Sung Chul Yoon

Soil bacteria accumulate polyesters (typically poly([R]-3-hydroxybutyrate (PHB), in which one end of the chain terminates with a carboxyl group) in the form of hydrated, amorphous nanogranules in cells. However, it is not clear what drives the structure of these biomaterials inside bacterial cells. Here, we determined that calcium guides intracellular formation of PHB nanogranules. Our systematic study using the surface zeta potential measurement and the carboxyl-specific SYTO-62 dye binding assay showed that the terminal carboxyl is not exposed to the granule surface but is buried inside native “unit-granules” comprising the mature granule. Extracellular Ca²⁺ was found to mediate the formation of these PHB unit-granules, with uptaken Ca²⁺ stored inside the granules. Comparative [Ca²⁺]-dependent fluorescence spectroscopy revealed that the native granules in Cupriavidus necator H16 act as a Ca²⁺ storage system, presumably for the regulation of its cytosolic Ca²⁺ level, but those from recombinant Escherichia coli do not. This study reveals intimate links between Ca²⁺ and native granule formation, and establishes a novel mechanism that intracellular PHB granules function as Ca²⁺ storage in order to relieve soil bacteria from Ca²⁺ stress.

Despite several advancements in chemotherapy, cancer is still the second most frequent cause of mortality worldwide. Drug delivery to solid tumors is one of the most challenging aspects in cancer therapy. In pharmaceutical industries biodegradable polymeric nanoparticles as drug carriers have attracted great research interest because of their biocompatibility, biodegradability and sustained release of drugs. In our study we prepared poly(4-hydroxybutyrate)-mPEG (P(4HB)-mPEG) nanocarriers for the delivery of cisplatin as anticancer drug to mouse hippocampal HT22 cells. P(4HB) is more suitable candidate to be utilized in pharmaceutical industries due to its wide medical applications. P(4HB) is a homopolymer of 4-hydroxybutyrate (4HB), and belongs to a diverse class of materials called polyhydroxyalkanoates (PHA) produced by microorganisms inside the cells as energy storage materials. P(4HB) has certain unique properties such as biocompatibility and rapid in vivo degradation, which differentiate it from others PHA based polymers. Novel amorphous amphiphilic block copolymer P(4HB)-mPEG nanocarriers were prepared and characterized. Flow cytometry, and confocal microscopy revealed a suppression effect by the cisplatin loaded nanocarriers on HT22 cell growth, and enhancement of apoptotic process of the cells compared to free drug treated cells. The amorphous polymeric nanocarriers could be effective vehicles for the sustained delivery of toxic anticancer drugs for the therapy of cancer.

Phasin protein (PhaP) is known to anchor into the matrix of phospholipid surrounding polyhydroxyalkanoic acid (PHA) inclusion bodies formed in bacterial cells and regulate the size of the granules, as well as the number of PHA granules. To investigate the effect of phasin on the formation of artificial poly(3‐hydroxybutyrate) (P(3HB)) granules in vitro, (His)₆‐tagged or GST‐fusion recombinant phasin was prepared and utilized for the artificial granule preparation. In addition, a P(3HB) depolymerase was coloaded with the recombinant phasin to prepare self‐degradable phasin‐coated P(3HB) granules. A water/chloroform two‐phase emulsion technique was used, in which the emulsification was carried out by sonication, and the chloroform in the emulsion was removed by stirring‐aided evaporation at room temperature or 65°C. Slower chloroform removal at room temperature produced better spherically shaped P(3HB) nanogranules, which were uniformly sized (∼100 to 200 nm in diameter). The self‐degradability of P(3HB) depolymerase‐loaded P(3HB) nanogranules was investigated. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41074.

Pseudomonas aeruginosa, an opportunistic human pathogen is known to synthesize rhamnolipid and polyhydroxyalkanoic acid (PHA) of which the acyl-group precursors (e.g., (R)-3-hydroxydecanoic acid) are provided through RhlA and PhaG enzyme, respectively, which have 57% gene sequence homology. The inhibitory effect of three 2-bromo-fatty acids of 2-bromohexanoic acid (2-BrHA), 2-bromooctanoic acid (2-BrOA) and 2-bromodecanoic acid (2-BrDA) was compared to get an insight into the biochemical nature of their probable dual inhibition against the two enzymes. The 2-bromo-compounds were found to inhibit rhamnolipid and PHA synthesis simultaneously in alkyl-chain-length dependent manner at several millimolar concentrations. The separate and dual inhibition of the RhlA and PhaG pathway by the 2-bromo-compounds in the wild-type cells was verified by investigating their inhibitory effects on the rhamnolipid and PHA synthesis in P. aeruginosa ΔphaG and ΔrhlA mutants. Unexpectedly, the order of inhibition strength was found 2-BrHA (≥90% at 2 mM) > 2-BrOA > 2-BrDA, equally for all of the rhamnolipids and PHA synthesis, swarming motility and biofilm formation. We suggest that the novel strongest inhibitor 2-BrHA could be potentially exploited to control the rhamnolipid-associated group behaviors of this pathogen as well as for its utilization as a lead compound in screening for antimicrobial agents based on new antimicrobial targets.

When dealing with nano targeted drug delivery process the significant area of virtual reality application can be visualizing real time process and simulating it at nano-scale, since the effectiveness of a drug primarily depends on the affected cell and targeted doze. This paper proposes virtual reality (VR) as a tool to analyze and simulate nanoparticles (NPs) manipulation, in this paper amorphous NPs are analyzed and simulated in virtual environment. Haptic guides virtualizing the atomic force microscope (AFM) is applied in the virtual environment which allows the operators to sense and touch the NPs when evaluating its structure, drug release time, and behavioral study. Cisplatin was loaded as a modal drug to the self-assembled amorphous copolymer P(3HV-co-4HB)-b-mPEG NPs, where the efficiency and bioavailability of Cisplatin was further investigated. The prepared NPs when simulated in virtual environment proved to show good biocompatibility. Results showed that amorphous polymeric NPs could be efficient vehicles for the constant and targeted delivery of toxic anticancer drugs.

Despite the recent research interest in the field of nanoparticles delivery system, their structure modification and transport behavior of various hydrophobic drugs is poorly developed. In this article the synthesis of novel amphiphilic diblock copolymer poly([R]-3-hydroxyvalerate)-block-monomethoxy poly(ethylene glycol) (PHV-block-mPEG) was undertaken by modifying the structure of biodegradable and hydrophobic poly([R]-3-hydroxyvalerate) (PHV) with hydrophilic monomethoxy poly(ethylene glycol) (mPEG). The chemical combination of the two blocks was carried out in the melt using bis(2-ethylhexanoate) tin as transesterification catalyst. The synthesized product was characterized by gel permeation chromatography (GPC), ¹H nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC) analysis. The block copolymer self-assembled into amphiphilic nanoparticles with a core of hydrophobic PHV and a shell of hydrophilic mPEG in aqueous solution. Characterization of the nanoparticles showed the formation of discrete, spherically shaped nanoparticles with mean particle size of 200±1 nm and zeta potential of −14±1 mV. A hydrophobic drug thymoquinone was efficiently incorporated into the core hydrophobic domain of the nanoparticles and its release kinetics was studied in vitro. The amphiphilic PEGylated nanoparticles showed biocompatibility when checked in neuronal hippocampal cells of prenatal rat. Our results suggest that the amphiphilic nanoparticles with core–shell structures are potentially useful to develop novel drug carriers.