Polylysine Research Articles

Generalized Multifunctional Coating Strategies Based on Polyphenol-Amine-Inspired Chemistry and Layer-by-Layer Deposition for Blood Contact Catheters.

Blood-contacting catheters play a pivotal role in contemporary medical treatments, particularly in the management of cardiovascular diseases. However, these catheters exhibit inappropriate wettability and lack antimicrobial characteristics, which often lead to catheter-related infections and thrombosis. Therefore, there is an urgent need for blood contact catheters with antimicrobial and anticoagulant properties. In this study, we employed tannic acid (TA) and 3-aminopropyltriethoxysilane (APTES) to create a stable hydrophilic coating under mild conditions. Heparin (Hep) and poly(lysine) (PL) were then modified on the TA-APTES coating surface using the layer-by-layer (LBL) technique to create a superhydrophilic TA/APTES/(LBL)4 coating on silicone rubber (SR) catheters. Leveraging the superhydrophilic nature of this coating, it can be effectively applied to blood-contacting catheters to impart antibacterial, antiprotein adsorption, and anticoagulant properties. Due to Hep's anticoagulant attributes, the activated partial thromboplastin time and thrombin time tests conducted on SR/TA-APTES/(LBL)4 catheters revealed remarkable extensions of 276 and 103%, respectively, when compared to uncoated commercial SR catheters. Furthermore, the synergistic interaction between PL and TA serves to enhance the resistance of SR/TA-APTES/(LBL)4 catheters against bacterial adherence, reducing it by up to 99.9% compared to uncoated commercial SR catheters. Remarkably, the SR/TA-APTES/(LBL)4 catheter exhibits good biocompatibility with human umbilical vein endothelial cells in culture, positioning it as a promising solution to address the current challenges associated with blood-contact catheters.

The Pseudomonas aeruginosa 1244 pilin glycan increases susceptibility to human beta defensin 2 but enhances twitching motility.

SHANIA DAVIS & JOSEPH HORZEMPA, Department of Biomedical Sciences, West LibertyUniversity, West Liberty, WV USA. The Pseudomonas aeruginosa 1244 pilin glycan increasessusceptibility to human beta defensin 2 but enhances twitching motility. Pseudomonas aeruginosa is an ESKAPE (highly drug resistant) pathogen that is commonlyacquired during hospital stays. This bacterium produces type IV pili which are adhesins andmotor appendages that mediate a surface motility referred to as “twitching.” These pili arepolymers of protein subunits referred to as pilin. The pilin subunit of P. aeruginosa 1244 isglycosylated. Previous studies have shown that the pilin glycan affects the efficiency oftwitching motility under certain conditions and the surface polarity of these fibers. Becausemodulation of the bacterial surface charge has been shown to mediate defensin resistance inother organisms, we tested whether pilin glycosylation affected sensitivity to human betadefensin 2 (HBD-2). Interestingly, the isogenic mutant strain lacking the pilin glycan (1244G7)showed increased resistance to HBD-2 compared to wild type bacteria and those completelylacking a type IV pilus (1244.47). This increased resistance to HBD-2 could explain data from arecent study in which various P. aeruginosa clinical strains were isolated that had pilinglycosylation defects. We also confirmed and extended previous findings that indicated that the1244 pilin glycan enhances twitching motility and we showed that this is especially true onpositively charged surfaces (poly L-lysine coated plastic). However, the positively chargedsurface was also capable of enhancing twitching of strains producing non-glycosylated pili or piliwith an incomplete glycan (1244.2.1).

Self-healing hydrogel based on poly (vinyl alcohol)-poly (lysine)-gum arabic accelerates diabetic wound healing under photothermal sterilization

Diabetic wounds are a significant clinical challenge. Developing effective antibacterial dressings is crucial for preventing wound ulcers caused by bacterial infections. In this study, a self-healing antibacterial hydrogel (polyvinyl alcohol (PVA)–polylysine–gum arabic, PLG hydrogels) with near-infrared photothermal response was prepared by linking PVA and a novel polysaccharide–amino acid compound (PG) through borate bonding combined with freeze–thaw cycling. Subsequently, the hydrogel was modified by incorporating inorganic nanoparticles (modified graphene oxide (GM)). The experimental results showed that the PLGM3 hydrogels (PLG@GM hydrogels, 3.0 wt%) could effectively kill bacteria and promote diabetic wound tissue healing under 808-nm near-infrared laser irradiation. Therefore, this hydrogel system provides a new idea for developing novel dressings for treating diabetic wounds.

Poly-l-lysine modified MOF nanoparticles with pH/ROS sensitive CIP release and CUR triggered photodynamic therapy against drug-resistant bacterial infection

The challenge of drug resistance in bacteria caused by the over use of biotics is increasing during the therapy process, which has attracted great attentions of the clinicians and scientists around the world. Recently, photodynamic therapy (PDT) triggered by photosensitizer (PS) has become a promising treatment method because of its high efficacy, easy operation, and low side effect. Herein, the poly-l-lysine (PLL) modified metal-organic framework (MOF) nanoparticles, ZIF/PLL-CIP/CUR, were synthesized to allow both reactive oxygen species (ROS) responsive drug release and photodynamic effect for synergistic therapy against drug resistant bacterial infections. The PLL was modified on the shell of the zeolite imidazole framework (ZIF) by the ROS-responsive thioketal linker for controllable CIP release. CUR were encapsulated in ZIF as the photosensitizer for blue light mediated photodynamic effect to produce singlet oxygen (1O2) and superoxide anion radical (O2−) for efficient inhibition towards methicillin-resistant Staphylococcus aureus (MRSA). The charge conversion from negative charge (−4.6 mV) to positive charge (2.6 mV) was observed at pH 7.4 and pH 5.5, and 70.9 % CIP was found released at pH 5.5 in the presence of H2O2, which suggests the good biosafety at physiological pH and ROS-responsive drug release of the as-prepared nanoparticle in the bacterial microenvironment. The as-prepared nanoparticles could effectively kill MRSA and disrupt bacterial biofilm by combination of chemo- and photodynamic therapy. In mice model, the as-prepared nanoparticles exhibited excellent biosafety and synergistic effect with 98.81 % healing rate in treatment of MRSA infection, which is considered as a promising candidate in combating drug resistant bacterial infection.

Biodegradable Local Chemotherapy Platform with Prolonged and Controlled Release of Doxorubicin for the Prevention of Local Tumor Recurrence.

Local recurrence after surgical and therapeutic treatment remains a significant clinical problem in oncology. Recurrence may be due to imperfections in existing therapies, particularly chemotherapy. To improve antitumor activity and prevent local cancer recurrence while keeping toxicity at acceptable levels, we have developed and demonstrated a biodegradable local chemotherapy platform that provides controlled and prolonged drug release. The platform consists of a polycaprolactone (PCL) substrate, which provides the structural integrity of the platform and the predominant unidirectional drug release, and a thin multilayer coating (∼200 nm) containing doxorubicin (DOX). The coating is an electrostatic complex obtained by the layer-by-layer (LbL) assembly and consists of natural polyelectrolytes [poly-γ-glutamic acid (γ-PGA) and chitosan (CS) or poly-l-lysine (PLL)]. To improve the release stability, an ionic conjugate of DOX and γ-PGA was prepared and incorporated into the multilayer coating. By varying the structure of the coating by adding empty (without DOX) bilayers, we were able to control the kinetics of drug release. The resulting platforms contained equal numbers of empty bilayers and DOX-loaded bilayers (15 + 15 or 30 + 30 bilayers) with a maximum loading of 566 ng/cm2. The platforms demonstrated prolonged and fairly uniform drug release for more than 5 months while retaining antitumor activity in vitro on ovarian cancer cells (SKOV-3). The empty platforms (without DOX) showed good cytocompatibility and no cytotoxicity to human fibroblasts and SKOV-3 cells. This study presents the development of a local chemotherapy platform consisting of a PCL-based substrate which provides structural stability and a biodegradable polyelectrolyte layered coating which combines layers containing a polyanion ionic complex with DOX with empty bilayers to ensure prolonged and controlled drug release. Our results may provide a basis for improving the efficacy of chemotherapy using drug delivery systems.

Co-delivery of siAEG-1 and doxorubicin to treat osteosarcoma via nanomicelles for azide−alkyne “click” conjugation of poly(l-lysine) dendrons onto Zein

Astrocyte elevated gene-1 (AEG-1) oncogene is a notorious and evolving target in a variety of human malignancies including osteosarcoma. The RNA interference (RNAi) has been clinically proven to effectively knock down specific genes. To successfully implement RNAi in vivo, protective vectors are required not only to protect unstable siRNAs from degradation, but also to deliver siRNAs to target cells with controlled release. Here, we synthesized a Zein-poly(l-lysine) dendrons non-viral modular system that enables efficient siRNA-targeted AEG-1 gene silencing in osteosarcoma and encapsulation of antitumor drugs for controlled release. The rational design of the ZDP integrates the non-ionic and low immunogenicity of Zein and the positive charge of the poly(l-lysine) dendrons (DPLL) to encapsulate siRNA and doxorubicin (DOX) payloads via electrostatic complexes and achieve pH-controlled release in a lysosomal acidic microenvironment. Nanocomplexes-directed delivery greatly improves siRNA stability, uptake, and AEG-1 sequence-specific knockdown in 143B cells, with transfection efficiencies comparable to those of commercial lipofectamine but with lower cytotoxicity. This AEG-1-focused RNAi therapy supplemented with chemotherapy inhibited, and was effective in inhibiting the growth in of osteosarcoma xenografts mouse models. The combination therapy is an alternative or combinatorial strategy that can produce durable inhibitory responses in osteosarcoma patients.

Swimming short fibrous nasal drops achieving intraventricular administration

Adequate drug delivery across the blood–brain barrier (BBB) is a critical factor in treating central nervous system (CNS) disorders. Inspired by swimming fish and the microstructure of the nasal cavity, this study is the first to develop swimming short fibrous nasal drops that can directly target the nasal mucosa and swim in the nasal cavity, which can effectively deliver drugs to the brain. Briefly, swimming short fibrous nasal drops with charged controlled drug release were fabricated by electrospinning, homogenization, the π-π conjugation between indole group of fibers, the benzene ring of leucine-rich repeat kinase 2 (LRRK2) inhibitor along with charge-dipole interaction between positively charged poly-lysine (PLL) and negatively charged surface of fibers; this enabled these fibers to stick to nasal mucosa, prolonged the residence time on mucosa, and prevented rapid mucociliary clearance. In vitro, swimming short fibrous nasal drops were biocompatible and inhibited microglial activation by releasing an LRRK2 inhibitor. In vivo, luciferase-labelled swimming short fibrous nasal drops delivered an LRRK2 inhibitor to the brain through the nasal mucosa, alleviating cognitive dysfunction caused by sepsis-associated encephalopathy by inhibiting microglial inflammation and improving synaptic plasticity. Thus, swimming short fibrous nasal drops is a promising strategy for the treatment of CNS diseases.

Nanoengineered Polymeric RNA Nanoparticles for Controlled Biodistribution and Efficient Targeted Cancer Therapy.

RNA nanotechnology, including rolling circle transcription (RCT), has gained increasing interest as a fascinating siRNA delivery nanoplatform for biostable and tumor-targetable RNA-based therapies. However, due to the lack of fine-tuning technologies for RNA nanostructures, the relationship between physicochemical properties and siRNA efficacy of polymeric siRNA nanoparticles (PRNs) with different sizes has not yet been fully elucidated. Herein, we scrutinized the effects of size/surface chemistry-tuned PRNs on the biological and physiological interactions with tumors. PRNs with adjusted size and surface properties were prepared using sequential engineering processes: RCT, condensation, and nanolayer deposition of functional biopolymers. Through the RCT process, nanoparticles of three sizes with a diameter of 50-200 nm were fabricated and terminated with three types of biopolymers: poly-l-lysine (PLL), poly-l-glutamate (PLG), and hyaluronic acid (HA) for different surface properties. Among the PRNs, HA-layered nanoparticles with a diameter of ∼200 nm exhibited the most effective systemic delivery, resulting in superior anticancer effects in an orthotopic breast tumor model due to the CD44 receptor targeting and optimized nanosized structure. Depending on the type of PRNs, the in vivo siRNA delivery with protein expression inhibition differed by up to approximately 20-fold. These findings indicate that the types of layered biopolymers and the PRNs size mediate efficient polymeric siRNA delivery to the targeted tumors, resulting in high RNAi-induced therapeutic efficacy. This RNA-nanotechnology-based size/surface editing can overcome the limitations of siRNA therapeutics and represents a potent built-in module method to design RNA therapeutics tailored for targeted cancer therapy.

Polyelectrolyte Platforms with Copper Nanoparticles as a Multifunctional System Aimed at Healing Process Support

(1) Purpose: The aim of the study was to develop a nanocomposite with copper nanoparticles constituting a bacteriostatic surface to maintain human lung cell function. (2) Methods: A polyelectrolyte layer coating that incorporated copper nanoparticles was designed. As a bacteriostatic factor, copper nanoparticles were applied as a colloidal solution of copper nanoparticles (ColloidCuNPs) and a solution of copper nanoparticles (CuNPs). The influence of the polyelectrolytes on selected Gram (+) and Gram (−) strains was examined. The function and morphology of the human adenocarcinoma A549 cell line, comprising human epithelial lung cells cultured in the presence of nanocomposite layer coatings, were evaluated. We applied fluorescence and scanning electron microscopies, as well as flow cytometry, for these studies. Furthermore, the layer coating material was characterized by atomic force microscopy (AFM) and energy dispersive X-ray analysis (EDX). (3) Results: It was observed that the polyelectrolytes polyethyleneimine (PEI) and poly-L-lysine (PLL) did not induce proliferation of the E. coli strain. However, they did induce the proliferation of the S. aureus strain. Due to the effectiveness of the CuNPs against the E. coli strain, CuNPs were selected for further research. The designed coatings of proper NPs shared the sustained function of human lung cells within 10 days of culture. The AFM and EDX characterization confirmed the presence of copper in the layer coating nanomaterial. The presence of CuNPs in polyethyleneimine-based nanocomposite deepened the bacteriostatic effect on E. coli compared with PEI alone. Meanwhile, incorporating CuNPs in PLL allowed A549 cell maintenance but did not exert a bacteriostatic influence on the examined strain. (4) Conclusions: The platform based on polyelectrolytes, incorporated with copper nanoparticles, that ensures the growth and appropriate morphology of the human lung epithelial cells, might be considered an element of a system for medical devices used to maintain the function of human lung cells.

Chemical and green synthesis of gold nanoparticles for mRNA delivery in vitro

Nanotechnology has paved the way for novel treatment strategies for diseases such as cancer. While chemical synthesis of nanoparticles (NPs) can introduce toxic and expensive reducing reagents, green synthesis offers an alternative with dual reducing and capping properties. Curcumin exhibits favourable pharmacological properties, enabling synergism with the therapeutic cargo. This study aimed to compare green and chemically synthesised gold NPs for the delivery of FLuc-mRNA in vitro. Chemical and green synthesised AuNPs were produced using trisodium citrate and curcumin, respectively, and functionalised with poly-L-lysine (PLL) and polyethylene glycol (PEG). The NP:mRNA nanocomplexes were characterised using nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), and UV–visible spectroscopy. Various mRNA binding studies assessed the optimal mRNA binding, compaction, and protection of the mRNA. All AuNPs were small (<150 nm) and had good colloidal stability, mRNA binding, and protection. The MTT (3-[4,5-dimethylthiazol-2-yl]-2.5-diphenyltetrazolium bromide) assay showed favourable cell viability, with significant transgene expression noted using the luciferase reporter gene assay. Higher transfection was achieved in the human cervical carcinoma (HeLa) than in the breast adenocarcinoma (MCF-7) and embryonic kidney (HEK293) cells. Both chemically and curcumin-synthesised AuNPs displayed similar activity in all cells, with curcumin-capped AuNPs marginally better at the same concentration.

Ultrasensitive, Label-Free Voltammetric Detection of Dibutyl Phthalate Based on Poly-l-lysine/poly(3,4-ethylenedioxythiophene)-porous Graphene Nanocomposite and Molecularly Imprinted Polymers.

Development of an efficient technique for accurate and sensitive dibutyl phthalate (DBP) determination is crucial for food safety and environment protection. An ultrasensitive molecularly imprinted polymers (MIP) voltammetric sensor was herein engineered for the specific determination of DBP using poly-l-lysine/poly(3,4-ethylenedioxythiophene)/porous graphene nanocomposite (PLL/PEDOT-PG) and poly(o-phenylenediamine)-imprinted film as a label-free and sensing platform. Fabrication of PEDOT-PG nanocomposites was achieved through a simple liquid-liquid interfacial polymerization. Subsequently, poly-l-lysine (PLL) functionalization was employed to enhance the dispersibility and stability of the prepared PEDOT-PG, as well as promote its adhesion on the sensor surface. In the presence of DBP, the imprinted poly(o-phenylenediamine) film was formed on the surface of PLL/PEDOT-PG. Investigation of the physical properties and electrochemical behavior of the MIP/PLL/PEDOT-PG indicates that the incorporation of PG into PEDOT, with PLL uniformly wrapping its surface, significantly enhanced conductivity, carrier mobility, stability, and provided a larger surface area for specific recognition sites. Under optimal experimental conditions, the electrochemical response exhibited a linear relationship with a logarithm of DBP concentration within the range of 1 fM to 5 µM, with the detection limit as low as 0.88 fM. The method demonstrated exceptional stability and repeatability and has been successfully applied to quantify DBP in plastic packaging materials.

Differences in Lipid Order and Dynamics in Plasma Membranes Assessed by Nonlinear Optical Microscopy.

When amphiphilic polar dyes were added to the cells, they intercalated predominantly in the outer leaf of the plasma membrane, making them active for second harmonic generation (SHG). The fluorescence of the dye enabled simultaneous 3D imaging of SHG and two-photon excited fluorescence (TPF). Because SHG intensity is sensitive to the alignment of the dyes, which reflects lipid ordering in the plasma membrane, we assessed the difference in lipid ordering by comparing the SHG intensity normalized to the TPF intensity. Together with an enzyme release assay that detects pore formation in the plasma membrane, our SHG assay revealed how polycations affect lipid ordering at low concentrations, where membrane damage has not yet been examined. By scaling the results of the assays with the charge concentration of the two polycations, polyethylenimine (PEI) and poly-l-lysine (PLL), we found that PEI reduced the lipid order more than PLL, and PLL formed more pores than PEI. A comparison of the SHG and TPF images of the wounded cells revealed that one of the lipid dynamics (flip-flop) was significantly enhanced in the bleb membrane. Moreover, the SHG assay indicated that the biocompatible polymer, poly(N-(2-hydroxypropyl)methacrylamide), did not affect the lipid order. Thus, our technique allows the assessment of the plasma membrane structure at the molecular level.

Poly(L-lysine) modified glassy carbon electrode for sensitive electrochemical measurement of 2,3,5,6-tetramethylpyrazine

2,3,5,6-Tetramethylpyrazine (TMP), an organic compound with numerous potential health benefits, is extensively used in medical and food products. This research introduces a novel approach for the precise quantification of TMP by employing a poly(L-lysine) modified glassy carbon electrode (pLL/GCE). The pLL/GCE is fabricated through the electrochemical polymerization of L-lysine onto a glassy carbon electrode (GCE) surface. This modification enhances the electrode's electrocatalytic efficiency, resulting in a significant increase in the reduction peak current of TMP. Exploiting this distinctive property, we establish an electrochemical method for quantifying TMP using cyclic voltammetry (CV). Optimized conditions reveal a robust linear correlation between the reduction peak current of TMP and its concentration within two adjacent linearity ranges: 40.0 nmol/L to 1.0 μmol/L and 1.0 μmol/L to 100.0 μmol/L. Notably, this method achieves an impressive detection limit of 20.0 nmol/L. To validate the practicality of this approach, we analyzed various real-world samples, obtaining recovery rates ranging from 98.2% to 100.8%. The developed method holds significant promise for the determination of TMP in medical and food products, underscoring its potential for widespread application.

Size-based characterization of dendrigraft poly(L-lysine) by free solution capillary electrophoresis using polyelectrolyte multilayer coatings

Dendrigraft poly(L-lysine) (DGL) constitutes a promising dendritic–like drug vehicle with high biocompatibility and straightforward access via ring-opening polymerization of N-carboxyanhydride in water. The characterization of the different generations of DGL is however challenging due to their heterogeneity in molar mass and branching ratio. In this work, free solution capillary electrophoresis was used to perform selective separation of the three first generations of DGL, and optimized conditions were developed to maximize inter-generation resolution. To reduce solute adsorption on the capillary wall, successive multiple ionic polymer layer coatings terminated with a polycation were deposited onto the inner wall surface. PEGylated polycation was also used as the last layer for the control of the electroosmotic flow (EOF), depending on the PEGylation degree and the methyl-polyethylene glycol (mPEG) chain length. 1 kDa mPEG chains and low grafting densities were found to be the best experimental conditions for a fine tuning of the EOF leading to high peak resolution. Molar mass polydispersity and polydispersity in effective electrophoretic mobility were successfully determined for the three first generations of DGL.

Nanogallium-poly(L-lactide) Composites with Contact Antibacterial Action.

In diverse biomedical and other applications of polylactide (PLA), its bacterial contamination and colonization are unwanted. For this reason, this biodegradable polymer is often combined with antibacterial agents or fillers. Here, we present a new solution of this kind. Through the process of simple solvent casting, we developed homogeneous composite films from 28 ± 5 nm oleic-acid-capped gallium nanoparticles (Ga NPs) and poly(L-lactide) and characterized their detailed morphology, crystallinity, aqueous wettability, optical and thermal properties. The addition of Ga NPs decreased the ultraviolet transparency of the films, increased their hydrophobicity, and enhanced the PLA structural ordering during solvent casting. Albeit, above the glass transition, there is an interplay of heterogeneous nucleation and retarded chain mobility through interfacial interactions. The gallium content varied from 0.08 to 2.4 weight %, and films with at least 0.8% Ga inhibited the growth of Pseudomonas aeruginosa PAO1 in contact, while 2.4% Ga enhanced the effect of the films to be bactericidal. This contact action was a result of unwrapping the top film layer under biological conditions and the consequent bacterial contact with the exposed Ga NPs on the surface. All the tested films showed good cytocompatibility with human HaCaT keratinocytes and enabled the adhesion and growth of these skin cells on their surfaces when coated with poly(L-lysine). These properties make the nanogallium-polyl(L-lactide) composite a promising new polymer-based material worthy of further investigation and development for biomedical and pharmaceutical applications.

Bone marrow stem cells with or without superparamagnetic iron oxide nanoparticles as a magnetic targeting tool: Which is better in regeneration of neurolysed facial nerve? An experimental study

AimThis study was performed to evaluate neural regenerative capacities of bone marrow stem cells (BMSCs) with or without superparamagnetic iron oxide nanoparticles (SPIONs) as a magnetic targeting tool after neurolysis of the facial nerve (FN) in albino rats. MethodsThirty-eight male albino rats were selected. Two of them were euthanized for normal FN histology assessment. Thirty-six rats were injected with ethanol in the FN nerve for neurolysis induction and assessed one week post-operatively by eye blinking test. Animals were divided into three groups, each containing twelve rats: Group I (positive control) was injected with Dulbecco Modified Eagle's medium (DMEM-F12), group II was injected with BMSCs in DMEM-F12, and group III was injected with BMSCs in DMEM-F12 with poly l-lysine coated SPIONs (0.5 mmol/mL). Monitoring of SPIONs in the rat's body was carried out by MRI. A circular neodymium magnet N52 (0.57 T, 2 × 5 mm) was placed on each rat in group III just below the right ear at the site of surgery to attract SPIONs labeled BMSCs, left in place for 24 h, and then removed. From each group, six rats were euthanized at the end of the 4th and 8th week of treatment, respectively. The right FN trunks were extracted for routine histological examination using H&E stain. Immunohistochemical examination by anti-S100B was performed to characterize the thickness of the myelin sheath formed by the Schwann cells. Ultra-structural examination was performed to study changes in axons, myelin sheaths, and Schwann cells. ResultsRegeneration of nerve fibers, Schwan cells, and myelin sheaths was better in group II than in groups I and III histologically, immunohistochemically, and ultra-structurally. ConclusionBMSCs alone could ameliorate FN regeneration better than magnetic targeting treatment using BMSCs labeled with SPIONs.

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.

Silver and Antimicrobial Polymer Nanocomplexes to Enhance Biocidal Effects.

Antimicrobial resistance has become a major problem over the years and threatens to remain in the future, at least until a solution is found. Silver nanoparticles (Ag-NPs) and antimicrobial polymers (APs) are known for their antimicrobial properties and can be considered an alternative approach to fighting resistant microorganisms. Hence, the main goal of this research is to shed some light on the antimicrobial properties of Ag-NPs and APs (chitosan (CH), poly-L-lysine (PLL), ε-poly-L-lysine (ε-PLL), and dopamine (DA)) when used alone and complexed to explore the potential enhancement of the antimicrobial effect of the combination Ag-NPs + Aps. The resultant nanocomplexes were chemically and morphologically characterized by UV-visible spectra, zeta potential, transmission electron microscopy, and Fourier-transform infrared spectroscopy. Moreover, the Ag-NPs, APs, and Ag-NPs + APs nanocomplexes were tested against Gram-positive Staphylococcus aureus (S. aureus) and the Gram-negative Escherichia coli (E. coli) bacteria, as well as the fungi Candida albicans (C. albicans). Overall, the antimicrobial results showed potentiation of the activity of the nanocomplexes with a focus on C. albicans. For the biofilm eradication ability, Ag-NPs and Ag-NPs + DA were able to significantly remove S. aureus preformed biofilm, and Ag-NPs + CH were able to significantly destroy C. albicans biofilm, with both performing better than Ag-NPs alone. Overall, we have proven the successful conjugation of Ag-NPs and APs, with some of these formulations showing potential to be further investigated for the treatment of microbial infections.

Disposable biosensor based on nanodiamond particles, ionic liquid and poly-l-lysine for determination of phenolic compounds

This study describes the development of a highly sensitive amperometric biosensor for the analysis of phenolic compounds such as catechol. The biosensor architecture is based on the immobilization of tyrosinase (Tyr) on a screen-printed carbon electrode (SPE) modified with nanodiamond particles (ND), 1-butyl-3-methylimidazolium hexafluorophosphate (IL) and poly-l-lysine (PLL). Surface morphologies of the electrodes during the modification process were evaluated by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical characteristics of the modified electrodes. Owing to the synergistic effect of the modification materials, the Tyr/PLL/ND−IL/SPE exhibited high sensitivity (328.2 μA mM−1) towards catechol with a wide linear range (5.0 × 10−8 – 1.2 × 10−5 M) and low detection limit (1.1 × 10−8 M). Furthermore, the method demonstrated good reproducibility and stability. The amperometric response of the biosensor towards other phenolic compounds such as bisphenol A, phenol, p-nitrophenol, m-cresol, p-cresol and o-cresol was also investigated. The analytical applicability of the biosensor was tested by the analysis of catechol in tap water. The results of the tap water analysis showed that the Tyr/PLL/ND−IL/SPE can be used as a practical and effective method for catechol determination.

Synthesis, monomer conversion, and mechanical properties of polylysine based dental composites

ObjectiveThe aim of this study was to synthesize a new bioactive and antibacterial composite by incorporating reactive calcium phosphate and antibacterial polylysine into a resin matrix and evaluate the effect of these fillers on structural analysis, degree of monomer conversion, mechanical properties, and bioactivity of these newly developed polypropylene based dental composites. MethodologyStock monomers were prepared by mixing urethane dimethacrylate and polypropylene glycol dimethacrylate and combined with 40 wt% silica to make experimental control (E-C). The other three experimental groups contained a fixed percentage of silica (40 wt%), monocalcium phosphate monohydrate, and β-tri calcium phosphate (5 wt% each) with varying amounts of polylysine (PL). These groups include E-CCP0 (0 wt% PL), E-CCP5 (5 wt% PL) and E-CCP10 (10 wt% PL). The commercial control used was Filtek™ Z250 3M ESPE. The degree of conversion was assessed by using Fourier transform infrared spectroscopy (FTIR). Compressive strength and Vicker’s micro hardness testing were evaluated after 24 h of curing the samples. For bioactivity, prepared samples were placed in simulated body fluid for 0, 1, 7, and 28 days and were analyzed using a scanning electron microscope (SEM). SPSS 23 was used to analyze the data and one-way ANOVA and post hoc tukey’s test were done, where the significant level was set ≤0.05. ResultsGroup E-C showed better mechanical properties than other experimental and commercial control groups. Group E-C showed the highest degree of conversion (72.72 ± 1.69%) followed by E-CCP0 (72.43 ± 1.47%), Z250 (72.26 ± 1.75%), E-CCP10 (71.07 ± 0.19%), and lowest value was shown by E-CCP5 (68.85 ± 7.23%). In shear bond testing the maximum value was obtained by E-C. The order in decreasing value of bond strength is E-C (8.13 ± 3.5 MPa) > Z250 (2.15 ± 1.1 MPa) > E-CCP10 (2.08 ± 2.1 MPa) > E-CCP5 (0.94 ± 0.8 MPa) > E-CCP0 (0.66 ± 0.2 MPa). In compressive testing, the maximum strength was observed by commercial control i.e., Z250 (210.36 ± 18 MPa) and E-C (206.55 ± 23 MPa), followed by E-CCP0 (108.06 ± 19 MPa), E-CCP5 (94.16 ± 9 MPa), and E-CCP10 (80.80 ± 13 MPa). The maximum number of hardness was shown by E-C (93.04 ± 8.23) followed by E-CCP0 (38.93 ± 9.21) > E-CCP10 (35.21 ± 12.31) > E-CCP5 (34.34 ± 12.49) > Z250 (25 ± 2.61). SEM images showed that the maximum apatite layer as shown by E-CCP10 and the order followed as E-CCP10 > E-CCP5 > E-CCP0 >Z250> E-C. ConclusionThe experimental formulation showed an optimal degree of conversion with compromised mechanical properties when the polylysine percentage was increased. Apatite layer formation and polylysine at the interface may result in remineralization and ultimately lead to the prevention of secondary caries formation.