Table 1.

Previous polarized Raman studies used altered instrumentation to analyze mineralized tissues and collagen.

Tissue	Instrumentation	Polarization	Laser (nm)	Factor(s)	Raman property	Reported trends	Ref.
Human tooth enamel	Spectrophotometer coupled to microscope with 100x and 50x objectives	Fully polarizeda	632.8, 514	Crystalline orientation	${\nu }_1{\mathrm{PO}}_4$, ${\nu }_2{\mathrm{PO}}_4$, ${\nu }_3{\mathrm{PO}}_4$, ${\nu }_4{\mathrm{PO}}_4$, ${\nu }_1{\mathrm{CO}}_3$, OH	Carbonation preserves the orientation of enamel crystals. Vibrational modes of enamel rods are reconciled to theory.	34
Human tooth enamel	Confocal microscope, 10x objective	Fully polarized	830	Caries and lesions	${\nu }_1{\mathrm{PO}}_4$	Depolarization ratio and anisotropy of $\nu 1{\mathrm{PO}}_4$ changes between sound enamel and caries Depolarization ratio and anisotropy of ${\nu }_1\mathrm{PO}4$ changes between sound enamel and caries.	35
Sheep tendon, fixed human femur	Confocal microscope, 100x objective $\mathrm{NA}=0.8$	Not reported	633	Collagen Fiber distribution along osteon radius, and bone rotation	${\nu }_3{\mathrm{PO}}_4/{\nu }_1{\mathrm{PO}}_4$, Amide I/Amide III, and Amide III ratio ($1271/1243$)	Polarization-sensitive peak ratios varied with distance from haversian canal.	29
Rat tail tendon collagen fibrils	Confocal microscope, 60x $\mathrm{NA}=1.0$ objective	Fully polarized	785	Mechanical stress	Amide I, Amide III	Stress changes orientation distribution but not vibration frequencies of collagen.	36
Whole and powdered mouse tibia	Custom confocal Raman microprobe, various objectives	Fully polarized	785	Osteogenesis Imperfecta (oim)	${\nu }_1{\mathrm{PO}}_4$, Amide I	Orientation distribution of mineral and collagen differ in oim mice.	30
Collagen from bovine achilles tendon	Confocal microscope 60x objective $\mathrm{NA}=0.75$	Collection arm polarized	633	Collagen fiber orientation	Amide I, Amide III, and Amide III ratio ($1245/1268$)	Amide III doublet is sensitive to orientation.	33
Turkey leg tendon, embedded mouse femurs	Confocal microscope, 60x $\mathrm{NA}=1.0$, 20x $\mathrm{NA}=0.4$	Fully polarized	785	Orientation of cut, depolarization	${\nu }_1{\mathrm{PO}}_4/\mathrm{Amide}\mathrm{I}$, ${\nu }_2{\mathrm{PO}}_4/\mathrm{Amide}\mathrm{III}$, $\text{Carbonate}/{\nu }_2{\mathrm{PO}}_4$	Tissue age affects Raman polarization. Collagen orientation obtained from polarized mapping.	19
Embedded human femur osteons	Confocal microscope, 100x $\mathrm{NA}=0.9$	Not reported	532	Tissue type and orientation	${\nu }_1{\mathrm{PO}}_4/\mathrm{Amide}\mathrm{I}$${\nu }_2{\mathrm{PO}}_4/\mathrm{Amide}\mathrm{III}$${\nu }_4{\mathrm{PO}}_4/\mathrm{Amide}\mathrm{III}$	Tissue types have differential polarization sensitivity.	28,37
Femoral head spongy bone	Confocal microscope, 50x objective $\mathrm{NA}=0.5$	Fully polarized	785	Specimens from osteoporotic fracture patients.	${\nu }_1{\mathrm{PO}}_4/\mathrm{Amide}\mathrm{I}$, ${\nu }_2{\mathrm{PO}}_4/\mathrm{Amide}\mathrm{III}$${\nu }_4{\mathrm{PO}}_4/\mathrm{Amide}\mathrm{III}$$\text{Carbonate}/{\nu }_2{\mathrm{PO}}_4$	Polarized Raman helps determine the location of collagen fibers within trabeculae.	38
Human femur	Confocal microscope, 50x objective $\mathrm{NA}=0.75$, 20x objective $\mathrm{NA}=0.4$	Inherent polarization	785	Tissue type and orientation	Various	Polarization sensitivity inherent in peaks and Raman instrumentation can be minimized by optimizing peak phase.	Current Study

^aFully polarized indicates the use of polarizing optics in the input and collection arm.