TY  - JOUR
A1  - Schmitz-Hertzberg, Sebastian-Tim
A1  - Mak, Wing Cheung
A1  - Lai, Kwok Kei
A1  - Teller, Carsten
A1  - Bier, Frank Fabian
T1  - Multifactorial design of Poly(D, L-lactic-co-glycolic acid) capsules with various release properties for differently sized filling agents
JF  - Journal of applied polymer science
N2  - The hydrolytic degradation and corresponding content release of capsules made of poly(d,l-lactic-co-glycolic acid) (PLGA) strongly depends on the composition and material properties of the initially applied copolymer. Consecutive or simultaneous release from capsule batches of combinable material compositions, therefore, offers high control over the bioavailability of an encapsulated drug. The keynote of this study was the creation of a superordinated database that addressed the correlation between the release kinetics of filling agents with different molecular weights from PLGA capsules of alternating composition. Fluorescein isothiocyanate (FITC)-dextran (with molecular weights of 4, 40, and 2000 kDa) was chosen as a model analyte, whereas the copolymers were taken from various 50:50 PLGA, 75:25 PLGA, and polylactide blends. With reference to recent publications, the capsule properties, such as the size, morphology, and encapsulation efficiency, were further modified during production. Hence, uniform microdisperse and polydisperse submicrometer nanocapsules were prepared by two different water-in-oil-in-water emulsification techniques, and additional effects on the size and morphology were achieved by capsule solidification in two different sodium salt buffers. The qualitative and quantitative examination of the physical capsule properties was performed by confocal laser scanning microscopy, scanning electron microscopy, and Coulter counting techniques to evaluate the capsule size distribution and the morphological appearance of the different batches. The corresponding agent release was quantified by fluorescence measurement of the FITC-dextran in the incubation media and by the direct measurement of the capsule brightness via fluorescence microscopy. In summary, the observed agent release showed a highly controllable flexibility depending on the PLGA blends, preparation methods, and molecular weight of the used filling substances. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4219-4228, 2013
KW  - biodegradable copolymers (PLGA)
KW  - microcapsules
KW  - submicrometer
KW  - nanocapsules
KW  - FITC-dextran release
KW  - drug delivery system
KW  - biomedical applications
Y1  - 2013
U6  - https://doi.org/10.1002/app.39537
SN  - 0021-8995
SN  - 1097-4628
VL  - 130
IS  - 6
SP  - 4219
EP  - 4228
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Mak, Wing Cheung
A1  - Cheung, Kwan Yee
A1  - Trau, Dieter
A1  - Warsinke, Axel
A1  - Scheller, Frieder W.
A1  - Renneberg, Reinhard
T1  - Electrochemical bioassay utilizing encapsulated electrochemical active microcrystal biolabels
N2  - 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 (SIP) ratio of 10(4)-10(5). 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  g(- 1) L-1 with a detection limit of 2.82  g L-1
Y1  - 2005
SN  - 0003-2700
ER  -