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Design and validation of a compressive tissue stimulator with high-throughput capacity and real-time modulus measurement capability.

ABSTRACT: Mechanical stimulation has been shown to impact the properties of engineered hyaline cartilage constructs and is relevant for engineering of cartilage and osteochondral tissues. Most mechanical stimulators developed to date emphasize precision over adaptability to standard tissue culture equipment and protocols. The realization of mechanical characteristics in engineered constructs approaching native cartilage requires the optimization of complex variables (type of stimulus, regimen, and bimolecular signals). We have proposed and validated a stimulator design that focuses on high construct capacity, compatibility with tissue culture plastic ware, and regimen adaptability to maximize throughput. This design utilizes thin force sensors in lieu of a load cell and a linear encoder to verify position. The implementation of an individual force sensor for each sample enables the measurement of Young's modulus while stimulating the sample. Removable and interchangeable Teflon plungers mounted using neodymium magnets contact each sample. Variations in plunger height and design can vary the strain and force type on individual samples. This allows for the evaluation of a myriad of culture conditions and regimens simultaneously. The system was validated using contact accuracy, and Young's modulus measurements range as key parameters. Contact accuracy for the system was excellent within 1.16% error of the construct height in comparison to measurements made with a micrometer. Biomaterials ranging from bioceramics (cancellous bone, 123?MPa) to soft gels (1% agarose, 20?KPa) can be measured without any modification to the device. The accuracy of measurements in conjunction with the wide range of moduli tested demonstrate the unique characteristics of the device and the feasibility of using this device in mapping real-time changes to Young's modulus of tissue constructs (cartilage, bone) through the developmental phases in ex vivo culture conditions.

SUBMITTER: Salvetti DJ

PROVIDER: S-EPMC3285600 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature

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Design and validation of a compressive tissue stimulator with high-throughput capacity and real-time modulus measurement capability.

Salvetti David J DJ Pino Christopher J CJ Manuel Steven G SG Dallmeyer Ian I Rangarajan Sanjeet V SV Meyer Tobias T Kotov Misha M Shastri V Prasad VP

Tissue engineering. Part C, Methods 20120104 3

Mechanical stimulation has been shown to impact the properties of engineered hyaline cartilage constructs and is relevant for engineering of cartilage and osteochondral tissues. Most mechanical stimulators developed to date emphasize precision over adaptability to standard tissue culture equipment and protocols. The realization of mechanical characteristics in engineered constructs approaching native cartilage requires the optimization of complex variables (type of stimulus, regimen, and bimolec ...[more]

PMID: 21988089

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Project description:In living tissues, mechanical stiffness and biological function are intrinsically linked. Alterations in the stiffness of tissues can induce pathological interactions that affect cellular activity and tissue function. Underlying connections between tissue stiffness and disease highlights the importance of accurate quantitative characterizations of soft tissue mechanics, which can improve our understanding of disease and inform therapeutic development. In particular, accurate measurement of lung mechanical properties has been especially challenging due to the anatomical and mechanobiological complexities of the lung. Discrepancies between measured mechanical properties of dissected lung tissue samples and intact lung tissues in vivo has limited the ability to accurately characterize integral lung mechanics. Here, we report a non-destructive vacuum-assisted method to evaluate mechanical properties of soft biomaterials, including intact tissues and hydrogels. Using this approach, we measured elastic moduli of rat lung tissue that varied depending on stress-strain distribution throughout the lung. We also observed that the elastic moduli of enzymatically disrupted lung parenchyma increased by at least 64%. The reported methodology enables assessment of the nonlinear viscoelastic characteristics of intact lungs under normal and abnormal (i.e., injured, diseased) conditions and allows measurement of mechanical properties of tissue-mimetic biomaterials for use in therapeutics or in vitro models. STATEMENT OF SIGNIFICANCE: Accurate quantification of tissue stiffness is critical for understanding mechanisms of disease and developing effective therapeutics. Current modalities to measure tissue stiffness are destructive and preclude accurate assessment of lung mechanical properties, as lung mechanics are determined by complex features of the intact lung. To address the need for alternative methods to assess lung mechanics, we report a non-destructive vacuum-based approach to quantify tissue stiffness. We applied this method to correlate lung tissue mechanics with tissue disruption, and to assess the stiffness of biomaterials. This method can be used to inform the development of tissue-mimetic materials for use in therapeutics and disease models, and could potentially be applied for in-situ evaluation of tissue stiffness as a diagnostic or prognostic tool.

Project description:BackgroundPatient reported outcome measures (PROMs) are widely used in mental healthcare research for quality of life assessment but most fail to capture the breadth of health and non-health domains that can be impacted. We report the psychometric validation of a novel, multi-dimensional instrument based on Amartya Sen's capability approach intended for use as an outcome measure in mental health research.MethodsThe Oxford Capabilities Questionnaire for Mental Health (OxCAP-MH) is a 16-item self-complete capability measure that covers multiple domains of functioning and welfare. Data for validation of the instrument were collected through a national randomised controlled trial of community treatment orders for patients with psychosis. Complete OxCAP-MH data were available for 172 participants. Internal consistency was established with Cronbach's alpha; an interclass correlation coefficient was used to assess test-retest reliability in a sub-sample (N = 50) tested one week apart. Construct validity was established by comparing OxCAP-MH total scores with established instruments of illness severity and functioning: EuroQol (EQ-5D), Brief Psychiatric Rating Scale (BPRS), Global Assessment of Functioning (GAF) and Objective Social Outcomes Index (SIX). Sensitivity was established by calculating standard error of measurement using distributional methods.ResultsThe OxCAP-MH showed good internal consistency (Cronbach's alpha 0.79) and test-retest reliability (ICC = 0.86). Convergent validity was evidenced by strong correlations with the EQ-5D (VAS 0.52, p < .001) (Utility 0.45, p < .001), and divergent validity through more modest associations with the BPRS (-0.41, p < .001), GAF (0.24, p < .001) and SIX (0.12, p = ns). A change of 9.2 points on a 0-100 scale was found to be meaningful on statistical grounds.ConclusionsThe OxCAP-MH has demonstrable reliability and construct validity and represents a promising multi-dimensional alternative to existing patient-reported outcome measures for quality of life used in mental health research.

Dataset Information

Design and validation of a compressive tissue stimulator with high-throughput capacity and real-time modulus measurement capability.

Publications

Design and validation of a compressive tissue stimulator with high-throughput capacity and real-time modulus measurement capability.

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