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Many cationic polymers with varied architectures either in backbones or in side chains have been used for gene delivery. However, these polymers yielding different DNA transfection efficiency cannot answer whether backbones or side chains have more influence on DNA delivery. In this research, polyurethanes (PUs) made from the reaction of l‐lysine diisocyanate and 1,4‐piperazinediethanol were synthesized. Together with poly(l‐lysine) (PLL), these polymers were further modified to carry side chains by connecting to low‐molecular‐weight polyethylenimine (PEI) via imine linkages. The PEI was either linear (423 Da) or branched (600 Da) and grafted to the backbone representing two distinct shapes (i.e. a twig with needle‐leaves or round‐leaves). In addition, one PU derivative was synthesized to have shorter side chains (as PU‐PEI S423) than PU‐PEI423 by aminolysis reaction. These synthesized polymers were compared for their transfection potential as gene vectors into cells. Electrophoretic mobility, dynamic light scattering and zeta potential analyses of polymer/DNA complexes confirmed that, after grafting of PEI (PEI423 or PEI600), PLL‐PEIs and PU‐PEIs were able to self‐assemble with plasmid DNA to form nano‐scaled (ca 200 nm) and positively charged (ca +25 mV) complexes. These cationic polymers hardly showed any cytotoxicity on COS‐7 cells. The outcome of fluorescence imaging and flow cytometry verified that the order of greater transfection efficiency is PLL‐PEI600 = PU‐PEI600 > PLL‐PEI423 = PU‐PEI423 > PEI25K (commercial standard) = PU‐PEI S423 >> PLL > PEI423 = PEI600 (starting materials). These results reveal that the polymers with longer side chains or higher charge density have positive influence on transfection efficiency. Nevertheless, different polymer backbones may reflect their biodegradability and cytotoxicity, but their effect on transfection efficiency is less significant. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Human mesenchymal stromal cells (hMSCs) are multipotent cells that have been proposed for the treatment of immune-mediated diseases. Culturing hMSCs on tissue culture plastic reduces their therapeutic potential in part due to the lack of extracellular matrix components. The aim of this study is to evaluate multilayers of heparin and poly(L-lysine) (HEP/PLL) as a bioactive surface for hMSCs stimulated with soluble interferon gamma (IFN-γ). Multilayers were formed, via layer-by-layer assembly, with HEP as the final layer and supplemented with IFN-γ in the culture medium. Multilayer construction and chemistry were confirmed using Azure A staining, quartz crystal microbalance, and X-ray photoelectron spectroscopy. hMSCs adhesion, viability, and differentiation, were assessed. Results showed that (HEP/PLL) multilayer coatings were poorly adhesive for hMSCs. However, performing chemical crosslinking using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide significantly enhanced hMSCs adhesion and viability. The immunosuppressive properties of hMSCs cultured on crosslinked (HEP/PLL) multilayers were confirmed by measuring indoleamine 2,3-dioxygenase activity. Lastly, hMSCs cultured on crosslinked (HEP/PLL) multilayers in the presence of soluble IFN- γ successfully differentiated towards the osteogenic and adipogenic lineages as confirmed by Alizarin red, and oil-red O staining, as well as alkaline phosphatase activity. This study suggests that crosslinked (HEP/PLL) films can modulate hMSCs response to soluble factors, which may improve hMSCs-based therapies aimed at treating several immune diseases. [ABSTRACT FROM AUTHOR]

Poly(L-lysine) (PLL)-3-hydroxyphenylboronic acid (3-PBA) composite was prepared onto an Au electrode via cyclic voltammetry (CV), which was characterized by electrochemical and quartz crystal microbalance (QCM) techniques, and used to promote adhesion of plant cells. 3-PBA can interact with glycosyl compounds on the cell wall to form negatively charged covalent compounds while PLL increases the number of positively charged sites, which enhances the electrostatic interactions with the negatively charged cell wall, both promoting cell adhesion. The PLL-poly(3-PBA) composite was successfully modified on the Au electrode surface, as demonstrated by QCM and Fourier transform infrared spectrophotometry (FTIR). Moreover, we confirmed the synergistic effect of PLL and 3-PBA to adhere rice suspension cells using CV, electrochemical impedance spectroscopy (EIS), QCM and optical microscope observations. Finally, the dynamic process of rice cells’ adhesion to PLL-poly(3-PBA)/Au followed by salt stress treatment of NaCl was monitored in real-time by QCM. The cells softened at first then hardened under the action of 40 mM NaCl. This work presents a novel and conventional way to immobilize plant cells onto sensors, and has importance in the study of the structure, function and behavior of plants under various stresses at the cellular level.

This work investigated the effect of poly(l -lysine) (PLL) molecular weight and concentration on chondrogenesis of cocultures of mesenchymal stem cells (MSCs) and articular chondrocytes (ACs) in PLL-loaded hydrogels. An injectable dual-network hydrogel composed of a poly(N -isopropylacrylamide)-based synthetic thermogelling macromer and a chondroitin sulfate-based biological network was leveraged as a model to deliver PLL and encapsulate the two cell populations. Incorporation of PLL into the hydrogel did not affect the hydrogel's swelling properties and degradation characteristics, nor the viability of encapsulated cells. Coculture groups demonstrated higher type II collagen expression compared to the MSC monoculture group. Expression of hypertrophic phenotype was also limited in the coculture groups. Histological analysis indicated that the ratio of MSCs to ACs was an accurate predictor of the degree of long-term chondrogenesis, while the presence of PLL was shown to have a more substantial short-term effect. Altogether, this study demonstrates that coculturing MSCs with ACs can greatly enhance the chondrogenicity of the overall cell population and offers a platform to further elucidate the short- and long-term effect of polycationic factors on the chondrogenesis of MSC and AC cocultures. Unlabelled Image • Coculturing mesenchymal stem cells (MSCs) with chondrocytes enhanced the chondrogenic differentiation of MSCs in vitro. • The presence of chondrocytes limited the expression of hypertrophic genes from MSCs. • Loaded poly(l -lysine) in the hydrogel transiently affected the gene expression profiles of the encapsulated cell populations. • The extent of cartilage-like matrix secretion depended on the coculture ratio. [ABSTRACT FROM AUTHOR]

A ternary hybrid material composed of Ni nanoparticles (NPs), TiO2 NPs, and poly(L-lysine) (Ply) was used as a sensing material. It was electrodeposited in situ onto a commercial 433-MHz surface acoustic wave (SAW) resonator to construct a Ni-TiO2-Ply/SAW sensor. The Ni-TiO2-Ply sensing layer fully covered the resonant cavity of the SAW resonator. As the sensing layer completely covers the interdigital transducer and piezoelectric substrate, the sensing area is significantly increased, and the resonator is protected from damage or contamination. To detect the level of dopamine (DA) in serum, the fabrication of the Ni-TiO2-Ply sensing layer, distributions of various components in the sensing layer, and responses of the SAW biosensor to DA were investigated in detail. In addition, an electric field-assisted liquid-phase oxidation technique was developed for loading analytes onto the SAW sensors. After optimizing the pH value and L-lysine content of the sensing layer electrolyte and the pH value of the DA solution, the SAW biosensor responded to DA with a linear concentration range of 1 to 1000 nM, sensitivity of 5.77 MHz nM−1 cm−2, and limit of detection of 0.067 nM. Moreover, the sensor exhibited good selectivity, reproducibility, and stability at ambient temperature. Graphical abstract [ABSTRACT FROM AUTHOR]

Dendritic cell (DC) vaccine is an effective strategy for cancer immunotherapy by carrying antigen into DCs and migrating these DCs to drain lymph nodes after inoculation. In this article, second near-infrared window (NIR-II) fluorescent nanoparticles have been used to uptake antigen and activate DCs. Ovalbumin (OVA), an antigen for immunization, can be loaded on the surface of these NIR-II fluorescent nanoparticles via electrostatic interaction by virtue of their functionalized poly(L-lysine) (PLL), which exhibits biocompatibility and strong selective interaction with OVA. In addition, these antigen-loaded complexes can efficiently be engulfed by immature DCs to induce DC maturation and cytokine secretion. After subcutaneous injection, highly sensitive NIR-II fluorescence signal from nanoparticles indicates that nanoparticle-labeled DCs can successfully migrate into lymph nodes in vivo, showing great promise in immunotherapy against cancer. [ABSTRACT FROM AUTHOR]

A new electrochemical biosensor is developed for the detection of diazinon. For this purpose, a glassy carbon electrode is modified with MWCNTs and poly-l-lysine to immobilize a double-strain DNA (ds-DNA) on the surface of the electrode. In the first step, the interaction of diazinon with ds-DNA is transduced by electrochemical impedance spectroscopy and UV–Vis spectroscopy to monitor the intercalation of diazinon with DNA helix. This interaction leads to reduced interfacial charge-transfer resistance (Rct). The difference in the Rct before and after the interaction is considered as a suitable signal for diazinon detection. The proposed biosensor has a low detection limit (0.3 nmol L−1), a wide linear dynamic range (0.001‒100 µmol L−1), and high selectivity for the determination of diazinon. Finally, the performance of the biosensor for detecting of diazinon is verified in real samples such as river water, agricultural wastewater, lettuce juice, and tomato juice. [ABSTRACT FROM AUTHOR]

• PDA/PLL hybrid coatings were developed to functionalize hydroxyapatite scaffolds. • The hybrid coatings realize tunable and sustained release of BMP2. • The hybrid coatings promote BMSC adhesion and differentiation. • The coating-functionalized scaffolds possess excellent osteoinductive properties. The scaffold for bone tissue engineering should possess proper porosity, adequate mechanical properties, cell affinity for cell attachment, and the capability to bind bioactive agents to induce cell differentiation. In this study, we successfully prepared a porous hydroxyapatite (HA) scaffold that is functionalized by poly(L-lysine)/polydopamine (PLL/PDA) hybrid coating. The PLL/PDA coating takes advantages of the high protein and cell affinity of PDA, as well as the biodegradability of PLL. Therefore, the coating can anchor bone morphogenic protein-2 (BMP2) to the HA scaffold via catechol chemistry under a mild condition so as to protect the bioactivity of BMP2. Meanwhile, the coating can also release BMP2 in a tunable and sustainable manner as the PLL degrades in the physiological environment. The BMP2-entrapped PLL/PDA coating on the HA scaffold can more efficiently promote osteogenic differentiation of bone marrow stromal cells (BMSCs) in vitro and induce ectopic bone formation to a much greater level in vivo compared with a bare HA scaffold that delivers BMP2 in a burst manner. All of these results suggest that the PDA-mediated catechol modification of the HA scaffold can be an effective strategy to develop sustainable protein delivery system, and that the PLL/PDA-coated HA scaffold could be a promising candidate for bone tissue engineering applications. [ABSTRACT FROM AUTHOR]

Highlights • γ-Fe 2 O 3 was modified with silica, PEI, PEG and phenolic compound-modified poly(l -lysine). • The particles were readily internalized by the glioma cells. • Poly(l -lysine)-based coating was responsible for the increased antioxidant effects. Abstract Natural antioxidants, such as epigallocatechin-3-gallate and related phenolic compounds from tea, enhance particle cell-interactions and cellular uptake. In this study, surface of superparamagnetic iron oxide nanoparticles prepared by co-precipitation of Fe chlorides was modified with silica, polyethylenimine, poly(ethylene glycol), and poly(l -lysine) to protect the iron oxide core from redox-reactions with phenols, enhance uptake by the cells, prevent the particle aggregation, or enable conjugation with several phenol-based antioxidants. To reveal the relation between the particle uptake and chemical structure of the phenolic antioxidants, five of them were selected, namely phenol, phloroglucinol, chlorogenic, gallic, and tannic acid. After incubation of the phenol-modified nanoparticles with U87MG human glioma cells, intracellular levels of the reactive oxygen species were reduced in a similar manner, as measured by flow cytometry. Colorimetric iron assay revealed a comparable level of cell-associated particles, which was mostly independent on the applied external magnetic field. The results suggest that the poly(l -lysine)-based coating is responsible for the antioxidant effects of the particles; the phenol- and poly(l -lysine)-coatings enable effective colloidal stability in aqueous media and enhance cellular internalization of the nanoparticles. [ABSTRACT FROM AUTHOR]

The structure and kinetics of the complex formed by hyaluronic acid (HA) and poly(L-lysine) (PLL) were studied by time-resolved laser light scattering, TEM, and AFM. Because HA has a hydrophilic backbone, the complexes formed by HA and PLL are different from those formed by oppositely charged polyelectrolytes both having hydrophobic backbones. Instead of forming strong aggregates and even precipitates, the complex in the presence of excess HA is stable in the studied time period. More importantly, the complex spontaneously forms core-corona structure by the rearrangement of HA chains. The core is composed of complex rich of PLL and the corona is mainly HA. Further analysis shows that the hydrogen bond formed by HA creates a barrier hindering the further relaxation of HA chains. The automatic formation of core-corona structure by PLL/HA is helpful not only to understand the relaxation of polyelectrolyte in complex, but also to develop drug carriers with desirable properties. [ABSTRACT FROM AUTHOR]

Background: Cell tracking is a powerful tool to understand cellular migration, dynamics, homing and function of stem cell transplants. Nanoparticles represent possible stem cell tracers, but they differ in cellular uptake and side effects. Their properties can be modified by coating with different biocompatible polymers. To test if a coating polymer, poly(L-lysine), can improve the biocompatibility of nanoparticles applied to neural stem cells, poly(L-lysine)-coated maghemite nanoparticles were prepared and characterized. We evaluated their cellular uptake, the mechanism of internalization, cytotoxicity, viability and proliferation of neural stem cells, and compared them to the commercially available dextran-coated nanomag®-D-spio nanoparticles.Results: Light microscopy of Prussian blue staining revealed a concentration-dependent intracellular uptake of iron oxide in neural stem cells. The methyl thiazolyl tetrazolium assay and the calcein acetoxymethyl ester/propidium iodide assay demonstrated that poly(L-lysine)-coated maghemite nanoparticles scored better than nanomag®-D-spio in cell labeling efficiency, viability and proliferation of neural stem cells. Cytochalasine D blocked the cellular uptake of nanoparticles indicating an actin-dependent process, such as macropinocytosis, to be the internalization mechanism for both nanoparticle types. Finally, immunocytochemistry analysis of neural stem cells after treatment with poly(L-lysine)-coated maghemite and nanomag®-D-spio nanoparticles showed that they preserve their identity as neural stem cells and their potential to differentiate into all three major neural cell types (neurons, astrocytes and oligodendrocytes).Conclusion: Improved biocompatibility and efficient cell labeling makes poly(L-lysine)-coated maghemite nanoparticles appropriate candidates for future neural stem cell in vivo tracking studies.

The deposition of polyelectrolyte (PEL) multilayers (PEMs) of poly(l-lysine)/cellulose sulfate (PLL/CS) onto germanium (Ge) substrates depending on salt concentration (cS) and deposition step z at constant PEL concentration cPEL = 0.01 M and pH = 7.0 was studied. In situ ATR-FTIR spectroscopy was used for the quantitative determination of alternate PLL/CS deposition profiles (adsorbed amount versus z) and total deposited PEM amount. By varying cS from 0 M to 1.0 M, a maximum of deposited amount was obtained at 0.1 M, so that both no salinity (0 M) and high salinity (1.0 M) revealed deposited amounts that were far lower than for mean salinity (0.1 M). Furthermore, in situ ATR-FTIR allowed to determine the detailed modulation of the PEL composition during the consecutive PEM deposition, which was interpreted as being due to both diffusion of given PEL from the PEM interior towards the outermost region and release of the PEM upon contact with the bulk oppositely charged PEL solution. Finally, ex situ ATR-FTIR measurements on the PEL solutions after deposition of PEM-20 revealed the distinct release of PEL from the PEM solely for cS = 1.0 M, due to the highest mobility of PEL under high salt conditions. These studies help to prepare functional PEM coatings with defined thicknesses and morphologies for the passivation and activation of material surfaces in the biomedical and food field.

Bacterial infections and the associated morbidity and mortality due to bacterial pathogens in wounds and medical implants have been increasing as most of current coatings cannot fulfill all the requirements including excellent intrinsically antibacterial activity, low cytotoxicity, and favorable physical properties. Herein, we present a kind of antibacterial hydrogel based on ε-poly(L-lysine) (EPL) grafted carboxymethyl chitosan (CMC-g-EPL) as the inherently antibacterial matrix and the surplus EPL as highly efficient antimicrobial agent. Such hydrogels possess tunable swelling abilities with water absorption percentages of 800%-2000% and modulus varying from 10 kPa to 100 kPa, and exhibit two-stage excellent antibacterial behavior. First, the free EPL can be released from the hydrogel network for quick and highly efficient bacteria killing with 99.99% of efficacy; second, the grafted EPL endows hydrogel matrix with prolonged intrinsically antibacterial activity, especially when most of free EPL is released from the hydrogel. Overall, we provide a new insight for preparing highly effective antibacterial hydrogels. [ABSTRACT FROM AUTHOR]

The polyplexes formed by nucleic acids and polycations have received a great attention owing to their potential application in gene therapy. In our study, we report experimental results and modeling outcomes regarding the optimization of polyplex formation between the double-stranded DNA (dsDNA) and poly(L-Lysine) (PLL). The quantification of the binding efficiency during polyplex formation was performed by processing of the images captured from the gel electrophoresis assays. The design of experiments (DoE) and response surface methodology (RSM) were employed to investigate the coupling effect of key factors (pH and N/P ratio) affecting the binding efficiency. According to the experimental observations and response surface analysis, the N/P ratio showed a major influence on binding efficiency compared to pH. Model-based optimization calculations along with the experimental confirmation runs unveiled the maximal binding efficiency (99.4%) achieved at pH 5.4 and N/P ratio 125. To support the experimental data and reveal insights of molecular mechanism responsible for the polyplex formation between dsDNA and PLL, molecular dynamics simulations were performed at pH 5.4 and 7.4. [ABSTRACT FROM AUTHOR]

Angiogenesis plays an important role in both soft and hard tissue regeneration, which can be modulated by therapeutic drugs. If nanoparticles (NP) are used as vectors for drug delivery, they have to encounter endothelial cells (EC) lining the vascular lumen, if applied intravenously. Herein the interaction of unloaded polyelectrolyte complex nanoparticles (PECNP) composed of cationic poly(l-lysine) (PLL) and various anionic polysaccharides with human vascular endothelial cells (HUVEC) was analyzed. In particular PECNP were tested for their cell adhesive properties, their cellular uptake and intracellular localization considering composition and net charge. PECNP may form a platform for both cell coating and drug delivery. PECNP, composed of PLL in combination with the polysaccharides dextran sulfate (DS), cellulose sulfate (CS) or heparin (HEP), either unlabeled or labeled with fluorescein isothiocyanate (FITC) and either with positive or negative net charge were prepared. PECNP were applied to human umbilical cord vein endothelial cells (HUVEC) in both, the volume phase and immobilized phase at model substrates like tissue culture dishes. The attachment of PECNP to the cell surface, their intracellular uptake, and effects on cell proliferation and growth behavior were determined. Immobilized PECNP reduced attachment of HUVEC, most prominently the systems PLL/HEP and PLL/DS. A small percentage of immobilized PECNP was taken up by cells during adhesion. PECNP in the volume phase showed no effect of the net charge sign and only minor effects of the composition on the binding and uptake of PECNP at HUVEC. PECNP were stored in endosomal vesicles in a cumulative manner without apparent further processing. During mitosis, internalized PECNP were almost equally distributed among the dividing cells. Both, in the volume phase and immobilized at the surface, PECNP composed of PLL/HEP and PLL/DS clearly reduced cell proliferation of HUVEC, however without an apparent cytotoxic effect, while PLL/CS composition showed minor impairment. PECNP have an anti-adhesive effect on HUVEC and are taken up by endothelial cells which may negatively influence the proliferation rate of HUVEC. The negative effects were less obvious with the composition PLL/CS. Since uptake and binding for PLL/HEP was more efficient than for PLL/DS, PECNP of PLL/HEP may be used to deliver growth factors to endothelial cells during vascularization of bone reconstitution material, whereas those of PLL/CS may have an advantage for substituting biomimetic bone scaffold material.

Narrowly distributed poly(l-lysine-b-N-isopropylacrylamide) (PLL-b-PNIPAM) was prepared through ring-opening polymerization of ε-benzyloxycarbonyl-l-lysine N-carboxy-α-amino anhydride and atom transfer radical polymerization of NIPAM, followed with the removal of ε-benzyloxycarbonyl group. Then gold nanoparticles (AuNPs) grafted with PLL-b-PNIPAM (PNIPAM-PLL-AuNPs) were obtained by the reduction of chloroauric acid with sodium citrate in the presence of PLL-b-PNIPAM. PNIPAM-PLL-AuNPs and its precursors were thoroughly characterized by proton magnetic resonance spectroscope, Fourier transform infrared spectroscope, UV-vis spectroscope, transmission electron microscopy, dynamic light scattering, thermogravimetric analysis, and circular dichroism. The obtained PNIPAM-PLL-AuNPs exhibited high colloid stability even at strong alkaline (pH = 12) and acidic (pH = 2) conditions. The thermal and pH dual-responsive behaviors of the grafting PLL-b-PNIPAM chains was observed to be affected by AuNPs, while not for the secondary structure of PLL chains. Correspondingly, the surface plasmon resonance (SPR) of AuNPs was found to be sensitive to both pH value and temperature. A blue shift in the SPR happened both with increasing pH value and increasing temperature. The stimuli-response was reversible in heating-cooling cycles. The gold nanoparticles with both pH and temperature response may have potential applications in biomedical areas and biosensors.

Cylindrical copolypeptide brush PLLF- g-(PLF- b-PLL), consisting of a poly(L-lysine- co-L-phenylalanine) (PLLF) backbone and poly(L-phenylalanine)- b-poly(L-lysine) (PLF- b-PLL) amphiphilic block copolypeptide side chains, has been synthesized, characterized, and evaluated as drug and gene carriers. PLLF- g-(PLF- b-PLL) brushes were synthesized by the multi-step ring-opening polymerization of amino acid N-carboxyanhydrides via a 'grafting from' strategy. Transmission electron microscopy measurements and pyrene probe fluorescence study revealed that the synthesized copolypeptide brushes adopted nanosized cylindrical morphologies which resembled unimolecular polymeric micelles with a hydrophobic PLF core and a hydrophilic PLL periphery. An encapsulation study demonstrated that hydrophobic molecules (e.g., pyrene and oil red O) can be solubilized in the core of the copolypeptide brushes, while anionic hydrophilic molecules (e.g., rose bengal and methyl orange) can be entrapped into the brush periphery. Hydrophobic molecules and hydrophilic guests can be encapsulated simultaneously in a site-isolated state. Furthermore, the in vitro gene transfection efficiencies of copolypeptide brushes were evaluated in HEK293 and HeLa cells. The synthesized copolypeptide brushes exhibited low cytotoxicity and mediated efficient gene transfection. Our research suggested that these cylindrical copolypeptide brushes with a brush-like PLL periphery could be used as promising carriers for the codelivery of drugs and genes. [ABSTRACT FROM AUTHOR]

A novel, simple and selective electrochemical method was investigated for the simultaneous detection of dopamine (DA) and uric acid (UA) on a poly(L-lysine)/graphene oxide (GO) modified glassy carbon electrode (PLL/GO/GCE) by differential pulse voltammetry (DPV). The electrochemically prepared PLL/GO sensory platform toward the oxidation of UA and DA exhibited several advantages, including high effective surface area, more active sites and enhanced electrochemical activity. Compared to the PLL-modified GCE (PLL/GCE), GO-modified GCE and bare GCE, the PLL/GO/GCE exhibited an increase in the anodic potential difference and a remarkable enhancement in the current responses for both UA and DA. For the simultaneous detection of DA and UA, the detection limits of 0.021 and 0.074 μM were obtained, while 0.031 and 0.018 μM obtained as the detection limits for the selective detection of UA and DA, using DPV in the linear concentration ranges of 0.5 to 20.0 and 0.5 to 35 μM, respectively. In addition, the PLL/GO/GCE demonstrated good reproducibility, long-term stability, excellent selectivity and negligible interference of ascorbic acid (AA). The proposed modified electrode was successfully implemented in the simultaneous detection of DA and UA in human blood serum, urine and dopamine hydrochloride injection with satisfactory results. [ABSTRACT FROM AUTHOR]

Highlights: [•] Characterization of polymer hydrophobicity. [•] Determination of polymer log D distributions. [•] Applications to cationic polylysines derivatives. [•] Comparison between MEKC and MEEKC. [Copyright &y& Elsevier]

Abstract: A hydrophilic star block co-polymer was synthesized, characterized, and evaluated as a protein nanocarrier. The star block co-polymer was composed of a hyperbranched polyethylenimine (PEI) core, a poly(l-lysine) (PLL) inner shell, and a poly(ethylene glycol) (PEG) outer shell. The model protein insulin can be rapidly and efficiently encapsulated by the synthesized polymer in aqueous phosphate buffer at physiological pH. Complexation between PEI–PLL–b-PEG and insulin was investigated using native polyacrylamide gel electrophoresis. The uptake of enhanced green fluorescent protein into Ad293 cells mediated by PEI–PLL–b-PEG was also investigated. The encapsulated insulin demonstrated sustained release at physiological pH and showed accelerated release when the pH was decreased. The insulin released from the star block co-polymer retained its chemical integrity and immunogenicity. [Copyright &y& Elsevier]

Abstract: Star-block copolymers PEI-g-(PLL-b-PEG) with a branched polyethylenimine (PEI) core, a poly(l-lysine) (PLL) inner shell, and a poly(ethylene glycol) (PEG) outer shell have been synthesised and evaluated as potential nanocarriers for anionic drugs. The star-block copolymers were synthesised by a ring-opening polymerisation of ɛ-benzyloxycarbonyl-l-lysine N-carboxyanhydride initiated by the peripheral primary amino groups of PEI, surface modification with activated PEG 4-nitrophenyl carbonate, and subsequent deprotection of benzyl groups on the side chains of the PLL inner shell. The synthesised star-block copolymers were characterised by 1H NMR, gel permeation chromatography (GPC), and dynamic light scattering (DLS). The encapsulation properties of these star-block copolymers were characterised by spectrophotometric titration and dialysis. These techniques demonstrated that anionic model dyes, such as methyl orange and rose Bengal, and the model drug diclofenac sodium can be encapsulated efficiently by PEI-g-(PLL-b-PEG) at physiological pH. The entrapped model compounds demonstrated sustained release at physiological pH and accelerated release when the pH was either increased to 10.0–11.0 or decreased to 2.0–3.0. The efficient encapsulation as well as the pH-responsive releasing properties of these star-block copolymers could be potentially used in the controlled release of anionic drugs. [Copyright &y& Elsevier]

Abstract: Poly(l-lysine) (PLL) has excellent plasmid DNA (pDNA) condensation capacity. However, the relatively high cytotoxicity and low transfection efficiency limit its application as gene delivery vectors. Here, well-defined glycopolymers are synthesized by reversible addition fragmentation transfer polymerization and grafted onto PLL to improve the gene delivery performance. After glycopolymer modification, PLL shows reduced cytotoxicity. By regulating the glycopolymer length and amino group substitution degree, the glycopolymer modified PLL can condense pDNA with proper strength, protect the condensed pDNA from degradation and release them in time. Transfection with NIH3T3 and HepG2 cells shows that the glycopolymer modified PLL has improved transfection efficiencies. The low cytotoxicity, effective pDNA protection and enhanced transfection efficiencies indicate that glycopolymer modification would be an effective strategy to improve the polycation properties for gene delivery. [Copyright &y& Elsevier]

Abstract: Thin films formed via the adsorption or layer-by-layer assembly of charged polymers are important in many sensing, energy, and biomedical applications. When the underlying substrate is a (semi)conductor, the opportunity exists to influence film formation and film properties through an applied electric potential. The recent literature on electrochemical influence of polyelectrolyte-based films is reviewed, with a focus on monolayer and multilayer film assembly and disassembly. Of particular interest are monolayer films grown to a tailored thickness on the 10–100nm scale, and polyelectrolyte multilayer films controllably disassembled, upon application of a modest electric potential. Experimental observations are discussed in terms of governing factors such as interfacial pH and ionic composition, counter-ion correlations, charge regulation, dielectric discontinuity, and short-range polymer–polymer interactions. Recent modeling efforts are also briefly addressed. [Copyright &y& Elsevier]

Abstract: Although polymers, polyplexes, and cells are exposed to various extracellular and intracellular pH environments during polyplex preparation and polymeric transfection, the impact of environmental pH on polymeric transfection has not yet been investigated. This study aims to understand the influence of environmental pH on polymeric transfection by modulating the pH of the transfection medium or the culture medium. Changes in the extracellular pH affected polymeric transfection by way of complex factors such as pH-induced changes in polymer characteristics (e.g., proton buffering capacity and ionization), polyplex characteristics (e.g., size, surface charge, and decomplexation), and cellular characteristics (e.g., cellular uptake, cell cycle phases, and intracellular pH environment). Notably, acidic medium delayed endocytosis, endosomal acidification, cytosolic release, and decomplexation of polyplexes, thereby negatively affecting gene expression. However, acidic medium inhibited mitosis and reduced dilution of gene expression, resulting in increased transfection efficiency. Compared to pH 7.4 medium, acidic transfection medium reduced gene expression 1.6–7.7-fold whereas acidic culture medium enhanced transfection efficiency 2.1–2.6-fold. Polymeric transfection was affected more by the culture medium than by the transfection medium. Understanding the effects of extracellular pH during polymeric transfection may stimulate new strategies for determining effective and safe polymeric gene carriers. [Copyright &y& Elsevier]

Starting from MPEG-NH, a series of amphiphilic triblock copolymers MPEG- b-PLL- b-PLA were synthesized through PEG-NH-initiated ring-open polymerization of Nbenzyloxycarbonyl- L-lysine, followed by acylation coupling between the amino-terminated MPEG- b-PZLL-NH and carboxyl-terminal PLA and the deprotection of amines. The block copolymers were characterized by FT-IR, H NMR, GPC, DSC and TEM. The copolymer functional groups, molecular and block structures were verified by FT-IR, H NMR and DSC, respectively. The GPC results indicate that the chain lengths of each block can be controlled by varying the feed ratios of the monomer and initiator, providing the polymer samples with a narrow molecular weight distribution ( M /M = 1.10 ~ 1.25). The TEM analysis shows that the triblock polymers can self-assemble into polymeric micelles in aqueous solution with spherical morphology. The cell-cytotoxicity assay indicates that the triblock polymers show no obvious cytotoxicity against Bel7402 human hepatoma cells. [ABSTRACT FROM AUTHOR]

Among the well-studied polypeptide-type gene carriers, transfection efficiency is empirically known to be higher for poly(L-arginine) (PR) than poly(L-lysine) (PK). The big difference between PR and PK should be determined at one of the intracellular trafficking steps based on the different charge densities, structures or PKa values. However, the endosomal escape and the intranuclear transcription efficiency in living cells have not been clarified yet. In this study, a novel method for quantifying the intranuclear transcription efficiency and the nuclear transport of the polyplex is established based on the nuclear and the cytosolic microinjection technique, and the results for PK and PR with different molecular weights (MWs) are compared in living cells. The intranuclear transcription efficiency is the same in PR and PK and it decreases rapidly with increasing MW, in spite of the commonly measured transfection efficiency. The transcription efficiency is strongly suppressed at high MW and strongly correlates with the polyplex forming ability expressed as a critical ratio of the number of polypeptide cationic groups to the number of pDNA anionic groups. When considered with the results of the cellular uptake and in vitro transfection with or without chloroquine, the rate-limiting step for their gene transfer is the buffering effect-independent endosomal escape. [ABSTRACT FROM AUTHOR]

A non-viral gene-delivery system has been used to deliver plasmid DNA into specific cell types because of its safety and ease of manufacture. Receptor-mediated gene transfer is currently a promising gene-delivery technique. To specifically target genes to asialoglycoprotein receptor of hepatocytes, a galactose moiety was combined into the poly(ethylene glycol) (PEG)-terminal end by reductive coupling using lactose and sodium cyanoborohydride. A synthesis method of conjugating poly(L-lysine) (PLL) derivatives with terminally galactose-graft-PEG was developed using ring-opening polymerization of Nε-benzyloxycarbonyl-L-lysine-Nα-carboxyan-hydride (Z-Lys-NCA) initiated onto galactose graft amine-terminated PEG (galactose-PEG-NH2) as a macro-initiator. The synthesis was characterized with 1H-, 13C-NMR, IR and UV spectroscopy, and all of them successfully verified the formation of the co-polymers. The gel-retardation assay of the complexes between galactose-PEG-PLL and plasmid DNA indicated that these polymeric gene carriers demonstrated the potent ability to condense plasmid DNA electrostatically as well as PLL. The particle size and zeta potential of polymer/DNA complexes were measured, and their cytotoxicity and transfection efficiency in different cells were evaluated. The results indicate that galactose-PEG-PLL can form a complex with plasmid DNA and serve as an effective gene-delivery carrier with lower cytotoxicity compared to that of PLL. Transfection experiments clearly showed that galactose-PEG-PLL effectively delivered DNA into hepatoma cells in vitro. Such data demonstrates that galactose and its complex with plasmid DNA may serve as a safe and effective gene-transfer system targeting hepatocytes. [ABSTRACT FROM AUTHOR]

Poly( l-lysine) is a water-soluble, synthetic polypeptide containing functional amine groups that help remove di- and trivalent metal ions from aqueous solutions. This polymer's removal properties were studied under different experimental conditions: (1) competitive and non-competitive conditions; (2) different pHs; and (3) filtration factors. Under the conditions of the Liquid-Phase Polymer-Based Retention (LPR) technique, the cooper (II) ion interaction was found to be selective and efficient when compared to other divalent metal ions studied. However, interestingly, this selectivity disappeared when trivalent metal ions were present. The polymer-metal ion interactions are based on the amino groups of the side-chains as well as the polypeptide backbone chain. The removal of metal ions was strongly dependent on the pH. By structural characterization with FT-IR and EPR spectroscopy, participation of the amide and mainly amine groups was found to take place for the coordination. For the Cu, coordination through four amine nitrogen donor atoms in the primary coordination sphere was detected. Antibacterial activity tests were conducted with the poly( l-lysine)-Cu complex and showed a higher activity in comparison with the precursors Cu and poly( l-lysine) at the same concentrations for E. coli (6538P), a Gram-negative bacterium, and S. aureus (ATCC), a Gram-positive bacterium. [ABSTRACT FROM AUTHOR]

Abstract: The adsorption behavior of poly(ethylene oxide)-b-poly(l-lysine) (PEO113-b-PLL10) copolymer onto silica nanoparticles was investigated in phosphate buffer at pH 7.4 by means of dynamic light scattering, zeta potential, adsorption isotherms and microcalorimetry measurements. Both blocks have an affinity for the silica surface through hydrogen bonding (PEO and PLL) or electrostatic interactions (PLL). Competitive adsorption experiments from a mixture of PEO and PLL homopolymers evidenced greater interactions of PLL with silica while displacement experiments even revealed that free PLL chains could desorb PEO chains from the particle surface. This allowed us to better understand the adsorption mechanism of PEO-b-PLL copolymer at the silica surface. At low surface coverage, both blocks adsorbed in flat conformation leading to the flocculation of the particles as neither steric nor electrostatic forces could take place at the silica surface. The addition of a large excess of copolymer favoured the dispersion of flocs according to a presumed mechanism where PLL blocks of incoming copolymer chains preferentially adsorbed to the surface by displacing already adsorbed PEO blocks. The gradual addition of silica particles to an excess of PEO-b-PLL copolymer solution was the preferred method for particle coating as it favoured equilibrium conditions where the copolymer formed an anchor-buoy (PLL-PEO) structure with stabilizing properties at the silica-water interface. [Copyright &y& Elsevier]

Abstract: A major challenge in gene therapy is the development of effective gene delivery vectors with low toxicity. In the present study, linear poly(ethylenimine) (lPEI) with low molecular weight was grafted onto the block copolymer (PPL) of poly(l-lysine) (PLL) and poly(ethylene glycol)(PEG), yielding a ternary copolymer PEG-b-PLL-g-lPEI (PPI) for gene delivery. In such molecular design, PLL, lPEI and PEG blocks were expected to render the vector biodegradability, proton buffering capacity, low cationic toxicity and potentially long circulation in vivo, respectively. Given proper control of molecular composition, the copolymers demonstrated lower cytotoxicity, proton buffering capacity, ability to condense pDNA and mediate effective gene transfection in various cell lines. With folate as an exemplary targeting ligand, the FA-PPI/pDNA complex showed much higher transgene activity than its nontargeting counterpart for both reporter and therapeutic genes in folate receptor(FR)-positive cells. FA-PPI mediated effective transfection of the TNF-related apoptosis-inducing ligand gene (TRAIL) in human hepatoma Bel 7402 cells, leading to cell apoptosis and great suppression of cell viability. Our results indicate that the copolymers might be a promising vector combining low cytotoxicity, biodegradability, and high gene transfection efficiency. [Copyright &y& Elsevier]

Time-lapse digital images were taken every 30 s of PC12 cells cultured on polystyrene dishes, collagen-coated dishes and poly(L-lysine)-coated dishes in high-serum medium, low-serum medium and neurite outgrowth factor (NGF)-containing medium to investigate their diffusion coefficients (i.e., self-diffusion coefficients), D and specific movement (i.e., specific frequent movement) using image analysis and Fast Fourier Transform (FFT) analysis. D for these cells was found to fluctuate as a function of time, D varying between 0 and 0.08 μm2/s. The trend observed upon examination of average D values was: D in high-serum medium ≥ D in low-serum medium ≥ D in NGF-containing medium. Image analysis and FFT analysis of single cells cultured on polymeric dishes in these three media did not have any specific frequency of cell movement between 0 and 0.0167 Hz. The high diffusion coefficient and high amplitude of power spectra of PC12 cells in high-serum medium might be attributed to the high energy necessary for their continual suppression of the mitogen-activated protein kinase (MAPK) cascade and for them to maintain their undifferentiated state. [ABSTRACT FROM AUTHOR]

Abstract: Central to gene therapy technology has been the use of cationic polymers as vectors for DNA and RNA (polyfectins). These have been presumed to be safer than viral systems which, for example, have been found to switch on oncogenes. Two key polycations that have been intensively researched for use as synthetic vectors are poly(ethylenimine) and poly(l-lysine). A frequent stumbling block with these polyfectins is that long-term gene expression in cell lines has not been achieved. Recently it has transpired that both of these polycations can induce mitochondrially mediated apoptosis. It is the aim of this review to discuss the mechanisms behind the observed polycation toxicity including roles for little studied cellular organelles in the process such as the lysosome and endoplasmic reticulum. [Copyright &y& Elsevier]

Abstract: Optical reflectometry was used to study adsorption behavior of poly(l-lysine) (PLL) on the water–silica interface for different pH and concentrations of the monovalent salt NaBr. At low salt level and low pH, the adsorbed amount increases with increasing salt concentration and pH. This adsorption behavior can be qualitatively explained by electrostatic interactions between the negatively charged substrate and the positively charged polyelectrolyte. At higher salt levels and pH, the adsorbed amount passes through a maximum. This maximum is probably related to the competition between adsorbing monovalent cations and the polyelectrolyte. The initial adsorption kinetics is mainly controlled by the mass transport to the surface. [Copyright &y& Elsevier]

Abstract: While multidrug resistance (MDR) has been a significant issue in cancer chemotherapy, delivery resistance to various anti-cancer biotherapeutics, including genes, has not been widely recognized as a property of MDR. This study aims to provide a better understanding of the transfection characteristics of drug-sensitive and drug-resistant cells by tracing microenvironmental pHs of two representative polymer vectors: poly(l-lysine) and polyethyleneimine. Drug-sensitive breast MCF7 cells had four- to seven-times higher polymeric transfection efficiencies than their counterpart drug-resistant MCF7/ADR-RES cells. Polyplexes in MCF7/ADR-RES cells after endocytosis were exposed to a more acidic microenvironment than those in MCF7 cells; the MDR cells show faster acidification rates in endosomes/lysosomes than the drug-sensitive cells after endocytosis (in the case of PLL/pDNA complexes, ∼ pH 5.1 for MCF7/ADR-RES cells vs. ∼ pH 6.8 for MCF7 cells at 0.5 h post-transfection). More polyplexes were identified trapped in acidic subcellular compartments of MCF7/ADR-RES cells than in MCF7 cells, suggesting that they lack endosomal escaping activity. These findings demonstrate that the design of polymer-based gene delivery therapeutics should take into account the pH of subcellular compartments. [Copyright &y& Elsevier]

Abstract: In this work, we fabricated a sensitivity chronocoulometric DNA sensor (CDS) based on gold nanoparticles (AuNPs)/poly(l-lysine) complex film modified glassy carbon electrode. Hexaammineruthenium(III) chloride ([Ru(NH3)6]3+) was used as the electroactive indicator. The assembled process was investigated by cyclic voltammetry (CV) and chronocoulometry (CC). CC is used to monitor the DNA hybridization event by measurement of electrostatic binding [Ru(NH3)6]3+. Under the optimal conditions, the signal of [Ru(NH3)6]3+ was linear with the logarithm of the concentration of the complementary oligonucleotides from 1.0×10−13 to 1.0×10−11 M, and the detection limit is 3.5×10−14 M. [Copyright &y& Elsevier]

Abstract: Hybrid coatings of poly(L-lysine) and apatite were formed on the micro-arc oxidized titania through a biomimetic process. Phosphorous (P)-containing titania films were prepared by micro-arc oxidation (MAO) of titanium (Ti) substrates in an electrolyte solution containing β-glycerol phosphate disodium salt pentahydrate. The hybrid coatings were grown by immersing MAO titania in the poly(L-lysine)-containing simulated body fluid (SBF) solution. After 72 h immersion, the globular precipitates appeared on the surface of titania films and grew up to ~10 µm. These precipitates consisted of 100–200 nm nano-flakes with a distorted (less straight) morphology. XRD and FT-IR confirmed that these precipitates were poly(L-lysine)-containing apatite nanocomposite. [Copyright &y& Elsevier]

Hyaluronic acid (HA) hydrogel was modified with poly(L-lysine) (PLL) and Nogo-66 Receptor antibody (antiNgR) to enhance the repair of central nervous system (CNS) injuries. The immobilization of PLL was characterized by X-ray photoelectron spectroscopy (XPS) and the immobilization of antiNgR was studied by immunofluorescence. The cytocompatibility of this modified hydrogel was analyzed by culturing primary hippocampal neurons. The quantity and morphology of the neurons were influenced by different modifications; the primary hippocampal neurons cultured with modified HA hydrogel exhibited multipolar and bipolar morphology were compared with unmodified hydrogel cultures. The number of neurons obtained by culturing with HA hydrogel modified with both PLL and antiNgR was almost twice the number of neurons cultured with HA modified with only PLL or antiNgR. This phenomenon was attributed to the collaborative effect of PLL and antiNgR on the neurons. The characteristics of this new hydrogel system, including pore structure, water absorption, hydrolysis degradation did not change much when compared with the hydrogel modified with PLL or antiNgR, respectively. It is expected that this modified HA hydrogel has potential as a CNS tissue engineering material. [ABSTRACT FROM AUTHOR]

The effect of surface charge on the protein resistance of adsorbed layers of poly(ethylene imine)‐[g]‐poly(ethylene glycol), PEI‐PEG, and poly(L‐lysine)‐[g]‐poly(ethylene glycol), PLL‐PEG, was studied. Mixed and monofunctional self‐assembled monolayers, SAMs, on gold were obtained by adsorption of 16‐mercapto‐1‐hexadecanoic acid and 16‐mercapto‐1‐hexadecanol. The surface charge was systematically varied by changing the ratio of the two alkanethiols. The graft copolymers PEI‐PEG and PLL‐PEG were adsorbed at the SAMs and tested for resistance towards human serum albumin and fibrinogen. The adsorbed amount of copolymers increased with increasing negative surface charge. However, the best protein resistance was found at an intermediate surface charge. The PLL‐PEG covered surfaces showed better protein resistance than the PEI‐PEG covered surfaces. Thus, this work demonstrates that an adsorbed layer of PEG‐grafted PEI and, in particular, PEG‐grafted PLL is efficient in preventing protein adsorption when there is charge neutralization between the copolymer and the underlying surface. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009 [ABSTRACT FROM AUTHOR]

Polylysine is a biocompatible, biodegradable, water soluble polypeptide. Thanks to the pendant primary amines it bears, it is susceptible to modification reactions. In this work Poly(L-lysine) (PLL) was partially modified via the effortless free-catalysed aza-Michael addition reaction at room temperature by grafting N-isopropylacrylamide (NIPAm) moieties onto the amines. The resulting PLL-g-NIPAm exhibited LCST-type thermosensitivity. The LCST can be tuned by the NIPAm content incorporated in the macromolecules. Importantly, depending on the NIPAm content, LCST is highly dependent on pH and ionic strength due to ionization capability of the remaining free lysine residues. PLL-g-NIPAm constitutes a novel biodegradable LCST polymer that could be used as "smart" block in block copolymers and/or terpolymers, of any macromolecular architecture, to design pH/Temperature-responsive self-assemblies (nanocarriers and/or networks) for potential bio-applications. [ABSTRACT FROM AUTHOR]

Abstract: Hyperbranched poly(amido amine)s containing vinyl and hydroxyl groups were successfully synthesized via Michael addition polymerization of triacrylamide (TT) and 3-amino-1,2-propanediol (APD) with equal molar ratio in feed. 1H, 13C and HSQC NMR techniques were used to clarify the structure of hyperbranched polymers and polymerization mechanism. The Michael addition reaction of hyperbranched poly(1TT-1APD)s with primary amine-terminated poly(ε-benzyloxycarbonyl-l-lysine)s [PLys(Z)] yielded a star-like hyperbranched polymers with poly(1TT-1APD) core and Plys(Z) shell. The Z groups in PLys(Z) were removed under acidolysis, and thus star-like hyperbranched polymers with hydroxyl groups inside and primary amine groups outside were obtained successfully. [Copyright &y& Elsevier]

Abstract: A promising application of the multivariate curve resolution based on alternating least squares (MCR-ALS) method is reported for the analysis of the temperature-dependent conformational changes in poly(l-lysine) (PLL). The MCR-ALS approach has enabled detection of three structural components developed during the melting experiment. Most important is an infrared signature of the intermediate component described as a mixture of native α-helical conformation and its extended forms. [Copyright &y& Elsevier]

The potential of novel amphiphilic water soluble and degradable poly(e-caprolactone)-g-poly(L-lysine) as carriers for DNA transfection has been investigated. Two graft copolymers having the same proportion of lysine units but different structures have been synthesized following two grafting techniques. The chemical composition of these copolymers, their expected architectures and their behaviour in aqueous solutions have been studied. The benefits resulting from the use of these degradable polycationic structures as well as their ability to form polyplexes are discussed. Finally, preliminary transfection assays of MCF-7 cells by pRL-TK plasmid using poly(ϵ-caprolactone)-g-poly(L-lysine) copolymers as carriers are reported. [ABSTRACT FROM AUTHOR]

Abstract: The current study compared the effectiveness of an amphiphilic biomaterial poly(l-lysine)-palmitic acid (PLL–PA), and the lipid-based transfection agent Lipofectamine™ 2000 for plasmid delivery to bone marrow stromal cells (BMSC). We investigated the utility of the carriers to deliver a plasmid containing enhanced green fluorescent protein (pEGFP) to BMSC in vitro. Confocal microscopy was used to investigate the intracellular trafficking of pEGFP/carrier complexes. pEGFP delivery and EGFP expression were assessed by flow cytometry. PLL–PA formed condensed structures with pEGFP and successfully delivered the plasmid into the nucleus within 5h of incubation with the cells. PLL–PA delivered the pEGFP to ∼80% of the cells, achieving a maximum transfection efficiency of ∼22%. This was significantly higher than Lipofectamine™ 2000-mediated transfection, which was 11% under most optimal conditions. Dosing the BMSC two or three times during the 24h period increased the transfection efficiency by 2–3 folds, without compromising cell viability. When chloroquine was employed as an ensomolytic agent, 100μm of the drug increased the transfection efficiency while reducing cell viability, but lower concentrations (1–10μm) were not beneficial for transfection. Combining PLL–PA with Lipofectamine™ 2000 created an additive effect, increasing the transfection efficiency of PLL–PA. Long-term evaluation of gene expression with pEGFP/PLL–PA yielded ∼17% transfection on day 1, which gradually decreased over a 12-day period. We conclude that PLL–PA is an effective biomaterial carrier and a promising candidate for non-viral gene delivery to BMSC. [Copyright &y& Elsevier]

Neural progenitor cells (NPCs) have shown promise in a number of models of disease and injury, but for these cells to be safe and effective, they must be directed to differentiate appropriately following transplantation. We have developed a photopolymerized hydrogel composed of macromers of poly(ethylene glycol) (PEG) bound to poly(L-lysine) (PLL) that supports NPC survival and directs differentiation. Green fluorescent protein (GFP) positive NPCs were encapsulated in these gels and demonstrated survival up to 17 days. When encapsulated in the gels at a photoinitiator concentration of 5.0 mg/ml, few NPCs (0.5 ± 0.25%) demonstrated apoptosis. Furthermore, 55 ± 6% of the NPCs cultured within the gels in epidermal growth factor (EGF) containing media differentiated into a mature neuronal cell type (neurofilament 200 positive) while the remainder 44 ± 8% were undifferentiated (nestin positive). A small percentage, 1 ± 0.4%, expressed the astrocytic marker glial acidic fibrilary protein. Photopolymerized PEG/PLL gels promote the survival and direct the differentiation of NPCs, making this system a promising delivery vehicle for NPCs in the treatment of injuries and diseases of the central nervous system. [ABSTRACT FROM AUTHOR]