Vignesh Muthuvijayan

Fluorophores are used for sensing biologically relevant ions, toxic metals or pathogenic markers. However, the mode of entry of such fluorophores into the cell greatly depends on their size, shape, surface charge, functional groups, and hydrophobicity. In particular, the influence of hydrophobicity on the intracellular uptake of fluorophores is poorly investigated. Self-assembly is a recent strategy to tune the intracellular uptake of fluorophores, facilitating increased intracellular sensing and fluorescence. Herein, self-assembly of three novel poly(aryl ether) dendron derivatives that contain rhodamine units was used to investigate the effect of hydrophobicity on the intracellular uptake of self-assembled fluorophores. The results suggest that monomer hydrophobicity plays an important role in the uptake. The dendron-based fluorophores, which upon self-assembly, formed stable spherical aggregates ranging from 300 to 500 nm. The rhodamine-based dendrons could selectively sense Hg 2+ ions in the presence of other competing metal cations. Intracellular imaging of the dendron-based fluorophores displayed bright red fluorescence in human embryonic kidney cells. The rate of intracellular uptake of the three dendron-based fluorophores was analyzed by flow cytometry. The results establish the importance of the hydrophilic-lipophilic balance of the self-assembled amphiphiles for tuning the intracellular uptake.

The increased threat of bacterial resistance against conventional antibiotics has warranted the need for development of membrane targeting antibacterial agents. Several self-assembled cationic amphiphiles with different supramolecular structures have been reported in recent years for potent antibacterial activity with increased specificity. In this study, we describe the self-assembly and antibacterial activity of four lower generation poly(aryl ether)-based amphiphilic dendrimers (AD-1, AD-2, AD-3, and AD-4) containing terminal amine (PAMAM-based), ester, and hydrazide functional groups with varied hydrophobicity. Among the four dendrimers under study, the amine-terminated dendrimer (AD-1) displayed potent antibacterial activity. The ratio of surface cationic charge to hydrophobicity had a significant effect on the antibacterial activity, where AD-3 dendrimer with increased surface cationic charges exhibited a higher minimum inhibitory concentration (MIC) than AD-1. AD-2 (ester terminated) and AD-4 (hydrazide terminated) dendrimers did not show any bactericidal activity. The amphiphilic dendrimer-bacteria interactions, further validated by binding studies, also showed significant changes in bacterial morphology, effective membrane permeation, and depolarization by AD-1 in comparison with AD-3. Molecular dynamics simulations of AD-1 and AD-3 on bacterial membrane patches further corroborated the experimental findings. The structural conformation of AD-1 dendrimer facilitated increased membrane interaction compared to AD-3 dendrimer. AD-1 also displayed selectivity to bacterial membranes over fibroblast cells (4× MIC), corroborating the significance of an optimal hydrophobicity for potent antibacterial activity with no cytotoxicity. The self-assembled (poly(aryl ether)-PAMAM-based) dendrimer (AD-1) also exhibited potent antibacterial activity in comparison with conventional higher generation dendrimers, establishing the implication of self-assembly for bactericidal activity. Moreover, the detailed mechanistic study reveals that optimal tuning of the hydrophobicity of amphiphilic dendrimers plays a crucial role in membrane disruption of bacteria. We believe that this study will provide valuable insights into the design strategies of amphiphilic dendrimers as antibacterial agents for efficient membrane disruption.

The authors regret not including the following statement in the original paper. Kindly include the following text: “CONFIDENTIAL - PATENT PENDING - <201741017579>” The authors would like to apologise for any inconvenience caused.

A rationally designed amphiphilic poly(aryl ether)-based dendrimer self-assembles into nanomicelles and exhibits tunable morphology upon varying the hydrophilic chain length. The 30 nm-sized dendrimer nanomicelles successfully entrapped Doxorubicin, demonstrated the sustained release of Doxorubicin and can successfully penetrate cancer cells through caveolae-dependent endocytosis, compared to the free drug.

Herein, we describe the design, synthesis and drug release kinetics of a low molecular weight gel based on an aryl ether dendron, under in vitro conditions. The first generation dendron self-assembles and forms gels, resulting in a robust three-dimensional fibrous network, to facilitate controlled release of molecules. While aryl ether dendrons are known for their enhanced self-assembling propensity, these systems have not been used for drug release studies. The self-assembled system was characterized using SEM, TEM, rheology and PXRD experiments. In vitro cytotoxicity of the dendron gel was studied and the results show that the dendron gel is biocompatible. The effect of gel leaching and the exposure time on NIH/3T3 cells is also studied. Further, the gel based on poly aryl ether dendron derivative (D1) is capable of entrapping model hydrophilic dyes and a local anaesthetic drug (prilocaine hydrochloride), where the D1 gel could effectively entrap about 1.5 mg of prilocaine hydrochloride per 5 mg of gelator. The in vitro drug release suggests that the release kinetics is inversely proportional to the gelator wt%, and the lowest release rate obtained is 1.75 min-n with 0.7 gelator wt%. The release profiles of prilocaine hydrochloride are fitted with the Peppas-Korsmeyer model, and the results depict a non-Fickian diffusion mechanism. These studies indicate that the poly aryl ether dendron based gel shows desirable characteristics and also displays promising possibilities of expanding dendron based drug delivery systems for transdermal applications.

Chronic wounds cost several billion dollars of public healthcare spending annually and continue to be a persistent threat globally. Several treatment methods have been explored, and all of them involve covering up the wound with therapeutic dressings that reduce inflammation and accelerate the healing process. In this present study, morin (MOR) was loaded onto hydrogel scaffolds prepared from psyllium seed husk polysaccharide (PSH), and human hair keratins (KER) crosslinked with sodium trimetaphosphate. ATR-FTIR confirmed the presence of the constituent chemical ingredients. SEM images of the scaffold surface reveal a highly porous architecture, with about 80% porosity measured by liquid displacement measurement, irrespective of the morin concentration. Swelling assays carried out on the scaffolds portray an ability to absorb up to seven times their dry weight of fluids. This makes them attractive for guiding moist wound healing on medium exuding wounds. An Alamar blue assay of NIH/3T3 fibroblast cells shows that cell viability decreases in the first 24 h but recovers to 85% in comparison to a control after 48 h. SEM images of fibroblast cells grown on the scaffolds confirm cellular attachment. An in vivo diabetic wound healing study showed that PSH + KER + MOR scaffold treatment significantly reduced the re-epithelialization time (p < 0.01) and enhanced the rate of wound contraction (p < 0.001), by accelerating collagen synthesis in diabetic rats compared to controls.

The aim of this article was to develop silk protein (SF) and l-proline (LP) loaded chitosan-(CS) based hydrogels via physical cross linking for tissue engineering and wound healing applications. Silk fibroin, a biodegradable and biocompatible protein, and l-proline, an important imino acid that is required for collagen synthesis, were added to chitosan to improve the wound healing properties of the hydrogel. Characterization of these hydrogels revealed that CS/SF/LP hydrogels were blended properly and LP incorporated hydrogels showed excellent thermal stability and good surface morphology. Swelling study showed the water holding efficiency of the hydrogels to provide enough moisture at the wound surface. In vitro biodegradation results demonstrated that the hydrogels had good degradation rate in PBS with lysozyme. LP loaded hydrogels showed approximately a twofold increase in antioxidant activity. In vitro cytocompatibility studies using NIH 3T3 L1 cells showed increased cell viability (p < 0.01), migration, proliferation and wound healing activity (p < 0.001) in LP loaded hydrogels compared to CS and CS/SF hydrogels. Cell adhesion on SF and LP hydrogels were observed using SEM and compared to CS hydrogel. LP incorporation showed 74-78% of wound closure compared to 35% for CS/SF and 3% for CS hydrogels at 48 h. These results suggest that incorporation of LP can significantly accelerate wound healing process compared to pure CS and SF-loaded CS hydrogels. Hence, CS/LP hydrogels could be a potential wound dressing material for the enhanced wound tissue regeneration and repair. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1401–1408, 2017.

We have developed a novel hydrogel composed of konjac glucomannan (KGM), human hair proteins (KER), and an ethanolic extract of Avena sativa (OAT) and evaluated its potential as a dressing material for diabetic wounds. KGM is an excellent biocompatible gelling agent that stimulates fibroblast proliferation and immunomodulation. Human hair proteins (KER) are biocompatible, biodegradable, and possess abundant cell adhesion sites. KER also promotes fibroblast attachment and proliferation, keratinocyte migration, and collagen expression, which can accelerate wound healing. OAT consists of oat β-glucans and several anti-inflammatory and antioxidant moieties that can reduce prolonged inflammation in chronic wounds. SEM images confirm the highly porous architecture of the scaffolds. When immersed in PBS, KGM + KER + OAT hydrogels absorb 7.5 times their dry weight. These hydrogels display a measured rate of degradation in lysozyme. KGM + KER + OAT hydrogels showed no significant cytotoxicity against NIH/3T3 fibroblasts. DAPI and SEM images obtained after 48 h of cell culture illustrate the attachment and infiltration of fibroblasts. In vivo studies performed using a diabetic rat excision wound model showed that KGM + KER + OAT hydrogels significantly accelerated wound healing compared to the control and the KGM + KER hydrogels.

Treatment of chronic non-healing wounds in diabetes is still a major clinical challenge. Here, we have developed reduced graphene oxide (rGO) loaded isabgol nanocomposite scaffolds (Isab + rGO) to treat normal and diabetic wounds. rGO was synthesized by rapid reduction of graphene oxide (GO) under focused solar radiation. Then, rGO was uniformly dispersed into isabgol solution to prepare Isab + rGO nanocomposite scaffolds. These scaffolds were characterized using various physiochemical techniques. Isab + rGO nanocomposite scaffolds showed suitable cell viability, proliferation, and attachment. In vivo experiments were performed using Wistar rats to study the wound healing efficacy of these scaffolds in normal and diabetic rats. Results revealed that rGO stimulated collagen synthesis, collagen crosslinking, wound contraction, and reduced the wound re-epithelialization time significantly compared to control. Histology and immunohistochemistry analyses showed that Isab + rGO scaffold treatment enhanced angiogenesis, collagen synthesis, and deposition in treated wounds. Isab + rGO scaffold treatment also played a major role in shortening the inflammation phase and recruiting macrophages to enhance the early phase of wound healing. Overall, this investigation showed that Isab + rGO scaffold dressing could significantly accelerate the healing of normal and diabetic wounds.

Composite 3D scaffolds using a natural, carbohydrate polymer, isabgol (Isab) and silk fibroin (SF) were prepared by a freeze drying method. 2 wt% solutions of both Isab and SF were blended in four different ratios to obtain the 3D scaffolds. ATR-FTIR results showed the presence of amide bonds and β sheet conformation in Isab/SF scaffolds. SEM micrographs showed the fibrous foam like architecture in the Isab/SF blend. Scaffolds showed sufficient porosity and absorbed higher amounts of PBS solution, enhancing the gas and nutrient supply to the cells. Subsequently, scaffolds showed significant in vitro biodegradation. In vitro cytocompatibility test in NIH 3T3 fibroblast cells showed better viability, proliferation and cell attachment for the Isab/SF 75/25 scaffolds compared to the control. Among all the scaffolds, Isab/SF 75/25 showed a faster wound contraction rate (p < 0.001) and reduced period of epithelialization (16 days) compared to the control (23 days). Shrinkage temperature and collagen content was also increased significantly (p < 0.001) in Isab/SF 75/25 scaffold treated rats compared to the control. Histopathology results strongly demonstrate higher cellular infiltration, increased fibroblasts, dense collagen fibers, and neovascularization in Isab/SF 75/25 treated rats, compared to other treatments. Overall, these results strongly authenticate that the Isab/SF 75/25 3D composite scaffolds enhanced the fluid uptake ability with enough fibroblast attachment and good viability. Also, it accelerated tissue regeneration during wound healing in rats without addition of any bioactive molecules.