A Short Review on Nanostructured Carbon Containing Biopolymer Derived Composites for Tissue Engineering Applications

The development of new scaffolds and materials for tissue engineering is a wide and open realm of material science. Among solutions, the use of biopolymers represents a particularly interesting area of study due to their great chemical complexity that enables creation of specific molecular architectures. However, biopolymers do not exhibit the properties required for direct application in tissue repair-such as mechanical and electrical properties-but they do show very attractive chemical functionalities which are difficult to produce through in vitro synthesis. The combination of biopolymers with nanostructured carbon fillers could represent a robust solution to enhance composite properties, producing composites with new and unique features, particularly relating to electronic conduction. In this paper, we provide a review of the field of carbonaceous nanostructure-containing biopolymer composites, limiting our investigation to tissue-engineering applications, and providing a complete overview of the recent and most outstanding achievements.

Recent advancement in polymer/halloysite nanotube nanocomposites for biomedical applications

Halloysite nanotubes (HNTs) have recently been the subject of extensive research as a reinforcing filler. HNT is a natural nanoclay, non-toxic and biocompatible, hence, applicable in biomedical fields. This review focuses on the mechanical, thermal, and functional properties of polymer nanocomposites with HNT as a reinforcing agent from an experimental and theoretical perspective. In addition, this review also highlights the recent applications of polymer/HNT nanocomposites in the biomedical fields.

Functional Ultra-High Molecular Weight Polyethylene Composites for Ligament Reconstructions and Their Targeted Applications in the Restoration of the Anterior Cruciate Ligament

The selection of biomaterials as biomedical implants is a significant challenge. Ultra-high molecular weight polyethylene (UHMWPE) and composites of such kind have been extensively used in medical implants, notably in the bearings of the hip, knee, and other joint prostheses, owing to its biocompatibility and high wear resistance. For the Anterior Cruciate Ligament (ACL) graft, synthetic UHMWPE is an ideal candidate due to its biocompatibility and extremely high tensile strength. However, significant problems are observed in UHMWPE based implants, such as wear debris and oxidative degradation. To resolve the issue of wear and to enhance the life of UHMWPE as an implant, in recent years, this field has witnessed numerous innovative methodologies such as biofunctionalization or high temperature melting of UHMWPE to enhance its toughness and strength. The surface functionalization/modification/treatment of UHMWPE is very challenging as it requires optimizing many variables, such as surface tension and wettability, active functional groups on the surface, irradiation, and protein immobilization to successfully improve the mechanical properties of UHMWPE and reduce or eliminate the wear or osteolysis of the UHMWPE implant. Despite these difficulties, several surface roughening, functionalization, and irradiation processing technologies have been developed and applied in the recent past. The basic research and direct industrial applications of such material improvement technology are very significant, as evidenced by the significant number of published papers and patents. However, the available literature on research methodology and techniques related to material property enhancement and protection from wear of UHMWPE is disseminated, and there is a lack of a comprehensive source for the research community to access information on the subject matter. Here we provide an overview of recent developments and core challenges in the surface modification/functionalization/irradiation of UHMWPE and apply these findings to the case study of UHMWPE for ACL repair.

Wear Resistance, Color Stability and Displacement Resistance of Milled PEEK Crowns Compared to Zirconia Crowns under Stimulated Chewing and High-Performance Aging

Recently, polyetheretherketone (PEEK) has been introduced to the dental market as a high-performance and chemically inert biomaterial. This study aimed to compare the wear resistance, abrasiveness, color stability, and displacement resistance of zirconia and PEEK milled crowns. An ideal tooth preparation of a first maxillary molar was done and scanned by an intraoral scanner to make a digital model. Then, the prosthetic crown was digitally designed on the CAD software, and the STL file was milled in zirconia (CaroZiir S, Carol Zircolite Pvt. Ltd., Gujarat, India) and PEEK (BioHpp, Bredent GmbH, Senden, Germany) crowns using five-axis CNC milling machines. The wear resistance, color stability, and displacement resistance of the milled monolithic zirconia with unfilled PEEK crowns using a chewing simulator with thermocyclic aging (120,000 cycles) were compared. The antagonist wear, material wear, color stability, and displacement were evaluated and compared among the groups using the Wilcoxon-Mann-Whitney U-test. Zirconia was shown to be three times more abrasive than PEEK (p value < 0.05). Zirconia had twice the wear resistance of PEEK (p value < 0.05). Zirconia was more color stable than PEEK (p value < 0.05). PEEK had more displacement resistance than zirconia (p value < 0.05). PEEK offers minimal abrasion, better stress modulation through plastic deformation, and good color stability, which make it a promising alternative to zirconia crown.

Process Optimization for Manufacturing PAN-Based Conductive Yarn with Carbon Nanomaterials through Wet Spinning

This study aimed to manufacture PAN-based conductive yarn using a wet-spinning process. Two types of carbon nanomaterials, multiwall carbon nanotubes (MWCNT) and carbon nanofiber (CNF), were used alone or in a mixture. First, to derive the optimal composite solution condition for the wet spinning process, a composite solution was prepared with carbon nanomaterials of the same total mass weight (%) and three types of mechanical stirring were performed: mechanical stirring, ultra-sonication, and ball milling. A ball milling process was finally selected by analyzing the viscosity. Based on the above results, 8, 16, 24, and 32 wt% carbon nanomaterial/PAN composite solutions were prepared to produce wet spinning-based composite films before preparing a conductive yarn, and their physical and electrical properties were examined. By measuring the viscosity of the composite solution and the surface resistance of the composite film according to the type and content of carbon nanomaterials, a suitable range of viscosity was found from 10³ cP to 10⁵ cP, and the electrical percolation threshold was from 16 wt% carbon nanomaterial/PAN, which showed a surface resistance of 10⁶ Ω/sq or less. Wet spinning was possible with a PAN-based composite solution with a high content of carbon nanomaterials. The crystallinity, crystal orientation, tenacity, and thermal properties were improved when CNF was added up to 24 wt%. On the other hand, the properties deteriorated when CNTs were added alone due to aggregation. Mixing CNT and CNF resulted in poorer properties than with CNF alone, but superior properties to CNT alone. In particular, the electrical properties after incorporating 8 wt% CNT/16 wt% CNF into the PAN, 10⁶ Ω/cm was similar to the PAN-based conductive yarn containing 32 wt% CNF. Therefore, this yarn is expected to be applicable to various smart textiles and wearable devices because of its improved physical properties such as strength and conductivity.

Effect of Nanofillers on Tribological Properties of Polymer Nanocomposites: A Review on Recent Development

Polymer nanocomposites with enhanced performances are becoming a trend in the current research field, overcoming the limitations of bulk polymer and meeting the demands of market and society in tribological applications. Polytetrafluoroethylene, poly(ether ether ketone) and ultrahigh molecular weight polyethylene are the most popular polymers in recent research on tribology. Current work comprehensively reviews recent advancements of polymer nanocomposites in tribology. The influence of different types of nanofiller, such as carbon-based nanofiller, silicon-based nanofiller, metal oxide nanofiller and hybrid nanofiller, on the tribological performance of thermoplastic and thermoset nanocomposites is discussed. Since the tribological properties of polymer nanocomposites are not intrinsic but are dependent on sliding conditions, direct comparison between different types of nanofiller or the same nanofiller of different morphologies and structures is not feasible. Friction and wear rate are normalized to indicate relative improvement by different fillers. Emphasis is given to the effect of nanofiller content and surface modification of nanofillers on friction, wear resistance, wear mechanism and transfer film formation of its nanocomposites. Limitations from the previous works are addressed and future research on tribology of polymer nanocomposites is proposed.

Manufacture and mechanical properties of knee implants using SWCNTs/UHMWPE composites

This article focuses on obtaining ultra high molecular weight polyethylene (UHMWPE) material reinforced with functionalized single-walled carbon nanotubes (f-SWCNTs) and the manufacturing of unicompartmental knee implants via Single-Point Incremental Forming process (SPIF). The physicochemical properties of the developed UHMWPE reinforced with 0.01 and 0.1 wt% concentrations of f-SWCNTs are investigated using Raman and Thermogravimetic Analysis (TGA). Tensile mechanical tests performed in the nanocomposite material samples reveal a 12% improvement in their Young's modulus when compare to that of the pure UHMWPE material samples. Furthermore, the surface biocompatibility of the UHMWPE reinforced with f-SWCNTs materials samples was evaluated with human osteoblast cells. Results show cell viability enhancement with good cell growth and differentiation after 14 incubation days, that validates the usefulness of the developed nanocomposite material in the production of hip and knee artificial implants, and other biomedical applications.

Advances in the Processing of UHMWPE-TiO2 to Manufacture Medical Prostheses via SPIF

This research focuses on developing a novel ultra high molecular weight polyethylene (UHMWPE) material reinforced with titanium dioxide (TiO2) nanoparticles for producing craniofacial prostheses via an incremental sheet forming process (SPIF). First, UHMWPE-TiO2 nanocomposite sheets were produced using incipient wetting and the compression molding process by considering different concentrations of TiO2 nanoparticles. Then, the influence that the compression molding fabrication process has on the crystallinity and structural properties of the produced sample sheets was investigated. Experimental characterizations via scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), tensile mechanical testing, and live/dead cell viability assays provided data that show an enhancement of the physical, mechanical, and biological properties. Finally, modifications on the nanocomposite material properties due to the SPIF manufacturing processes of a craniofacial prosthesis are addressed.

The preparation of carbon nanofillers and their role on the performance of variable polymer nanocomposites

New synergic behavior is always inspiring scientists toward the formation of nanocomposites aiming at getting advanced materials with superior performance and/or novel properties. Carbon nanotubes (CNT), graphene, fullerene, and graphite as carbon-based are great fillers for polymeric materials. The presence of these materials in the polymeric matrix would render it several characteristics, such as electrical and thermal conductivity, magnetic, mechanical, and as sensor materials for pressure and other environmental changes. This review presents the most recent works in the use of CNT, graphene, fullerene, and graphite as filler in different polymeric matrixes. The primary emphasis of this review is on CNT preparation and its composites formation, while others carbon-based nano-fillers are also introduced. The methods of making polymer nanocomposites using these fillers and their impact on the properties obtained are also presented and discussed.

Overview of Carbon Nanotubes for Biomedical Applications

The unique combination of mechanical, optical and electrical properties offered by carbon nanotubes has fostered research for their use in many kinds of applications, including the biomedical field. However, due to persisting outstanding questions regarding their potential toxicity when considered as free particles, the research is now focusing on their immobilization on substrates for interface tuning or as biosensors, as load in nanocomposite materials where they improve both mechanical and electrical properties or even for direct use as scaffolds for tissue engineering. After a brief introduction to carbon nanotubes in general and their proposed applications in the biomedical field, this review will focus on nanocomposite materials with hydrogel-based matrices and especially their potential future use for diagnostics, tissue engineering or targeted drug delivery. The toxicity issue will also be briefly described in order to justify the safe(r)-by-design approach offered by carbon nanotubes-based hydrogels.

Magnetic multiwalled carbon nanotubes with controlled release of epirubicin: an intravesical instillation system for bladder cancer

Background

Traditional intravesical instillation treatment in bladder cancer has limited efficacy, which results in a high frequency of recurrence.

Purpose

The aim of this study was to report on an epirubicin (EPI)-loaded magnetic multi-walled carbon nanotube (mMWCNTs-EPI) system for intravesical instillation in place of the current formulation.

Methods

The mMWCNTs-EPI system was formulated with carboxylated MWCNTs, Fe₃O₄ magnetic nanoparticles, and EPI. Features and antitumor activity of the system were investigated.

Results

Under the effect of external magnets, the mMWCNTs-EPI system showed sustained release and prolonged retention behavior and better antitumor activity than free EPI. The mMWCNTs-EPI system had higher efficiency in enhancing cytotoxicity and inhibiting proliferation in vitro and in vivo than free EPI. Our studies also revealed the atoxic nature of mMWCNTs.

Conclusion

These findings suggested that mMWCNTs are effective intravesical instillation agents with great potential for clinical application.