In vitro biocompatibility and antimicrobial activity of poly(ε-caprolactone)/montmorillonite nanocomposites

A Review on Montmorillonite-Based Nanoantimicrobials: State of the Art

One of the crucial challenges of our time is to effectively use metal and metal oxide nanoparticles (NPs) as an alternative way to combat drug-resistant infections. Metal and metal oxide NPs such as Ag, Ag2O, Cu, Cu2O, CuO, and ZnO have found their way against antimicrobial resistance. However, they also suffer from several limitations ranging from toxicity issues to resistance mechanisms by complex structures of bacterial communities, so-called biofilms. In this regard, scientists are urgently looking for convenient approaches to develop heterostructure synergistic nanocomposites which could overcome toxicity issues, enhance antimicrobial activity, improve thermal and mechanical stability, and increase shelf life. These nanocomposites provide a controlled release of bioactive substances into the surrounding medium, are cost effective, reproducible, and scalable for real life applications such as food additives, nanoantimicrobial coating in food technology, food preservation, optical limiters, the bio medical field, and wastewater treatment application. Naturally abundant and non-toxic Montmorillonite (MMT) is a novel support to accommodate NPs, due to its negative surface charge and control release of NPs and ions. At the time of this review, around 250 articles have been published focusing on the incorporation of Ag-, Cu-, and ZnO-based NPs into MMT support and thus furthering their introduction into polymer matrix composites dominantly used for antimicrobial application. Therefore, it is highly relevant to report a comprehensive review of Ag-, Cu-, and ZnO-modified MMT. This review provides a comprehensive overview of MMT-based nanoantimicrobials, particularly dealing with preparation methods, materials characterization, and mechanisms of action, antimicrobial activity on different bacterial strains, real life applications, and environmental and toxicity issues.

Modified Polymer Surfaces: Thin Films of Silicate Composites via Polycaprolactone Melt Fusion

Polymer/layered silicate composites have gained huge attention in terms of research and industrial applications. Traditional nanocomposites contain particles regularly dispersed in a polymer matrix. In this work, a strategy for the formation of a composite thin film on the surface of a polycaprolactone (PCL) matrix was developed. In addition to the polymer, the composite layer was composed of the particles of saponite (Sap) modified with alkylammonium cations and functionalized with methylene blue. The connection between the phases of modified Sap and polymer was achieved by fusing the chains of molten polymer into the Sap film. The thickness of the film of several μm was confirmed using electron microscopy and X-ray tomography. Surfaces of precursors and composite materials were analyzed in terms of structure, composition, and surface properties. The penetration of polymer chains into the silicate, thus joining the phases, was confirmed by chemometric analysis of spectral data and changes in some properties upon PCL melting. Ultimately, this study was devoted to the spectral properties and photoactivity of methylene blue present in the ternary composite films. The results provide directions for future research aimed at the development of composite materials with photosensitizing, photodisinfection, and antimicrobial surfaces.

New PCL/PEC Blends: In Vitro Cell Response of Preosteoblasts and Human Mesenchymal Stem Cells

In this study, new blends of PCL/PEC have been prepared in an easy manner by casting with the objective of obtaining new biomaterials to apply to tissue engineering and bone regeneration. The PCL/PEC blends obtained, together with neat polymer blends, were characterized by infrared spectroscopy (FTIR), atomic force microscopy (AFM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). This full characterization is the key to disentangle the miscibility, which means good compatibility, of the polymer blends used in this work. The addition of increasing amounts of PEC, has shown in the new biomaterials obtained, a remarkable improvement in relation with the mechanical properties (manageable materials) and above all, in terms of an increase in their hydrophilic character with respect to the PCL neat polymer. The improvement of all these properties is reflected in their biological properties. With these thoughts in mind, the blends obtained were tested through the assessment of several biological parameters such as cell viability, proliferation, and differentiation of both the MC3T3-E1 osteoblastic cell line and hMSCs to evaluate their cell response to different polymer membranes aimed at bone tissue regeneration. “In vitro” biocompatibility methods have been chosen rather than in vivo studies due to their lower cost, faster procedure time, and minimum ethical concerns, and because it was the first time that the biological effects of these blends were studied. The results show that the PCL/PEC blends obtained, with tunable properties in terms of hydrophilic character and hydrolytic degradation, may be regarded as good candidates to perform “in vivo” tests and check their real-life applicability for bone regeneration. The polymer acronym (the weight percentage in the sub index) is PCLx/PECy as noted in table one with the summary of compositions.

Evolution of Black Talc upon Thermal Treatment

Black talc is a natural silicate clay mineral with a typical 2:1 layered structure, low electrical conductivity, large specific surface area, and high thermal stability. The world’s largest black talc mine, with known reserves of one billion tons, is located in China’s Jiangxi province. Due to the restriction of its color, the application of black talc is only limited to ceramic raw materials, coating filler, waterproof materials, and other low-end application industries. Thermal treatment is a common method of clay mineral modification. It is vital to examine the structural and physical changes of black talc during calcination in order to prepare black-talc-based composites and to broaden their applications. This work discusses the evolution of black talc upon thermal treatment (30–1000 °C) and the corresponding structural changes. The thermal stability of minerals was analyzed via thermogravimetric (TG) analysis and thermogravimetry–mass spectrometry (TG-MS). The decomposition of minerals during calcination consists of four processes: dehydration, organic carbon decomposition, dihydroxylation, and phase transformation. In situ FTIR and in situ XRD were employed to track changes in black talc in real time during thermal treatment. At 800 °C, black talc was found to begin to go through dihydroxylation, and the crystallinity index decreased significantly. The XRD pattern of samples at 950 °C (T950) showed the reflection of the enstatite structure, and the relative crystallinity index was 27.3%, indicating that the mineral had undergone phase transformation. In addition, the Brunauer–Emmet–Teller (BET), laser particle size analyzer, Zeta potential, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques were used to systematically characterize the physicochemical properties of minerals at different temperatures. The results show that black talc’s particle size and specific surface area increase with the calcination temperature. The surface charge changes, and more amorphous SiO2 and MgO appear, indicating that thermal treatment could induce structural changes and activate the surface of black talc.

Behaviours of poly(ε-caprolactone)/silver-montmorillonite nanocomposite in membrane ultrafiltration for wastewater treatment

The scope of this work consists in studying the possibility of using the long-lasting antimicrobial poly(ε-caprolactone)/silver-montmorillonite (PCL/Ag-MMT) materials which we have developed in our previous research, as new class of nanocomposite membranes, finding their application in the wastewater treatment. The surface properties of these hybrid membranes were investigated by scanning electron microscopy (SEM) analysis and contact angle measurements. The SEM results showed that the synthesized membranes exhibited homogeneous sponge microstructures. It was found that the gradual inclusion of nanoparticles (2, 3 and 5 wt. %) into PCL matrix induced a remarkable increase of the membrane thickness. Moreover, these hybrid materials exhibited an enhancement of the surface hydrophilicity attributed to the hydrophilic nature of clay incorporated. The water contact angle of the PCL membrane surface noticeably decreased after the Ag-MMT addition: dropping from 82.60° for PCL 0%Ag-MMT to 64.28° for PCL 5%Ag-MMT membrane. The antimicrobial properties of the membranes were confirmed using Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) as the model bacteria. Quality parameters including total suspended solids (TSS), electric conductivity (EC), nitrates, chlorides, bicarbonates, heavy metals and other trace elements, were determined before and after treatment of real wastewater. A decrease of nitrates by 15.12%, a diminution of sulphates by 45.61% and a removal of 41.38%, 53.57% and61.11% for heavy metals Pb, Zn and Cd respectively indicating clearly that the ultrafiltration process using PCL/AgMMT nanocomposite membranes is an effective way to eliminate the wastewater effluents.

Preparations of Silver/Montmorillonite Biocomposite Multilayers and Their Antifungal Activity

In this study, the results about the influence of the surface morphology of layers based on montmorillonite (MMT) and silver (Ag) on antimicrobial properties are reported. The coating depositions were performed in the plasma of a radio frequency (RF) magnetron sputtering discharge. The studied layers were single montmorillonite layers (MMT) and silver/montmorillonite multilayers (MMT-Ag) obtained by magnetron sputtering technique with a different surface thickness. The resultant MMT-Ag biocomposite multilayers exhibited a uniform distribution of constituent elements and enhanced antimicrobial properties against fungal biofilm development. Glow-discharge optical emission spectroscopy (GDOES) analysis revealed the formation of MMT-Ag biocomposite multilayers following the deposit of a silver layer for an MMT layer that was initially deposited on a Si substrate. The surface morphology and thickness evaluation of deposited biocomposite layers were performed by scanning electron microscopy (SEM). A qualitative analysis of the chemical composition of thin layers was performed and the elements O, Ag, Mg, Fe, Al, and Si were identified in the MMT-Ag biocomposite multilayers. The in vitro antifungal assay proved that the inhibitory effect against the growth of Candida albicans ATCC 101231 CFU was more emphasized in the case of MMT-Ag biocomposite multilayers that in the case of the MMT layer. Cytotoxicity studies performed on HeLa cells showed that the tested layers did not show significant toxicity at the time intervals during which the assay was performed. On the other hand, it was observed that the MMT layers exhibited slightly higher biocompatible properties than the MMT-Ag composite layers.

Curcumin-loaded electrospun polycaprolactone/montmorillonite nanocomposite: wound dressing application with anti-bacterial and low cell toxicity properties

Materials and scaffolds with antimicrobial properties are of great importance in wound dressing and other tissue engineering applications. The objective of the present work was to fabricate scaffolds made from nanocomposites of polycaprolactone (PCL) and quaternary ammonium salt-modified montmorillonite (MMT) by the electrospinning technique, and then characterize their antimicrobial and other properties for wound dressing applications. The effect of MMT on the structure, morphology, and thermal behavior of the electrospun wound dressings was assessed by means of X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM); the swelling capacity, antibacterial activity, and cytotoxicity were also evaluated. The results of XRD and SEM analyses showed MMT was successfully incorporated into the PCL polymeric matrix and its inclusion reduced the size and thickness of the electrospun fibers compared to pure PCL fibers. The TGA results illustrated an increase in the thermal stability of nanocomposites upon incorporation of nanoclay into the PCL matrix. The swelling capacity of the wound dressings was reduced by increasing the amount of MMT in the PCL matrix due to the increased hydrophobicity of the original MMT resulting from its modification with quaternary ammonium salt. The in vitro curcumin (Cur) release profile revealed an initial burst release followed by a sustained release, with the burst release level reduced by the introduction of MMT into the polymeric matrix. Increasing the nanoclay content further reduced the curcumin release, with the PCL/20% MMT/Cur dressings having the lowest curcumin release of all those tested. The beneficial effect of MMT on the antibacterial behavior of electrospun wound dressings based on PCL/MMT nanocomposites was confirmed, with the introduction of both MMT and curcumin into the PCL matrix resulting in lower bacterial viability. PCL/10% MMT/Cur demonstrated higher antimicrobial activity and the greatest bacterial colony reduction compared to both pure PCL and PCL/10% MMT. The cytotoxicity evaluation indicated low toxicity and confirmed the potential of PCL/MMT nanocomposite scaffolds for wound dressing applications.

A muscle mimetic polyelectrolyte–nanoclay organic–inorganic hybrid hydrogel: its self-healing, shape-memory and actuation properties

In this investigation, we report a non-covalent (ionic interlocking and hydrogen bonding) strategy of self-healing in a covalently crosslinked organic–inorganic hybrid nanocomposite hydrogel, with specific emphasis on tuning its properties fitting into a muscle mimetic material.

In vitro biocompatibility analysis of functionalized poly(vinyl chloride)/layered double hydroxide nanocomposites

The aim of this study was to examine the cytotoxicity and biocompatibility of functionalized poly(vinyl chloride) (PVC)/layered double hydroxide (LDH) nanocomposites.

Graphene-Montmorillonite Composite Sponge for Safe and Effective Hemostasis

Montmorillonite (MMT) is considered to be the most effective hemostat among natural phyllosilicates. However, there is a barrier against using MMT for the commercial hemostatics because the invaded MMT powders might cause thrombosis in vessel. Until now, it is still a challenge to manage the release of MMT and eliminate its side effect. Herein, we present a graphene-MMT composite sponge (GMCS), synthesized under a hydrothermal reaction, fixing MMT powders into the cross-linked graphene sheets. We demonstrate that only a few embedded MMT can evoke remarkable platelet stimulation at the sponge interface, while maintaining fast plasma absorbency of the innate sponge. In the synergy of the above hemostatic mechanisms, the GMCS can rapidly stop bleeding in approximately 85 s in rabbit artery injury test. More importantly, computed tomography angiography certifies that the GMCS does not cause thrombus or blood clot in vessels. Cytotoxicity assay further highlights its biocompatibility. In-depth analysis proposes that two-dimensional graphene overmatches one-dimensional linear polymers in the composite construction, and dimension transformation of blood distribution plays a crucial role for reinforcing the hemostatic performance. This GMCS hemostat not only opens a new perspective for graphene composite, but also makes a new chance of using clays for trauma therapy.

Synthesis of functional polyester for fabrication of nano-fibrous scaffolds and its effect on PC12 cells

An ideal scaffold should mimic the advantageous characteristics of a natural extracellular matrix for cell attachment, proliferation, and differentiation. In this study, well-defined block copolymer with functional groups was synthesized. The structure of the block copolymer was characterized by nuclear magnetic resonance, gel permeation chromatography, and differential scanning calorimetry. Thermally induced phase separation was employed to fabricate nano-fibrous scaffolds based on the synthesized block copolymer. The scaffold, with fiber diameter ranging from 400 to 500 nm, was fabricated for in vitro culture of PC12 cells. The carboxyl groups on the side chain resulted in increased hydrophilicity of nano-fibrous scaffolds and enhanced cell proliferation. In addition, this scaffold structure was beneficial in directing the growth of regenerating axons in nerve tissue engineering. Results of 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) assay and scanning electron microscopy confirmed that the nano-fibrous scaffolds with functional groups were suitable for PC12 cells growth. Moreover, the carboxyl groups were suitable for coupling with biological signals. Thus, the nano-fibrous scaffolds have potential applications in tissue engineering.

Estudo das células Neuro2A sobre os biomateriais PCL e PLLA

Os biomateriais poli L-ácido lático (PLLA) e o poli caprolactona (PCL) são os polímeros mais estudadas na área dos materiais bioreabsorvíveis. Dentre as suas principais características que contribuem para a interação celular, temos a especificidade química da superfície, elétrica, hidrofobicidade e topografia. Ainda, observa-se o tempo de degradação, porosidade, biocompatibilidade com o tecido biológico, bem como, a confecção com as mais variadas formas e dimensões. Já a prática da cultura celular, tem como objetivo estudar a adesão, migração, diferenciação e a proliferação celular utilizando-se um determinado material ou substância. Contudo, poucos trabalhos utilizando os biomateriais ora supracitados e a aplicação em células neuro2A foram realizados. Sabe-se que este tipo celular é derivado de células embrionárias da crista neural, as quais originam em neurônios simpáticos e apresentam como característica a imortalidade, portanto, são excelentes modelos em ensaios in vitro. Nesse sentido, o presente estudo avalia a adesão e a proliferação desta linhagem celular sobre os biopolímeros poli caprolactona (PCL) e poli L-ácido lático (PLLA).