Live-cell encapsulation

It appears that none of these process techniques is dominant, at least with the lactide/glycolide materials. Researchers have considerable choices available in regard to fabrication of microspheres from these polymers. The most commonly used procedures employ relatively mild conditions of pH and temperature and are usually quite compatible with the bioactive agents to be entrapped, including proteins and other macromolecules. Only in the case of live virus and living cell encapsulation have serious deactivation problems been encountered and those problems were due to solvents used in the process. 

Figure 2 Neurotech s proprietary encapsulated cell therapy. Encapsulated cell implants consist of living cells encapsulated within semipermeable polymer membranes and supportive matrices (A) longitudinal view of a cell-containing implant (B) intraocular placement of an encapsulated cell implant. Source From Ref. 11.

Diaspro A, Silvano D, Krol S, Cavalleri O, Gliozzi A. 2002. Single living cell encapsulation in nano organized polyelectrol5de shells. Langmuir 18(13) 5047 5050. 

Chen, H. Ouyang, W. Jones, M. Metz, T. Martoni, C. Haque, T. Cohen, R. Lawuyi, B. Prakash, S. Preparation and characterization of novel polymeric microcapsules for live cell encapsulation and therapy. Cell Biochem. Biophys. 2007, 47 (1), 159-167. 

POLYMER MODIFICATIONS AND RECENT TECHNOLOGICAL ADVANCES TOWARD LIVE CELL ENCAPSULATION AND DELIVERY... 

Poly-L-glutamic acid Glycol-CS Platelets NR Model for live cell encapsulation [38]... 

Lu HF, Targonsky ED, Wheeler MB, Cheng YL. Thermally induced gelable p>olymer networks for living cell encapsulation. Biotechnol Bioeng 2007 96 146-155. 

Griffin, D. R. and Kasko, A. M. (2012). Photodegradable macromers and hydrogels for live cell encapsulation and release. Journal of the American Chemical Society, 134,13103-13107. 

Lu, H.F., Targonsky, E.D., Wheeler, M.B., Cheng, Y.L., 2007. Thermally induced gelable polymer networks for living cell encapsulation. Biotechnol. Bioeng. 96 (1), 146-155. 

Chenite et al. reported on thermosensitive chitosan gels for encapsulating living cells and therapeutic proteins they are liquid below room temperature but form monolithic gels at body temperature [220-223]. 

Fig. 16 Fluorescence images of LIVE/DEAD assays of the L929 cells encapsulated for 4 days (a) in the miniaturized PMBV/PVA hydrogel formed in the microfluidic chip, and (b) in the bulk PMBV/PVA hydrogel formed in the 96-well microplate. Green fluorescence indicates live cells and red fluorescence indicates dead cells. Scale bar 100 pm...

Teramura Y, Iwata H (2009) Islet encapsulation with living cells for improvement of biocompatibility. Biomaterials 30 2270-2275... 

Release of DNA in vivo takes place due to the increased acidic conditions inside living cells that result in the destabilization of the ORMOSIL-DNA complex. SiCVbased nanoparticles, in fact, do not release encapsulated biomolecules because of the strong hydrogen bonding between the biomolecule s polar centres and the silanols at the cage surface (as ORMOSIL-entrapped hydrophobic molecules are not leached in aqueous systems due to strong hydrophobic interactions).17... 

Bucka SM, Xua H, Brasuel M, Philbert MA, Kopelman R (2004) Nanoscale probes encapsulated by biologically localized embedding (PEBBLEs) for ion sensing and imaging in live cells. Talanta 63 41-59... 

Miwa and Yamamoto (31) described a simple and rapid method with high accuracy and reliability for the determination of C8 0-C22 6 fatty acids, which occur in esterified forms in dietary fats and oils and in living cells [the biological effects of routinely consumed fats and oils are of wide interest because of their impact on human health and nutrition (28,29), in particular, the ratio of cu-3 polyunsaturated fatty acid to w-6 polyunsaturated fatty acids (w-3/cu-6) seems to be associated with atherosclerosis and breast and colon cancers (30)]. They report improved separation of 29 saturated and mono- and polyunsaturated fatty acids (C8-C22), including cis-trans isomers and double-bond positional isomers, as hydrazides formed by direct derivatization with 2-nitrophenylhydrazine hydrochloride (2-NPH HC1) of saponified samples without extraction. The column consisted of a J sphere ODS-M 80 column (particle size 4 /xm, 250 X 4.6-mm ID), packed closely with spherical silica encapsulated to reach a carbon content of about 14% with end-capped octadecyl-bonded-spherical silica (ODS), maintained at 50°C. The solvent system was acetonitrile-water (86 14, v/v) maintained at pH 4-5 by adding 0.1 M hydrochloric acid with a flow rate of 2.0 ml/min. Separation was performed within only 22 min by a simple isocratic elution (Fig. 6). The resolution of double-bond positional isomers, such as y-linolenic ( >-6) and a-linolenic acid ( >-3) hydrazides and w-9, >-12, and >-15 eicosenoic acid hydrazides was achieved by use of this column. 

Field cages can also be used to create layered particle aggregates of defined shape which can then be made permanent by e.g. photopolymerisation (Fig. 6) [44]. Possible applications of this technique range from the encapsulation of drugs in micron scale structures with controlled release pores to the creation of ordered aggregates of living cells. 

Skirtach AG, Javier AM, Kreft O et al (2006) Laser-induced release of encapsulated materials inside living cells. Angew Chem Int Ed 45 4612-4617... 

PEBBLEs are water-soluble nanoparticles based on biologically inert matrices of cross-linked polymers, typically poly(acrylamide), poly(decylmethacrylate), silica, or organically modified silicates (ORMOSILs), which encapsulate a fluorescent chemo-sensor and, often, a reference dye. These matrices have been used to make sensors for pH, metal ions, as well as for some nonionic species. The small size of the PEBBLE sensors (from 20 to 600 nm) enables their noninvasive insertion into a living cell, minimizing physical interference. The semipermeable and transparent nature of the matrix allows the analyte to interact with the indicator dye that reports the interaction via a change in the emitted fluorescence. Moreover, when compared to naked chemosensors, nanoparticles can protect the indicator from chemical interferences and minimize its toxicity. Another important feature of PEBBLEs, particularly valuable in intracellular sensing applications, is that the polymer matrix creates a separate... 

A membrane, whether naturally occurring or synthetic, is taken to be a structure with a large aspect ratio in which one of its three dimensions is much thinner than the other two dimensions. The simplest form of a membrane is thus a flat diaphragm, but the above description also applies to hollow fiber, or even a spherical or bag-like encapsulation domain surrounding living cells. 

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