communication. The designed sensors provided a linear and stable performance within the physiologically relevant range of the GI tract (pH: 1-8 and ORP: -500 to +500 mV). Additionally, systematic design optimization of the wireless interface electronics offered an efficient sampling rate of 10 ms for long-running measurements up to 48 h for a complete evaluation of the entire gastrointestinal tract. As a proof-of-concept, the capsule the capsule's performance in detecting inflammation risks was validated by conducting tests on in vitro cell culture conditions, simulating healthy and inflamed gut-like environments. The capsule presented here achieves a new milestone in addressing the emerging need for smart ingestible electronics for better diagnosis and treatment of digestive diseases.
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Affiliation(s)
- Sarath Gopalakrishnan
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - Rithu Thomas
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, 47907, USA
| | - Sotoudeh Sedaghat
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
- School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA
| | - Akshay Krishnakumar
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - Sadid Khan
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Trevor Meyer
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Hans Ajieren
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Sina Nejati
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
- School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA
| | - Jiangshan Wang
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
- Department of Agricultural and Biological Engineering, West Lafayette, IN, 47907, USA
| | - Mohit S. Verma
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
- Department of Agricultural and Biological Engineering, West Lafayette, IN, 47907, USA
- Weldon School of Biomedical Engineering, West Lafayette, IN, 47907, USA
| | - Pedro Irazoqui
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Rahim Rahimi
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
- School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA
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Nejati S, Wang J, Sedaghat S, Balog NK, Long AM, Rivera UH, Kasi V, Park K, Johnson JS, Verma MS, Rahimi R. Smart capsule for targeted proximal colon microbiome sampling. Acta Biomater 2022; 154:83-96. [PMID: 36162763 PMCID: PMC9986838 DOI: 10.1016/j.actbio.2022.09.050] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 09/03/2022] [Accepted: 09/19/2022] [Indexed: 12/14/2022]
Abstract
The gastrointestinal (GI) tract, particularly the colon region, holds a highly diverse microbial community that plays an important role in the metabolism, physiology, nutrition, and immune function of the host body. Accumulating evidence has revealed that alteration in these microbial communities is the pivotal step in developing various metabolic diseases, including obesity, inflammatory bowel disease (IBD), and colorectal cancer. However, there is still a lack of clear understanding of the interrelationship between microbiota and diet as well as the effectiveness of chemoprevention strategies, including pre and probiotic agents in modifying the colonic microbiota and preventing digestive diseases. Existing methods for assessing these microbiota-diet interactions are often based on samples collected from the feces or endoscopy techniques which are incapable of providing information on spatial variations of the gut microbiota or are considered invasive procedures. To address this need, here we have developed an electronic-free smart capsule that enables site-specific sampling of the gut microbiome within the proximal colon region of the GI tract. The 3D printed device houses a superabsorbent hydrogel bonded onto a flexible polydimethylsiloxane (PDMS) disk that serves as a milieu to collect the fluid in the gut lumen and its microbiome by rapid swelling and providing the necessary mechanical actuation to close the capsule after the sampling is completed. The targeted colonic sampling is achieved by coating the sampling aperture on the capsule with a double-layer pH-sensitive enteric coating, which delays fluid in the lumen from entering the capsule until it reaches the proximal colon of the GI tract. To identify the appropriate pH-responsive double-layer coating and processing condition, a series of systematic dissolution characterizations in different pH conditions that mimicked the GI tract was conducted. The effective targeted microbial sampling performance and preservation of the smart capsule with the optimized design were validated using both realistic in vitro GI tract models with mixed bacteria cultures and in vivo with pigs as an animal model. The results from 16s rRNA and WideSeq analysis in both in vitro and in vivo studies showed that the bacterial population sampled within the retrieved capsule closely matched the bacterial population within the targeted sampling region (proximal colon). Herein, it is envisioned that such smart sampling capsule technology will provide new avenues for gastroenterological research and clinical applications, including diet-host-microbiome relationships, focused on human GI function and health. STATEMENT OF SIGNIFICANCE: The colonic microbiota plays a major role in the etiology of numerous diseases. Extensive efforts have been conducted to monitor the gut microbiome using sequencing technologies based on samples collected from feces or mucosal biopsies that are typically obtained by colonoscopy. Despite the simplicity of fecal sampling procedures, they are incapable of preserving spatial and temporal information about the bacteria through the gastrointestinal (GI) tract. In contrast, colonoscopy is an invasive and impractical approach to frequently assess the effect of dietary and therapeutic intake on the microbiome and their impact on the health of the patient. Here, we developed a non-invasive capsule that enables targeted sampling from the ascending colon, thereby providing crucial information for disease prediction and monitoring.
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Affiliation(s)
- Sina Nejati
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, United States; Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, United States
| | - Jiangshan Wang
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, United States; Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN 47907, United States
| | - Sotoudeh Sedaghat
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, United States; Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, United States
| | - Nicole K Balog
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, United States; Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, United States
| | - Amanda M Long
- USDA-ARS Livestock Behavior Research Unit, West Lafayette, IN 47907, United States
| | - Ulisses Heredia Rivera
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, United States; Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, United States
| | - Venkat Kasi
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, United States; Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, United States
| | - Kinam Park
- Departments of Biomedical Engineering and Pharmaceutics, Purdue University, West Lafayette, IN 47907, United States
| | - Jay S Johnson
- USDA-ARS Livestock Behavior Research Unit, West Lafayette, IN 47907, United States
| | - Mohit S Verma
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, United States; Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN 47907, United States; Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, United States
| | - Rahim Rahimi
- School of Materials Engineering, Purdue University, West Lafayette, IN 47907, United States; Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, United States.
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Waimin J, Gopalakrishnan S, Heredia-Rivera U, Kerr NA, Nejati S, Gallina NLF, Bhunia AK, Rahimi R. Low-Cost Nonreversible Electronic-Free Wireless pH Sensor for Spoilage Detection in Packaged Meat Products. ACS Appl Mater Interfaces 2022; 14:45752-45764. [PMID: 36173396 DOI: 10.1021/acsami.2c09265] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Contamination of meat with pathogenic microorganisms can cause severe illnesses and food waste, which has significant negative impacts on both general health and the economy. In many cases, the expiration date is not a good indicator of meat freshness as there is a high risk of contamination during handling throughout the supply chain. Many biomarkers, including color, odor, pH, temperature, and volatile compounds, are used to determine spoilage. Among these, pH presents a simple and effective biomarker directly linked to the overgrowth of bacteria and degradation of the meat tissue. Low-cost methods for wireless pH monitoring are crucial in detecting spoilage on a large commercial scale. Existing technologies are often limited to short-range detection, with the use of batteries and different electronic components that increases both the manufacturing complexity and cost of the final device. To address these shortcomings, we have developed a cost-effective wireless pH sensor, which uses passive resonant frequency (RF) sensing, combined with a pH-responsive polymer that can be placed within packaged meat products and provide a remote assessment of the risk of microbial spoilage throughout the supply chain. The sensor tag consists of a sensing resonator coated with a pH-sensitive material and a passivated reference resonator operating in a differential frequency configuration. Upon exposure to elevated pH levels >6.8, the coating on the sensing resonator dissolves, which in turn results in a distinct change in the resonant frequency with respect to the reference resonator. Systematic theoretical and experimental results at different pH levels demonstrated that a 20% shift in resonant frequency demarcates the point for spoilage detection. As a proof of concept, the performance of the sensor in remotely detecting the risk of food spoilage was validated in packaged poultry over 10 days. The sensor fabrication process takes advantage of recent developments in the scalable manufacturing of flexible, low-cost devices, including selective laser etching of metalized plastic films and doctor-blade coating of stimuli-responsive polymer films. Furthermore, the biocompatibility of all the materials used in the sensor was confirmed with human intestinal cells (HCT-8 cells).
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Affiliation(s)
- Jose Waimin
- School of Material Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Sarath Gopalakrishnan
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Ulisses Heredia-Rivera
- School of Material Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Nicholas A Kerr
- School of Material Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Sina Nejati
- School of Material Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Nicholas L F Gallina
- Molecular Food Microbiology Laboratory, Department of Food Science, Purdue University, West Lafayette, Indiana 47907, United States
| | - Arun K Bhunia
- Molecular Food Microbiology Laboratory, Department of Food Science, Purdue University, West Lafayette, Indiana 47907, United States
- Department of Comparative Pathobiology, Purdue University, West Lafayette, Indiana 47907, United States
- Purdue Institute of Inflammation Immunology and Infectious Disease, Purdue University, West Lafayette, Indiana 47907, United States
| | - Rahim Rahimi
- School of Material Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
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Heredia Rivera U, Kadian S, Nejati S, White J, Sedaghat S, Mutlu Z, Rahimi R. Printed Low-Cost PEDOT:PSS/PVA Polymer Composite for Radiation Sterilization Monitoring. ACS Sens 2022; 7:960-971. [PMID: 35333058 DOI: 10.1021/acssensors.1c02105] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
During the γ-radiation sterilization process, the levels of radiation exposure to a medical device must be carefully monitored to achieve the required sterilization without causing deleterious effects on its intended physical and chemical properties. To address this issue, here we have demonstrated the development of an all-printed disposable low-cost sensor that exploits the change in electrical impedance of a semi-interpenetrating polymer network (SIPN) composed of poly(vinyl alcohol) (PVA) and poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) as a functional polymer composite for radiation sterilization monitoring applications. Specifically, the PEDOT:PSS acts as the electrically conductive medium, while the PVA provides the ductility and stability of the printed sensors. During irradiation exposure, chain scission and cross-linking events occur concurrently in the PEDOT:PSS and PVA polymer chains, respectively. The concurrent scissoring of the PEDOT polymer and cross-linking of the PVA polymer network leads to the formation of a stable SIPN with reduced electrical conductivity, which was verified through FTIR, Raman, and TGA analysis. Systematic studies of different ratios of PEDOT:PSS and PVA mixtures were tested to identify the optimal ratio that provided the highest radiation sensitivity and stability performance. The results showed that PEDOT:PSS/PVA composites with 10 wt % PVA produced sensors with relative impedance changes of 30% after 25 kGy and up to 370% after 53 kGy (which are two of the most commonly used radiation exposure levels for sterilization applications). This composition showed high electrical impedance stability with less than ±5% change over 18 days after irradiation exposure. These findings demonstrate the feasibility of utilizing a printing technology for scalable manufacturing of low-cost, flexible radiation sensors for more effective monitoring of radiation sterilization processes.
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Affiliation(s)
- Ulisses Heredia Rivera
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Sachin Kadian
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Sina Nejati
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Julia White
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Sotoudeh Sedaghat
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Zeynep Mutlu
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Rahim Rahimi
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
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Kasi V, Sedaghat S, Alcaraz AM, Maruthamuthu MK, Heredia-Rivera U, Nejati S, Nguyen J, Rahimi R. Low-Cost Flexible Glass-Based pH Sensor via Cold Atmospheric Plasma Deposition. ACS Appl Mater Interfaces 2022; 14:9697-9710. [PMID: 35142483 DOI: 10.1021/acsami.1c19805] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Many commercially available pH sensors are fabricated with a glass membrane as the sensing component because of several advantages of glass-based electrodes such as versatility, high accuracy, and excellent stability in various conditions. However, because of their bulkiness and poor mechanical properties, conventional glass-based sensors are not ideal for wearable or flexible applications. Here, we report for the first time the fabrication of a flexible glass-based pH sensor suitable for biomedical and environmental applications where flexibility and stability of the sensor are critical for long-term and real-time monitoring. The sensor was fabricated via a simple and facile approach using the cold atmospheric plasma technique in which a pH sensitive silica coating was deposited from a siloxane precursor onto a carbon electrode. In order to increase the sensitivity and stability of the sensor, we employed a postprocessing step which involves annealing of the silica coated electrode at elevated temperatures. This process was optimized to ensure that the crucial properties such as porosity and hydration functionality were balanced to obtain the best and most reliable sensitivity of the sensor. Our sensitivity test results indicated that these sensors exhibit excellent and stable sensitivity with a slope of about 48 mV/pH (r2 = 0.998) and selectivity across a pH range of 4 to 10 in the presence of various cations. The optimized sensor has shown stable sensitivity for a long period of time (30 h of immersion) and in different bending conditions. We demonstrate in this investigation that this flexible cost-effective pH sensor can withstand the sterilization process resulting from ultraviolet radiation and shows repeatable sensitivity with less than ±5 mV potential drift from the sensitivity values of the standard optimized sensor.
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Affiliation(s)
- Venkat Kasi
- School of Material Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Sotoudeh Sedaghat
- School of Material Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Alejandro M Alcaraz
- School of Material Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Murali Kannan Maruthamuthu
- Division of Pharmacoengineering and Molecular Pharmaceutics, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Ulisses Heredia-Rivera
- School of Material Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Sina Nejati
- School of Material Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Juliane Nguyen
- Division of Pharmacoengineering and Molecular Pharmaceutics, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Rahim Rahimi
- School of Material Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
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Nejati S, Wang J, Heredia-Rivera U, Sedaghat S, Woodhouse I, Johnson JS, Verma M, Rahimi R. Small intestinal sampling capsule for inflammatory bowel disease type detection and management. Lab Chip 2021; 22:57-70. [PMID: 34826326 DOI: 10.1039/d1lc00451d] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Although serum and fecal biomarkers (e.g., lactoferrin, and calprotectin) have been used in management and distinction between inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS), none are proven to be a differential diagnostic tool between Crohn's disease (CD) and ulcerative colitis (UC). The main challenge with laboratory-based biomarkers in the stool test is the inability to indicate the location of the disease/inflammation in the gastrointestinal (GI) tract due to the homogenous nature of the collected fecal sample. For the first time, we have designed and developed a battery-free smart capsule that will allow targeted sampling of inflammatory biomarkers inside the gut lumen of the small intestine. The capsule is designed to provide a simple and non-invasive complementary tool to fecal biomarker analysis to differentiate the type of IBD by pinpointing the site of inflammatory biomarkers secretion (e.g., small or large bowel) throughout the GI tract. The capsule takes advantage of the rapid change from an acidic environment in the stomach to higher pH levels in the small intestine to dissolve a pH-sensitive polymeric coating as a means to activate the sampling process of the capsule within the small intestine. A swelling polyacrylamide hydrogel is placed inside the capsule as a milieu to collect the sampled GI fluid while also providing the required mechanical actuation to close the capsule once the sampling is completed. The hydrogel component along with the collected GI fluid can be easily obtained from the capsule through the screw-cap design for further extraction and analysis. As a proof of concept, the capsule's performance in sampling and extraction of bovine serum albumin (BSA) and calprotectin - a key biomarker of inflammation - was assessed within the physiologically relevant ranges. The ratio of extracted biomarkers relative to that in the initial sampling environment remained constant (∼3%) and independent of the sampling matrix in both in vitro and ex vivo studies. It is believed that the demonstrated technology will provide immediate impact in more effective IBD type differential diagnostic and treatment strategies by providing a non-invasive assessment of inflammation biomarkers profile throughout the digestive tract.
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Affiliation(s)
- Sina Nejati
- School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - Jiangshan Wang
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
- Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN 47907, USA
| | - Ulisses Heredia-Rivera
- School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - Sotoudeh Sedaghat
- School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - Ian Woodhouse
- School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - Jay S Johnson
- USDA-ARS Livestock Behavior Research Unit, West Lafayette, IN 47907, USA
| | - Mohit Verma
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
- Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN 47907, USA
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA
| | - Rahim Rahimi
- School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
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Woodhouse I, Nejati S, Selvamani V, Jiang H, Chittiboyina S, Grant J, Mutlu Z, Waimin J, Abutaleb NS, Seleem MN, Rahimi R. Flexible Microneedle Array Patch for Chronic Wound Oxygenation and Biofilm Eradication. ACS Appl Bio Mater 2021; 4:5405-5415. [PMID: 35006756 DOI: 10.1021/acsabm.1c00087] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Chronic nonhealing wounds are a growing socioeconomic problem that affects more than 6 million people annually solely in the United States. These wounds are colonized by bacteria that often develop into biofilms that act as a physical and chemical barrier to therapeutics and tissue oxygenation leading to chronic inflammation and tissue hypoxia. Although wound debridement and vigorous mechanical abrasion techniques are often used by clinical professionals to manage and remove biofilms from wound surfaces, such methods are highly nonselective and painful. In this study, we have developed a flexible polymer composite microneedle array that can overcome the physicochemical barriers (i.e., bacterial biofilm) present in chronic nonhealing wounds and codeliver oxygen and bactericidal agents. The polymeric microneedles are made by using a facile UV polymerization process of polyvinylpyrrolidone and calcium peroxide onto a flexible polyethylene terephthalate substrate for conformable attachment onto different locations of the human body surface. The microneedles effectively elevate the oxygen levels from 8 to 12 ppm once dissolved over the course of 2 h while also providing strong bactericidal effects on both liquid and biofilm bacteria cultures of both Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) bacterial strains commonly found in dermal wounds. Furthermore, the results from the ex vivo assay on a porcine wound model indicated successful insertion of the microneedles into the tissue while also providing effective bactericidal properties against both Gram-positive and Gram-negative within the complex tissue matrix. Additionally, the microneedles demonstrate high levels of cytocompatibility with less than 10% of apoptosis throughout 6 days of continuous exposure to human dermal fibroblast cells. The demonstrated flexible microneedle array can provide a better approach for increasing the effectiveness of topical tissue oxygenation as well as the treatment of infected wounds with intrinsically antibiotic resistant biofilms.
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Affiliation(s)
- Ian Woodhouse
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907-2057, United States.,School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907-2045, United States
| | - Sina Nejati
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907-2057, United States.,School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907-2045, United States
| | - Vidhya Selvamani
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907-2057, United States.,School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907-2045, United States
| | - Hongjie Jiang
- Shien-Ming Wu School of Intelligent Engineering, South China University of Technology, Guangzhou 511442, China
| | - Shirisha Chittiboyina
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907-2057, United States.,Department of Basic Medical Sciences, Purdue University, 625 Harrison Street, West Lafayette, Indiana 47907, United States
| | - Jesse Grant
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907-2057, United States.,School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907-2045, United States
| | - Zeynep Mutlu
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907-2057, United States.,School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907-2045, United States
| | - Jose Waimin
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907-2057, United States.,School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907-2045, United States
| | - Nader S Abutaleb
- Department of Biomedical Sciences and Pathobiology, Virginia Polytechnic Institute and State University, 1410 Prices Fork Road, Blacksburg, Virginia 24061, United States
| | - Mohamed N Seleem
- Department of Biomedical Sciences and Pathobiology, Virginia Polytechnic Institute and State University, 1410 Prices Fork Road, Blacksburg, Virginia 24061, United States
| | - Rahim Rahimi
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907-2057, United States.,School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907-2045, United States.,School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907-2035, United States
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10
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Jiang H, Carter NM, Zareei A, Nejati S, Waimin JF, Chittiboyina S, Niedert EE, Soleimani T, Lelièvre SA, Goergen CJ, Rahimi R. A Wireless Implantable Strain Sensing Scheme Using Ultrasound Imaging of Highly Stretchable Zinc Oxide/Poly Dimethylacrylamide Nanocomposite Hydrogel. ACS Appl Bio Mater 2020; 3:4012-4024. [PMID: 35025476 DOI: 10.1021/acsabm.9b01032] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Hongjie Jiang
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907-2057, United States
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907-2035, United States
- Shenzhen MSU-BIT University, Shenzhen, Guangdong 518172, China
| | - Natalie M. Carter
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907-2045, United States
| | - Amin Zareei
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907-2057, United States
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907-2045, United States
| | - Sina Nejati
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907-2057, United States
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907-2045, United States
| | - Jose F. Waimin
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907-2057, United States
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907-2045, United States
| | - Shirisha Chittiboyina
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907-2057, United States
- Department of Basic Medical Sciences, Purdue University, 625 Harrison Street, West Lafayette, Indiana 47907, United States
| | - Elizabeth E. Niedert
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana 47907-2032, United States
| | - Tahereh Soleimani
- College of Human Medicine, Michigan State University, East Lansing, Michigan 48824, United States
| | - Sophie A. Lelièvre
- Department of Basic Medical Sciences, Purdue University, 625 Harrison Street, West Lafayette, Indiana 47907, United States
| | - Craig J. Goergen
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana 47907-2032, United States
- Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907-2032, United States
| | - Rahim Rahimi
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907-2057, United States
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907-2035, United States
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907-2045, United States
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Waimin JF, Nejati S, Jiang H, Qiu J, Wang J, Verma MS, Rahimi R. Smart capsule for non-invasive sampling and studying of the gastrointestinal microbiome. RSC Adv 2020; 10:16313-16322. [PMID: 35498852 PMCID: PMC9052936 DOI: 10.1039/c9ra10986b] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2019] [Accepted: 03/30/2020] [Indexed: 12/12/2022] Open
Abstract
Microbes in regions within the gut, which have been inaccessible so far, can now be retrieved and analyzed through a passive sampling mechanism in the form of a 3D printed capsule equipped with a superabsorbent hydrogel.
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Affiliation(s)
- Jose Fernando Waimin
- School of Materials Engineering
- Purdue University
- West Lafayette
- USA
- Birck Nanotechnology Center
| | - Sina Nejati
- School of Materials Engineering
- Purdue University
- West Lafayette
- USA
- Birck Nanotechnology Center
| | - Hongjie Jiang
- Birck Nanotechnology Center
- Purdue University
- West Lafayette
- USA
- School of Electrical Engineering
| | - Jake Qiu
- Birck Nanotechnology Center
- Purdue University
- West Lafayette
- USA
- Department of Agricultural and Biological Engineering
| | - Jianghsan Wang
- Birck Nanotechnology Center
- Purdue University
- West Lafayette
- USA
- Department of Agricultural and Biological Engineering
| | - Mohit S. Verma
- Birck Nanotechnology Center
- Purdue University
- West Lafayette
- USA
- Department of Agricultural and Biological Engineering
| | - Rahim Rahimi
- School of Materials Engineering
- Purdue University
- West Lafayette
- USA
- Birck Nanotechnology Center
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12
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Petersson EL, Wikberg C, Westman J, Ariai N, Nejati S, Björkelund C. Effects on work ability, job strain and quality of life of monitoring depression using a self-assessment instrument in recurrent general practitioner consultations: A randomized controlled study. Work 2018; 60:63-73. [PMID: 29733038 PMCID: PMC6027947 DOI: 10.3233/wor-182717] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND: Depression reduces individuals’ function and work ability and is associated with both frequent and long-term sickness absence. OBJECTIVE: Investigate if monitoring of depression course using a self-assessment instrument in recurrent general practitioner (GP) consultations leads to improved work ability, decreased job strain, and quality of life among primary care patients. METHODS: Primary care patients n = 183, who worked. In addition to regular treatment (control group), intervention patients received evaluation and monitoring and used the MADRS-S depression scale during GP visit at baseline and at visits 4, 8, and 12 weeks. Work ability, quality of life and job strain were outcome measures. RESULTS: Depression symptoms decreased in all patients. Significantly steeper increase of WAI at 3 months in the intervention group. Social support was perceived high in a significantly higher frequency in intervention group compared to control group. CONCLUSIONS: Monitoring of depression course using a self-assessment instrument in recurrent GP consultations seems to lead to improved self-assessed work ability and increased high social support, but not to reduced job strain or increased quality of life compared to TAU. Future studies concerning rehabilitative efforts that seek to influence work ability probably also should include more active interventions at the workplace.
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Affiliation(s)
- E-L Petersson
- Department of Primary Health Care/Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Sweden.,Region Västra Götaland, Närhälsan Research and Development Primary Health Care, Gothenburg, Sweden
| | - C Wikberg
- Department of Primary Health Care/Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Sweden
| | - J Westman
- Department of Neurobiology, Division for Family Medicine, Care Sciences and Society, Karolinska Institutet, Stockholm, Sweden
| | - N Ariai
- Department of Primary Health Care/Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Sweden
| | - S Nejati
- Department of Primary Health Care/Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Sweden
| | - C Björkelund
- Department of Primary Health Care/Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Sweden
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Alemzadeh I, Nejati S. Phenols removal by immobilized horseradish peroxidase. J Hazard Mater 2009; 166:1082-6. [PMID: 19144465 DOI: 10.1016/j.jhazmat.2008.12.026] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2007] [Revised: 09/30/2008] [Accepted: 12/02/2008] [Indexed: 05/05/2023]
Abstract
Application of immobilized horseradish peroxidase (HRP) in porous calcium alginate (ca-alginate) for the purpose of phenol removal is reported. The optimal conditions for immobilization of HRP in ca-alginate were identified. Gelation (encapsulation) was optimized at 1.0% (w/v) sodium alginate in the presence of 5.5% (w/v) of calcium chloride. Upon immobilization, pH profile of enzyme activity changes as it shows higher value at basic and acidic solution. Increasing initial phenol concentration results in a decrease in % conversion. The highest conversion belongs to phenol concentration of 2mM. Investigation into time course of phenol removal for both encapsulated and free enzymes showed that encapsulated enzyme had lower efficiency in comparison with the same concentration of free enzyme; however the capsules were reusable up to four cycles without any changes in their retention activity. Increasing enzyme concentration from 0.15 to 0.8 units/g alginate results in gradual increase in phenol removal. The ratio of hydrogen peroxide/phenol at which highest phenol removal obtained is found to be dependent on initial phenol concentration and in the solution of 2 and 8mM phenol it was 1.15 and 0.94 respectively.
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Affiliation(s)
- I Alemzadeh
- Chemical and Petroleum Engineering Department, Sharif University of Technology, P.O. Box 11365-9465, Tehran, Iran.
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