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Open Access Publications from the University of California

Scholarly Works (6 results)

  • Thesis
  • Peer Reviewed
UC Irvine Electronic Theses and Dissertations (2020)

Second harmonic generation (SHG) microscopy has been a widely used method to image collagen-based tissues due to its non-invasive nature and ability to determine collagen changes with appropriate analysis. This technique has recently been applied to analyze the collagen structure of fresh corneal tissue, overcoming the limitations and challenges that occur with traditional microscopy and imaging techniques requiring fixation and dyes. Orientation and organization of the corneal collagen fibers is critical for optimal transparency and optical functionality. Corneal chemical injuries (CCIs) may result in the cornea to become opaque and thus obscuring vision. Other conditions, such as myopia or astigmatism, are a consequence of corneal shape deviations. Current treatments for vision correction are invasive, costly, or fail to fully restore a patient’s vision. Most corneal reshaping methods are either passive using rigid/semi-rigid contact lenses to gradually alter corneal shape (orthokeratology) or rely upon laser technology to perform precision ablation of corneal tissue. An alternative approach relies upon the in-situ generation of localized pH gradient that alter stress-strain relationships within the cornea, leading to potentially sustained shape change. This novel, minimally invasive approach (“electrochemical therapy”- ECT) is currently being evaluated to clear corneal opacification following a chemical injury and corneal reshaping. ECT has been previously used to reshape cartilage and chemically alter the collagen structure of skin. The objective of this thesis is to study corneal collagen structure using SHG microscopy to examine chemical injuries and electrochemical reshaping. Image processing techniques were developed to gauge structural changes observed with SHG imaging. Fresh ex-vivo rabbit corneas were imaged using SHG. Native fresh corneal tissue was examined and compared with alkaline-injured corneas before and after ECT-clearing. ECT reshaped cornea was examined as well. The extracted images were then processed through ImageJ and a customized MATLAB code to determine the collagen fiber orientation and compared to identify potential statistical indicators of structural change. Collagen distribution patterns throughout the thickness of the cornea were determined in all samples. Knowledge of the collagen structure obtained through SHG combined with white light photography and microscopic data provides information of the changing corneal extracellular matrix. This analysis can be utilized for collagen studies for future projects.

    Cover page: Analysis of Corneal Change Mechanisms Through Second Harmonic Generation Microscopy
    • Article
    • Peer Reviewed
    UC Irvine Previously Published Works (2019)

    Objective

    Surgical simulators aimed at mimicking elements of rhinoplasty surgery, specifically those aimed at improving cartilage suturing, are not available. Here, we present a surgical simulator for spreader graft placement that uses cartilage rather than synthetic materials and gauge improvement using objective measures for suture placement accuracy, speed, and efficiency of hand motion.

    Methods

    Twenty-two otolaryngologists in two groups (residents [10] and experts [12]) were instructed to secure the two spreader graft specimen into position with three mattress sutures on a nose model that used porcine septal cartilage as a proxy for the human counterpart. Hand motion was tracked using an electromagnetic position sensing device. The time required to complete the suture task, total hand displacement, cumulative number of hand motion direction changes, and accuracy of suture insertion were measured. These measurements were compared between the two cohort groups for construct validity. The subjects completed a survey to evaluate realism and value of the model.

    Results

    The expert group had a lower mean time required to complete the task (P < 0.05), total hand displacement (P < 0.01), and number of hand motion direction changes (P < 0.001). No significant difference was observed between the two groups in suture precision measurement. The subjects agreed on the face validity and usefulness of the trainer.

    Conclusions

    Our study suggests that the simulator may be a useful tool to objectively gauge suturing efficiency. Devices such as this may be useful for developing skill with suturing cartilage tissue and potentially be used to assess resident acquisition of surgical skill.

    Level of evidence

    NA Laryngoscope, 129:344-350, 2019.
      Cover page: Development and evaluation of rhinoplasty spreader graft suture simulator for novice surgeonsCreative Commons 'BY' version 4.0 license
      • Article
      • Peer Reviewed
      UC Irvine Previously Published Works (2021)

      Objectives

      To examine the acid-base and histological changes in in vivo rabbit cutaneous tissue after electrochemical therapy.

      Study design

      In vivo rabbit tissue study.

      Methods

      The shaved skin on the backs of female Oryctolagus cuniculi were assigned to treatments with or without tumescence with normal saline. Two platinum-needle electrodes were inserted into each treatment area and connected to a direct current (DC) power supply. Voltage (3-5 V) was varied and applied for 5 minutes. The wound-healing process was monitored via digital photography and ultrasonography until euthanasia at day 29. Treatment areas were biopsied, and specimens were sectioned through a sagittal midline across both electrode insertion sites. Samples were then evaluated utilizing light microscopy (hematoxylin and eosin, Masson's Trichrome, and Picrosirius red).

      Results

      Treatment sites developed mild inflammation that dissipated at lower voltages or became scabs at higher voltages. Ultrasonography demonstrated acoustic shadowing with spatial spread that increased with increasing voltage application. The 4- and 5-V sites treated with saline had localized areas of increased tissue density at day 29. Although specimens treated with 3 V did not look significantly different from control tissue, 4- and 5-V samples with and without saline tumescence had finer, less-organized collagen fibers and increased presence of fibrocytes and inflammatory infiltrates.

      Conclusions

      Electrochemical therapy caused localized injury to in vivo rabbit cutaneous tissue, prompting regenerative wound repair. With future development, this technology may offer precise, low-cost rejuvenation to restore the functionality and appearance of dermal scars and keloids.

      Level of evidence

      NA Laryngoscope, 131:E2196-E2203, 2021.
        Cover page: Electrochemical Therapy of In Vivo Rabbit Cutaneous TissueCreative Commons 'BY' version 4.0 license
        • Article
        • Peer Reviewed
        UC Irvine Previously Published Works (2024)
        Refractive errors remain a global health concern, as a large proportion of the world's population is myopic. Current ablative approaches are costly, not without risks, and not all patients are candidates for these procedures. Electromechanical reshaping (EMR) has been explored as a viable cost-effective modality to directly shape tissues, including cartilage. In this study, stromal collagen structure and fibril orientation was examined before and after EMR with second-harmonic generation microscopy (SHG), a nonlinear multiphoton imaging method that has previously been used to study native corneal collagen with high spatial resolution. EMR, using a milled metal contact lens and potentiostat, was performed on the corneas of five extracted rabbit globes. SHG was performed using a confocal microscopy system and all images underwent collagen fibril orientation analysis. The collagen SHG signal in controls is uniform and is similarly seen in samples treated with pulsed potential, while continuous EMR specimens have reduced, nonhomogeneous signal. Collagen fibril orientation in native tissue demonstrates a broad distribution with suggestion of another peak evolving, while with EMR treated eyes a bimodal characteristic becomes readily evident. Pulsed EMR may be a means to correct refractive errors, as when comparing its SHG signal to negative control, preservation of collagen structures with little to no damage is observed. From collagen fiber orientation analysis, it can be inferred that simple DC application alters the structure of collagen. Future studies will involve histological assessment of these layers and multi-modal imaging analysis of dosimetry.
          Cover page: Second harmonic generation microscopy of electromechanical reshaping on corneal collagenCreative Commons 'BY' version 4.0 license
          • Article
          • Peer Reviewed
          UC Irvine Previously Published Works (2022)

          Purpose

          Corneal chemical injuries (CCI) obscure vision by opacifying the cornea; however, current treatments may not fully restore clarity. Here, we investigated potential-driven electrochemical treatment (P-ECT) to restore clarity after alkaline-based CCI in ex vivo rabbit corneas and examined collagen fiber orientation changes using second harmonic generation (SHG).

          Methods

          NaOH was applied to the corneas of intact New Zealand white rabbit globes. P-ECT was performed on the opacified cornea while optical coherence tomography (OCT) imaging (∼35 frames per second) was simultaneously performed. SHG imaging evaluated collagen fiber structure before NaOH application and after P-ECT. Irrigation with water served as a control.

          Results

          P-ECT restored local optical clarity after NaOH exposure. OCT imaging shows both progression of NaOH injury and the restoration of clarity in real time. Analysis of SHG z-stack images show that collagen fibril orientation is similar between control, NaOH-damaged, and post-P-ECT corneas. NaOH-injured corneas flushed with water (15 minutes) show no restoration of clarity.

          Conclusions

          P-ECT may be a means to correct alkaline CCI. Collagen fibril orientation does not change after NaOH exposure or P-ECT, suggesting that no irreversible matrix level fiber changes occur. Further studies are required to determine the mechanism for corneal clearing and to ascertain the optimal electrical dosimetry parameters and electrode designs.

          Translational relevance

          Our findings suggest that P-ECT is a potentially effective, low-cost treatment for alkaline CCI.
            Cover page: Potential-Driven Electrochemical Clearing of Ex Vivo Alkaline Corneal Injuries
            • Article
            • Peer Reviewed
            UC Irvine Previously Published Works (2020)
            Body contouring achieved via subcutaneous adipose tissue reduction has notably advanced over the past century, from suction assisted lipectomy to techniques with reduced degrees of invasiveness including laser, radiofrequency, high frequency focused ultrasound, cryolipolysis, and drug-based injection approaches. These costly techniques have focused on damaging adipocyte cell membranes, hydrolyzing triglycerides (TGs), or inducing apoptosis. Here, we present a simple, low-cost technique, termed electrochemical lipolysis (ECLL). During ECLL, saline is injected into the subcutaneous adipose tissue, followed by insertion of needle electrodes and application of an electrical potential. Electrolysis of saline creates localized pH gradients that drive adipocyte death and saponification of TGs. Using pH mapping, various optical imaging techniques, and biochemical assays, we demonstrate the ability of ECLL to induce acid and base injury, cell death, and the saponification of triglycerides in ex vivo porcine adipose tissue. We define ECLL's potential role as a minimally-invasive, ultra-low-cost technology for reducing and contouring adipose tissue, and present ECLL as a potential new application of an emerging electrochemical redox based treatment modality.
              Cover page: Electrochemical degradation and saponification of porcine adipose tissue
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