ABSTRACT
Fluorescent pH biosensors have gained importance owing to their low cost utilization in real time monitoring of biological and food samples in comparison to conventional pH meters. The research reports a novel method of ultrasonic atomization for developing a fluorescent pH sensor for real-time analysis made of Fluorescein isothiocyanate (FITC)-dextran/FITC-dextran-Tris (2, 2'-bipyridyl) dichlororuthenium (II) hexahydrate as indicator and reference fluorophores, respectively. The process of ultrasonic atomization ensures formation of monodisperse dye immobilized alginate microspheres ensuring efficient pH sensing. The developed biosensor was tested on milk samples, which has a short life span and shows a significant fall in pH with time due to microbial spoilage. The proposed biosensor showed a linear range of pH 4-8 (R2 between 0.96-0.99 for different single/dual fluorophore biosensors) which suitably cover the pH of milk during the entire storage period and spoilage. The % recovery for predicted pH falls between 90-110% compared against standard pH meter, indicating a good accuracy of estimation and low turnaround time (10 min). Thus, real-time monitoring using fluorescent pH biosensor for milk samples may profoundly improve the economics of losses occurring in processing and storage with capability of in-package continuous quality assessment.
ABSTRACT
Near infrared (NIR) fluorophores like Pt-porphyrin along with analyte specific enzymes require co-encapsulation in biocompatible and biodegradable carriers in order to be transformed into implantable biosensors for efficient and continuous monitoring of analytes in patients. The main objective of this research is to develop natural, biodegradable, biocompatible and a novel co-encapsulated system of Pt-porphyrin encapsulated polymeric nanoparticle and nano-micro hybrid carriers. A sequential emulsification-solvent evaporation and an air driven atomization technique was used for developing above matrices and testing them for fluorescence based oxygen and glucose biosensing. The results indicate Pt-porphyrin can be efficiently encapsulated in Poly-lactic acid (PLA) nanoparticles and PLA-alginate nano-micro particles with sizes ~450 nm and 10 µm, respectively. Biosensing studies have showed a linear fluorescent response in oxygen concentrations ranging from of 0-6 mM (R2 = 0.992). The Oxygen sensitivity was transformed into a linear response of glucose catalytic reaction in the range of 0-10 mM (R2 = 0.968) with a response time of 4 minutes and a stability over 15 days. We believe that the investigated NIR fluorophores like Pt-Porphyrin based nano/nano-micro hybrid carrier systems are novel means of developing biocompatible biodegradable carriers for developing implantable glucose biosensors which can efficiently manage glucose levels in diabetes.
Subject(s)
Biosensing Techniques/methods , Glucose/chemistry , Nanoparticles/chemistry , Oxygen/chemistry , Platinum/chemistry , Polymers/chemistry , Porphyrins/chemistry , Animals , Biocompatible Materials/chemistry , Biocompatible Materials/metabolism , Biocompatible Materials/pharmacology , Biosensing Techniques/instrumentation , Cell Line , Cell Survival/drug effects , Drug Carriers/chemistry , Drug Compounding , Fluorescent Dyes/chemistry , Fluorescent Dyes/metabolism , Glucose/metabolism , Humans , Mice , Microscopy, Electron , Nanoparticles/ultrastructure , Oxygen/metabolism , Particle Size , Polyesters/chemistry , Polymers/metabolism , Spectrometry, FluorescenceABSTRACT
Kidney diseases remain often undiagnosed due to inefficient screening methods available at patient's disposal. Early diagnosis and effective management of kidney problems can best be addressed by the development of biosensors for commonly occurring clinical biomarkers. Here we report the development of single fluorophore and dual fluorophore ratiometric biosensors based on alginate microspheres for pH and urea analysis in urine samples. A facile method of air driven atomization was used for developing these polymeric fluorophore and enzyme based biosensors. Ratiometric biosensors were developed using layer-by-layer coating of polyelectrolyte conjugated to reference fluorophores. Biosensing studies using these biosensors showed that samples in pathophysiological range can be measured having pH range of 4-8 and urea levels between 0-50 mM. Testing of urine samples using these biosensors showed that both pH and urea detection can be accurately performed without interference. Thus, we believe that FITC-Dextran and FITC-Dextran/RuBpy based pH and urea biosensors show a great potential to be translated as a point of care device for pH and urea biosensing in early detection and continuous monitoring of kidney diseases.
Subject(s)
Biosensing Techniques/methods , Fluorescent Dyes/chemistry , Urea/urine , Humans , Hydrogen-Ion Concentration , Reproducibility of ResultsABSTRACT
This research aims to develop and investigate a multifunctional implantable system capable of biosensing, drug delivery and magnetic resonance imaging (MRI) for continuous monitoring, controlled anti-inflammatory drug delivery and imaging, respectively. A glucose biosensor, diclofenac sodium (Diclo) and magnetic nanoparticles (MNP) were used as the biosensor component, anti-inflammatory agent and MRI contrast agent, respectively. MNP were synthesized by the co-precipitation technique and loaded with the sensor and drug components into alginate microspheres using a commercial droplet generator. The multifunctional system was then characterized using optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, vibrating sample magnetometry (VSM) and MRI. The MNP were found to be in the size range of 5-15 nm. The final system, comprising the biosensor, drug and MNP loaded inside alginate microspheres, was found to be in the size range of 10-60 µm. Biosensing studies indicated an excellent glucose response curve, with a regression coefficient of 0.974 (0-10mM of glucose, response time: 4 min). In vitro Diclo release shows that MNP loading in alginate microspheres increases the burst release percentage by 11-12% in both 60 and 10 µm particles. However, the duration of release for 85% drug release decreases with MNP loading by 7 and 6 days for 39 the 60 and 10 µm particles, respectively. Super-paramagnetism was confirmed by VSM, with 2.09 and 1.368 emu g(-1), respectively, for the 60 and 10 µm particles, with no hysteresis. MRI showed significant contrast for both sizes. The particles showed an excellent biocompatibility (>80%) for all combinations of formulations. The system shows a great potential for biosensing with concurrent drug delivery and visualization for biomedical applications.
