| 1. |
- Chan, Cangel Pui Yee, et al.
(författare)
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Evidence-Based Point-of-Care Diagnostics: Current Status and Emerging Technologies
- 2013
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Ingår i: Annual Review of Analytical Chemistry. - : Annual Reviews. - 1936-1327 .- 1936-1335. - 9780824344061 ; 6, s. 191-211
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Tidskriftsartikel (refereegranskat)abstract
- Point-of-care (POC) diagnostics brings tests nearer to the site of patient care. The turnaround time is short, and minimal manual interference enables quick clinical management decisions. Growth in POC diagnostics is being continuously fueled by the global burden of cardiovascular and infectious diseases. Early diagnosis and rapid initiation of treatment are crucial in the management of such patients. This review provides the rationale for the use of POC tests in acute coronary syndrome, heart failure, human immunodeficiency virus, and tuberculosis. We also consider emerging technologies that are based on advanced nanomaterials and microfluidics, improved assay sensitivity, miniaturization in device design, reduced costs, and high-throughput multiplex detection, all of which may shape the future development of POC diagnostics.
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| 2. |
- Kei Lai, Kwok, et al.
(författare)
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Bioinspired protein microparticles fabrication by peptide mediated disulfide interchange
- 2014
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 4:23, s. 11802-11810
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we report an innovative green chemistry approach for the fabrication of protein microparticles based on peptide mediated disulfide interchange reactions. The concept is based on using a redox reactive peptide, glutathione, as a natural crosslink reagent triggering the formation of intermolecular disulfide bonds between adjacent protein molecules leading to the assembly of protein molecules within a CaCO3 template into a microparticle structure. The CaCO3 template is highly biocompatible and is completely removed by simply adjusting the solution to pH 5.0, leaving behind the pure protein microparticles. Moreover, the GSH is only involved in the intermediate step without being incorporated into the resulting protein microparticles, therefore producing protein microparticles composed of purely protein molecules. This technology provides a simple and robust method to fabricate protein microparticles under physiological aqueous conditions, and more importantly avoiding the extensive use of synthetic chemical crosslinking reagents. We have further demonstrated that this method is versatile to fabricate microparticles with various proteins such as BSA, enzymes and antibodies. The biological functions such as catalytic properties and affinity interactions of the resulting protein microparticles are highly conserved which demonstrate the potential applications of the protein microparticles in the area of biocatalysis, bioseparation and targeted drug delivery.
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| 3. |
- Kwok Kei, Lai, et al.
(författare)
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Multifunctional protein particles with dual analytical channels for colorimetric enzymatic bioassays and fluorescent immunoassays
- 2012
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Ingår i: Biosensors & bioelectronics. - : Elsevier BV. - 0956-5663 .- 1873-4235. ; 32:1, s. 169-176
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Tidskriftsartikel (refereegranskat)abstract
- Advanced multifunctional protein particles encapsulated enzymes and antibodies were developed for enzymatic bioassays and immunoassays with colorimetric and fluorescent channels. A colorimetric channel based on color-substrate precipitation was assigned for enzymatic bioassays for the measurement of hydrogen peroxide with the lowest detectable concentration of 10 μM. A fluorescent channel based on fluorescent labeled antibodies was assigned for immunoassays for the measurement of mouse immunoglobulin G (M IgG) with the lowest detectable concentration of 1.25 μg L−1. The protein microparticles were fabricated with a template-assisted self-assembly technique termed “Protein Activation Spontaneous Self-assemble” (PASS). The multifunctional protein particles prepared with the PASS method have the advantages of high loading of analytical biomolecules, integrated biological functions, porous structure, and more importantly, they are optically transparent and fluorescence inactive. These unique features make our protein particles a new generation of bead-based platforms to perform enzyme bioassays and immunoassays.
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| 4. |
- Lademann, Jürgen, et al.
(författare)
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Drug delivery with topically applied nanoparticles : science fiction or reality
- 2013
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Ingår i: Skin Pharmacology and Physiology. - : S. Karger. - 1660-5527 .- 1660-5535. ; 26:4-6, s. 227-233
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Tidskriftsartikel (refereegranskat)abstract
- The efficacy of topically applied drugs is determined by their action mechanism and their potential capacity of passing the skin barrier. Nanoparticles are assumed to be efficient carrier systems for drug delivery through the skin barrier. For flexible nanoparticles like liposomes, this effect has been well demonstrated. The penetration properties of solid nanoparticles are currently under intensive investigation. The crucial advantage of nanoparticles over non-particulate substances is their capability to penetrate deeply into the hair follicles where they can be stored for several days. There is no evidence, yet, that solid particles ≥40 nm are capable of passing through the healthy skin barrier. Therefore and in spite of the long-standing research efforts in this field, commercially available solid nanoparticle-based products for drug delivery through the healthy skin are still missing. Nevertheless, the prospects for the clinical use of nanoparticles in drug delivery are tremendous. They can be designed as transport systems delivering drugs efficiently into the hair follicles in the vicinity of specific target structures. Once deposited at these structures, specific signals might trigger the release of the drugs and exert their effects on the target cells. In this article, examples of such triggered drug release are presented.
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| 5. |
- Lai, Kwok Kei, et al.
(författare)
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High efficiency single-step biomaterial-based microparticle fabrication via template-directed supramolecular coordination chemistry
- 2016
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Ingår i: Green Chemistry. - : Royal Society of Chemistry (RSC). - 1463-9262 .- 1463-9270. ; 18:6, s. 1715-1723
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Tidskriftsartikel (refereegranskat)abstract
- Biomaterial-based microparticles have attracted much attention for medical and biological applications such as pharmaceutics, bioseparation and cosmetics. Emerging technologies enable versatile and facile fabrication of microparticles, with key features being purity, precise size control, mild preparation conditions and minimal processing. Here, an innovative approach combining template synthesis, biomolecule assembly and partial-purification within a single step for high efficiency fabrication of pure biomaterial-based microparticles is reported. This concept is based on facile co-precipitation of biomolecules within CaCO3 templates and simultaneous crosslinking of entrapped biomolecules via Ca2+ driven supramolecular coordination chemistry, followed by template removal. Carbohydrate (alginate) and proteins (casein and fresh milk) are used as models of biomolecules. The process driven by selective crosslinking automatically excludes non-specific materials from the template and thus provides the additional function of partial-purification, as demonstrated using highly complexed fresh milk. This green approach to fabrication of biomaterial-based microparticles offers three critical advantages (i) mild conditions to preserve the chemical and secondary structures of biomolecules; (ii) single processing step to facilitate scale-up production; and (iii) partial-purification without the need for upstream raw material purification. This innovative approach not only addresses fundamental issues in fabrication techniques, but also marks progress in energy and environmental conservation during manufacturing processes.
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| 6. |
- Mak, Wing Cheung, et al.
(författare)
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Biofunctionalized indigo-nanoparticles as biolabels for the generation of precipitated visible signal in immunodipsticks
- 2011
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Ingår i: Biosensors & bioelectronics. - : Elsevier. - 0956-5663 .- 1873-4235. ; 26:7, s. 3148-3153
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Tidskriftsartikel (refereegranskat)abstract
- A novel class of organic nanoparticles as biolabels that can generate an instant visible signal was applied to immunodipsticks. A new principle for signal generation based on hydrolysis of colourless signal precursor molecules to produce coloured signal molecules followed by signal precipitation and localization was demonstrated. The nanoparticle biolabels were applied to sandwich immunoassays for the detection of mouse immunoglobulin G (M IgG). In the presence of M IgG, a nanoparticle-immunocomplex was formed and bound on the test zone immobilized with goat anti M IgG (Gt α M IgG). A blue line was developed on the test zone upon the addition of a signal developing reagent. An optical signal could be simply assessed using naked eyes or quantified using a reading device. The lowest visible signal that could be observed using naked eyes was found to be 1.25 μg L−1 M IgG. The nanoparticle biolabel also showed a better sensitivity (signal-to-noise ratio) compared with the conventional colloidal gold biolabel. This novel class of organic nanoparticles offers an alternative biolabel system for the development of point-of-care immunodipsticks.
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| 7. |
- Mak, Wing Cheung, et al.
(författare)
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Biosensor for rapid phosphate monitoring in sequencing batch reactor (SBR) system
- 2003
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Ingår i: Biosensors & bioelectronics. - : Elsevier. - 0956-5663 .- 1873-4235. ; 19:3, s. 233-237
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Tidskriftsartikel (refereegranskat)abstract
- A thick-film phosphate biosensor based on hydrogel immobilized pyruvate oxidase (POD) has been developed for rapid phosphate process control monitoring in an experimental sequencing batch reactor (SBR) system. We have employed a phosphate biosensor in an off-line monitoring of phosphate concentrations in a bench scale SBR. Measurements with biosensor show a good correlation (r2=0.98) with those of commercial colorimetric phosphate testing kits. The signal response time was 1 min with a detection limit of 5 microM. The biosensor method showed a good operational stability, needed less experimental procedures and a small sample size (approximately 20 microl). This allows its practical application for rapid phosphate measurements to obtain real time process data in a SBR system.
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| 8. |
- Mak, Wing Cheung, 1977-, et al.
(författare)
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Drug delivery into the skin by degradable particles
- 2011
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Ingår i: European journal of pharmaceutics and biopharmaceutics. - : Elsevier. - 0939-6411 .- 1873-3441. ; 79:1, s. 23-27
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Tidskriftsartikel (refereegranskat)abstract
- Recently, it was demonstrated that particles could be utilized as carrier systems for drugs into the hair follicles. In the present study, a two-component drug delivery system is presented consisting of degradable particles loaded with fluorescein isothiocyanate and a separate protease formulation for degradation. The particles were applied alone, 30 min previous to the protease application and simultaneously with the protease onto porcine skin. Subsequently, biopsies were removed, and the penetration depths of the particles were analyzed using laser scanning microscopy.The obtained results demonstrate that the particles alone achieved a penetration depth of around 900 μm. Similar results were obtained for the successive application of particles and protease, whereas a release of the fluorescent dye was only observed in the upper 250 μm corresponding to the penetration depth of the protease. In the case of the simultaneous application, the particles were partly dissolved before application, leading to a reduced particle size and diminished penetration depth.The results revealed that degradable particles are a promising tool for drug delivery into the skin.
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| 9. |
- Mak, Wing Cheung, et al.
(författare)
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Electrochemical bioassay utilizing encapsulated electrochemical active microcrystal biolabels
- 2005
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 77:9, s. 2835-2841
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Tidskriftsartikel (refereegranskat)abstract
- A new approach to perform electrochemical immunoassay based on the utilization of encapsulated microcrystal was developed. The microcrystal labels create a “supernova effect” upon exposure to a desired releasing agent. The microcrystal cores dissolve, and large amounts of signal-generating molecules diffuse across the capsule wall into the outer environment. Layer-by-Layer (LbL) technology was employed for the encapsulation of electrochemical signal-generating microcrystals (ferrocene microcrystals). The encapsulated microcrystals were conjugated with antibody molecules through the adsorption process. The biofunctionalized microcrystals were utilized as a probe for immunoassays. The microcrystal-based label system provided a high-signal molecule to antibody (S/P) ratio of 104−105. Microcrystal biolabels with different antibody surface coverage (1.60−5.05 mg m-2) were subjected to a solid-phase immunoassay for the detection of mouse immunoglobulin G (M-IgG) molecules. The microcrystal-based immunoassay for the detection of M-IgG performed with microcrystals having antibody surface coverage of 5.05 mg m-2 showed a sensitivity of 3.93 nA μg-1 L-1 with a detection limit of 2.82 μg L-1.
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| 10. |
- Mak, Wing Cheung, et al.
(författare)
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Nanoscale surface engineered living cells with extended substrate spectrum
- 2004
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Ingår i: IEE Proceedings - Nanobiotechnology. - : IEEE. - 1478-1581. ; 151:2, s. 67-72
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Tidskriftsartikel (refereegranskat)abstract
- We report on cell surface engineering of living microorganisms by using Layer-by-Layer (LbL) technology to extend the substrate spectrum. The yeast Arxula adeninivorans LS3 (Arxula) was employed as a model organism and biological template. By using LbL technology, Arxula cells were encapsulated by polyelectrolyte and enzyme layers. The biological activity of the Arxula was retained after the encapsulation process. The polymeric capsule surrounding the Arxula provides a stable interface for surface engineering of living cells. LbL of polyelectrolytes followed by an enzyme layer of lactate oxidase were assembled. The outer enzyme layer provides an additional biological function for Arxula to convert the unfavourable substrate lactate into the favourable substrate pyruvate, thus extending the substrate spectrum of the organism. Moreover, capsule stability and enzyme conjugate stability of the surface engineered Arxula were studied.
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| 11. |
- Mak, Wing Cheung, et al.
(författare)
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Novel biosensors for quantitative phytic acid and phytase measurement
- 2004
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Ingår i: Biosensors & bioelectronics. - : Elsevier. - 0956-5663 .- 1873-4235. ; 19:9, s. 1029-1035
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Tidskriftsartikel (refereegranskat)abstract
- Phytase (EC 3.1.3.26) and phytic acid (myo-inositol hexaphosphate) play an important environmental role in poultry industry and have a health aspect in food industry. Novel biosensors have been developed for simple, one step quantitative phytic acid and phytase detection. A system based on the sequentially acting enzyme phytase and pyruvate oxidase (POD) was employed for the development of phytase and phytic acid biosensors. Poly(carbamoylsulphonate) (PCS) hydrogel immobilized POD electrode was applied for the detection of phytase. It was based on the indication of phosphate ions produced by the hydrolysis of phytic acid. The phytase biosensor showed a linear response ranging from 0.5 to 6.0 units/ml. A bi-enzyme sensor based on co-immobilization of phytase and POD was developed for the detection of phytic acid on the basis of amperometric detection of the enzymatically-generated hydrogen peroxide at 0.6 V versus Ag/AgCl. It showed a linear response ranging from 0.2 to 2.0 mM with a detection limit of 0.002 mM.
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| 12. |
- Mak, Wing Cheung, et al.
(författare)
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Protein particles formed by protein activation and spontaneous self-assembly
- 2010
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Ingår i: Advanced Functional Materials. - : John Wiley & Sons. - 1616-301X .- 1616-3028. ; 20:23, s. 4139-4144
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Tidskriftsartikel (refereegranskat)abstract
- In this article, a non-chemical crosslinking method is used to produce pure protein microparticles with an innovative approach, so-called protein activation spontaneous and self-assembly (PASS). The fabrication of protein microparticles is based on the idea of using the internal disulfide bridges within protein molecules as molecular linkers to assemble protein molecules into a microparticle form. The assembly process is triggered by an activating reagent–dithiothreitol (DTT), which only involved in the intermediate step without being incorporated into the resulting protein microparticles. Conventional protein microparticle fabrication methods usually involve emulsification process and chemical crosslink reactions using amine reactive reagents such as glutaraldehdye or EDC/NHS. The resulting protein microparticles are usually having various size distributions. Most importantly crosslinking reactions using amine reactive reagents will result in producing protein microparticles with undesired properties such as auto-fluorescence and high toxicity. In contrast to the conventional methods, our technology provides a simple and robust method to produce highly homogeneous, stable and non-fluorescence pure protein microparticles under mild conditions at physiological pH and temperature. The protein microparticles are found to be biodegradable, non-toxic to MDCK cells and with preserved biological activities. Results on the cytotoxcity study and enzyme function demonstrate the potential applications of the protein microparticles in the area of pharmaceutics and analytical chemistry.
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| 13. |
- Renneberg, Reinhard, et al.
(författare)
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Frieder scheller and the short history of biosensors
- 2008
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Ingår i: Advances in Biochemical Engineering/Biotechnology. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 0724-6145 .- 1616-8542. - 9783540752004 ; 109, s. 1-18
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This is a first attempt at a brief sketch of the history of biosensors. It is far from complete and rather unsystematic. Many names are still missing, and we apologize for this. But the authors hope to have laid a humble cornerstone for a future "Complete History of Biosensors". We hope that many of our colleagues will contribute!
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| 14. |
- Wen, Xiaogang, et al.
(författare)
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Dendritic nanostructures of silver : Facile synthesis, structural characterizations, and sensing applications
- 2006
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 22:10, s. 4836-4842
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Tidskriftsartikel (refereegranskat)abstract
- Silver nanodendrites are synthesized by a simple surfactant-free method using a suspension of zinc microparticles as a heterogeneous reducing agent. Structural characterizations suggest the preferential growth along <100> and <111> directions by oriented attachment of silver nanocrystals in the diffusion limit, leading to the formation of silver nanodendrites 20−30 nm in stem and branch diameter and 5−50 μm in length. Surface-enhanced Raman scattering studies show that the silver nanodentrites give an intensive and enhanced Raman scattering when pyridine was used as a probing molecule. We have also demonstrated that the silver nanodendrites increase the sensitivity of an electrochemical glucose biosensor by as much as 1−2 orders of magnitude.
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| 15. |
- Wing Cheung, Mak, et al.
(författare)
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Triggering of drug relase of particles in hair follicles
- 2012
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Ingår i: Journal of Controlled Release. - : Elsevier. - 0168-3659 .- 1873-4995. ; 160, s. 509-514
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Tidskriftsartikel (refereegranskat)abstract
- Particulate drug delivery via hair follicles represents a promising concept, although requirements are high. This process must be realized at the desired depth and at the appropriate time, due to the fact that the particles themselves are not able to overcome the follicular skin barrier.In the present study, a novel triggering concept for the release of a model drug from the delivering particles is presented based on the application of two different particle types of the same size, where one particle type is the drug carrier, and the second one is loaded with a protease. The latter particle type is supposed to interact with the drug-carrying particles to trigger the drug release. A mixture of both particles was applied onto porcine skin samples, followed by follicular analysis. As a control, the particles were applied unaided without protease, whereas one skin area remained untreated. The investigations revealed that the protease was able to release the model drug from the delivering particles in significant depths within the hair follicle (866 ± 62 nm). Additionally, an uptake of the model drug in the sebaceous gland was observed after release providing a promising novel approach for the development of treatment strategies for different skin diseases.
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