Nanocomposite scaffold fabrication by incorporating gold nanoparticles into biodegradable polymer matrix: Synthesis, characterization, and photothermal effect

Vat photopolymerization-based 3D printing of polymer nanocomposites: current trends and applications

The synthesis and manufacturing of polymer nanocomposites have garnered interest in recent research and development because of their superiority compared to traditionally employed industrial materials. Specifically, polymer nanocomposites offer higher strength, stronger resistance to corrosion or erosion, adaptable production techniques, and lower costs. The vat photopolymerization (VPP) process is a group of additive manufacturing (AM) techniques that provide the benefit of relatively low cost, maximum flexibility, high accuracy, and complexity of the printed parts. In the past few years, there has been a rapid increase in the understanding of VPP-based processes, such as high-resolution AM methods to print intricate polymer parts. The synergistic integration of nanocomposites and VPP-based 3D printing processes has opened a gateway to the future and is soon expected to surpass traditional manufacturing techniques. This review aims to provide a theoretical background and the engineering capabilities of VPP with a focus on the polymerization of nanocomposite polymer resins. Specifically, the configuration, classification, and factors affecting VPP are summarized in detail. Furthermore, different challenges in the preparation of polymer nanocomposites are discussed together with their pre- and post-processing, where several constraints and limitations that hinder their printability and photo curability are critically discussed. The main focus is the applications of printed polymer nanocomposites and the enhancement in their properties such as mechanical, biomedical, thermal, electrical, and magnetic properties. Recent literature, mainly in the past three years, is critically discussed and the main contributing results in terms of applications are summarized in the form of tables. The goal of this work is to provide researchers with a comprehensive and updated understanding of the underlying difficulties and potential benefits of VPP-based 3D printing of polymer nanocomposites. It will also help readers to systematically reveal the research problems, gaps, challenges, and promising future directions related to polymer nanocomposites and VPP processes.

Multimodal Potentials of Gold Nanoparticles for Bone Tissue Engineering and Regenerative Medicine: Avenues and Prospects

Osseous tissue repair has advanced due to the introduction of tissue engineering. The key elements required while engineering new tissues involve scaffolds, cells, and bioactive cues. The macrostructural to the nanostructural framework of such complex tissue has engrossed the intervention of nanotechnology for efficient neo-bone formation. Gold nanoparticles (GNPs) have recently gained interest in bone tissue regeneration due to their multimodal functionality. They are proven to modulate the properties of scaffolds and the osteogenic cells significantly. GNPs also influence different metabolic functions within the body, which directly or indirectly govern the mechanism of bone regeneration. Therefore, this review highlights nanoparticle-mediated osteogenic development, focusing on different aspects of GNPs ranging from scaffold modulation to cellular stimulation. The toxic aspects of gold nanoparticles studied so far are critically explicated, while further insight into the advancements and prospects of these nanoparticles in bone regeneration is also highlighted.

Nanomaterial Additives for Fabrication of Stimuli-Responsive Skeletal Muscle Tissue Engineering Constructs

Volumetric muscle loss necessitates novel tissue engineering strategies for skeletal muscle repair, which have traditionally involved cells and extracellular matrix-mimicking scaffolds and have thus far been unable to successfully restore physiologically relevant function. However, the incorporation of various nanomaterial additives with unique physicochemical properties into scaffolds has recently been explored as a means of fabricating constructs that are responsive to electrical, magnetic, and photothermal stimulation. Herein, several classes of nanomaterials that are used to mediate external stimulation to tissue engineered skeletal muscle are reviewed and the impact of these stimuli-responsive biomaterials on cell growth and differentiation and in vivo muscle repair is discussed. The degradation kinetics and biocompatibilities of these nanomaterial additives are also briefly examined and their potential for incorporation into clinically translatable skeletal muscle tissue engineering strategies is considered. Overall, these nanomaterial additives have proven efficacious and incorporation in tissue engineering scaffolds has resulted in enhanced functional skeletal muscle regeneration.

Advances in Biodegradable 3D Printed Scaffolds with Carbon-Based Nanomaterials for Bone Regeneration

Bone possesses an inherent capacity to fix itself. However, when a defect larger than a critical size appears, external solutions must be applied. Traditionally, an autograft has been the most used solution in these situations. However, it presents some issues such as donor-site morbidity. In this context, porous biodegradable scaffolds have emerged as an interesting solution. They act as external support for cell growth and degrade when the defect is repaired. For an adequate performance, these scaffolds must meet specific requirements: biocompatibility, interconnected porosity, mechanical properties and biodegradability. To obtain the required porosity, many methods have conventionally been used (e.g., electrospinning, freeze-drying and salt-leaching). However, from the development of additive manufacturing methods a promising solution for this application has been proposed since such methods allow the complete customisation and control of scaffold geometry and porosity. Furthermore, carbon-based nanomaterials present the potential to impart osteoconductivity and antimicrobial properties and reinforce the matrix from a mechanical perspective. These properties make them ideal for use as nanomaterials to improve the properties and performance of scaffolds for bone tissue engineering. This work explores the potential research opportunities and challenges of 3D printed biodegradable composite-based scaffolds containing carbon-based nanomaterials for bone tissue engineering applications.

Folic Acid-Functionalized Composite Scaffolds of Gelatin and Gold Nanoparticles for Photothermal Ablation of Breast Cancer Cells

Photothermal therapy (PTT) has been developed as a useful therapeutic method for cancer treatment. Localization of PTT agents in cancer sites and targeting capacity are required to further increase therapeutic efficacy. In this study, gold nanoparticles (AuNPs) and gelatin were functionalized with folic acid (FA) and hybridized to prepare FA-functionalized gelatin-AuNPs composite scaffolds. AuNPs with rod and star shapes of three sizes (40, 70, and 110 nm) were used for the hybridization to investigate the influence of AuNPs shape and size. The composite scaffolds showed porous structures with good interconnectivity. Modification with FA increased capture capacity of the composite scaffolds. Hybridization with AuNPs rendered the composite scaffold a good photothermal conversion property under near-infrared (NIR) laser irradiation. Temperature change during laser irradiation increased with the laser power intensity and irradiation time. The shape and size of AuNPs also affected their photothermal conversion property. The composite scaffold of gold nanorods 70 (FA-G/R70) had the highest photothermal conversion capacity. Breast cancer cells cultured in the FA-G/R70 composite scaffold were killed under NIR laser irradiation. Mouse subcutaneous implantation further demonstrated the excellent photothermal ablation capability of FA-G/R70 composite scaffold to breast cancer cells. The FA-functionalized composite scaffolds were demonstrated a high potential for local PPT of breast cancer.

3D printed nanomaterial-based electronic, biomedical, and bioelectronic devices

The ability to seamlessly integrate functional materials into three-dimensional (3D) constructs has been of significant interest, as it can enable the creation of multifunctional devices. Such integration can be achieved with a multiscale, multi-material 3D printing strategy. This technology has enabled the creation of unique devices such as personalized tissue regenerative scaffolds, biomedical implants, 3D electronic devices, and bionic constructs which are challenging to realize with conventional manufacturing processes. In particular, the incorporation of nanomaterials into 3D printed devices can endow a wide range of constructs with tailorable mechanical, chemical, and electrical functionalities. This review highlights the advances and unique possibilities in the fabrication of novel electronic, biomedical, and bioelectronic devices that are realized by the synergistic integration of nanomaterials with 3D printing technologies.

Engineered 3D Polymer and Hydrogel Microenvironments for Cell Culture Applications

The realization of biomimetic microenvironments for cell biology applications such as organ-on-chip, in vitro drug screening, and tissue engineering is one of the most fascinating research areas in the field of bioengineering. The continuous evolution of additive manufacturing techniques provides the tools to engineer these architectures at different scales. Moreover, it is now possible to tailor their biomechanical and topological properties while taking inspiration from the characteristics of the extracellular matrix, the three-dimensional scaffold in which cells proliferate, migrate, and differentiate. In such context, there is therefore a continuous quest for synthetic and nature-derived composite materials that must hold biocompatible, biodegradable, bioactive features and also be compatible with the envisioned fabrication strategy. The structure of the current review is intended to provide to both micro-engineers and cell biologists a comparative overview of the characteristics, advantages, and drawbacks of the major 3D printing techniques, the most promising biomaterials candidates, and the trade-offs that must be considered in order to replicate the properties of natural microenvironments.

Gold Nanoparticle-Integrated Scaffolds for Tissue Engineering and Regenerative Medicine

The development of scaffolding materials that recapitulate the cellular microenvironment and provide cells with physicochemical cues is crucial for successfully engineering functional tissues that can aid in repairing damaged organs. The use of gold nanoparticles for tissue engineering and regenerative medicine has raised great interest in recent years. In this mini review, we describe the shape-dependent properties of gold nanoparticles, and their versatile use in creating tunable nanocomposite scaffolds with improved mechanical and electrical properties for tissue engineering. We further describe using gold nanoparticle-integrated scaffolds to achieve improved stem cells proliferation and differentiation. Finally, we discuss the main challenges and prospects for clinical translation of gold nanoparticles-hybrid scaffolds.

Poly(propylene fumarate)-based materials: Synthesis, functionalization, properties, device fabrication and biomedical applications

Poly(propylene fumarate) (PPF) is a biodegradable polymer that has been investigated extensively over the last three decades. It has led many scientists to synthesize and fabricate a variety of PPF-based materials for biomedical applications due to its controllable mechanical properties, tunable degradation and biocompatibility. This review provides a comprehensive overview of the progress made in improving PPF synthesis, resin formulation, crosslinking, device fabrication and post polymerization modification. Further, we highlight the influence of these parameters on biodegradation, biocompatibility, and their use in a number of regenerative medicine applications, especially bone tissue engineering. In particular, the use of 3D printing techniques for the fabrication of PPF-based scaffolds is extensively reviewed. The recent invention of a ring-opening polymerization method affords precise control of PPF molecular mass, molecular mass distribution (Ɖ_M) and viscosity. Low Ɖ_M facilitates time-certain resorption of 3D printed structures. Novel post-polymerization and post-printing functionalization methods have accelerated the expansion of biomedical applications that utilize PPF-based materials. Finally, we shed light on evolving uses of PPF-based materials for orthopedics/bone tissue engineering and other biomedical applications, including its use as a hydrogel for bioprinting.

Using Impedance Measurements to Characterize Surface Modified with Gold Nanoparticles

With the increased practice of preventative healthcare to help reduce costs worldwide, sensor technology improvement is vital to patient care. Point-of-care (POC) diagnostics can reduce time and lower labor in testing, and can effectively avoid transporting costs because of portable designs. Label-free detection allows for greater versatility in the detection of biological molecules. Here, we describe the use of an impedance-based POC biosensor that can detect changes in the surface modification of a micro-fabricated chip using impedance spectroscopy. Gold nanoparticles (GNPs) have been employed to evaluate the sensing ability of our new chip using impedance measurements. Furthermore, we used impedance measurements to monitor surface functionalization progress on the sensor's interdigitated electrodes (IDEs). Electrodes made from aluminum and gold were employed and the results were analyzed to compare the impact of electrode material. GNPs coated with mercaptoundecanoic acid were also used as a model of biomolecules to greatly enhance chemical affinity to the silicon substrate. The portable sensor can be used as an alternative technology to ELISA (enzyme-linked immunosorbent assays) and polymerase chain reaction (PCR)-based techniques. This system has advantages over PCR and ELISA both in the amount of time required for testing and the ease of use of our sensor. With other techniques, larger, expensive equipment must be utilized in a lab environment, and procedures have to be carried out by trained professionals. The simplicity of our sensor system can lead to an automated and portable sensing system.

Photoinitiator-free 3D scaffolds fabricated by excimer laser photocuring

Photoinitiator-free fabrication of poly(ethylene glycol) diacrylate (PEGDA) scaffolds is achieved using a novel three-dimensional (3D) printing method called mask projected excimer laser stereolithography (MPExSL). The spatial resolution of photoinitiator-free curing is suitable for 3D layer-by-layer fabrication with a single layer thickness well controllable at tens to hundreds of microns using 248 nm wavelength for the irradiation. The photoinitiator-free scaffolds are superior compared to their counterparts fabricated by using photoinitiator molecules, showing a higher level of biocompatibility. A release of toxic chemicals from the photoinitiator containing scaffolds is proven by cell proliferation tests. In contrast, no toxic release is found from the photoinitiator-free scaffolds, resulting in the very same level of cell proliferation as the control sample. The demonstration of photoinitiator-free PEGDA scaffolds enables the fabrication of 3D scaffolds with the highest level of biocompatibility for both in vitro and in vivo applications.

Fabrication of hybrid nanocomposite scaffolds by incorporating ligand-free hydroxyapatite nanoparticles into biodegradable polymer scaffolds and release studies

We report on the optical fabrication approach of preparing free-standing composite thin films of hydroxyapatite (HA) and biodegradable polymers by combining pulsed laser ablation in liquid and mask-projection excimer laser stereolithography (MPExSL). Ligand-free HA nanoparticles were prepared by ultrafast laser ablation of a HA target in a solvent, and then the nanoparticles were dispersed into the liquid polymer resin prior to the photocuring process using MPExSL. The resin is poly(propylene fumarate) (PPF), a photo-polymerizable, biodegradable material. The polymer is blended with diethyl fumarate in 7:3 w/w to adjust the resin viscosity. The evaluation of the structural and mechanical properties of the fabricated hybrid thin film was performed by means of SEM and nanoindentation, respectively, while the chemical and degradation studies were conducted through thermogravimetric analysis, and FTIR. The photocuring efficiency was found to be dependent on the nanoparticle concentration. The MPExSL process yielded PPF thin films with a stable and homogenous dispersion of the embedded HA nanoparticles. Here, it was not possible to tune the stiffness and hardness of the scaffolds by varying the laser parameters, although this was observed for regular PPF scaffolds. Finally, the gradual release of the hydroxyapatite nanoparticles over thin film biodegradation is reported.

Tuning the size and the photocatalytic performance of gold nanoparticles in situ generated in photopolymerizable glycomonomers

Polymer nanocomposites containing Au NPs in situ photogenerated during the UV-curing process were prepared starting from methacrylated glycomonomers with α-d-glucofuranose or d-mannitol structural units, other mono(di)methacrylates and AuCl₃.