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Thanks to the beneficial properties of probiotic bacteria, there exists an immense demand for their consumption in probiotic foods worldwide. Nevertheless, it is difficult to retain a high number of viable cells in probiotic food products during their storage and gastrointestinal transit. Microencapsulation of probiotic bacteria is an effective way of enhancing probiotic viability by limiting cell exposure to extreme conditions via the gastrointestinal tract before releasing them into the colon. This research aims to develop a new coating material system of microencapsulation to protect probiotic cells from adverse environmental conditions and improve their recovery rates. Hence, Lactobacillus rhamnosus was encapsulated with emulsion/internal gelation techniques in a calcium chloride solution. Alginate–probiotic microbeads were coated with xanthan gum, gum acacia, sodium caseinate, chitosan, starch, and carrageenan to produce various types of microcapsules. The alginate+xanthan microcapsules exhibited the highest encapsulation efficiency (95.13 ± 0.44%), they were simulated in gastric and intestinal juices at pH 3 during 1, 2, and 3 h incubations at 37 °C. The research findings showed a remarkable improvement in the survival rate of microencapsulated probiotics under simulated gastric conditions of up to 83.6 ± 0.89%. The morphology, size, and shape of the microcapsules were analyzed using a scanning electron microscope. For the protection of probiotic bacteria under simulated intestinal conditions, alginate microbeads coated with xanthan gum played an important role, and exhibited a survival rate of 87.3 ± 0.79%, which was around 38% higher than that of the free cells (49.4 ± 06%). Our research findings indicated that alginate+xanthan gum microcapsules have a significant potential to deliver large numbers of probiotic cells to the intestines, where cells can be released and colonized for the consumer’s benefit.

Graphene quantum dots (GQDs) are considerably a new member of the carbon family and shine amongst other members, thanks to their superior electrochemical, optical, and structural properties as well as biocompatibility features that enable us to engage them in various bioengineering purposes. Especially, the quantum confinement and edge effects are giving GQDs their tremendous character, while their heteroatom doping attributes enable us to specifically and meritoriously tune their prospective characteristics for innumerable operations. Considering the substantial role offered by GQDs in the area of biomedicine and nanoscience, through this review paper, we primarily focus on their applications in bio-imaging, micro-supercapacitors, as well as in therapy development. The size-dependent aspects, functionalization, and particular utilization of the GQDs are discussed in detail with respect to their distinct nano-bio-technological applications.

In the area of biomedicine, research for designing electrochemical sensors has evolved over the past decade, since it is crucial to selectively quantify biomarkers or pathogens in clinical samples for the efficacious diagnosis and/or treatment of various diseases. To fulfil the demand of rapid, specific, economic, and easy detection of such biomolecules in ultralow amounts, numerous nanomaterials have been explored to effectively enhance the sensitivity, selectivity, and reproducibility of immunosensors. Graphene quantum dots (GQDs) have garnered tremendous attention in immunosensor development, owing to their special attributes such as large surface area, excellent biocompatibility, quantum confinement, edge effects, and abundant sites for chemical modification. Besides these distinct features, GQDs acquire peroxidase (POD)-mimicking electro-catalytic activity, and hence, they can replace horseradish peroxidase (HRP)-based systems to conduct facile, quick, and inexpensive label-free immunoassays. The chief motive of this review article is to summarize and focus on the recent advances in GQD-based electrochemical immunosensors for the early and rapid detection of cancer, cardiovascular disorders, and pathogenic diseases. Moreover, the underlying principles of electrochemical immunosensing techniques are also highlighted. These GQD immunosensors are ubiquitous in biomedical diagnosis and conducive for miniaturization, encouraging low-cost disease diagnostics in developing nations using point-of-care testing (POCT) and similar allusive techniques.

Polymers were synthesized and utilized for aflatoxin detection coupled with a novel lab-on-a-chip biosensor: MiSens and high performance liquid chromatography (HPLC). Non-imprinted polymers (NIPs) were preferred to be designed and used due to the toxic nature of aflatoxin template and also to avoid difficult clean-up protocols. Towards an innovative miniaturized automated system, a novel biochip has been designed that consists of 6 working electrodes (1 mm diameter) with shared reference and counter electrodes. The aflatoxin detection has been achieved by a competition immunoassay that has been performed using the new biochips and the automated MiSens electrochemical biosensor device. For the assay, aflatoxin antibody has been captured on the Protein A immobilized electrode. Subsequently the sample and the enzyme-aflatoxin conjugate mixture has been injected to the electrode surfaces. The final injection of the enzyme substrate results in an amperometric signal. The sensor assays for aflatoxin B1 (AFB1) in different matrices were also performed using enzyme link immunosorbent assay (ELISA) and HPLC for confirmation. High recovery was successfully achieved in spiked wheat samples using NIP coupled HPLC and NIP coupled MiSens biosensor [2 ppb of aflatoxin was determined as 1.86 ppb (93% recovery), 1.73 ppb (86.5% recovery), 1.96 ppb (98% recovery) and 1.88 ppb (94.0% recovery) for immunoaffinity column (IAC)-HPLC, NIP-HPLC, Supel (TM) Tox SPE Cartridges (SUP)-HPLC and NIP-MiSens, respectively]. Aflatoxin detection in fig samples were also investigated with MiSens biosensor and the results were compared with HPLC method. The new biosensor allows real-time and on-site detection of AFB1 in foods with a rapid, sensitive, fully automated and miniaturized system and expected to have an immense economic impact for food industry. (C) 2016 Elsevier B.V. All rights reserved.

Zeynep Altintas, Ibtisam E Tothill Biomedical Engineering, Cranfield University, Cranfield, UK Abstract: Over the last decade, an increasing number of researchers have focused on developing rapid techniques based on biosensor technology for the detection of various human health-related conditions. Cardiovascular disease, cancer, diabetes, and infectious diseases are at the top of these investigations. Huge advances have taken place in a wide range of disciplines, with improved sensitivity, specificity, and reproducibility of the designed methodologies. Advances in other scientific disciplines, including genetics, chemical and microelectronic engineering, computational sciences, and medicine have also impacted on the developments taking place in the diagnostics field. As a result of these developments, more stable, rapid, and reliable sensing platforms have been successfully constructed for specific and ultrasensitive biomarker-based disease diagnostics. These achievements were also a result of improving sensor production quality, developing appropriate surface chemistries, selection of high affinity ligands for target biomarkers, and using nanomaterials such as carbon nanotubes, magnetic/gold nanoparticles, or quantum dots for signal amplification. Moreover, use of bioinformatics tools, combined with proteomics and genomics technologies and metabolomics, has significantly improved the knowledge and discovery of new biomarkers that can be used for early detection. Due to these significant outputs, coupled with advances in miniaturization and nanotechnology, the demand for development and production of sensor systems, including optical, piezoelectric/acoustic, electrochemical, and colorimetric, has gradually increased during the last decade. Moreover, not only protein and gene markers, but also secondary metabolites and cell signaling pathway molecules can be used for disease detection. To date, diagnostic tests for the early detection of cancer biomarkers are available on the market, and these provide noninvasive/minimally invasive tests that can play a crucial role both in successful treatment and patient survival. This paper reviews disease biomarkers, post-genomic technology, and use of molecular biosensors for early detection of cancer.Keywords: cancer, biomarker discovery, post-genomic technology, molecular biosensors, disease diagnostics

Cardiovascular disease (CVD) is currently globally the biggest cause of mortality, with rising figures, especially now in the developing world. Early and accurate diagnosis of CVD, (especially acute myocardial infarction (AMI) is important in being able to provide appropriate, timely and cost effective treatment, or to take preventative action. Biomarkers and biosensors are playing an increasingly important role in this diagnosis, especially those based on immunoassays. As technology improves and becomes cheaper, there is the potential to develop immunosensors which use optical techniques such as surface plasmon resonance (SPR) for biomarker measurement which could be used effectively in point-of-care diagnostics for real-time detection. This thesis describes the development and optimisation of a sensitive immunosensor for the AMI specific biomarker, cardiac Troponin T (cTnT), on an SPR platform. Early diagnosis of AMI requires an assay methodology which can determine very low concentrations of cTnT in human serum. The work conducted includes the development of a set of optimised conditions for the immobilisation of the capture antibody (anti-cardiac Troponin T 1C11 antibody) onto a gold surfaced SPR sensor chip, to which a self-assembled monolayer of 11-mercaptoundecanoic acid has been applied. A direct immunoassay for cTnT in buffer was examined and a limit of detection (LOD) of 25 ng ml-1 cTnT was achieved. A sandwich immunoassay format was then developed to enhance the sensitivity of the assay. The use of a detection antibody (anti-cardiac Troponin T 7G7 antibody) was shown to successfully amplify the SPR response five-fold, with the LOD improving to 5 ng ml-1 cTnT. The second stage of the project involved examining the extent of non-specific binding of the cTnT and of serum proteins, and investigating how best to minimise and control for it. Non-specific binding of cTnT was eliminated, and serum protein binding was reduced by 93% in 10% serum and 73% in 50% serum. To achieve greater sensitivity, amplification of the signal through the use of detector antibodies conjugated to gold nanoparticles (AuNPs) for the sandwich assay was investigated. The performance of the cTnT immunosensor sandwich assay in human serum was evaluated using non-modified and AuNP modified detector antibodies. The LOD of the immunosensor in 50% serum was assessed as 5 ng ml-1 cTnT for the standard sandwich assay, and 0.5 ng ml-1 cTnT when using AuNP conjugated detector antibodies to enhance the sensitivity.