Microfluidic Fabrication of Polymeric and Biohybrid Fibers with Predesigned Size and Shape

A “sheath” fluid passing through a microfluidic channel at low Reynolds number can be directed around another “core” stream and used to dictate the shape as well as the diameter of a core stream. Grooves in the top and bottom of a microfluidic channel were designed to direct the sheath fluid and shape the core fluid. By matching the viscosity and hydrophilicity of the sheath and core fluids, the interfacial effects are minimized and complex fluid shapes can be formed. Controlling the relative flow rates of the sheath and core fluids determines the cross-sectional area of the core fluid. Fibers have been produced with sizes ranging from 300 nm to ~1 mm, and fiber cross-sections can be round, flat, square, or complex as in the case with double anchor fibers. Polymerization of the core fluid downstream from the shaping region solidifies the fibers. Photoinitiated click chemistries are well suited for rapid polymerization of the core fluid by irradiation with ultraviolet light. Fibers with a wide variety of shapes have been produced from a list of polymers including liquid crystals, poly(methylmethacrylate), thiol-ene and thiol-yne resins, polyethylene glycol, and hydrogel derivatives. Minimal shear during the shaping process and mild polymerization conditions also makes the fabrication process well suited for encapsulation of cells and other biological components.     

Antibacterial Activity of Vancomycin Encapsulated in Poly(DL-lactide-co-glycolide) Nanoparticles Using Electrospraying

Probiotics and Antimicrobial Proteins - Vancomycin is often used to treat infections caused by β-lactam-resistant bacteria. However, methicillin-resistant strains of Staphylococcus aureus...     

新型载药高分子囊泡的制备与抗菌性能研究

相对于小分子抗菌剂,高分子抗菌材料会对细菌的胞膜产生物理破坏,从而降低病原体产生耐药性的可能;另外,高分子抗菌材料不但具有较高的抗菌性能,抗菌作用时效长,环境污染小,而且对人体伤害小,具有更好的选择性。因此,高分子抗菌材料的研究受到广泛关注。此外,还可以将小分子抗生素负载到高分子纳米载体中,实现小分子抗菌剂的传输与协同抗菌。本文构筑了两亲性高分子聚(N,N-二甲氨基乙酯-嵌段-聚苯氧异丙醇)(PDMAEMA-b-PPOPMA),自组装得到纳米囊泡,被用来物理包埋万古霉素(Vancomycin),对金黄色葡萄球菌(S.aureus)表现出良好的抗菌活性。     

Formulation of Diblock Polymeric Nanoparticles through Nanoprecipitation Technique

Nanotechnology is a relatively new branch of science that involves harnessing the unique properties of particles that are nanometers in scale (nanoparticles). Nanoparticles can be engineered in a precise fashion where their size, composition and surface chemistry can be carefully controlled. This enables unprecedented freedom to modify some of the fundamental properties of their cargo, such as solubility, diffusivity, biodistribution, release characteristics and immunogenicity. Since their inception, nanoparticles have been utilized in many areas of science and medicine, including drug delivery, imaging, and cell biology^1-4. However, it has not been fully utilized outside of "nanotechnology laboratories" due to perceived technical barrier. In this article, we describe a simple method to synthesize a polymer based nanoparticle platform that has a wide range of potential applications. The first step is to synthesize a diblock co-polymer that has both a hydrophobic domain and hydrophilic domain. Using PLGA and PEG as model polymers, we described a conjugation reaction using EDC/NHS chemistry⁵ (Fig 1). We also discuss the polymer purification process. The synthesized diblock co-polymer can self-assemble into nanoparticles in the nanoprecipitation process through hydrophobic-hydrophilic interactions.The described polymer nanoparticle is very versatile. The hydrophobic core of the nanoparticle can be utilized to carry poorly soluble drugs for drug delivery experiments6. Furthermore, the nanoparticles can overcome the problem of toxic solvents for poorly soluble molecular biology reagents, such as wortmannin, which requires a solvent like DMSO. However, DMSO can be toxic to cells and interfere with the experiment. These poorly soluble drugs and reagents can be effectively delivered using polymer nanoparticles with minimal toxicity. Polymer nanoparticles can also be loaded with fluorescent dye and utilized for intracellular trafficking studies. Lastly, these polymer nanoparticles can be conjugated to targeting ligands through surface PEG. Such targeted nanoparticles can be utilized to label specific epitopes on or in cells^7-10.Download video file.^{(41M, mov)}     

Fabrication and Optical Properties of Au-Coated Polystyrene Nanosphere Arrays with Controlled Gaps

Large area monolayer of self-assembled polystyrene sphere (PS) arrays were formed by an interface self-assembly method and the gap of PS was adjusted by O₂ plasma treatment (OPT). After different duration of OPT, the spacing between the PSs varied from 5 to 88 nm. Then, 20 nm Au film was deposited on the PS arrays by electron beam deposition. The absorption peaks of Au-coated PS array red-shifted obviously by changing the gap of PS. The new absorption peaks emerged when the gap of the PS decreased to about 20 nm. The surface plasmon resonance (SPR) was employed to explain the absorption proportion of this Au-PS structure. These micro-nano structures exhibit tunable SPR bands, which may be useful to the applications in some research fields, such as biosensing, single molecule detection, and novel optoelectronic devices.     

Ohmic Contact Fabrication Using a Focused-ion Beam Technique and Electrical Characterization for Layer Semiconductor Nanostructures

Layer semiconductors with easily processed two-dimensional (2D) structures exhibit indirect-to-direct bandgap transitions and superior transistor performance, which suggest a new direction for the development of next-generation ultrathin and flexible photonic and electronic devices. Enhanced luminescence quantum efficiency has been widely observed in these atomically thin 2D crystals. However, dimension effects beyond quantum confinement thicknesses or even at the micrometer scale are not expected and have rarely been observed. In this study, molybdenum diselenide (MoSe₂) layer crystals with a thickness range of 6-2,700 nm were fabricated as two- or four-terminal devices. Ohmic contact formation was successfully achieved by the focused-ion beam (FIB) deposition method using platinum (Pt) as a contact metal. Layer crystals with various thicknesses were prepared through simple mechanical exfoliation by using dicing tape. Current-voltage curve measurements were performed to determine the conductivity value of the layer nanocrystals. In addition, high-resolution transmission electron microscopy, selected-area electron diffractometry, and energy-dispersive X-ray spectroscopy were used to characterize the interface of the metal–semiconductor contact of the FIB-fabricated MoSe₂ devices. After applying the approaches, the substantial thickness-dependent electrical conductivity in a wide thickness range for the MoSe₂-layer semiconductor was observed. The conductivity increased by over two orders of magnitude from 4.6 to 1,500 Ω⁻¹ cm⁻¹, with a decrease in the thickness from 2,700 to 6 nm. In addition, the temperature-dependent conductivity indicated that the thin MoSe₂ multilayers exhibited considerably weak semiconducting behavior with activation energies of 3.5-8.5 meV, which are considerably smaller than those (36-38 meV) of the bulk. Probable surface-dominant transport properties and the presence of a high surface electron concentration in MoSe₂ are proposed. Similar results can be obtained for other layer semiconductor materials such as MoS₂ and WS₂.     

可控多孔结构支架制备及灌注式体外培养

利用CAD和快速成形技术设计制造具有可控多孔结构的支架。构建灌注式生物反应器系统,实现氧气和营养物质的大量输送,同时产生一定流体剪应力,调节细胞功能的发挥。根据支架负型结构制造出相应的树脂原型,用磷酸钙骨水泥进行填充烧结,得到与设计相符的多孔支架。接种兔成骨细胞,分别采用静态和灌注式三维动态培养方法,观察不同培养条件下细胞在支架表面以及所构造微管道内的生长情况。试验结果表明,灌注式体外培养方法更有利于细胞在支架微管道内的存活和功能的发挥,此灌注式系统能够改善支架微管道内细胞生存的微环境,增强黏附在支架微管道内细胞的活性,促进细胞进一步的增殖和矿化基质的产生。     

Fabrication of Large-scale Nanostructure by Langmuir-Blodgett Technique

Monolayer of polymer latex spheres was prepared at the air/water interface and deposited onto glass slides through Langmuir-Blodgett （LB） technique. Large-scale, high quality hexagonally close-packed domains were found in scanning electron microscopic pictures. Details of the monolayer-forming ability were discussed. Suitable surface characteristics of the colloidal particles, especially the hydrophilic and hydrophobic properties, are the keys for the formation of ordered monolayer films. The film can be transferred onto various kinds of substrates, even high curvature surface articles, such as fibers, decorations etc, can also be used as substrates. The advantages of this fabrication method of polymer latex spheres monolayer are fast, flexible, simple and very neat.     

Controlled Fabrication of Gold Nanoparticle and Fluorescent Protein Conjugates

The unique optical properties of gold nanoparticles make them attractive for a wide range of applications which require optical detection and manipulation techniques. Here, we experimentally demonstrate the use of single femtosecond pulses at resonance wavelength for a controlled conjugation of gold nanoparticles and fluorescent proteins. This optically driven reaction is rigorously studied and analyzed using a variety of experimental techniques, and a detailed model is proposed which describes the adsorption of the proteins onto the nanoparticles' surface, as well as their subsequent desorption by a reducing agent. Potential applications of the resulting nanoparticle?Cprotein conjugates include controlled delivery of fluorescent markers and local sensing of biochemical processes.     

A Micro-Extraction Technique Using a New Digitally Controlled Syringe Combined with UHPLC for Assessment of Urinary Biomarkers of Oxidatively Damaged DNA

The formation of reactive oxygen species (ROS) within cells causes damage to biomolecules, including membrane lipids, DNA, proteins and sugars. An important type of oxidative damage is DNA base hydroxylation which leads to the formation of 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) and 5-hydroxymethyluracil (5-HMUra). Measurement of these biomarkers in urine is challenging, due to the low levels of the analytes and the matrix complexity. In order to simultaneously quantify 8-oxodG and 5-HMUra in human urine, a new, reliable and powerful strategy was optimised and validated. It is based on a semi-automatic microextraction by packed sorbent (MEPS) technique, using a new digitally controlled syringe (eVol^®), to enhance the extraction efficiency of the target metabolites, followed by a fast and sensitive ultrahigh pressure liquid chromatography (UHPLC). The optimal methodological conditions involve loading of 250 µL urine sample (1∶10 dilution) through a C8 sorbent in a MEPS syringe placed in the semi-automatic eVol^® syringe followed by elution using 90 µL of 20% methanol in 0.01% formic acid solution. The obtained extract is directly analysed in the UHPLC system using a binary mobile phase composed of aqueous 0.1% formic acid and methanol in the isocratic elution mode (3.5 min total analysis time). The method was validated in terms of selectivity, linearity, limit of detection (LOD), limit of quantification (LOQ), extraction yield, accuracy, precision and matrix effect. Satisfactory results were obtained in terms of linearity (r² > 0.991) within the established concentration range. The LOD varied from 0.00005 to 0.04 µg mL⁻¹ and the LOQ from 0.00023 to 0.13 µg mL⁻¹. The extraction yields were between 80.1 and 82.2 %, while inter-day precision (n = 3 days) varied between 4.9 and 7.7 % and intra-day precision between 1.0 and 8.3 %. This approach presents as main advantages the ability to easily collect and store urine samples for further processing and the high sensitivity, reproducibility, and robustness of eVol^®MEPS combined with UHPLC analysis, thus retrieving a fast and reliable assessment of oxidatively damaged DNA.     

Low-Cost Fabrication of Pt Thin Films with Controlled Nanostructures and Their Effects on SERS

We fabricated nanostructured Pt thin films with two different morphologies and studied their effects on the Raman spectrum of rhodamine 6G. The syntheses were achieved by templating mesoporous silica thin films which are characterized by 8-nm-sized pore channels and 3–4-nm-thick walls in two different orientations of the channels. Therefore, the resultant nanostructured Pt thin films are composed of Pt nanorods of 8 nm in diameter vertically standing in one morphology and horizontally lying in the other. The latter produced stronger Raman signals than the former. Simulations based the discrete-dipole approximation on model nanostructures showed that the horizontally lying nanorods produce stronger local electromagnetic field than the vertically standing ones, in agreement with the experimental observations.     

Detection and Measurement of Staphylococcus epidermidis Slime Using an ELISA Technique

A polyclonal rabbit anti-serum against the strong slime-producing Staphylococcus epidermidis strain RP62A was absorbed with the slime-negative phase variant of this strain PV1 in order to remove not slime-specific antibodies. Using this antiserum we established an ELISA which enables detection of slime production in S. epidermidis extracts. The ELISA showed high absorbance when extracts from slime-positive strains (confirmed in the tissue culture tube test) were used as antigens. The high absorbance of slime-positive strains was greatly reduced by periodate oxidation of the extracts and was resistant to proteinase digestion suggesting that the detected antigen is composed of polysaccharides. In contrast to other rapid and simple laboratory detection methods for S. epidermidis slime, the slime-specific ELISA gave positive results in the presence of human serum.     

肉桂高聚原花青素的氢化降解工艺研究

低聚原花青素具有显著的生物活性,高聚体由于空间位阻的影响,活性受到抑制。肉桂在41种食品中原花青素含量位居第一,但高聚体占50％以上。为了充分利用肉桂原花青素资源,采用氢化降解法将肉桂高聚原花青素降解为低聚体。以10％钯碳做催化剂,高压氢气参加反应,考察温度、压强、反应时间和催化剂用量对降解效果的影响。结果表明,平均聚合度为8．2的肉桂高聚原花青素,在100℃,压强3．5MPa,反应200min,催化剂用量0．2g/100mL的条件下,平均聚合度降为2．68。降解产物经HPLC分析表明,此工艺确实实现了肉桂高聚原花青素的降解。     

Enhancement of Bioavailability of Cefpodoxime Proxetil Using Different Polymeric Microparticles

Poorly water-soluble drugs such as cefpodoxime proxetil (400 μg/ml) offer a challenging problem in drug formulation as poor solubility is generally associated with poor dissolution characteristics and thus poor oral bioavailability. According to these characteristics, preparation of cefpodoxime proxetil microparticle has been achieved using high-speed homogenization. Polymers (methylcellulose, sodium alginate, and chitosan) were precipitated on the surface of cefpodoxime proxetil using sodium citrate and calcium chloride as salting-out agents. The pure drug and the prepared microparticles with different concentrations of polymer (0.05–1.0%) were characterized in terms of solubility, drug content, particle size, thermal behavior (differential scanning calorimeter), surface morphology (scanning electron microscopy), in vitro drug release, and stability studies. The in vivo performance was assessed by pharmacokinetic study. The dissolution studies demonstrate a marked increase in the dissolution rate in comparison with pure drug. The considerable improvement in the dissolution rate of cefpodoxime proxetil from optimized microparticle was attributed to the wetting effect of polymers, altered surface morphology, and micronization of drug particles. The optimized microparticles exhibited excellent stability on storage at accelerated condition. The in vivo studies revealed that the optimized formulations provided improved pharmacokinetic parameter in rats as compared with pure drug. The particle size of drug was drastically reduced during formulation process of microparticles.     

Fabrication of Polymeric Visual Decoys for the Male Emerald Ash Borer (Agrilus planipennis)

Through a bioreplication approach, we have fabricated artificial visual decoys for the invasive species Agrilus planipennis—commonly known as the Emerald Ash Borer (EAB). The mating behavior of this species involves an overflying EAB male pouncing on an EAB female at rest on an ash leaflet before copulating. The male spots the female on the leaflet by visually detecting the iridescent green color of the female's elytra. As rearing EAB and then deploying dead females as decoys for trapping is both arduous and inconvenient, we decided to fabricate artificial decoys. We used a dead female to make a negative die of nickel and a positive die of epoxy. Decoys were then made by first depositing a quarter-wave-stack Bragg reflector on a polymer sheet and then stamping it with a pair of matched negative and positive dies to take the shape of the upper surface of an EAB female. As nearly 100 artificial decoys were fabricated from just one EAB female, this bioreplication process is industrially scalable. Preliminary results from a field trapping test are indicative of success.     

Lifestyle Intervention Using an Internet-Based Curriculum with Cell Phone Reminders for Obese Chinese Teens: A Randomized Controlled Study

ObjectivesObesity is an increasing public health problem affecting young people. The causes of obesity are multi-factorial among Chinese youth including lack of physical activity and poor eating habits. The use of an internet curriculum and cell phone reminders and texting may be an innovative means of increasing follow up and compliance with obese teens. The objectives of this study were to determine the feasibility of using an adapted internet curriculum and existing nutritional program along with cell phone follow up for obese Chinese teens.ResultsThe use of the internet-based curriculum was shown to be feasible as evidenced by the high recruitment rate, internet log-in rate, compliance with completing the curriculum and responses to phone reminders. No significant differences in weight were found between IT, sLMP and control groups.ConclusionAn internet-based curriculum with cell phone reminders as a supplement to usual care of obesity is feasible. Further study is required to determine whether an internet plus text intervention can be both an effective and a cost-effective adjunct to changing weight in obese youth.

Trial Registration

Chinese Clinical Trial Registry ChiCTR-TRC-12002624     

Diffusion of Large Molecules into Assembling Nuclei Revealed Using an Optical Highlighting Technique

The nuclear envelope (NE) defines the nuclear compartment, and nuclear pore complexes (NPCs) on the NE form aqueous passages through which small water-soluble molecules can passively diffuse. It is well known that proteins smaller than 50 kDa can diffuse though NPCs, whereas proteins larger than 60 kDa rarely enter by passive diffusion. Little, however, is known about how this size cutoff develops as the NE reassembles and the nucleus expands. In 1987, a well-known study identified an efficient mechanism by which large diffusing proteins (>60 kDa) were excluded from the reassembling nucleus after mitosis. Since then, it has been generally accepted that after mitosis, newly formed nuclei completely exclude all proteins except those that are initially bound to the mitotic chromosomes and those that are selectively imported through NPCs. Here, the tetrameric complex of the photoconvertible fluorescent protein KikGR (∼103 kDa) was optically highlighted in the cytoplasm and followed to examine its entry into nuclei. Remarkably, highlighted complexes efficiently entered newly assembled nuclei during an ∼20-min period after the completion of cytokinesis. Because KikGR contains no known nuclear-localization or chromosome-binding sequences, our results indicate the diffusion barrier is less restrictive during nuclear reassembly.     

A Novel Capsulorhexis Technique Using Shearing Forces with Cystotome

Purpose:To demonstrate a capsulorhexis technique using predominantly shearing forces with a cystotome on a virtual reality simulator and on a human eye.Method:Our technique involves creating the initial anterior capsular tear with a cystotome to raise a flap. The flap left unfolded on the lens surface. The cystotome tip is tilted horizontally and is engaged on the flap near the leading edge of the tear. The cystotome is moved in a circular fashion to direct the vector forces. The loose flap is constantly swept towards the centre so that it does not obscure the view on the tearing edge.Results:Our technique has the advantage of reducing corneal wound distortion and subsequent anterior chamber collapse. The capsulorhexis flap is moved away from the tear leading edge allowing better visualisation of the direction of tear. This technique offers superior control of the capsulorhexis by allowing the surgeon to change the direction of the tear to achieve the desired capsulorhexis size.Conclusions:The EYESI Surgical Simulator is a realistic training platform for surgeons to practice complex capsulorhexis techniques. The shearing forces technique is a suitable alternative and in some cases a far better technique in achieving the desired capsulorhexis.     

Kinetically Controlled Peptide Synthesis Mediated by Papain Using the Carbamoylmethyl Ester as an Acyl Donor

A series of dipeptides were synthesized generally in good yields with carbamoylmethyl (Cam) esters as acyl donors in the presence of a cysteine protease, papain, immobilized on Celite. Several segment condensations were also achieved generally in high yields without danger of racemization and formation of the secondary-hydrolysis product. Moreover, partial sequences of some bioactive peptides were prepared through segment condensations, and aimed-at peptides were obtained generally in high yields without the racemization of C-terminal residues of the carboxyl components. Thus, the superiority of the Cam ester in the kinetically controlled peptide synthesis was once again ascertained in couplings mediated by the cysteine protease as in those catalyzed by the serine proteases reported earlier.