In this study, we introduce five unique scanning probes developed in our laboratory for different fields of application. These probes are the results of excellent collaborations with many external partners. Each probe possesses many advanced features that one can hardly obtain with plane probes for conventional optical deflection system. The applications of these probes are very versatile, from atomic force microscope for the exploration of Mars to in vivo measurements of human knee cartilage. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

We have explored indentation-type scanning force microscopy (IT SFM) that allows for a direct, quantitative inspection of cartilage morphology and biomechanical properties from the millimeter to the nanometer scale ex vivo, and ultimately, in situ (Stolz et al., 2004). Here we present three examples of using IT SFM where morphological and biomechanical changes could only be spotted at the sub-micrometer scale: We employed IT SFM for quality control of engineered cartilage cultured under various conditions. These measurements harbor the prospect to optimize and yield engineered cartilage that exhibits long-term mechanical stability, functionality and biocompatibility for joint arthroplasty. For a more rational understanding of cartilage biology and pathology, we have recently investigated the articular cartilage of mice lacking the β1-integrin in chondrocytes. The β1-integrin gene knock-out mice differed only in stiffness when measured at the nanometer scale, i.e., exhibiting a softer extracellular matrix compared to their wild-type controls. We inspected the changes of aging articular cartilage by employing a mouse model. Accordingly, the stiffness of the aging cartilage increased concomitant with a decrease of its glycosaminoclycan (GAG) moiety. Frequently, aging articular cartilage takes a pathological turn called osteoarthritis (OA), which usually ends with a complete disappearance of the articular cartilage layer. Towards an early detection of OA in the human body, we inspected the morphological and biomechanical status of articular cartilage biopsies representing different grades of OA according to the ‘Outerbridge scale’. Most significantly, the early changes (grades 0 to 2) were only detectable at the nanometer scale, but not at the micrometer or millimeter scale. Based on such ex vivo indentation testing, we started to move from the bench to the patient, aiming to directly inspect the quality of human articular knee cartilage by an arthroscopic SFM (Imer et al., 2006). The arthroscopic SFM might just be the beginning of a new generation of nano tools designed for endoscopic or catheter-based interventions of other parts of the body. For such prophylactic interventions to eventually being tolerated by the patient, not only have these to be ambulant and minimally invasive, but they will require a change of paradigm vis-a-vis the patient, namely to undergo an invasive procedure without feeling sick – indeed a big challenge for nanomedicine and managed health care!

The pathological changes in osteoarthritis—a degenerative joint disease prevalent among older people—start at the molecular scale and spread to the higher levels of the architecture of articular cartilage to cause progressive and irreversible structural and functional damage. At present, there are no treatments to cure or attenuate the degradation of cartilage. Early detection and the ability to monitor the progression of osteoarthritis are therefore important for developing effective therapies. Here, we show that indentation-type atomic force microscopy can monitor age-related morphological and biomechanical changes in the hips of normal and osteoarthritic mice. Early damage in the cartilage of osteoarthritic patients undergoing hip or knee replacements could similarly be detected using this method. Changes due to aging and osteoarthritis are clearly depicted at the nanometre scale well before morphological changes can be observed using current diagnostic methods. Indentation-type atomic force microscopy may potentially be developed into a minimally invasive arthroscopic tool to diagnose the early onset of osteoarthritis in situ .

We have recently demonstrated that indentation-type atomic force microscopy (IT-AFM) is capable of detecting early onset osteoarthritis (OA) (Stolz, 2009). This study was based on biopsies, using a desk-top commercial atomic force microscope (AFM). However, cartilage analysis in the knee joints needs to be non-destructive to avoid new seeding points for OA by the taking of biopsies. This requires bringing the probe tip in contact with the articular cartilage (AC) surface inside the joint. Here we present our recent progress towards a medical instrument for performing such IT-AFM measurements for in-vivo knee diagnostics. The scanning force arthroscope (SFA) integrates a miniaturized AFM into a standard arthroscopic sleeve, and is used for direct, quantitative, in situ inspection of AC (Imer et al., 2006). The stabilization and the positioning of the instrument relative to the surface under investigation were performed by means of eight inflatable balloons. An integrated three-dimensional, piezoelectric scanner allowed raster scanning and probing of a small area of cartilage around the point of insertion. An AFM probe with an integrated deflection sensor was mounted at the distal end of the instrument. Using this instrument, several measurements were performed on agarose gel and on porcine cartilage samples. The load-displacement curves obtained were analyzed and the dynamic elastic moduli | E* | were calculated. A good correlation between these values and those published in the scientific literature was found. Therefore, we concluded that the SFA can provide quantitative measurements to detect early pathological changes in OA.

1. Department of Biophysical and Electronic Engineering, University of Genova, Italy; 2. M.E. Muller Institute for Structural Biology, Biozentrum University of Basel, Switzerland; 3. Department of Orthopaedic Surgery & Traumatology, Kantonsspital, Bruderholz/Basel, Switzerland; 4. Laboratory for Tissue Engineering, Department of Surgery & Research, University Hospital of Basel, Switzerland; 5. Center for Microscopy, University of Basel, Switzerland; 6. Institute of Microtechnology, University of Neuchâtel, Switzerland.

The development of new tools and instruments for biomedical applications based on nano- (NEMS) or microelectromechanical systems technology (MEMS) are bridging the gap between the macro- and the nano-world. The well mastered microtechnique allows controlling many parameters of these instruments, which is essential for conducting reproducible and repeatable experiments in the life sciences. Examples are multifunctional scanning probe sensors for cell biology, an arthroscopic scanning force microscope for minimally invasive medical interventions and a nanopore sensor for single molecule experiments in biochemistry. This paper reviews some of the activities conducted in a fruitful interdisciplinary collaboration between physicists, engineers, biologists and physicians.

Osteoarthritis is a painful and disabling progressive joint disease, characterized by degradation of articular cartilage. In order to study this disease at early stages, we have miniaturized and integrated a complete scanning force microscope into a standard arthroscopic device fitting through a standard orthopedic canula. This instrument will allow orthopedic surgeons to measure the mechanical properties of articular cartilage at the nanometer and micrometer scale in-vivo during a standard arthroscopy. An orthopedic surgeon assessed the handling of the instrument. First measurements of the elasticity-modulus of human cartilage were recorded in a cadaver knee non minimal invasive. Second, minimally invasive experiments were performed using arthroscopic instruments. Load-displacement curves were successfully recorded.

A recent Study, based on ex vivo unconfined compression testing of normal, diseased, and enzymatically altered cartilage, revealed that a scanning force microscope (SFM), used as a nano-intender, is sensitive enough to enable measurement of alterations in the biomechanical properties of cartilage. Based oil these ex vivo measurements, we have designed a quantitative diagnosis tool, the scanning force arthroscope (SFA), able to perform in vivo measurements during a standard arthroscopic procedure. For stabilizing and positioning the instrument relative to the surface Under investigation, a pneumatic system has been developed. A segmented piezoelectric tube was used to perform the indentation displacement, and a pyramidal nanometer-scale silicon tip mounted on a cantilever with an integrated deflection sensor measured the biomechanical properties of cartilage. Mechanical means were designed to protect the fragile cantilever during the insertion of the instrument into the knee joint. The stability of the pneumatic stage was checked with it prototype SFA. In a series of tests, load-displacement curves were recorded in a knee phantom and, more recently, in a pig's leg.