Treating osteoarthritis (OA) pain has not been very effective to date – clinically available options typically offer just a few hours of relief or have substantial side effects. The clinical trials of the antibody directed against the OA pain-triggering protein – the nerve growth factor (NGF) – commenced about a decade ago has been hailed by some as a game-changer in the search for a highly effective OA painkiller. But the tests have also revealed potential side effects that rapidly worsen a patient’s OA.

Furthermore, there have been few available means to diagnose OA patients’ pain, let alone pinpointing precisely where they have pain.

A PolyU research team led by Professor Yang Mo, Associate Head (Research) of the Department of Biomedical Engineering and his colleague, associate professor Dr Wen Chunyi, made a breakthrough in tackling both problems by utilising the concept of targeted cancer therapy. They developed a groundbreaking, imaging-guided nanoparticle photothermal treatment for osteoarthritis pain.

The novel targeted osteoarthritis pain theranostics are made of gold nanorods coated with a two-dimensional nanomaterial, molybdenum disulfide. The coated nanorods are further fused with antibodies directed against the NGF.

The novel technique enables a new and accurate diagnostics approach – osteoarthritis pain imaging, as the nanorods localised to the injured joints can be tracked using photoacoustic imaging – a new non-invasive imaging modality that combines high contrast and good specificity of optical imaging, while delivering the high resolution and penetration depth offered by ultrasound imaging.

For OA pain treatment, NGF molecules are directly bound to the antibody-fused nanorods, which can transfer light energy to local heat. When it is heated with a near-infrared laser, the NGF protein is destroyed. The targeted and photothermal approach means only around 1/100 of the therapeutic dosage of the anti-NGF agent used in previous clinical trials is required.

The research team said testing with mouse models proved the novel theranostics hold good promise for clinical translation to achieve long-lasting pain relief for days and improvement of an OA patient’s quality of life. Their findings have been published in the prestigious journal ACS Nano by the American Chemical Society and were reported by Nature Reviews Rheumatology.