Early Detection of Cartilage Degeneration: A Comparison of Histology, Fiber Bragg Grating-Based Micro-Indentation, and Atomic Force Microscopy-Based Nano-Indentation

Abstract

We have determined the sensitivity and detection limit of a new fiber Bragg grating (FBG)-based optoelectronic micro-indenter for biomechanical testing of cartilage and compared the results to indentation-type atomic force microscopy (IT-AFM) and histological staining. As test samples, we used bovine articular cartilage, which was enzymatically degraded ex vivo for five minutes using different concentrations of collagenase (5, 50, 100 and 500 µg/mL) to mimic moderate extracellular matrix deterioration seen in early-stage osteoarthritis (OA). Picrosirius Red staining and polarization microscopy demonstrated gradual, concentration-dependent disorganization of the collagen fibrillar network in the superficial zone of the explants. Osteoarthritis Research Society International (OARSI) grading of histopathological changes did not discriminate between undigested and enzymatically degraded explants. IT-AFM was the most sensitive method for detecting minute changes in cartilage biomechanics induced by the lowest collagenase concentration, however, it did not distinguish different levels of cartilage degeneration for collagenase concentrations higher than 5 µg/mL. The FBG micro-indenter provided a better and more precise assessment of the level of cartilage degeneration than the OARSI histological grading system but it was less sensitive at detecting mechanical changes than IT-AFM. The FBG-sensor allowed us to observe differences in cartilage biomechanics for collagenase concentrations of 100 and 500 µg/mL. Our results confirm that the FBG sensor is capable of detecting small changes in articular cartilage stiffness, which may be associated with initial cartilage degeneration caused by early OA.

Biosensors for Detection of Biochemical Markers Relevant to Osteoarthritis

“…The articles selected included 19 NRCTs (11 cross-sectional and 8 case-control). Studies were published between 2003 [ 12 ] and 2020 [ 2 , 33 ]. Biomarkers were found in the synovial fluid [ 8 , 12 , 31 , 32 , 34 , 35 ] in serum and urine [ 2 , 4 , 5 , 10 , 14 , 36 , 37 ]; in blood and uCTX-II control [ 8 , 22 , 38 ] in DNA extracted; in epithelial cells and in bovine articular cartilage [ 24 , 33 , 39 ].…”

“…The most common biosensors adopted were FOPPR [ 31 , 32 , 35 ], SPRi and FMGC biosensors [ 8 , 10 , 12 , 36 ]. Other biosensors used were MIP, Quartz crystal microbalance biosensor, AMPK, FBG, anti-COMP, DdRFP, FCD, IDE, QCM, SAM, hand-held optical biosensing system utilizing a smartphone-embedded illumination sensor that is integrated with the immunoblotting assay method and amperometric biosensor [ 2 , 4 , 5 , 10 , 14 , 22 , 24 , 25 , 33 , 34 , 37 , 39 ].…”

“…The most common biomarkers were CTX-II, both uCTX-II and sCTX-II [ 2 , 10 , 14 , 22 , 37 , 38 ], followed by COMP, MMP-1 and MMP-3 [ 4 , 5 , 8 , 31 , 32 , 34 ]. Other biomarkers adopted were: CRP, GPI, TNF, ECM, Mitochondrial DNA, Interleukin-1B, Protease matriptase and Uricase enzyme layer thickness [ 12 , 24 , 25 , 33 , 35 , 36 , 39 ].…”

“…The MINORS tool was adopted to assess the quality of evidence of the included papers. Among these studies, ten studies (55%) [ 5 , 8 , 10 , 12 , 25 , 32 , 33 , 35 , 38 , 39 ] had a low risk of bias, and nine studies (45%) [ 4 , 5 , 14 , 22 , 24 , 31 , 34 , 36 , 37 ] had a high risk of bias. The MINORS was reported in Table 2 .…”

“…Twelve studies were included (9 cross-sectional and 3 case-control) [ 4 , 5 , 8 , 12 , 14 , 22 , 24 , 32 , 33 , 34 , 35 ]. Authors of these studies reported that biosensors have high selectivity for the detection of OA biomarkers.…”