Lipase-mediated synthesis of sugar–PEG-based amphiphiles for encapsulation and stabilization of indocyanine green

Bio-catalytically synthesized sugar–PEG-based copolymers form stable micelles in an aqueous medium. These micelles from amphiphilic copolymer are able to efficiently solubilize and stabilize indocyanine green dye (ICG) under physiological conditions.

Synthesis of macromolecular systems via lipase catalyzed biocatalytic reactions: applications and future perspectives

This review highlights the application of lipases in the synthesis of pharmaceutically important small molecules and polymers for diverse applications.

Self-assembly, photoresponsive behavior and transport potential of azobenzene grafted dendronized polymeric amphiphiles

An azobenzene based light responsive polymeric system was developed to study the transport potential and photo-controlled release of encapsulated guests.

Novozym 435-catalyzed syntheses of polyesters and polyamides of medicinal and industrial relevance

The adverse impact of chemical and biochemical waste on the environment and human health poses a serious challenge in today's World. The best way to address these challenges is to reduce the waste by developing more efficient processes and technologies, based on the principles of "green chemistry". Some of these synthetic approaches involving the chemoenzymatic synthetic methodologies are discussed herein. These lead to the formation of unique nanomaterials with diverse applications, such as drugs/gene delivery systems, flame retardant materials, conducting polymers, controlled release systems, diagnostic agents, and polymeric electrolytes for nanocrystalline solar cells.

A bifunctional nanocarrier based on amphiphilic hyperbranched polyglycerol derivatives

We here report on the synthesis of a bifunctional nanocarrier system based on amphiphilic hyperbranched polyglycerol (hPG), which is modified by introducing hydrophobic aromatic groups to the core and retaining hydrophilic groups in the shell. "Selective chemical differentiation" and chemo-enzymatic reaction strategies were used to synthesize this new core-shell type nanocarrier. The system shows an innovative bifunctional carrier capacity with both polymeric and unimolecular micelle-like transport properties. Hydrophobic guest molecules such as pyrene were encapsulated into the hydrophobic core of modified hPG via hydrophobic interactions as well as π-π stacking, analogous to a unimolecular micelle system. A second guest molecule, which has a high affinity to the shell like nile red, was solubilized in the outer shell of the host molecule, thus connecting the nanocarrier molecules to form aggregates. This model is confirmed by UV-Vis, fluorescence, atomic force microscopy, and dynamic light scattering, as well as release studies triggered by pH-changes and enzymes. Encapsulated guest molecules, respectively in the core and in the shell, present different controlled release profiles. The bifunctional nanocarrier system is a promising candidate for simultaneous delivery of different hydrophobic drugs for a combination therapy, e.g., in tumor treatment.

Non-ionic dendronized multiamphiphilic polymers as nanocarriers for biomedical applications

A new class of non-ionic dendronized multiamphiphilic polymers is prepared from a biodegradable (AB)n-type diblock polymer synthesized from 2-azido-1,3-propanediol (azido glycerol) and polyethylene glycol (PEG)-600 diethylester using Novozym-435 (Candida antarctica lipase) as a biocatalyst, following a well-established biocatalytic route. These polymers are functionalized with dendritic polyglycerols (G1 and G2) and octadecyl chains in different functionalization levels via click chemistry to generate dendronized multiamphiphilic polymers. Surface tension measurements and dynamic light scattering studies reveal that all of the multiamphiphilic polymers spontaneously self-assemble in aqueous solution. Cryogenic transmission electron microscopy further proves the formation of multiamphiphiles towards monodisperse spherical micelles of about 7-9 nm in diameter. The evidence from UV-vis and fluorescence spectroscopy suggests the effective solubilization of hydrophobic guests like pyrene and 1-anilinonaphthalene-8-sulfonic acid within the hydrophobic core of the micelles. These results demonstrate the potential of these dendronized multiamphiphilic polymers for the development of prospective drug delivery systems for the solubilization of poorly water soluble drugs.

Biocatalytic route to sugar-PEG-based polymers for drug delivery applications

Sugar-PEG-based polymers were synthesized by enzymatic copolymerization of 4-C-hydroxymethyl-1,2-O-isopropylidene-β-L-threo-pentofuranose/4-C-hydroxymethyl-1,2-O-benzylidene-β-L-threo-pentofuranose/4-C-hydroxymethyl-1,2-O-isopropylidene-3-O-pentyl-β-L-threo-pentofuranose with PEG-600 dimethyl ester using Novozyme-435 (Candida antarctica lipase immobilized on polyacrylate). Carbohydrate monomers were obtained by the multistep synthesis starting from diacetone-D-glucose and PEG-600 dimethyl ester, which was in turn obtained by the esterification of the commercially available PEG-600 diacid. Aggregation studies on the copolymers revealed that in aqueous solution those polymers bearing the hydrophobic pentyl/benzylidene moiety spontaneously self-assembled into supramolecular aggregates. The critical aggregation concentration (CAC) of polymers was determined by surface tension measurements, and the precise size of the aggregates was obtained by dynamic light scattering. The polymeric aggregates were further explored for their drug encapsulation properties in buffered aqueous solution of pH 7.4 (37 °C) using nile red as a hydrophobic model compound by means of UV/vis and fluorescence spectroscopy. There was no significant encapsulation in polymer synthesized from 4-C-hydroxymethyl-1,2-O-isopropylidene-β-L-threo-pentofuranose because this sugar monomer does not contain a big hydrophobic moiety as the pentyl or the benzylidene moiety. Nile red release study was performed at pH 5.0 and 7.4 using fluorescence spectroscopy. The release of nile red from the polymer bearing benzylidene moiety and pentyl moiety was observed with a half life of 3.4 and 2.0 h, respectively at pH 5.0, whereas no release was found at pH 7.4.

Synthesis of biodegradable amphiphilic nanocarriers by chemo-enzymatic transformations for the solubilization of hydrophobic compounds

Polymeric nanocarriers possess advanced physicochemical properties that improve bioavailability, enhance cellular dynamics, and control target ability in drug delivery. In particular, dendritic polyglycerol is a promising new biocompatible scaffold for drug delivery. The present study explores the chemo-enzymatic modifications on dendritic hyperbranched polyglycerol (dPG) leading to amphiphilic polymeric architectures with easily hydrolysable ester linkages. Furthermore, these architectures were studied for nile red solubilization with capacity up to 5.6 mg/L at 0.1 wt % polymer conc. This corresponds to an ~10 fold increase in solubility of nile red. The release of nile red from these polymers was observed with a half life of 8 hours at pH 5.0, while no release was found at pH 7.4. The cell viability studies of our polymeric architectures showed them to be relatively nontoxic and to have the potential for future drug delivery applications.