Browsing by Author "Rahimi, Rahim"

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    Integrated sensing and delivery of oxygen for next-generation smart wound dressings
    (Springer Nature, 2020-05-18) Ochoa, Manuel; Rahimi, Rahim; Zhou, Jiawei; Jiang, Hongjie; Yoon, Chang Keun; Maddipatla, Dinesh; Narakathu, Binu Baby; Jain, Vaibhav; Oscai, Mark Michael; Morken, Thaddeus Joseph; Oliveira, Rebeca Hannah; Campana, Gonzalo L.; Cummings, Oscar W.; Zieger, Michael A.; Sood, Rajiv; Atashbar, Massood Z.; Ziaie, Babak; Pathology and Laboratory Medicine, School of Medicine
    Chronic wounds affect over 6.5 million Americans and are notoriously difficult to treat. Suboptimal oxygenation of the wound bed is one of the most critical and treatable wound management factors, but existing oxygenation systems do not enable concurrent measurement and delivery of oxygen in a convenient wearable platform. Thus, we developed a low-cost alternative for continuous O2 delivery and sensing comprising of an inexpensive, paper-based, biocompatible, flexible platform for locally generating and measuring oxygen in a wound region. The platform takes advantage of recent developments in the fabrication of flexible microsystems including the incorporation of paper as a substrate and the use of a scalable manufacturing technology, inkjet printing. Here, we demonstrate the functionality of the oxygenation patch, capable of increasing oxygen concentration in a gel substrate by 13% (5 ppm) in 1 h. The platform is able to sense oxygen in a range of 5–26 ppm. In vivo studies demonstrate the biocompatibility of the patch and its ability to double or triple the oxygen level in the wound bed to clinically relevant levels.
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    Rapid prototyping of a novel and flexible paper based oxygen sensing patch via additive inkjet printing process
    (RSC, 2019) Maddipatla, Dinesh; Narakathu, Binu B.; Ochoa, Manuel; Rahimi, Rahim; Zhou, Jiawei; Yoon, Chang K.; Jiang, Hongjie; Al-Zubaidi, Hazim; Obare, Sherine O.; Zieger, Michael A.; Ziaie, Babak; Atashbar, Massood Z.; Surgery, School of Medicine
    A novel and flexible oxygen sensing patch was successfully developed for wearable, industrial, food packaging, pharmaceutical and biomedical applications using a cost-efficient and rapid prototypable additive inkjet print manufacturing process. An oxygen sensitive ink was formulated by dissolving ruthenium dye and ethyl cellulose polymer in ethanol in a 1 : 1 : 98 (w/w/w) ratio. The patch was fabricated by depositing the oxygen sensitive ink on a flexible parchment paper substrate using an inkjet printing process. A maximum absorbance from 430 nm to 480 nm and a fluorescence of 600 nm was observed for the oxygen sensitive ink. The capability of the oxygen sensitive patch was investigated by measuring the fluorescence quenching lifetime of the printed dye for varying oxygen concentration levels. A fluorescence lifetime decay (τ) from ≈4 μs to ≈1.9 μs was calculated for the printed oxygen sensor patch, for oxygen concentrations varying from ≈5 mg L−1 to ≈25 mg L−1. A sensitivity of 0.11 μs mg L−1 and a correlation coefficient of 0.9315 was measured for the printed patches. The results demonstrated the feasibility of employing an inkjet printing process for the rapid prototyping of flexible and moisture resistant oxygen sensitive patches which facilitates a non-invasive method for monitoring oxygen and its concentration levels.
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    Skin Regeneration Using Dermal Substrates that Contain Autologous Cells and Silver Nanoparticles to Promote Antibacterial Activity: In Vitro Studies
    (AMSUS, 2017-03) Zieger, Michael A. J.; Ochoa, Manuel; Rahimi, Rahim; Campana, Gonzalo; Tholpady, Sunil; Ziaie, Babak; Sood, Rajiv; Surgery, School of Medicine
    We hypothesized that the addition of silver nanoparticles (AgNP) to a dermal substrate would impart antibacterial properties without inhibiting the proliferation of contained cells. Our in vitro model was based on the commercial substrate, Integra. The substrate was prepared by simple immersion into 0 to 1% suspension of AgNP (75 or 200 nm diameter) followed by rinsing for 20 minutes and sterilization under an ultraviolet C lamp. A total of 107 human adipose stem cells per cubic centimeter were injected and after 1 hour, 6 × 105 keratinocytes/cm2 were seeded and cultured for up to 14 days. Constructs were evaluated using a metabolic assay (WST-1), and hematoxylin and eosin and immunoperoxidase staining. Bactericidal activity was measured using a log reduction assay against bacteria that are prevalent in burns. The presence of AgNP did not significantly change the metabolic activity of constructs after 14 days of culture, and the distribution of cells within the substrate was unchanged from the controls that did not have AgNP. Antibacterial activity of Integra containing AgNP (75 nm diameter) was concentration dependent. In conclusion, the addition of AgNP to the dermal substrate suppressed bacterial growth but did not significantly affect cell proliferation, and may represent an important property to incorporate into a future clinical skin regeneration system.
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    A wireless strain sensor for wound monitoring with direct laser-defined patterning on a commercial dressing
    (IEEE, 2016-01) Rahimi, Rahim; Ochoa, Manuel; Zieger, Michael; Sood, Rajiv; Ziaie, Babak; Department of Surgery, IU School of Medicine
    Controlled mechanical strain or stress on a wound site can promote accelerated neovascularization and cellular proliferation for improved wound healing; however, these mechanical forces have not been properly quantified due to a lack of standardized technique. As a solution, we developed a wireless strain sensor on a commercial wound dressing. The sensor consists of a flexible antenna coil whose resonant frequency changes in response to applied strain. The frequency change of the sensor is observed to be a linear function of applied strain in the range of 0-35%, with an average sensitivity of 150 kHz/%strain and negligible hysteresis. The sensor is fabricated through a simple process that consist of defining a screen-printing mask directly over the wound dressing using laser machining. The fabrication technique can be scaled up for mass production using roll-to-roll methods.