Biosensor Development and Innovation in Healthcare and Medical Applications.

The pandemic necessitated a change to the historical diagnostics model [...].

3D printed antimicrobial PLA constructs functionalised with zinc- coated halloysite nanotubes-Ag-chitosan oligosaccharide lactate.

The control and inhibition of microbial infection are of critical importance for patients undergoing dental or orthopedic surgery. A critical requirement is the prevention of bacterial growth, subsequent bacterial colonization of implant surfaces, and biofilm formation. Among biofilm-forming bacteria, S. aureus and S. epidermidis are the most common bacteria responsible for causing implant-related infections. The ability to produce customized and patient-specific antimicrobial treatments will significantly reduce infections leading to enhanced patient recovery. We propose that 3D-printed antimicrobial biomedical devices for on-demand infection prophylaxis and disease prevention are a rational solution for the prevention of infection. In this study, we modified 3D printed polylactic acid (PLA) constructs using an alkali treatment to increase hydrophilicity and functionalized the surface of the constructs using a suspension of Zinc/HNTs-Ag-Chitosan Oligosaccharide Lactate (ZnHNTs-Ag-COS). The morphologies of printed constructs were analyzed using Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS), and chemical analysis by Fourier-transform infrared spectroscopy (FTIR). Assessment of the antimicrobial potential of our constructs was assessed using agar diffusion and biofilm assays. The surface of 3D printed PLA constructs were chemically modified to increase hydrophilicity and suspensions of COS-ZnHNTs-Ag were adsorbed on the construct surface. Surface adsorption of ZnHNTs-Ag-COS on PLA printed constructs was determined to be a function of relative pore size. Morphological surface characterization using SEM-EDS confirmed the presence of the suspension coatings on the constructs, and FTIR analysis confirmed the presence of COS-ZnHNTs-Ag in the coatings. The inhibition of bacterial growth was evaluated using the agar diffusion method. Results obtained confirmed the antimicrobial potential of the PLA constructs (which was a function of the Ag content in the material).

Effectiveness and Applications of a Metal-Coated HNT/Polylactic Acid Antimicrobial Filtration System.

A broad-spectrum antimicrobial respiration apparatus designed to fight bacteria, viruses, fungi, and other biological agents is critical in halting the current pandemic's trajectory and containing future outbreaks. We applied a simple and effective electrodeposition method for metal (copper, silver, and zinc) coating the surface of halloysite nanotubes (HNTs). These nanoparticles are known to possess potent antiviral and antimicrobial properties. Metal-coated HNTs (mHNTs) were then added to polylactic acid (PLA) and extruded to form an mHNT/PLA 3D composite printer filament. Our composite 3D printer filament was then used to fabricate an N95-style mask with an interchangeable/replaceable filter with surfaces designed to inactivate a virus and kill bacteria on contact, thus reducing deadly infections. The filter, made of a multilayered antimicrobial/mHNT blow spun polymer and fabric, is disposable, while the mask can be sanitized and reused. We used several in vitro means of assessing critical clinical features and assessed the bacterial growth inhibition against commonly encountered bacterial strains. These tests demonstrated the capability of our antimicrobial filament to fabricate N95 masks and filters that possessed antibacterial capabilities against both Gram-negative and Gram-positive bacteria.

Creating Structured Hydrogel Microenvironments for Regulating Stem Cell Differentiation.

The development of distinct biomimetic microenvironments for regulating stem cell behavior and bioengineering human tissues and disease models requires a solid understanding of cell-substrate interactions, adhesion, and its role in directing cell behavior, and other physico-chemical cues that drive cell behavior. In the past decade, innovative developments in chemistry, materials science, microfabrication, and associated technologies have given us the ability to manipulate the stem cell microenvironment with greater precision and, further, to monitor effector impacts on stem cells, both spatially and temporally. The influence of biomaterials and the 3D microenvironment's physical and biochemical properties on mesenchymal stem cell proliferation, differentiation, and matrix production are the focus of this review chapter. Mechanisms and materials, principally hydrogel and hydrogel composites for bone and cartilage repair that create "cell-supportive" and "instructive" biomaterials, are emphasized. We begin by providing an overview of stem cells, their unique properties, and their challenges in regenerative medicine. An overview of current fabrication strategies for creating instructive substrates is then reviewed with a focused discussion of selected fabrication methods with an emphasis on bioprinting as a critical tool in creating novel stem cell-based biomaterials. We conclude with a critical assessment of the current state of the field and offer our view on the promises and potential pitfalls of the approaches discussed.

Cellular Analysis and Chemotherapeutic Potential of a Bi-Functionalized Halloysite Nanotube.

The surface of halloysite nanotubes (HNTs) was bifunctionalized with two ligands-folic acid and a fluorochrome. In tandem, this combination should selectively target cancer cells and provide a means for imaging the nanoparticle. Modified bi-functionalized HNTs (bi-HNTs) were then doped with the anti-cancer drug methotrexate. bi-HNTs were characterized and subjected to in vitro tests to assess cellular growth and changes in cellular behavior in three cell lines-colon cancer, osteosarcoma, and a pre-osteoblast cell line (MC3T3-E1). Cell viability, proliferation, and cell uptake efficiency were assessed. The bi-HNTs showed cytocompatibility at a wide range of concentrations. Compared with regular-sized HNTs, reduced HNTs (~6 microns) were taken up by cells in more significant amounts, but increased cytotoxicity lead to apoptosis. Multi-photon images confirmed the intracellular location of bi-HNTs, and the method of cell entry was mainly through caveolae-mediated endocytosis. The bi-HNTs showed a high drug loading efficiency with methotrexate and a prolonged period of release. Most importantly, bi-HNTs were designed as a drug carrier to target cancer cells specifically, and imaging data shows that non-cancerous cells were unaffected after exposure to MTX-doped bi-HNTs. All data provide support for our nanoparticle design as a mechanism to selectively target cancer cells and significantly reduce the side-effects caused by off-targeting of anti-cancer drugs.

Differential antimicrobial and cellular response of electrolytically metalized halloysite nanotubes having different amounts of surface metallization.

We demonstrate an electrolytic method to metalize the outer surface of halloysite nanotubes (HNTs). Different metal HNT (mHNT) combinations (copper, silver, zinc) were produced with metal content in the 5-30 wt% range. mHNTs were characterized using a Scanning Electron Microscope (SEM), energy-dispersive spectroscopy (EDS), X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD). Different amounts of surface/lumen metal content of a system can confer differing antimicrobial/cellular response; hence, it is essential to assess the antimicrobial/cellular response as a function of metal content. Cellular response after exposure to mHNTs was studied in Staphylococcus aureus and pre-osteoblasts, respectively. Coated mHNTs could easily be identified using the characterization methods, and contrasting bacterial and cellular responses were obtained, which we propose was due to the extent of metallization. These findings demonstrate the potential of this method for creating metal-coated HNTs and suggest they have potential as an implant coating solution.

The Effect of Halloysite Addition on the Material Properties of Chitosan-Halloysite Hydrogel Composites.

Chitosan-based hydrogels are being widely used in biomedical applications due to their eco-friendly, biodegradable, and biocompatible properties, and their ability to mimic the extracellular matrix of many tissues. However, the application of chitosan hydrogels has been limited due to their inherent mechanical weakness. Halloysite nanotubes (HNTs) are naturally occurring aluminosilicate clay minerals and are widely used as a bulk filler to improve the performance characteristics of many polymeric materials. HNTs have also been shown to be a viable nanocontainer able to provide the sustained release of antibiotics, chemicals, and growth factors. This study's objective was to develop a stable drug delivery chitosan/HNT nanocomposite hydrogel that is biocompatible, biodegradable, and provides sustained drug release. In this study, chitosan/HNTs hydrogels containing undoped or gentamicin-doped HNTs were combined in different wt./wt. ratios and cross-linked with tripolyphosphate. The effects of chitosan and HNTs concentration and combination ratios on the hydrogel surface morphology, degradability, and mechanical properties, as well as its drug release capability, were analyzed. The results clearly showed that the addition of HNTs improved chitosan mechanical properties, but only within a narrow range. The nanocomposite hydrogels provided a sustained pattern of drug release and inhibited bacterial growth, and the live/dead assay showed excellent cytocompatibility.

Antibiotics in 3D-printed implants, instruments and materials: benefits, challenges and future directions.

3D printing is an additive manufacturing technology, which permits innovative approaches for incorporating antibiotics into 3D printed constructs. Antibiotic-incorporating applications in medicine have included medical implants, prostheses, along with procedural and surgical instruments. 3D-printed antibiotic-impregnated devices offer the advantages of increased surface area for drug distribution, sequential layers of antibiotics produced through layer-by-layer fabrication, and the ability to rapidly fabricate constructs based on patient-specific anatomies. To date, fused deposition modeling has been the main 3D printing method used to incorporate antibiotics, although inkjet and stereolithography techniques have also been described. This review offers a state-of-the-art summary of studies that incorporate antibiotics into 3D-printed constructs and summarizes the rationale, challenges, and future directions for the potential use of this technology in patient care.

3D Printing Custom Bioactive and Absorbable Surgical Screws, Pins, and Bone Plates for Localized Drug Delivery.

Additive manufacturing has great potential for personalized medicine in osseous fixation surgery, including maxillofacial and orthopedic applications. The purpose of this study was to demonstrate 3D printing methods for the fabrication of patient-specific fixation implants that allow for localized drug delivery. 3D printing was used to fabricate gentamicin (GS) and methotrexate (MTX)-loaded fixation devices, including screws, pins, and bone plates. Scaffolds with different infill ratios of polylactic acid (PLA), both without drugs and impregnated with GS and MTX, were printed into cylindrical and rectangular-shaped constructs for compressive and flexural strength mechanical testing, respectively. Bland PLA constructs showed significantly higher flexural strength when printed in a Y axis at 100% infill compared to other axes and infill ratios; however, there was no significant difference in flexural strength between other axes and infill ratios. GS and MTX-impregnated constructs had significantly lower flexural and compressive strength as compared to the bland PLA constructs. GS-impregnated implants demonstrated bacterial inhibition in plate cultures. Similarly, MTX-impregnated implants demonstrated a cytotoxic effect in osteosarcoma assays. This proof of concept work shows the potential of developing 3D printed screws and plating materials with the requisite mechanical properties and orientations. Drug-impregnated implants were technically successful and had an anti-bacterial and chemotherapeutic effect, but drug addition significantly decreased the flexural and compressive strengths of the custom implants.

4D anisotropic skeletal muscle tissue constructs fabricated by staircase effect strategy.

Like the morphology of native tissue fiber arrangement (such as skeletal muscle), unidirectional anisotropic scaffolds are highly desired as a means to guide cell behavior in anisotropic tissue engineering. In contrast, contour-like staircases exhibit directional topographical cues and are judged as an inevitable defect of fused deposition modeling (FDM). In this study, we will translate this staircase defect into an effective bioengineering strategy by integrating FDM with surface coating technique (FCT) to investigate the effect of topographical cues on regulating behaviors of human mesenchymal stem cells (hMSCs) toward skeletal muscle tissues. This integrated approach serves to fabricate shape-specific, multiple dimensional, anisotropic scaffolds using different biomaterials. 2D anisotropic scaffolds, first demonstrated with different polycaprolactone concentrations herein, efficiently direct hMSC alignment, especially when the scaffold is immobilized on a support ring. By surface coating the polymer solution inside FDM-printed sacrificial structures, 3D anisotropic scaffolds with thin wall features are developed and used to regulate seeded hMSCs through a self-established rotating bioreactor. Using layer-by-layer coating, along with a shape memory polymer, smart constructs exhibiting shape fix and recovery processes are prepared, bringing this study into the realm of 4D printing. Immunofluorescence staining and real-time quantitative polymerase chain reaction analysis confirm that the topographical cues created via FCT significantly enhance the expression of myogenic genes, including myoblast differentiation protein-1, desmin, and myosin heavy chain-2. We conclude that there are broad application potentials for this FCT strategy in tissue engineering as many tissues and organs, including skeletal muscle, possess highly organized and anisotropic extracellular matrix components.

3D Printed Antibiotic and Chemotherapeutic Eluting Catheters for Potential Use in Interventional Radiology: In Vitro Proof of Concept Study.

RATIONALE AND OBJECTIVES: Additive manufacturing may be used as a form of personalized medicine in interventional radiology by allowing for the creation of customized bioactive constructs such as catheters that can act as a form of localized drug delivery. The purpose of the present in vitro study was to use three-dimensional (3D) printing to construct bioactive-laden bioabsorbable catheters impregnated with antibiotics and chemotherapeutics. MATERIALS AND METHODS: Polylactic acid bioplastic pellets were coated with the powdered bioactive compounds gentamicin sulfate (GS) or methotrexate (MTX) to incorporate these drugs into the 3D printed constructs. The pellets were then extruded into drug-impregnated filament for fused deposition modeling 3D printing. Computer-aided design files were generated in the shapes of 14-F catheters. Scanning electron microscope imaging was used to visualize the presence of the additive powders on the surface of the printed constructs. Elution profiles were run on the antibiotic-laden catheter and MTX-laden catheters. Antibiotic-laden catheters were tested on bacterial broth and plate cultures. RESULTS: Both GS and MTX catheter constructs had sustained drug release up to the 5-day limit of testing. The 3D printed GS-enhanced catheters inhibited all bacterial growth in broth cultures and had an average zone of inhibition of 858 ± 118 mm2 on bacterial plates, whereas control catheters had no effect. CONCLUSION: The 3D printing manufacturing method to create instruments in percutaneous procedures is feasible. Further in vivo studies will substantiate these findings.

Studies on the cytocompatibility, mechanical and antimicrobial properties of 3D printed poly(methyl methacrylate) beads.

Osteomyelitis is typically a bacterial infection (usually from Staphylococcus) or, more rarely, a fungal infection of the bone. It can occur in any bone in the body, but it most often affects the long bones (leg and arm), vertebral (spine), and bones of the foot. Microbial success in osteomyelitis is due to their ability to form biofilms which inhibit the wound healing process and increases resistance to anti-infective agents. Also, biofilms do not allow easy penetration of antibiotics into their matrix making clinical treatment a challenge. The development of local antibiotic delivery systems that deliver high concentrations of antibiotics to the affected site is an emerging area of research with great potential. Standard treatment includes antibiotic therapy, either locally or systemically and refractory cases of osteomyelitis may lead to surgical intervention and a prolonged course of antibiotic treatment involving placement of antibiotic-doped beads or spacers within the wound site. There are disadvantages with this treatment modality including insufficient mixing of the antibiotic, lack of uniform bead size, resulting in lower antibiotic availability, and limitations on the antibiotics employed. Thus, a method is needed to address biofilm formations in the wound and on the surface of the surgical implants to prevent osteomyelitis. In this study, we show that all antibiotics studied were successfully doped into PMMA and antibiotic-doped 3D printed beads, disks, and filaments were easily printed. The growth inhibition capacity of the antibiotic-loaded PMMA 3D printed constructs was also demonstrated.

Personalized Bioactive Nasal Supports for Postoperative Cleft Rhinoplasty.

PURPOSE: After cleft lip and palate surgical procedures, patients often need nostril supports to help the reconstructed nostrils retain their shape during healing. Many postoperative nasal stents use a one-size-fits-all approach, in which a standard rubber tube retainer is trimmed and used to support the healing nares. The purpose of this study was to examine photogrammetry and 3-dimensional (3D) printing as a fabrication tool for postoperative patient-specific nasal supports that can be loaded with bioactive agents for localized delivery. MATERIALS AND METHODS: A "normal" right nostril injection mold was prepared from a left-sided unilateral cleft defect, and the negative-space impression was modeled using a series of photographs taken at different rotation angles with a commercial mobile phone camera. These images were "stitched" together using photogrammetry software, and the computer-generated models were reflected, joined, and digitally sculpted to generate hollow bilateral supports. Three-dimensional prints were coated with polyvinylpyrrolidone-penicillin and validated for their ability to inhibit Escherichia coli using human blood agar diffusion assays. RESULTS: The results showed that our approach had a high level of contour replication and the antibiotic coating was able to inhibit bacterial growth with a mean zone of inhibition of 15.15 ± 0.99 mm (n = 9) (P < .0001) in disc diffusion assays. CONCLUSIONS: Consumer-grade 3D printing displays potential as a fabrication method for postoperative cleft bilateral nasal supports and may support the surgically reconstructed internal contours. The results of this study suggest that such types of bioactive 3D prints may have potential applications in personalized drug-delivery systems and medical devices.

Three-Dimensional Printing Antimicrobial and Radiopaque Constructs.

Three-dimensional (3D) printing holds tremendous potential as a tool for patient-specific devices. This proof-of- concept study demonstrated the feasibility, antimicrobial properties, and computed tomography(CT) imaging characteristics of iodine/polyvinyl alcohol (PVA) 3D meshes and stents. Under scanning electron microscopy, cross-linked PVA displays smoother and more compacted filament arrangements. X-ray and transaxial CT images of iodized PVA vascular stents show excellent visibility and significantly higher Hounsfield units of radiopacity than control prints. Three-dimensional PVA prints stabilized by glutaraldehyde cross-linking and loaded with iodine through sublimation significantly suppressed Escherichia coli and Staphylococcus aureus growth in human blood agar disk diffusion assays. It is suggested that PVA 3D printing with iodine represents an important new synthetic platform for generating a wide variety of antimicrobial and high-visibility devices.

Bio-Based Polymers for 3D Printing of Bioscaffolds.

Three-dimensional (3D) printing technologies enable not only faster bioconstructs development but also on-demand and customized manufacturing, offering patients a personalized biomedical solution. This emerging technique has a great potential for fabricating bioscaffolds with complex architectures and geometries and specifically tailored for use in regenerative medicine. The next major innovation in this area will be the development of biocompatible and histiogenic 3D printing materials with bio-based printable polymers. This review will briefly discuss 3D printing techniques and their current limitations, with a focus on novel bio-based polymers as 3D printing feedstock for clinical medicine and tissue regeneration.

Doped Halloysite Nanotubes for Use in the 3D Printing of Medical Devices.

Previous studies have established halloysite nanotubes (HNTs) as viable nanocontainers capable of sustained release of a variety of antibiotics, corrosion agents, chemotherapeutics and growth factors either from their lumen or in outer surface coatings. Accordingly, halloysite nanotubes (HNTs) hold great promise as drug delivery carriers in the fields of pharmaceutical science and regenerative medicine. This study explored the potential of 3D printing drug doped HNT constructs. We used a model drug, gentamicin (GS) and polylactic acid (PLA) to fabricate GS releasing disks, beads, and pellets. Gentamicin was released from 3D printed constructs in a sustained manner and had a superior anti-bacterial growth inhibition effect that was dependent on GS doping concentration. While this study focused on a model drug, gentamicin, combination therapy is possible through the fabrication of medical devices containing HNTs doped with a suite of antibiotics or antifungals. Furthermore, tailored dosage levels, suites of antimicrobials, delivered locally would reduce the toxicity of individual agents, prevent the emergence of resistant strains, and enable the treatment of mixed infections.

Medication eluting devices for the field of OBGYN (MEDOBGYN): 3D printed biodegradable hormone eluting constructs, a proof of concept study.

3D printing has the potential to deliver personalized implants and devices for obstetric and gynecologic applications. The aim of this study is to engineer customizable and biodegradable 3D printed implant materials that can elute estrogen and/or progesterone. All 3D constructs were printed using polycaprolactone (PCL) biodegradable polymer laden with estrogen or progesterone and were subjected to hormone-release profile studies using ELISA kits. Material thermal properties were tested using thermogravimetric analysis and differential scanning calorimetry. The 3D printed constructs showed extended hormonal release over a one week period. Cytocompatibility and bioactivity were assessed using a luciferase assay. The hormone-laden 3D printed constructs demonstrated an increase in luciferase activity and without any deleterious effects. Thermal properties of the PCL and hormones showed degradation temperatures above that of the temperature used in the additive manufacturing process-suggesting that 3D printing can be achieved below the degradation temperatures of the hormones. Sample constructs in the shape of surgical meshes, subdermal rods, intrauterine devices and pessaries were designed and printed. 3D printing of estrogen and progesterone-eluting constructs was feasible in this proof of concept study. These custom designs have the potential to act as a form of personalized medicine for drug delivery and optimized fit based on patient-specific anatomy.

Effect of barium-coated halloysite nanotube addition on the cytocompatibility, mechanical and contrast properties of poly(methyl methacrylate) cement.

Halloysite nanotubes (HNTs) were investigated as a platform for tunable nanoparticle composition and enhanced opacity in poly(methyl methacrylate) (PMMA) bone cement. Halloysite has been widely used to increase the mechanical properties of various polymer matrices, in stark contrast to other fillers such as barium sulfate that provide opacity but also decrease mechanical strength. The present work describes a dry deposition method for successively fabricating barium sulfate nanoparticles onto the exterior surface of HNTs. A sintering process was used to coat the HNTs in barium sulfate. Barium sulfate-coated HNTs were then added to PMMA bone cement and the samples were tested for mechanical strength and tailored opacity correlated with the fabrication ratio and the amount of barium sulfate-coated HNTs added. The potential cytotoxic effect of barium-coated HNTs in PMMA cement was also tested on osteosarcoma cells. Barium-coated HNTs were found to be completely cytocompatible, and cell proliferation was not inhibited after exposure to the barium-coated HNTs embedded in PMMA cement. We demonstrate a simple method for the creation of barium-coated nanoparticles that imparted improved contrast and material properties to native PMMA. An easy and efficient method for coating clay nanotubes offers the potential for enhanced imaging by radiologists or orthopedic surgeons.

Validation of Acoustic Wave Induced Traumatic Brain Injury in Rats.

BACKGROUND: This study looked to validate the acoustic wave technology of the Storz-D-Actor that inflicted a consistent closed-head, traumatic brain injury (TBI) in rats. We studied a range of single pulse pressures administered to the rats and observed the resulting decline in motor skills and memory. Histology was observed to measure and confirm the injury insult. METHODS: Four different acoustic wave pressures were studied using a single pulse: 0, 3.4, 4.2 and 5.0 bar (n = 10 rats per treatment group). The pulse was administered to the left frontal cortex. Rotarod tests were used to monitor the rats' motor skills while the water maze test was used to monitor memory deficits. The rats were then sacrificed ten days post-treatment for histological analysis of TBI infarct size. RESULTS: The behavioral tests showed that acoustic wave technology administered an effective insult causing significant decreases in motor abilities and memory. Histology showed dose-dependent damage to the cortex infarct areas only. CONCLUSIONS: This study illustrates that the Storz D-Actor effectively induces a repeatable TBI infarct, avoiding the invasive procedure of a craniotomy often used in TBI research.

From solvent-free microspheres to bioactive gradient scaffolds.

A solvent-free microsphere sintering technique was developed to fabricate scaffolds with pore size gradient for tissue engineering applications. Poly(D,L-Lactide) microspheres were fabricated through an emulsification method where TiO2 nanoparticles were employed both as particulate emulsifier in the preparation procedure and as surface modification agent to improve bioactivity of the scaffolds. A fine-tunable pore size gradient was achieved with a pore volume of 30±2.6%. SEM, EDX, XRD and FTIR analyses all confirmed the formation of bone-like apatite at the 14th day of immersion in Simulated Body Fluid (SBF) implying the ability of our scaffolds to bond to living bone tissue. In vitro examination of the scaffolds showed progressive activity of the osteoblasts on the scaffold with evidence of increase in its mineral content. The bioactive scaffold developed in this study has the potential to be used as a suitable biomaterial for bone tissue engineering and hard tissue regeneration.