Peptide Cross-Linked Poly(2-oxazoline) as a Sensor Material for the Detection of Proteases with a Quartz Crystal Microbalance.

Inflammatory conditions are frequently accompanied by increased levels of active proteases, and there is rising interest in methods for their detection to monitor inflammation in a point of care setting. In this work, new sensor materials for disposable single-step protease biosensors based on poly(2-oxazoline) hydrogels cross-linked with a protease-specific cleavable peptide are described. The performance of the sensor material was assessed targeting the detection of matrix metalloproteinase-9 (MMP-9), a protease that has been shown to be an indicator of inflammation in multiple sclerosis and other inflammatory conditions. Films of the hydrogel were formed on gold-coated quartz crystals using thiol-ene click chemistry, and the cross-link density was optimized. The degradation rate of the hydrogel was monitored using a quartz crystal microbalance (QCM) and showed a strong dependence on the MMP-9 concentration. A concentration range of 0-160 nM of MMP-9 was investigated, and a lower limit of detection of 10 nM MMP-9 was determined.

Peptide Cross-Linked Poly (Ethylene Glycol) Hydrogel Films as Biosensor Coatings for the Detection of Collagenase.

Peptide cross-linked poly(ethylene glycol) hydrogel has been widely used for drug delivery and tissue engineering. However, the use of this material as a biosensor for the detection of collagenase has not been explored. Proteases play a key role in the pathology of diseases such as rheumatoid arthritis and osteoarthritis. The detection of this class of enzyme using the degradable hydrogel film format is promising as a point-of-care device for disease monitoring. In this study, a protease biosensor was developed based on the degradation of a peptide cross-linked poly(ethylene glycol) hydrogel film and demonstrated for the detection of collagenase. The hydrogel was deposited on gold-coated quartz crystals, and their degradation in the presence of collagenase was monitored using a quartz crystal microbalance (QCM). The biosensor was shown to respond to concentrations between 2 and 2000 nM in less than 10 min with a lower detection limit of 2 nM.

α-Amylase sensor based on the degradation of oligosaccharide hydrogel films monitored with a quartz crystal sensor.

α-Amylase hydrolyses starch molecules to produce smaller oligosaccharides and sugars. Amylases are of great importance in biotechnology and find application in fermentation, detergents, food and the paper industry. The measurement of α-amylase activity in serum and urine has been used in the diagnosis of acute pancreatitis. Salivary amylase has also been shown to be a stress indicator. Sensor coatings suitable for the detection of α-amylase activity have been developed. Oligosaccharides such as glycogen and amylopectin were spin-coated onto gold coated quartz crystals with a base frequency of 10 MHz. The films were subsequently cross-linked with hexamethylene diisocyanate. Film degradation was monitored with a quartz crystal microbalance (QCM) and electrochemical impedance measurements. The films were shown to be stable in phosphate buffered saline (PBS). Addition of α-amylase to the solution resulted in the rapid degradation of the films. The maximum rate of degradation was found to be strongly dependent on the amylase activity in the range typically found in serum when diagnosing pancreatitis (0.08-8 U/ml). Sensor responses in serum were found to be very similar to those obtained in buffer indicating the absence of non-specific binding.