Thermal characterization of poly(ethylene glycol)-poly(D,L-lactide) block copolymer micelles based on pyrene excimer formation

Poly(ethylene glycol)--poly(D,L-lactide) (PEG-PDLLA) block copolymers were prepared by anionic ring-opening polymerization, resulting in block sizes effectively controlled by initial monomer/initiator ratios and low molecular weight distributions (<1.12). A pyrene derivative (1-pyrenyl carbonyl cyanide--Py) was conjugated to the end of the hydrophobic block (PDLLA) in a quantitative manner, with coupling efficiencies >95%. The so-obtained PEG-PDLLA-Py copolymers displayed fluorescent properties that were associated with the pyrene monomers, when placed in good solvents for both the hydrophilic and hydrophobic blocks. When placed in selective solvents, these copolymers self-assembled into micelles in the 30-nm range, also with low particle size distributions (<0.09), within which Py could be readily entrapped in the hydrophobic PDLLA core. Py entrapment resulted in the formation of excimers, as evident from fluorescence measurements. Observation of excimer formation/dissociation further conveyed information on the physicochemical properties of the core. Thermal characterization of these systems showed that an increase in the temperature resulted in changes in the properties of excimer fluorescence, an occurrence attributed to a higher mobility of the otherwise glassy PDLLA. This, in turn, greatly affected the inter-molecular distance between pyrene molecules, a crucial factor for excimer formation. The glass transition of the PDLLA block, approximately 38 degrees C, defined the onset for increasing chain mobility and whence excimer dissociation. Excimer fluorescence appeared to be time-dependent. Based on these observations, chain exchange processes were clearly evidenced through the time-dependent dissociation of excimers into unimers, a process that was influenced by changes in temperature.

Ligand-installed PEGylated bionanosphere

The synthesis of poly(ethylene glycol)-b-poly(2-N,N-dimethylaminoethylmethacrylate) processing an acetal group at the PEG chain end (acetal-PEGPAMA) is reported. The obtained acetal-PEGPAMA block copolymer was found to reduce tetrachloroauric acid at room temperature to produce gold nanoparticles. The size of these nanoparticles was controllable in the range of 6 to 13 nm by changing the initial Au3+: polymer ratio. In addition to the reduction of tetrachloroauric acid, acetal-PEGPAMA bonds on the surface of the obtained gold nanoparticles to improve their dispersion stability in an aqueous medium even at a salt concentration as high as two. Biotinyl-PEGPAMA-anchored gold nanoparticles undergo specific aggregation in the presence of streptavidin thereby revealing their promising utility as colloidal sensing systems for use in biological systems. Biotin-PEGPAMA can also be utilised for the preparation of a functionally PEGylated quantum dot (QD). When CdCl2 and Na2S were mixed in aqueous media in the presence of the biotin-PEGPAMA, a CdS QD with an approximately 5 nm size was prepared. The polyamine segment was anchored onto the surface of the formed CdS nanoparticle, whereas the PEG segment was tethered onto the surface to form a hydrophilic palisade, thus improving the dispersion stability in aqueous media even under a high salt concentration condition. An effective fluorescent resonance energy transfer (FRET) was observed by the specific interaction of the biotin-PEGPAMA stabilised CdS QD with TexasRed-labelled streptavidin with the physiological ionic strength of 0.15 M. The extent of the energy transfer was in proportion to the concentration of the TexasRed-streptavidin. This FRET system using the PEGylated CdS QD coupled with fluorescent-labelled protein can be utilised as a highly sensitive bioanalytical system.

Characterization of aldehyde-PEG tethered surfaces: influence of PEG chain length on the specific biorecognition

A functionalized poly(ethylene glycol) (PEG) layer possessing a reactive aldehyde group at the free end of the tethered PEG chain was constructed by simple coating on the substrate, using the acetal-PEG/poly(DL-lactide) block copolymer, followed by the hydrolysis of the acetal end group by an acid treatment. The reactivity of the aldehyde group at the distal end of the PEG tethered chain was evaluated via a reductive amination using 4-amino-2,2,6,6-tetramethylpiperidinyloxy as the model compound. Further conjugation of the aldehyde group with sugar moieties has demonstrated an increased recognition ability with lectins with an increasing PEG chain length, which was attributable to the mobility of the chain end. These results provide a novel idea for highly sensitive biorecognition, suggesting a method to create highly selective biosensing surfaces that are able to prevent the undesired nonspecific adsorption of biocomponents.

Polyion Complex Micelles of pDNA with Acetal-poly(ethylene glycol)-poly(2-(dimethylamino)ethyl methacrylate) Block Copolymer as the Gene Carrier System: Physicochemical Properties of Micelles Relevant to Gene Transfection Efficacy

An acetal-poly(ethylene glycol)-poly(2-(dimethylamino)ethyl methacrylate) (acetal-PEG-PAMA) block copolymer spontaneously associated with plasmid DNA (pDNA) to form water-soluble complexes (polyion complex micelle: PIC micelle) in aqueous solution. Physicochemical characteristics and transfection efficiency of the PIC micelles thus prepared were studied here, focusing on the residual molar mixing ratio (N/P ratio) of AMA units in acetal-PEG-PAMA to the phosphate units in pDNA. With the N/P ratio increasing to unity, acetal-PEG-PAMA cooperatively formed complex micelles with pDNA through electrostatic interaction, allowing pDNA to condense effectively. Dynamic light scattering measurements revealed that the PIC micelle at N/P > or = 3 had a constant size of approximately 90-100 nm. Eventually, acetal-PEG-PAMA/pDNA micelles underwent no precipitation even after long-term storage for more than 1 month at all N/P ratios. The PIC micelles were stable even in the presence of excess polyanions, poly(vinyl sulfate), in contrast to polyplexes based on the PAMA homopolymer, yet this stabilization effect was highly dependent on the N/P ratio to reach a plateau at N/P = 3-4. This character may be attributed to the increased hydrophobicity in the vicinity of the complexed pDNA. Furthermore, the pDNA in the micelle was adequately protected from DNase I attack. The transfection ability of the PIC micelles toward 293 cells was remarkably enhanced with an increasing N/P ratio as high as 25. The zeta-potential of the micelles with a high N/P ratio was an appreciably large positive value, suggesting a noncooperative micelle formation. This deviated micellar composition with an excess cationic nature as well as the presence of free acetal-PEG-PAMA may play a substantial role in the enhanced transfection efficiency of the PIC micelle system in the high N/P ratio (approximately 25) region.

Novel molecular recognition via fluorescent resonance energy transfer using a biotin-PEG/polyamine stabilized CdS quantum dot

A novel functionally PEGylated quantum dot (QD) was prepared by a coprecipitation method in the presence of the biotin-PEG/polyamine block copolymer. When CdCl2 and Na2S were mixed in aqueous media in the presence of the biotin-PEG-b-poly(2-(N,N-dimethylamino)ethyl methacrylate) [biotin-PEG/PAMA], a CdS QD with a size of ca. 5 nm was prepared. The polyamine segment was anchored on the surface of the formed CdS nanoparticle, whereas the PEG segment was tethered on the surface to form a hydrophilic palisade, thus improving the dispersion stability in aqueous media even under a high salt concentration condition. An effective fluorescent resonance energy transfer (FRET) was observed by the specific interaction of the biotin-PEG/PAMA stabilized CdS QD with TexasRed-labeled streptavidin of the physiological ionic strength of 0.15 M. The extent of the energy transfer was in proportion to the concentration of the TexasRed-streptavidin. This FRET system using the PEGylated CdS QD coupled with fluorescent-labeled protein can be utilized as a highly sensitive bioanalytical system.

Lactose-conjugated polyion complex micelles incorporating plasmid DNA as a targetable gene vector system: their preparation and gene transfecting efficiency against cultured HepG2 cells

alpha-Lactosyl-poly(ethylene glycol)-poly(2-(dimethylamino)ethyl methacrylate) block copolymer (lactose-PEG-PAMA) was synthesized to construct a PIC micellar-type gene vector potentially useful for selective transfection of hepatic cells. Lactose-PEG-PAMA spontaneously formed a polyion complex (PIC) micelle with plasmid DNA (pDNA) encoding luciferase (pGL3-Luc) in aqueous solution without any precipitate formation. The lactosylated PIC micelle thus prepared achieved substantially higher transfection efficiency compared to the control PIC micelle without lactose moieties against HepG2 cells possessing asialoglycoprotein (ASGP) receptors recognizing the beta-d-galactose residue. This pronounced transfection efficacy of the lactosylated PIC micelle was inhibited by the addition of excess asialofetuin (ASF), a natural ligand against the ASGP receptor, indicating ASGP receptor-mediated endocytosis to be a major route of the cellular uptake of the lactosylated micelles. Notably, the lactosylated PIC micelle revealed enhanced transfection compared to the control PIC micelle at a lower dose of pDNA, demonstrating the feasibility of using the ligand-conjugated PIC micellar vector for gene delivery to targeted cells.

Synthesis of Heterotelechelic Poly(ethylene glycol) Derivatives Having α-Benzaldehyde and ω-Pyridyl Disulfide Groups by Ring Opening Polymerization of Ethylene Oxide Using 4-(Diethoxymethyl)benzyl Alkoxide as a Novel Initiator

New heterotelechelic PEG-containing benzaldehyde and 2-pyridyldithio endgroup (CHO-Bz-PEG-SSpyl) was synthesized with high efficiency and high selectivity. An alpha-benzylacetal-omega-methansulfonyl PEG was prepared as the first step to CHO-Bz-PEG-SSpyl through the ring-opening polymerization of ethylene oxide (EO) initiated by potassium 4-(diethoxymethyl)benzyl alkoxide (PDA), followed by the successive conversion of the end-alkoxide group to a methanesulfonyl group and then to dithiocarbonate derivative. Further, deprotection of the dithiocarbonate derivative and subsequent conversion to the 2-pyridyldithio group at the omega-end was successfully performed through a one-step reaction to form alpha-benzylacetal-omega-2-pyridyldithio PEG (aceBz-PEG-SSpyl). The aceBz-PEG-SSpyl was then treated with an aqueous HCl solution (pH 5.0) to generate the benzaldehyde group at the alpha-end. Molecular functionalities of the benzaldehyde and the 2-pyridyldithio end group of the heterotelechelic PEG (CHO-Bz-PEG-SSpyl) thus prepared were characterized by (1)H and (13)C NMR, showing that the reaction proceeded almost quantitatively. The benzaldehyde end group is available to conjugate various ligands having a primary amino group by forming the pH-sensitive imine linkage (-N=CHC(6)H(4)-).

Nanospheres for DNA separation chips

We report here a technology to carry out separations of a wide range of DNA fragments with high speed and high resolution. The approach uses a nanoparticle medium, core-shell type nanospheres, in conjunction with a pressurization technique during microchip electrophoresis. DNA fragments up to 15 kilobase pairs (kbp) were successfully analyzed within 100 s without observing any saturation in migration rates. DNA fragments migrate in the medium while maintaining their characteristic molecular structure. To guarantee effective DNA loading and electrofocusing in the nanosphere solution, we developed a double pressurization technique. Optimal pressure conditions and concentrations of packed nanospheres are critical to achieve improved DNA separations.

Preparation of functionally Pegylated gold nanoparticles with narrow distribution through autoreduction of auric cation by alpha-biotinyl-PEG-block-[poly(2- (N,N-dimethylamino)ethyl methacrylate)]

PEGylated gold nanoparticles with biotin moieties installed at the distal end of the PEG tethered chains were prepared by the autoreduction of HAuCl4 catalyzed by alpha-biotinyl-PEG-block-poly[2-(N,N-dimethylamino)ethyl methacrylate] (biotinyl-PEG/PAMA) in aqueous medium at room temperature. The size of the gold nanoparticles was controllable in a range of 6-13 nm by changing the initial Au3+/polymer ratio, while retaining their narrow size distribution. The dispersion stability of the nanoparticles in aqueous medium was extremely high even under the condition of salt concentration as high as I = 2.0. Biotinyl-PEG/PAMA-anchored gold nanoparticles underwent specific aggregation in the presence of streptavidin, revealing their promising utility as colloidal sensing systems applicable under biological condition.

A Core−Shell-Type Fluorescent Nanosphere Possessing Reactive Poly(ethylene glycol) Tethered Chains on the Surface for Zeptomole Detection of Protein in Time-Resolved Fluorometric Immunoassay

To increase the sensitivity and to depress the nonspecific binding in biochemical assays, a new core-shell-type fluorescent nanosphere (106.7 nm) covalently conjugated with antibody was prepared. The core-shell-type nanosphere was constructed by dispersion radical polymerization of styrene in the presence of heterotelechelic poly(ethylene glycol) (PEG) macromonomer, which has a polymerizable vinylbenzyl group at one end and a primary amino group at the other chain end and used as well as a surfactant. The resulting nanosphere had PEG tethered chains on the surface, which possesses a primary amino group at the distal end of the PEG chain (NH(2) nanosphere). The fluorescent NH(2) nanosphere was constructed by incorporating fluorescent europium chelates with beta-diketonate ligands in the core of the NH(2) nanosphere by means of a physical entrapment method. The primary amino groups on the fluorescent NH(2) nanosphere were then converted to maleimide groups using a hetero cross-linker. The resulting nanosphere had maleimide groups on the surface (maleimide nanosphere), onto which proteins having SH group in the molecule could be covalently conjugated quantitatively without any denaturation of the proteins under the milder reaction condition. The applicability of the fluorescent nanosphere was tested in a model sandwich immunoassay for alpha-fetoprotein (AFP) determination. Anti-human AFP Fab' fragment was covalently conjugated onto the maleimide nanosphere (Fab' nanosphere), and it was used for the solid-phase time-resolved fluorometric immunoassay of AFP. The detection limit (mean + 2 SD) was 0.040 pg/mL or 57.1 zmol (57.1 x 10(-)(21) mol, M(w,AFP) = 70000) for AFP. The imprecision (concentration CV) over the whole assay range was 1.1% (100 pg/mL) - 17.1% (0.1 pg/mL), even though with this conjugation of antibody to the nanosphere, the nonspecific binding was practically negligible (0.0008%) and even when approximately 1.9 x 10(9) particles of the Fab' nanosphere were applied to the microtitration well.

pH-responsive oligodeoxynucleotide (ODN)-poly(ethylene glycol) conjugate through acid-labile beta-thiopropionate linkage: preparation and polyion complex micelle formation

An oligodeoxynucleotide (ODN) conjugated to poly(ethylene glycol) (PEG) through a pH-responsive ester linkage (PEG-ODN conjugate) was successfully synthesized by the Michael reaction of 3'-thiol-modified ODN with a heterobifunctional PEG bearing an acetal group at the alpha-end and an acrylate group at the omega-end (acetal-PEG-acrylate), aimed at the development of a novel ODN delivery system. The prepared PEG-ODN conjugate and linear-poy(ethyleneimine) (L-PEI) spontaneously associated to form a polyion complex (PIC) micelle whose diameter and polydispersity index micro(2)/Gamma(2)) were 102.5 nm and 0.096 as determined by DLS measurements, respectively. Both the PEG-ODN conjugate and PIC micelle showed cleavage of the ester linkage at the endosomal pH (=5.5), suggesting that the PIC micelle is anticipated to release the ODN in the intracellular compartment. Furthermore, the PEG-ODN conjugate in the PIC micelle was stable against deoxyribonuclase (DNase I) digestion and has no interaction with the serum component because of the steric stabilization of the highly dense PEG corona surrounding the PIC core. These characteristics of the PIC micelles entrapping the PEG-ODN conjugate are promising for their utility as a novel ODN delivery system.

Sugar-installed block copolymer micelles: their preparation and specific interaction with lectin molecules

Several types of sugar-installed poly(ethylene glycol)/poly(DL-lactide) (sugar-PEG/PLA) block copolymers were synthesized. The synthesized block copolymer forms a core-shell type polymeric micelle in aqueous media possessing sugar molecules on its surface. Specific recognition of lectin proteins with the sugar molecules on the micelle surface was observed. Both the galactose- and lactose-installed micelles specifically interacted with RCA-1; on the other hand the mannose-installed micelle interacted specifically with Con A. With a lectin-immobilized affinity column, the cluster effect of the sugar molecule on the micelle surface was clearly observed.

PEGylated nanoparticles for biological and pharmaceutical applications

The utility of polymeric micelles formed through the multimolecular assembly of block copolymer was comprehensively described as novel core-shell typed colloidal carriers for drug and gene targeting. Particularly, novel approaches for the formation of functionalized poly(ethylene glycol) (PEG) layers as hydrophilic outer shell were focused to attain receptor-mediated drug and gene delivery through PEG-conjugated ligands with a minimal non-specific interaction with other proteins. Surface organization of block copolymer micelles with cross-linking core was also described from a standpoint of the preparation of a new functional surface-coating with a unique macromolecular architecture. The micelle-attached surface and the thin hydrogel layer made by layered micelles exhibited nonfouling properties and worked as the reservoir for hydrophobic reagents. Furthermore, the potential utility of multimolecular assembly derived from heterobifunctional PEGs and block copolymers were explored to systematically modify the properties of metal and semiconductor nanostructures by controlling their structure and their surface properties, making them extremely attractive for use in biological and biomedical applications.

Lactose-installed poly(ethylene glycol)-poly(d,l-lactide) block copolymer micelles exhibit fast-rate binding and high affinity toward a protein bed simulating a cell surface. A surface plasmon resonance study

Lactose molecules were installed on the surface of poly(ethylene glycol)-poly(d,l-lactide) (PEG-PLA) block copolymer micelles in the scope of seeking specific recognition by cell surface receptors at hepatic sites. This, in turn, is expected to result in the formation of a complex displaying prolonged retention times and thus enhanced cellular internalization by receptor-mediated endocytosis. The so-obtained particles based on a block copolymer of molecular weight 9400 g/mol (4900/4500 g/mol for the PEG and PLA blocks, respectively) were found to have an average hydrodynamic diameter of 31.8 nm, as measured by dynamic light scattering. Further, the particle size distribution (micro(2)/Gamma(2)) was found to be lower than 0.08. Lactose-PEG-PLA micelles (Lac-micelles) were then injected over a gold surface containing Ricinus communis agglutinin lectins simulating the aforementioned glycoreceptors, and their interaction was studied by surface plasmon resonance. Then, a kinetic evaluation was carried out, by fitting the observed data mathematically. It appears that Lac-micelles bind in a multivalent manner to the lectin protein bed, which logically results in low dissociation constants. Micelles bearing a ligand density of 80% (Lac-micelles 80%: 80 lactose molecules per 100 copolymer chains) exhibit fast association phases (k(a1) = 3.2 x 10(4) M(-)(1) s(-)(1)), but also extremely slow dissociation phases (k(d1) = 1.3 x 10(-)(4) s(-)(1)). Recorded sensorgrams were fitted with a trivalent model, conveying a calculated equilibrium dissociation constant (K(D1) = k(d1)/k(a1)) of about 4 nM. The importance of cooperative binding was also assessed, by preparing Lac-micelles bearing different ligand densities, and by discussing the influence of the latter on kinetic constants. Interestingly enough, whereas Lac-micelles 80% bind in a trivalent manner to the protein bed, Lac-micelles 20% are still capable of forming bivalent complexes with the same protein bed (K(D1) = 1360 nM). Therefore, despite enhanced kinetic values brought about by a supplementary bond, lower ligand densities appear to be more effective on a molecular basis.

Temperature-related change in the properties relevant to drug delivery of poly(ethylene glycol)-poly(D,L-lactide) block copolymer micelles in aqueous milieu

The block copolymers of poly(ethylene glycol) and poly(D,L-lactide) (PEG-PDLLA), the latter having a glass transition temperature (T(g)) around the physiological condition, was self-assembled into polymer micelles with a narrow and unimodal distribution in aqueous milieu either by dialysis or by the ultrasonication-aided dispersion method. The 1H NMR measurement of the PEG-PDLLA micelles in D(2)O revealed a gradual increase in the chain mobility of PDLLA segment in the core of the micelles at a temperature range above the T(g) of PDLLA. The critical association concentration (c.a.c.) of the PEG-PDLLA micelles was determined at various temperatures (25-55 degrees C) using pyrene as a probe to monitor the change in the polarity of the microenvironment in the micelle. An Arrhenius plot of the c.a.c. (ln(c.a.c.) versus 1/T) exhibited a break near T(g) of PDLLA. In sharp contrast with the linear decrease in ln(c.a.c.) versus 1/T in the region above the T(g), there was observed an almost constant c.a.c. (7-8 mg/l) regardless of the temperature change below the T(g). Furthermore, the chain exchange reaction between micelles was investigated based on the migration of the end-tagged block copolymers (alpha-lactosyl-PEG-PDLLA and omega-pyrenyl-PEG-PDLLA). The change in the binding affinity of the fluorescent micelles toward the RCA-1 lectin immobilized column was monitored with time to estimate the chain exchange. Consequently, appreciable acceleration in the chain exchange rate was revealed by increasing the surrounding temperature indicating the core mobility to be a substantial factor for inter-micellar chain migration. These results indicate that the engineering of the thermal characteristics of the core-forming segment of the block copolymer should be one of the crucial factors for optimizing the properties of the polymer micelles used for drug delivery.

Surface characterization of functionalized polylactide through the coating with heterobifunctional poly(ethylene glycol)/polylactide block copolymers

An AB-type block copolymer composed of alpha-acetalpoly(ethylene glycol) (PEG) as the hydrophilic segment and polylactide (PLA) as the hydrophobic segment was synthesized and utilized to construct a functionalized PEG layer possessing a reactive aldehyde group at the free end of the tethered PEG chain by simple coating on polylactide substrates. Detailed characterization of the functionalized PEGylated surfaces was done from the physicochemical (contact angle and zeta potential) as well as the biological (protein adsorption) point of view to highlight their potential utility as biofunctional interfaces. The amount of protein adsorption was inversely correlated with the degree of water structuring around the PEG molecules, which facilitates the formation of a strongly bound water film to increase the surface hydration. For these surfaces investigated, the extent of surface hydration was more important in determining the materials biocompatibility rather than the actual PEG molecular weight, as evidenced by an extremely low receding contact angle directly related to the adhesive energy of a water molecule. Furthermore, the contact angle relaxation less than a few minutes proved to be determinant for the receding contact angle and resultant hysteresis, caused by rearrangement of the hydrophilic PEG component. Aldehyde groups were confirmed to be present at the tethered PEG chain end using an electron spin resonance probe and can be derivatized with bioactive molecules with amino or hydrazide functionality. The functionalized PEG layer thus prepared on a biodegradable polylactide surface has both nonfouling and ligand-binding properties and may have promising utility as engineered biomaterials including tissue engineering scaffolds.

Long-circulating poly(ethylene glycol)-poly(D,L-lactide) block copolymer micelles with modulated surface charge

Reactive polymeric micelles consisting of an alpha-acetal-poly(ethylene glycol)-poly(D,L-lactide) block copolymer (acetal-PEG-PDLLA) with a narrow size distribution were prepared in this study to conjugate small peptidyl ligands, tyrosine (Tyr) and tyrosyl-glutamic acid (Tyr-Glu), through reductive amination after converting the alpha-acetal group to an aldehyde group, allowing modulation of the surface charge of the micelles from neutral (Tyr-) to anionic (Tyr-Glu-). Both of these micelles showed a significantly long circulating time in the blood compartment with 25% of injected dose still circulating even at 24 h. Further, an appreciably lowered uptake into the liver and spleen was demonstrated for the anionic Tyr-Glu-conjugated PEG-PDLLA micelle compared with a neutral Tyr-conjugated micelle, suggesting a substantial role of the slight anionic charge on the micelle surface in avoiding non-specific organ uptake. Stability of the micelle form in the blood compartment was directly observed for the Tyr-PEG-PDLLA micelle by a gel filtration assay of a plasma sample collected from the micelle-injected mice at 24 h. These results demonstrated that a surface-modulated PEG-PDLLA micelle with a suitable size and a narrowly distributed nature has promising potential as a long-circulating carrier system with desirable biocompatibility and biofunctionality.

A case of hemosuccus pancreaticus associated with hereditary pancreatitis

We report a 25-year-old male with hemosuccus pancreaticus associated with hereditary pancreatitis. He was originally diagnosed as having familial chronic pancreatitis at the age of 12, because his brother was also diagnosed as having pancreatitis. No history of pancreatitis was found in their parents. The patient was admitted because of a growing pancreatic pseudocyst. While he had undergone conservative treatment for the pseudocyst, computed tomography incidentally revealed a pancreatic pseudoaneurysm. Endoscopic examination revealed spontaneous bleeding from the major papilla. Interventional embolization was successfully performed. An R122H mutation in the cationic trypsinogen gene was identified in this patient, his brother, and his mother, indicating that they have hereditary pancreatitis. To our knowledge, this is the first report of hemosuccus pancreaticus associated with hereditary pancreatitis. Mutational screening is useful for the diagnosis of hereditary pancreatitis, especially in patients whose diagnosis is inconclusive based on the traditional clinical criteria.

Analysis of the human pancreatic secretory trypsin inhibitor (PSTI) gene mutations in Japanese patients with chronic pancreatitis

Chronic pancreatitis (CP) is a continuing or relapsing inflammatory disease of the pancreas. Several studies have demonstrated that mutations in the cationic trypsinogen (PRSS1) gene and the cystic fibrosis transmembrane conductance regulator (CFTR) gene are causative of the pathogenesis in a subset of hereditary and/or idiopathic CP cases. Recently, the N34S alteration of the pancreatic secretory trypsin inhibitor (PSTI) gene has been suggested to be closely associated with the pathogenesis of hereditary and/or idiopathic CP. Herein we analyzed genetic alterations of the PSTI gene in 32 unrelated Japanese CP patients who developed juvenile-onset CP or had a family history of CP; 5 patients were found to harbor alterations in this gene. In 3 of these 5 patients, heterozygous N34S alterations were found; this frequency is significantly lower than that in Caucasian patients reported previously. Moreover, a novel homozygous G-to-A transition in the promoter region of PSTI at 215bp upstream from the translation initiation site (-215G>A) was observed in 2 patients. We further surveyed the -215G>A alteration in 117 normal individuals; none of these individuals harbored this alteration. Our results suggested that the -215G>A alteration, as well as the N34S alteration, is a predisposing factor for CP.

Quantitative and reversible lectin-induced association of gold nanoparticles modified with alpha-lactosyl-omega-mercapto-poly(ethylene glycol)

Gold nanoparticles (1-10 nm size range) were prepared with an appreciably narrow size distribution by in situ reduction of HAuCl(4) in the presence of heterobifunctional poly(ethylene glycol) (PEG) derivatives containing both mercapto and acetal groups (alpha-acetal-omega-mercapto-PEG). The alpha-acetal-PEG layers formed on gold nanoparticles impart appreciable stability to the nanoparticles in aqueous solutions with elevated ionic strength and also in serum-containing medium. The PEG acetal terminal group was converted to aldehyde by gentle acid treatment, followed by the reaction with p-aminophenyl-beta-D- lactopyranoside (Lac) in the presence of (CH(3))(2)NHBH(3). Lac-conjugated gold nanoparticles exhibited selective aggregation when exposed to Recinus communis agglutinin (RCA(120)), a bivalent lectin specifically recognizing the beta-D-galactose residue, inducing significant changes in the absorption spectrum with concomitant visible color change from pinkish-red to purple. Aggregation of the Lac-functionalized gold nanoparticles by the RCA(120) lectin was reversible, recovering the original dispersed phase and color by addition of excess galactose. Further, the degree of aggregation was proportional to lectin concentration, allowing the system to be utilized to quantitate lectin concentration with nearly the same sensitivity as ELISA. This simple, yet highly effective, derivatization of gold nanoparticles with heterobifunctional PEG provides a convenient method to construct various colloidal sensor systems currently applied in bioassays and biorecognition.

Block copolymer micelles for drug delivery: design, characterization and biological significance

Recently, colloidal carrier systems have been receiving much attention in the field of drug targeting because of their high loading capacity for drugs as well as their unique disposition characteristics in the body. This paper highlights the utility of polymeric micelles formed through the multimolecular assembly of block copolymers as novel core-shell typed colloidal carriers for drug and gene targeting. The process of micellization in aqueous milieu is described in detail based on differences in the driving force of core segregation, including hydrophobic interaction, electrostatic interaction, metal complexation, and hydrogen bonding of constituent block copolymers. The segregated core embedded in the hydrophilic palisade is shown to function as a reservoir for genes, enzymes, and a variety of drugs with diverse characteristics. Functionalization of the outer surface of the polymeric micelle to modify its physicochemical and biological properties is reviewed from the standpoint of designing micellar carrier systems for receptor-mediated drug delivery. Further, the distribution of polymeric micelles is described to demonstrate their long-circulating characteristics and significant tumor accumulation, emphasizing their promising utility in tumor-targeting therapy. As an important perspective on carrier systems based on polymeric micelles, their feasibility as non-viral gene vectors is also summarized in this review article.

[11C]methionine positron emission tomography for the evaluation of pancreatic exocrine function in chronic pancreatitis

Positron emission tomography (PET) can be used for the quantitative analysis of amino acid metabolism. The aim of this study was to investigate whether pancreatic exocrine function can be evaluated by [11C]methionine PET in chronic pancreatitis (CP) patients. Dynamic PET scan of the pancreas and liver was performed in eight healthy subjects and seven patients with CP after intravenous (i.v.) injection of [11C]methionine. Simultaneously, duodenal juice was collected with the background of continuous i.v. administration of secretin (125 ng/kg/h). The radioactivity ratio of the pancreas to that of the liver (PLR) was calculated by regions of interest (ROI) analysis. Amylase output and bicarbonate concentration were measured in the duodenal aspirates. The PLR of CP patients was significantly lower than that of healthy subjects at all time points after methionine injection. The PLRs at 4.5 minutes (PLR4.5) after methionine injection were positively correlated with the amylase output, mean bicarbonate concentration, and volume of duodenal aspirates (R = 0.74, 0.69, 0.46). It is concluded that [11C]methionine PET would be a noninvasive method for the evaluation of exocrine pancreatic function, which may represent total amino acids uptake of viable acinar cells in the pancreas.

Selective synthesis of heterobifunctional poly(ethylene glycol) derivatives containing both mercapto and acetal terminals

A novel synthetic route to heterobifunctional poly(ethylene glycol) (PEG) derivatives containing both mercapto and acetal terminal groups was established in this study using anionic ring opening polymerization of ethylene oxide (EO) using potassium 3, 3-diethoxypropanolate (PDP) as the initiator, followed by the successive conversion of the end-alkoxide group to a methanesulfonic group, and then to an ethyldithiocarbonate moiety. Molecular functionalities of the acetal and the mercapto terminal groups of the heterotelechelic PEG (acetal-PEG-SH) thus prepared were confirmed to 1.00 and 0.85, respectively, indicating that the reaction proceeds almost quantitatively. The obtained acetal-PEG-SH products, including 2-pyridyldithio derivatives, have a promising utility for bioconjugation in the fields of medicine and biology.

Adenovirus-mediated in utero gene transfer in mice and guinea pigs: tissue distribution of recombinant adenovirus determined by quantitative TaqMan-polymerase chain reaction assay

Fetal somatic cell gene therapy could become an attractive solution for some congenital genetic diseases or the disorders which manifest themselves during the fetal period. We performed adenovirus-mediated gene transfer to mice and guinea pig fetuses in utero and evaluated the efficiency of gene transfer by histochemical analysis and a quantitative TaqMan-polymerase chain reaction (TaqMan-PCR) assay. We first injected a replication-deficient recombinant adenovirus containing the Escherichia coli LacZ gene driven by a CAG promoter (AxCALacZ) into pregnant mice through the amniotic space, placenta, or intraperitoneal space of the fetus. Histochemical analysis showed limited transgene expression in fetal tissues. We then administered AxCALacZ to guinea pig fetuses in the late stage of pregnancy through the umbilical vein. The highest beta-galactosidase expression was observed in liver followed by moderate expression in heart, spleen, and adrenal gland. The transgene expression was also present in kidney, intestine, and placenta to a lesser degree. No positively stained cells were observed in lung, muscle, or pancreas except in the vascular endothelium of these organs. Quantitative measurement of recombinant adenoviral DNA by the TaqMan-PCR assay showed that the vast majority of the injected viruses was present in liver. The current study indicated that adenovirus-mediated gene transfer into guinea pig fetus through the umbilical vein is feasible and results in efficient transgene expression in fetal tissues. The experimental procedures using pregnant guinea pigs might serve as a good experimental model for in utero gene transfer. Since our TaqMan-PCR assay detects the LacZ gene, one of the most widely used reporter genes, it may be generally applicable to adenovirus quantification in various gene transfer experiments.