Kopsileuconines A-D: bisindole alkaloids with cytotoxic activity from Kopsia hainanensis.

Kopsileuconines A-D (1-4), four monoterpenoid bisindole alkaloids with unprecedented skeletons, along with their biosynthetically related precursors (5-8) were isolated from the roots of Kopsia hainanensis. Compound 1 possessed an undescribed C-6-C-5' dimerization pattern of aspidofractinine-type alkaloids. Compounds 2-4 were rhazinilam-kopsine (2) and rhazinilam-aspidofractinine type (3 and 4) bisindole alkaloids with undescribed skeletons, respectively. Their structures with absolute configurations were fully accomplished by extensive spectroscopic analysis, quantum-chemical calculations, and X-ray crystallography. A plausible biosynthetic pathway for 1-4 was proposed. Compound 2 exhibited a significant inhibitory effect against human lung cancer cell lines PC9 (EGFR mutant), with an IC50 value of 15.07 ± 1.19 µM.

Block Sequence Effects on the Self-Assembly Behaviors of Polypeptide-Based Penta-Block Copolymer Hydrogels.

Peptide-based hydrogels have great potential for applications in tissue engineering, drug delivery, and so on. We systematically synthesize, characterize, and investigate the self-assembly behaviors of a series of polypeptide-based penta-block copolymers by varying block sequences and lengths. The copolymers contain hydrophobic blocks of poly(γ-benzyl-l-glutamate) (PBG, Bx) and two kinds of hydrophilic blocks, poly(l-lysine) (PLL, Ky) and poly(ethylene glycol) (PEG, EG34), where x and y are the number of repeating units of each block, where PBG and PLL blocks have unique functions for nerve regeneration and cell adhesion. It shows that a sufficient length of the middle hydrophilic segment capped with hydrophobic end PBG blocks is required. They first self-assemble into flower-like micelles and sequentially form transparent hydrogels (as low as 2.3 wt %) with increased polymer concentration. The hydrogels contain a microscale porous structure, a desired property for tissue engineering to facilitate the access of nutrient flow for cell growth and drug delivery systems with high efficiency of drug storage. We hypothesize that the structure of Bx-Ky-EG34-Ky-Bx agglomerates is beyond micron size (transparent), while that of Ky-Bx-EG34-Bx-Ky is on the submicron scale (opaque). We establish a working strategy to synthesize a polypeptide-based block copolymer with a wide window of sol-gel transition. The study offers insight into rational polypeptide hydrogel design with specific morphology, exploring the novel materials as potential candidates for neural tissue engineering.

Injectable Hydrogel Guides Neurons Growth with Specific Directionality.

Visual disabilities affect more than 250 million people, with 43 million suffering from irreversible blindness. The eyes are an extension of the central nervous system which cannot regenerate. Neural tissue engineering is a potential method to cure the disease. Injectability is a desirable property for tissue engineering scaffolds which can eliminate some surgical procedures and reduce possible complications and health risks. We report the development of the anisotropic structured hydrogel scaffold created by a co-injection of cellulose nanofiber (CNF) solution and co-polypeptide solution. The positively charged poly (L-lysine)-r-poly(L-glutamic acid) with 20 mol% of glutamic acid (PLLGA) is crosslinked with negatively charged CNF while promoting cellular activity from the acid nerve stimulate. We found that CNF easily aligns under shear forces from injection and is able to form hydrogel with an ordered structure. Hydrogel is mechanically strong and able to support, guide, and stimulate neurite growth. The anisotropy of our hydrogel was quantitatively determined in situ by 2D optical microscopy and 3D X-ray tomography. The effects of PLLGA:CNF blend ratios on cell viability, neurite growth, and neuronal signaling are systematically investigated in this study. We determined the optimal blend composition for stimulating directional neurite growth yielded a 16% increase in length compared with control, reaching anisotropy of 30.30% at 10°/57.58% at 30°. Using measurements of calcium signaling in vitro, we found a 2.45-fold increase vs. control. Based on our results, we conclude this novel material and unique injection method has a high potential for application in neural tissue engineering.

Oligo(ethylene glycol) side chain effect on the physical properties and molecular arrangement of oligothiophene-isoindigo based conjugated polymers.

Oligo(ethylene glycol) (OEG) side chains are widely used in donor-acceptor conjugated polymers (D-A CPs) and enable the polymers to dissolve and be processed in environmentally friendly and cost-effective nonchlorinated solvents, such as water. However, the OEG effect on the physical properties of D-A CPs has not been thoroughly studied and sometimes the results are controversial. In this study, two oligothiophene-isoindigo based conjugated polymers, P3TI and P4TI, are selected as model polymers to investigate the OEG effect. PnTI has octyl side chains on the oligothiophene unit and 2-hexyldecyl side chains on the isoindigo unit. The replacement of an alkyl side chain with OEG not only changes the optical and thermal properties but also the molecular arrangements of the polymers such as π-π d-spacing, crystallinity, and packing orientation. The domination of the crystallization behavior changes from the oligothiophene unit to the isoindigo unit when the bulky alkyl group is replaced by the flexible and linear OEG. The packing changes from edge-on to face-on orientation. The results are intriguing and provide new insights into this class of polymers.

Polybenzyl Glutamate Biocompatible Scaffold Promotes the Efficiency of Retinal Differentiation toward Retinal Ganglion Cell Lineage from Human-Induced Pluripotent Stem Cells.

Optic neuropathy is one of the leading causes of irreversible blindness caused by retinal ganglion cell (RGC) degeneration. The development of induced pluripotent stem cell (iPSC)-based therapy opens a therapeutic window for RGC degeneration, and tissue engineering may further promote the efficiency of differentiation process of iPSCs. The present study was designed to evaluate the effects of a novel biomimetic polybenzyl glutamate (PBG) scaffold on culturing iPSC-derived RGC progenitors. The iPSC-derived neural spheres cultured on PBG scaffold increased the differentiated retinal neurons and promoted the neurite outgrowth in the RGC progenitor layer. Additionally, iPSCs cultured on PBG scaffold formed the organoid-like structures compared to that of iPSCs cultured on cover glass within the same culture period. With RNA-seq, we found that cells of the PBG group were differentiated toward retinal lineage and may be related to the glutamate signaling pathway. Further ontological analysis and the gene network analysis showed that the differentially expressed genes between cells of the PBG group and the control group were mainly associated with neuronal differentiation, neuronal maturation, and more specifically, retinal differentiation and maturation. The novel electrospinning PBG scaffold is beneficial for culturing iPSC-derived RGC progenitors as well as retinal organoids. Cells cultured on PBG scaffold differentiate effectively and shorten the process of RGC differentiation compared to that of cells cultured on coverslip. The new culture system may be helpful in future disease modeling, pharmacological screening, autologous transplantation, as well as narrowing the gap to clinical application.

Peptide-Based Polyelectrolyte Promotes Directional and Long Neurite Outgrowth.

Neural tissue engineering has emerged as a promising technology to cure neural damages. Although various synthetic polymers with good biocompatibility and biodegradability have been adopted as candidate materials for scaffolds, most of them require the incorporation of biomolecules or conductive materials to promote the growth of long axons. Herein we demonstrate for the first time a unique peptide-based polyelectrolyte that is ionically conductive and contains a neurotransmitter, glutamic acid. The designed polymer, sodium salt of poly(γ-benzyl-l-glutamate)-r-poly(l-glutamic acid) (PBGA20-Na), was synthesized and fabricated into a 3D fibrous scaffold with aligned fibers. Neuron-like rat pheochromocytoma (PC12) cells were cultured on the scaffolds to evaluate cell proliferation and differentiation with or without electrical stimulation. The results show that with both electrical and biochemical cues presented in the polyelectrolyte, PBGA20-Na promotes longer neurite outgrowth compared with the neutral poly(γ-benzyl-l-glutamate) (PBG) and the poly(γ-benzyl-l-glutamate)-r-poly(l-glutamic acid) (PBGA20). Furthermore, the neurite length of the cells cultured on PBGA20-Na is more than twice as long compared with the conventional biopolymer, polycaprolactone. In conclusion, PBGA20-Na is a promising biomaterial for neural tissue engineering and drug-screening platforms.

Novel 3D Neuron Regeneration Scaffolds Based on Synthetic Polypeptide Containing Neuron Cue.

Neural tissue engineering has become a potential technology to restore the functionality of damaged neural tissue with the hope to cure the patients with neural disorder and to improve their quality of life. This paper reports the design and synthesis of polypeptides containing neuron stimulate, glutamic acid, for the fabrication of biomimetic 3D scaffold in neural tissue engineering application. The polypeptides are synthesized by efficient chemical reactions. Monomer γ-benzyl glutamate-N-carboxyanhydride undergoes ring-opening polymerization to form poly(γ-benzyl-l-glutamate), then hydrolyzes into poly(γ-benzyl-l-glutamate)-r-poly(glutamic acid) random copolymer. The glutamic acid amount is controlled by hydrolysis time. The obtained polymer molecular weight is in the range of 200 kDa for good quality of fibers. The fibrous 3D scaffolds of polypeptides are fabricated using electrospinning techniques. The scaffolds are biodegradable and biocompatible. The biocompatibility and length of neurite growth are improved with increasing amount of glutamic acid in scaffold. The 3D scaffold fabricated from aligned fibers can guide anisotropic growth of neurite along the fiber and into 3D domain. Furthermore, the length of neurite outgrowth is longer for scaffold made from aligned fibers as compared with that of isotropic fibers. This new polypeptide has potential for the application in the tissue engineering for neural regeneration.

Plasmonic nanoparticle-film calipers for rapid and ultrasensitive dimensional and refractometric detection.

In this study, we develop an ultrasensitive nanoparticle (NP)-film caliper that functions with high resolution (angstrom scale) in response to both the dimensions and refractive index of the spacer sandwiched between the NPs and the film. The anisotropy of the plasmonic gap mode in the NP-film caliper can be characterized readily using spectroscopic ellipsometry (SE) without the need for further optical modeling. To the best of our knowledge, this paper is the first to report the use of SE to study the plasmonic gap modes in NP-film calipers and to demonstrate that SE is a robust and convenient method for analyzing NP-film calipers. The high sensitivity of this system originates from the plasmonic gap mode in the NP-film caliper, induced by electromagnetic coupling between the NPs and the film. The refractometric sensitivity of this NP-film caliper reaches up to 314 nm per RIU, which is superior to those of other NP-based sensors. The NP-film caliper also provides high dimensional resolution, down to the angstrom scale. In this study, the shift in wavelength in response to the change in gap spacing is approximately 9 nm Å(-1). Taking advantage of the ultrasensitivity of this NP-film caliper, we develop a platform for discriminating among thiol-containing amino acids.

Low pressure radio-frequency oxygen plasma induced oxidation of titanium--surface characteristics and biological effects.

OBJECTIVE: This research was designed to investigate the effects of low pressure radio-frequency (RF) oxygen plasma treatment (OPT) on the surface of commercially pure titanium (CP-Ti) and Ti6Al4V. Surface topography, elemental composition, water contact angle, cell viability, and cell morphology were surveyed to evaluate the biocompatibility of titanium samples with different lengths of OP treating time. MATERIALS AND METHODS: CP-Ti and Ti6Al4V discs were both classified into 4 groups: untreated, treated with OP generated by using oxygen (99.98%) for 5, 10, and 30 min, respectively. After OPT on CP-Ti and Ti6Al4V samples, scanning probe microscopy, X-ray photoelectron spectrometry (XPS), and contact angle tests were conducted to determine the surface topography, elemental composition and hydrophilicity, respectively. The change of surface morphology was further studied using sputtered titanium on silicon wafers. 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay and F-actin immunofluorescence stain were performed to investigate the viability and spreading behavior of cultivated MG-63 cells on the samples. RESULTS: The surface roughness was most prominent after 5 min OPT in both CP-Ti and Ti6Al4V, and the surface morphology of sputtered Ti sharpened after the 5 min treatment. From the XPS results, the intensity of Ti(°), Ti(2+), and Ti(3+) of the samples' surface decreased indicating the oxidation of titanium after OPT. The water contact angles of both CP-Ti and Ti6Al4V were increased after 5 min OPT. The results of MTT assay demonstrated MG-63 cells proliferated best on the 5 min OP treated titanium sample. The F-actin immunofluorescence stain revealed the cultivated cell number of 5 min treated CP-Ti/Ti6Al4V was greater than other groups and most of the cultivated cells were spindle-shaped. CONCLUSIONS: Low pressure RF oxygen plasma modified both the composition and the morphology of titanium samples' surface. The CP-Ti/Ti6Al4V treated with 5 min OPT displayed the roughest surface, sharpest surface profile and best biocompatibility.

Biphenyl liquid crystalline epoxy resin as a low-shrinkage resin-based dental restorative nanocomposite.

Low-shrinkage resin-based photocurable liquid crystalline epoxy nanocomposite has been investigated with regard to its application as a dental restoration material. The nanocomposite consists of an organic matrix and an inorganic reinforcing filler. The organic matrix is made of liquid crystalline biphenyl epoxy resin (BP), an epoxy resin consisting of cyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (ECH), the photoinitiator 4-octylphenyl phenyliodonium hexafluoroantimonate and the photosensitizer champhorquinone. The inorganic filler is silica nanoparticles (∼70-100 nm). The nanoparticles were modified by an epoxy silane of γ-glycidoxypropyltrimethoxysilane to be compatible with the organic matrix and to chemically bond with the organic matrix after photo curing. By incorporating the BP liquid crystalline (LC) epoxy resin into conventional ECH epoxy resin, the nanocomposite has improved hardness, flexural modulus, water absorption and coefficient of thermal expansion. Although the incorporation of silica filler may dilute the reinforcing effect of crystalline BP, a high silica filler content (∼42 vol.%) was found to increase the physical and chemical properties of the nanocomposite due to the formation of unique microstructures. The microstructure of nanoparticle embedded layers was observed in the nanocomposite using scanning and transmission electron microscopy. This unique microstructure indicates that the crystalline BP and nanoparticles support each other and result in outstanding mechanical properties. The crystalline BP in the LC epoxy resin-based nanocomposite was partially melted during exothermic photopolymerization, and the resin expanded via an order-to-disorder transition. Thus, the post-gelation shrinkage of the LC epoxy resin-based nanocomposite is greatly reduced, ∼50.6% less than in commercialized methacrylate resin-based composites. This LC epoxy nanocomposite demonstrates good physical and chemical properties and good biocompatibility, comparable to commercialized composites. The results indicate that this novel LC nanocomposite is worthy of development and has potential for further applications in clinical dentistry.

Eco-friendly plasmonic sensors: using the photothermal effect to prepare metal nanoparticle-containing test papers for highly sensitive colorimetric detection.

Convenient, rapid, and accurate detection of chemical and biomolecules would be a great benefit to medical, pharmaceutical, and environmental sciences. Many chemical and biosensors based on metal nanoparticles (NPs) have been developed. However, as a result of the inconvenience and complexity of most of the current preparation techniques, surface plasmon-based test papers are not as common as, for example, litmus paper, which finds daily use. In this paper, we propose a convenient and practical technique, based on the photothermal effect, to fabricate the plasmonic test paper. This technique is superior to other reported methods for its rapid fabrication time (a few seconds), large-area throughput, selectivity in the positioning of the NPs, and the capability of preparing NP arrays in high density on various paper substrates. In addition to their low cost, portability, flexibility, and biodegradability, plasmonic test paper can be burned after detecting contagious biomolecules, making them safe and eco-friendly.

Cell tracking and detection of molecular expression in live cells using lipid-enclosed CdSe quantum dots as contrast agents for epi-third harmonic generation microscopy.

We demonstrated that lipid-enclosed CdSe quantum dots (LEQDs) can function as versatile contrast agents in epi-detection third harmonic generation (THG) microscopy for biological applications in vivo. With epi-THG intensities 20 times stronger than corresponding fluorescence intensities from the same LEQDs under the same conditions of energy absorption, such high brightness LEQDs were proved for the abilities of cell tracking and detection of specific molecular expression in live cancer cells. Using nude mice as an animal model, the distribution of LEQD-loaded tumor cells deep in subcutaneous tissues were imaged with high THG contrast. This is the first demonstration that THG contrast can be manipulated in vivo with nanoparticles. By linking LEQDs with anti-Her2 antibodies, the expression of Her2/neu receptors in live breast cancer cells could also be easily detected through THG. Compared with fluorescence modalities, the THG modality also provides the advantage of no photobleaching and photoblinkin g effects. Combined with a high penetration 1230 nm laser, these novel features make LEQDs excellent THG contrast agents for in vivo deep-tissue imaging in the future.