Spatially offset Raman spectroscopy: from instrumentation to applications in monitoring bone regeneration
Publication Date
December 8, 2021
Creator
Abstract
Spatially offset Raman spectroscopy (SORS) is a method for measuring Raman signal from much deeper within a sample than is achievable with traditional Raman spectroscopy, and relies on the diffuse scattering of photons within turbid materials. This makes SORS a promising tool in the field of medical imaging.
A SORS device was built, based around a digital micro mirror device. This allowed for the detection offset to be selected in software and gave the SORS device a huge flexibility. The instrument was then applied to the study of bone regeneration.
Using phantom samples, we investigated the feasibility of using SORS as a tool for monitoring non-invasively the mineralization of bone tissue engineering scaffold in vivo. The phantom samples consisted of 3D-printed scaffolds of poly-caprolactone (PCL) and hydroxyapatite (HA) blends, with varying concentrations of HA, to mimic the mineralisation process. The scaffolds were covered by a 4 mm layer of skin to simulate real in vivo measurement conditions. At a concentration of HA approximately 1/3 that of bone (~0.6 g/cm3), the characteristic Raman band of HA (960 cm-1) was detectable when the PCL:HA layer was located at 14 mm depth within the scaffold (i.e. 8 mm below the skin surface), and concentrations of ~10% of bone were detectable at 4 mm depth.
We then investigated the feasibility of using SORS to monitor changes in collagen concentration at levels similar to those expected to occur in vivo during bone regeneration (0 – 0.84 g/cm3). A partial least squares (PLS) regression model was developed to quantify collagen concentration in plugs consisting of mixtures of collagen and hydroxyapatite (predictive power of ±0.16 g/cm3). The PLS model was then applied to SORS spectra acquired from rat cadavers after implanting the collagen:hydroxyapatite plugs in drilled skull defects. The PLS model successfully predicted the profile of collagen concentration, but with an increased predictive error of ±0.30 g/cm3. These results demonstrate the potential of SORS to quantify collagen concentrations in the range relevant to those occurring during new bone formation.
Item Type
ethesis
Thesis Type
PhD
Supervisors
Subjects (LC)
Associated Schools / Departments
School of Physics and Astronomy
eprints ID
66801
UoN Repository URI
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FINAL THESIS Corrections Complete.pdf
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