Treatment of severe porcine tracheomalacia with a 3-dimensionally printed, bioresorbable, external airway splint

3D printing chronicles in medical devices and pharmaceuticals: tracing the evolution and historical milestones

The objective of this study is to collect the significant advancements of 3D printed medical devices in the biomedical area in recent years. Especially related to a range of diseases and the polymers employed in drug administration. To address the existing limitations and constraints associated with the method used for producing 3D printed medical devices, in order to optimize their suitability for degradation. The compilation and use of research papers, reports, and patents that are relevant to the key keywords are employed to improve comprehension. According to this thorough investigation, it can be inferred that the 3D Printing method, specifically Fuse Deposition Modeling (FDM), is the most suitable and convenient approach for preparing medical devices. This study provides an analysis and summary of the development trend of 3D printed implantable medical devices, focusing on the production process, materials specially the polymers, and typical items associated with 3D printing technology. This study offers a comprehensive examination of nanocarrier research and its corresponding discoveries. The FDM method, which is already facing significant challenges in terms of achieving optimal performance and cost reduction, will experience remarkable advantages from this highly valuable technology. The objective of this analysis is to showcase the efficacy and limitations of 3D-printing applications in medical devices through thorough research, highlighting the significant technological advancements it offers. This article provides a comprehensive overview of the most recent research and discoveries on 3D-printed medical devices, offering significant insights into their study.

3D printing modality effect: Distinct printing outcomes dependent on selective laser sintering (SLS) and melt extrusion

A direct and comprehensive comparative study on different 3D printing modalities was performed. We employed two representative 3D printing modalities, laser- and extrusion-based, which are currently used to produce patient-specific medical implants for clinical translation, to assess how these two different 3D printing modalities affect printing outcomes. The same solid and porous constructs were created from the same biomaterial, a blend of 96% poly-ε-caprolactone (PCL) and 4% hydroxyapatite (HA), using two different 3D printing modalities. Constructs were analyzed to assess their printing characteristics, including morphological, mechanical, and biological properties. We also performed an in vitro accelerated degradation study to compare their degradation behaviors. Despite the same input material, the 3D constructs created from different 3D printing modalities showed distinct differences in morphology, surface roughness and internal void fraction, which resulted in different mechanical properties and cell responses. In addition, the constructs exhibited different degradation rates depending on the 3D printing modalities. Given that each 3D printing modality has inherent characteristics that impact printing outcomes and ultimately implant performance, understanding the characteristics is crucial in selecting the 3D printing modality to create reliable biomedical implants.

Enhancement of tracheal cartilage regeneration by local controlled release of stromal cell-derived factor 1α with gelatin hydrogels and systemic administration of high-mobility group box 1 peptide

Introduction

This present study evaluated the effect of combination therapy with stromal cell-derived factor 1α (SDF-1α) and high-mobility group box 1 (HMGB1) peptide on the regeneration of tracheal injury in a rat model.

Methods

To improve this effect, SDF-1α was incorporated into a gelatin hydrogel, which was then applied to the damaged tracheal cartilage of rats for local release. Furthermore, HMGB1 peptide was repeatedly administered intravenously. Regeneration of damaged tracheal cartilage was evaluated in terms of cell recruitment.

Results

Mesenchymal stem cells (MSC) with C-X-C motif chemokine receptor 4 (CXCR4) were mobilized more into the injured area, and consequently the fastest tracheal cartilage regeneration was observed in the combination therapy group eight weeks after injury.

Conclusions

The present study demonstrated that combination therapy with gelatin hydrogel incorporating SDF-1α and HMGB1 peptide injected intravenously can enhance the recruitment of CXCR4-positive MSC, promoting the regeneration of damaged tracheal cartilage.

Robot-Assisted Correction of a Supra-Long Tracheal Stenosis Using C-Type Nickel-Titanium Alloy Exterior Stenting and Suspension Fixation Technique: A Case Report

T-tubes and airway stents are commonly used but have limited effectiveness and frequent complications. A 50-year-old male patient presented with severe tracheal stenosis, affecting an 8.7 cm length of the airway. We employed an innovative approach known as external suspension fixation of tracheal stent using robotic assistance. This method involves surgically attaching the stent to the exterior of the trachea to provide support and stabilize the softened or collapsed tracheal segments. We designed a C-shaped nickel-titanium alloy exterior stent and successfully fixed it using robotic assistance. This intervention effectively restored tracheal function and led to a favorable postoperative recovery. The technique does not affect tracheal membrane function or airway mucociliary clearance. It could potentially be considered as a new option for treating long-segment benign tracheal softening or collapse.

A novel ex vivo tracheobronchomalacia model for airway stent testing and in vivo model refinement

OBJECTIVES

We sought to develop an ex vivo trachea model capable of producing mild, moderate, and severe tracheobronchomalacia for optimizing airway stent design. We also aimed to determine the amount of cartilage resection required for achieving different tracheobronchomalacia grades that can be used in animal models.

METHODS

We developed an ex vivo trachea test system that enabled video-based measurement of internal cross-sectional area as intratracheal pressure was cyclically varied for peak negative pressures of 20 to 80 cm H2O. Fresh ovine tracheas were induced with tracheobronchomalacia by single mid-anterior incision (n = 4), mid-anterior circumferential cartilage resection of 25% (n = 4), and 50% per cartilage ring (n = 4) along an approximately 3-cm length. Intact tracheas (n = 4) were used as control. All experimental tracheas were mounted and experimentally evaluated. In addition, helical stents of 2 different pitches (6 mm and 12 mm) and wire diameters (0.52 mm and 0.6 mm) were tested in tracheas with 25% (n = 3) and 50% (n = 3) circumferentially resected cartilage rings. The percentage collapse in tracheal cross-sectional area was calculated from the recorded video contours for each experiment.

RESULTS

Ex vivo tracheas compromised by single incision and 25% and 50% circumferential cartilage resection produce tracheal collapse corresponding to clinical grades of mild, moderate, and severe tracheobronchomalacia, respectively. A single anterior cartilage incision produces saber-sheath type tracheobronchomalacia, whereas 25% and 50% circumferential cartilage resection produce circumferential tracheobronchomalacia. Stent testing enabled the selection of stent design parameters such that airway collapse associated with moderate and severe tracheobronchomalacia could be reduced to conform to, but not exceed, that of intact tracheas (12-mm pitch, 0.6-mm wire diameter).

CONCLUSIONS

The ex vivo trachea model is a robust platform that enables systematic study and treatment of different grades and morphologies of airway collapse and tracheobronchomalacia. It is a novel tool for optimization of stent design before advancing to in vivo animal models.

Innovation in rigid bronchoscopy-past, present, and future

German laryngologist Gustav Killian performed the first "Direkte Bronchoskopie" using a rigid bronchoscope to extract a foreign airway body from the right main bronchus over a hundred years ago, transforming the practice of respiratory medicine. The procedure instantaneously became popular throughout the world. Chevalier Jackson Sr from the United States further advanced the instrument, technique, safety, and application. In the 1960s, Professors Harold H. Hopkins and N.S. Kapany introduced optical rods as well as fiberoptics that led Karl Storz to develop the cold light system improving endoluminal illumination, achievements that ushered in the modern era of flexible endoscopy. Several diagnostic and therapeutic procedures became possible such as transbronchial needle biopsy, transbronchial lung biopsy, airway electrosurgery, or cryotherapy. Dr. Jean-François Dumon from France advanced the use of Nd-YAG laser in the endobronchial tree and created the dedicated Dumon silicone stent introducing the whole new field of interventional pulmonology (IP). This major milestone revitalized interest in rigid bronchoscopy (RB). Now, advancements are being made in stenting, instrumentation, and education. RB robotic technology advancements are currently anticipated and can potentially revolutionize the practice of pulmonary medicine. In this review, we describe some of the most substantial advances related to RB from its beginning to the modern era.

Three Dimensional Printing and Its Applications Focusing on Microneedles for Drug Delivery

Microneedles (MNs) are considered to be a novel smart injection system that causes significantly low skin invasion upon puncturing, due to the micron-sized dimensions that pierce into the skin painlessly. This allows transdermal delivery of numerous therapeutic molecules, such as insulin and vaccines. The fabrication of MNs is carried out through conventional old methods such as molding, as well as through newer and more sophisticated technologies, such as three-dimensional (3D) printing, which is considered to be a superior, more accurate, and more time- and production-efficient method than conventional methods. Three-dimensional printing is becoming an innovative method that is used in education through building intricate models, as well as being employed in the synthesis of fabrics, medical devices, medical implants, and orthoses/prostheses. Moreover, it has revolutionary applications in the pharmaceutical, cosmeceutical, and medical fields. Having the capacity to design patient-tailored devices according to their dimensions, along with specified dosage forms, has allowed 3D printing to stand out in the medical field. The different techniques of 3D printing allow for the production of many types of needles with different materials, such as hollow MNs and solid MNs. This review covers the benefits and drawbacks of 3D printing, methods used in 3D printing, types of 3D-printed MNs, characterization of 3D-printed MNs, general applications of 3D printing, and transdermal delivery using 3D-printed MNs.

Current Status and Future Outlook of Additive Manufacturing Technologies for the Reconstruction of the Trachea

Tracheal stenosis and defects occur congenitally and in patients who have undergone tracheal intubation and tracheostomy due to long-term intensive care. Such issues may also be observed during tracheal removal during malignant head and neck tumor resection. However, to date, no treatment method has been identified that can simultaneously restore the appearance of the tracheal skeleton while maintaining respiratory function in patients with tracheal defects. Therefore, there is an urgent need to develop a method that can maintain tracheal function while simultaneously reconstructing the skeletal structure of the trachea. Under such circumstances, the advent of additive manufacturing technology that can create customized structures using patient medical image data provides new possibilities for tracheal reconstruction surgery. In this study, the three-dimensional (3D) printing and bioprinting technologies used in tracheal reconstruction are summarized, and various research results related to the reconstruction of mucous membranes, cartilage, blood vessels, and muscle tissue, which are tissues required for tracheal reconstruction, are classified. The prospects for 3D-printed tracheas in clinical studies are also described. This review serves as a guide for the development of artificial tracheas and clinical trials using 3D printing and bioprinting.

Bioengineering and Clinical Translation of Human Lung and its Components

Clinical lung transplantation has rapidly established itself as the gold standard of treatment for end-stage lung diseases in a restricted group of patients since the first successful lung transplant occurred. Although significant progress has been made in lung transplantation, there are still numerous obstacles on the path to clinical success. The development of bioartificial lung grafts using patient-derived cells may serve as an alternative treatment modality; however, challenges include developing appropriate scaffold materials, advanced culture strategies for lung-specific multiple cell populations, and fully matured constructs to ensure increased transplant lifetime following implantation. This review highlights the development of tissue-engineered tracheal and lung equivalents over the past two decades, key problems in lung transplantation in a clinical environment, the advancements made in scaffolds, bioprinting technologies, bioreactors, organoids, and organ-on-a-chip technologies. The review aims to fill the lacuna in existing literature toward a holistic bioartificial lung tissue, including trachea, capillaries, airways, bifurcating bronchioles, lung disease models, and their clinical translation. Herein, the efforts are on bridging the application of lung tissue engineering methods in a clinical environment as it is thought that tissue engineering holds enormous promise for overcoming the challenges associated with the clinical translation of bioengineered human lung and its components.

Novel Therapy for Acquired Tracheomalacia with a Tissue-Engineered Extraluminal Tracheal Splint and Autologous Mesenchymal-Derived Chondrocytes

Introduction Acquired tracheomalacia (ATM) is characterized by a loss of structural strength of the tracheal framework, resulting in airway collapse during breathing. Near half of the patients undergoing prolonged invasive mechanical ventilation will suffer tracheal lesions. Treatment for ATM includes external splinting with rib grafts, prosthetic materials, and tracheal resection. Failure in the use of prosthetic materials has made reconsidering natural origin scaffolds and tissue engineering as a suitable alternative.

Objective To restore adequate airway patency in an ovine model with surgically-induced ATM employing a tissue-engineered extraluminal tracheal splint (TE-ETS).

Methods In the present prospective pilot study, tracheal rings were partially resected to induce airway collapse in 16 Suffolk sheep (Ovis aries). The TE-ETS was developed with autologous mesenchymal-derived chondrocytes and allogenic decellularized tracheal segments and was implanted above debilitated tracheal rings. The animals were followed-up at 8, 12, and 16 weeks and at 1-year postinsertion. Flexible tracheoscopies were performed at each stage. After sacrifice, a histopathological study of the trachea and the splint were performed.

Results The TE-ETS prevented airway collapse for 16 weeks and up to 1-year postinsertion. Tracheoscopies revealed a noncollapsing airway during inspiration. Histopathological analyses showed the organization of mesenchymal-derived chondrocytes in lacunae, the proliferation of blood vessels, and recovery of epithelial tissue subjacent to the splint. Splints without autologous cells did not prevent airway collapse.

Conclusion It is possible to treat acquired tracheomalacia with TE-ETS without further surgical removal since it undergoes physiological degradation. The present study supports the development of tissue-engineered tracheal substitutes for airway disease.

3D printing in Ophthalmology: From medical implants to personalised medicine

3D printing was invented thirty years ago. However, its application in healthcare became prominent only in recent years to provide solutions for drug delivery and clinical challenges, and is constantly evolving. This cost-efficient technique utilises biocompatible materials and is used to develop model implants to provide a greater understanding of human anatomy and diseases, and can be used for organ transplants, surgical planning and for the manufacturing of advanced drug delivery systems. In addition, 3D printed medical devices and implants can be customised for each patient to provide a more tailored treatment approach. The advantages and applications of 3D printing can be used to treat patients with different eye conditions, with advances in 3D bioprinting offering novel therapy applications in ophthalmology. The purpose of this review paper is to provide an in-depth understanding of the applications and advantages of 3D printing in treating different ocular conditions in the cornea, glaucoma, retina, lids and orbits.

Mathematical surface function-based design and 3D printing of airway stents

BACKGROUND

Three-dimensional (3D) printing is a method applied to build a 3D object of any shape from a digital model, and it provides crucial advantages especially for transferring patient-specific designs to clinical settings. The main purpose of this study is to introduce the newly designed complex airway stent models that are created through mathematical functions and manufactured with 3D printing for implementation in real life.

METHODS

A mathematical modeling software (MathMod) was used to design five different airway stents. The highly porous structures with designated scales were fabricated by utilizing a stereolithography-based 3D printing technology. The fine details in the microstructure of 3D printed parts were observed by a scanning electron microscope (SEM). The mechanical properties of airway stents with various designs and porosity were compared by compression test.

RESULTS

The outputs of the mathematical modeling software were successfully converted into 3D printable files and airway stents with a porosity of more than 85% were 3D printed. SEM images revealed the layered topography of high-resolution 3D printed parts. Compression tests have shown that the mathematical function-based design offers the opportunity to adjust the mechanical strength of airway stents without changing the material or manufacturing method.

CONCLUSIONS

A novel approach, which includes mathematical function-based design and 3D printing technology, is proposed in this study for the fabrication of airway stents as a promising tool for future treatments of central airway pathologies.

Tracheobronchomalacia and Excessive Dynamic Airway Collapse: Current Concepts and Future Directions

Tracheobronchomalacia (TBM) and excessive dynamic airway collapse (EDAC) are airway abnormalities that share a common feature of expiratory narrowing but are distinct pathophysiologic entities. Both entities are collectively referred to as expiratory central airway collapse (ECAC). The malacia or weakness of cartilage that supports the tracheobronchial tree may occur only in the trachea (ie, tracheomalacia), in both the trachea and bronchi (TBM), or only in the bronchi (bronchomalacia). On the other hand, EDAC refers to excessive anterior bowing of the posterior membrane into the airway lumen with intact cartilage. Clinical diagnosis is often confounded by comorbidities including asthma, chronic obstructive pulmonary disease, obesity, hypoventilation syndrome, and gastroesophageal reflux disease. Additional challenges include the underrecognition of ECAC at imaging; the interchangeable use of the terms TBM and EDAC in the literature, which leads to confusion; and the lack of clear guidelines for diagnosis and treatment. The use of CT is growing for evaluation of the morphology of the airway, tracheobronchial collapsibility, and extrinsic disease processes that can narrow the trachea. MRI is an alternative tool, although it is not as widely available and is not used as frequently for this indication as is CT. Together, these tools not only enable diagnosis, but also provide a road map to clinicians and surgeons for planning treatment. In addition, CT datasets can be used for 3D printing of personalized medical devices such as stents and splints. An invited commentary by Brixey is available online. Online supplemental material is available for this article. ^©RSNA, 2022.

Tissue-engineered composite tracheal grafts create mechanically stable and biocompatible airway replacements

We tested composite tracheal grafts (CTG) composed of a partially decellularized tracheal graft (PDTG) combined with a 3-dimensional (3D)-printed airway splint for use in long-segment airway reconstruction. CTG is designed to recapitulate the 3D extracellular matrix of the trachea with stable mechanical properties imparted from the extraluminal airway splint. We performed segmental orthotopic tracheal replacement in a mouse microsurgical model. MicroCT was used to measure graft patency. Tracheal neotissue formation was quantified histologically. Airflow dynamic properties were analyzed using computational fluid dynamics. We found that CTG are easily implanted and did not result in vascular erosion, tracheal injury, or inflammation. Graft epithelialization and endothelialization were comparable with CTG to control. Tracheal collapse was absent with CTG. Composite tracheal scaffolds combine biocompatible synthetic support with PDTG, supporting the regeneration of host epithelium while maintaining graft structure.

Early preclinical evaluation of a novel, computer aided designed, 3D printed, bioresorbable posterior cricoid scaffold

OBJECTIVES

The posterior cricoid split with rib graft is a procedure that elegantly corrects pediatric posterior glottic stenosis and subglottic stenosis. Currently, the procedure requires harvesting of rib cartilage which leaves room for optimization. With use of three dimensional printing technology, our objective was to design a device that would negate the need for costal cartilage harvesting in this procedure.

METHODS

An optimized, novel polycaprolactone scaffold was designed using computer aided design software and three dimensional printing. A pilot proof of concept study was conducted with implantation of the device in three porcine animal subjects. Device was evaluated by post-procedural clinical course, endoscopic exams, post-mortem exam, and histological evaluation.

RESULTS

A series of variably sized scaffolds were created. The scaffolds showed structural integrity and successfully expanded the cricoid cartilage in the porcine model study. Post-operative endoscopy and clinical exams demonstrated no signs of implant instability or failure. Gross and histologic exams showed successful mucosalization over the scaffold and cartilage ingrowth by six weeks.

CONCLUSION

This porcine animal pilot study demonstrated early success of a computer-aided designed, 3D printed, bioresorbable PCL posterior graft scaffold. The scaffolds eliminate the need for costal cartilage harvesting and had excellent surgical usability. The scaffolds functioned as designed, offering proof of concept and grounds for further evaluation to expand on this small pilot study with larger animal studies and continued design refinement.

3D Printing-A Cutting Edge Technology for Treating Post-Infarction Patients

The increasing complexity of cardiovascular interventions requires advanced peri-procedural imaging and tailored treatment. Three-dimensional printing technology represents one of the most significant advances in the field of cardiac imaging, interventional cardiology or cardiovascular surgery. Patient-specific models may provide substantial information on intervention planning in complex cardiovascular diseases, and volumetric medical imaging from CT or MRI can be translated into patient-specific 3D models using advanced post-processing applications. 3D printing and additive manufacturing have a great variety of clinical applications targeting anatomy, implants and devices, assisting optimal interventional treatment and post-interventional evaluation. Although the 3D printing technology still lacks scientific evidence, its benefits have been shown in structural heart diseases as well as for treatment of complex arrhythmias and corrective surgery interventions. Recent development has enabled transformation of conventional 3D printing into complex 3D functional living tissues contributing to regenerative medicine through engineered bionic materials such hydrogels, cell suspensions or matrix components. This review aims to present the most recent clinical applications of 3D printing in cardiovascular medicine, highlighting also the potential for future development of this revolutionary technology in the medical field.

Resorbable airway splint, stents, and 3D reconstruction and printing of the airway in tracheobronchomalacia

Tracheobronchomalacia (TBM) is the most common tracheobronchial obstruction. Most cases are mild to moderate; therefore, they do not need surgical treatment. Severe tracheomalacia, however, represents a diagnostic and therapeutic challenge since they are very heterogeneous. In the armamentarium of resources for the treatment of dynamic airway collapse, splints and stents are two underused strategies and yet, they may represent the best alternative in selected cases. Lately, computed tomography 3D reconstruction of the airway has been used for the design of virtual models that can be 3D-printed for the creation of novel devices to address training, simulation, and biotechnological implants for refractory and severe airway malformations. This manuscript examines the role of resorbable stents, splints, and the 3D reconstruction and printing of the pediatric airway in tracheobronchomalacia.

Current concepts in tracheobronchomalacia: diagnosis and treatment

Airway collapse from dynamic tracheobronchomalacia (TBM), static compression from vascular compression, and/or tracheobronchial deformation are challenging conditions. Patients are best assessed and managed by a multidisciplinary team in centers specializing in complex pediatric airway disorders. Suspicion is made through clinical history and physical examination, diagnosis of location and severity by dynamic 3-phase bronchoscopy, and surgical treatment planning by MDCT and other studies as necessary to completely understand the problems. The treatment plan should be patient-based with a thorough approach to the underlying pathology, clinical concerns, and combined abnormalities. Patients should undergo maximum medical therapy prior to committing to other interventions. For those children considered candidates for surgical intervention, all other associated conditions, including vascular anomalies, chest wall deformities, mediastinal lesions, or other airway pathologies, should also be considered. Our preference is to correct the airway lesions at the same operation as other comorbidities, if possible, to prevent multiple reoperations with their attendant increased risks. We also strongly advocate for the use of recurrent laryngeal nerve monitoring in all cases of cervical or thoracic surgery to minimize the risks to vocal cord function and laryngeal sensation. Studies that evaluate the effect of these interventions on the patient and caregiver's quality of life are needed to fully grasp the impact of TBM on this challenging patient population.

Motility Improvement of Biomimetic Trachea Scaffold via Hybrid 3D-Bioprinting Technology

A trachea has a structure capable of responding to various movements such as rotation of the neck and relaxation/contraction of the conduit due to the mucous membrane and cartilage tissue. However, current reported tubular implanting structures are difficult to impelement as replacements for original trachea movements. Therefore, in this study, we developed a new trachea implant with similar anatomical structure and mechanical properties to native tissue using 3D printing technology and evaluated its performance. A 250 µm-thick layer composed of polycaprolactone (PCL) nanofibers was fabricated on a rotating beam using electrospinning technology, and a scaffold with C-shaped cartilage grooves that mimics the human airway structure was printed to enable reconstruction of cartilage outside the airway. A cartilage type scaffold had a highest rotational angle (254°) among them and it showed up to 2.8 times compared to human average neck rotation angle. The cartilage type showed a maximum elongation of 8 times higher than that of the bellows type and it showed the elongation of 3 times higher than that of cylinder type. In cartilage type scaffold, gelatin hydrogel printed on the outside of the scaffold was remain 22.2% under the condition where no hydrogel was left in other type scaffolds. In addition, after 2 days of breathing test, the amount of gelatin remaining inside the scaffold was more than twice that of other scaffolds. This novel trachea scaffold with hydrogel inside and outside of the structure was well-preserved under external flow and is expected to be advantageous for soft tissue reconstruction of the trachea.

Tracheobronchomalacia, Tracheobronchial Compression, and Tracheobronchial Malformations: Diagnostic and Treatment Strategies

Tracheobronchomalacia (TBM) is an excessive dynamic narrowing of the airway that is greatest with increased mediastinal pressure such as coughing, Valsalva, and forced expiration. Airway compression and/or cartilage malformation is a fixed or static narrowing of the airway typically caused by great vessel malposition and/or abnormalities and may also contribute to airway narrowing. Although imprecise and misleading, the term TBM is often used to represent both problems, static and dynamic airway narrowing, which only serves to confuse and may mislead the treatment team into ineffective therapies. The consequences of airway narrowing caused by dynamic TBM and/or static compression includes a range of clinical signs and symptoms, depending on the location, extent, and severity of the airway collapse. All patients with mild to severe TBM benefit from medical management to optimize airway clearance of mucus. The milder cases of TBM may become asymptomatic with this therapy, allowing time for the child to grow and the airway to enlarge without the consequences of recurrent infections. In cases of more severe TBM with clinical sequelae, more aggressive management may be warranted. Multiple options for surgical intervention are available. This article discusses the details of clinical presentation, evaluation, diagnosis, and a variety of treatments.

SARS-CoV-2 and tissue damage: current insights and biomaterial-based therapeutic strategies

The effect of SARS-CoV-2 infection on humanity has gained worldwide attention and importance due to the rapid transmission, lack of treatment options and high mortality rate of the virus. While scientists across the world are searching for vaccines/drugs that can control the spread of the virus and/or reduce the risks associated with infection, patients infected with SARS-CoV-2 have been reported to have tissue/organ damage. With most tissues/organs having limited regenerative potential, interventions that prevent further damage or facilitate healing would be helpful. In the past few decades, biomaterials have gained prominence in the field of tissue engineering, in view of their major role in the regenerative process. Here we describe the effect of SARS-CoV-2 on multiple tissues/organs, and provide evidence for the positive role of biomaterials in aiding tissue repair. These findings are further extrapolated to explore their prospects as a therapeutic platform to address the tissue/organ damage that is frequently observed during this viral outbreak. This study suggests that the biomaterial-based approach could be an effective strategy for regenerating tissues/organs damaged by SARS-CoV-2.

A Two-Scale Multi-Resolution Topologically Optimized Multi-Material Design of 3D Printed Craniofacial Bone Implants

Bone replacement implants for craniofacial reconstruction require to provide an adequate structural foundation to withstand the physiological loading. With recent advances in 3D printing technology in place of bone grafts using autologous tissues, patient-specific additively manufactured implants are being established as suitable alternates. Since the stress distribution of these structures is complicated, efficient design techniques, such as topology optimization, can deliver optimized designs with enhanced functionality. In this work, a two-scale topology optimization approach is proposed that provides multi-material designs for both macrostructures and microstructures. In the first stage, a multi-resolution topology optimization approach is used to produce multi-material designs with maximum stiffness. Then, a microstructure with a desired property supplants the solid domain. This is beneficial for bone implant design since, in addition to imparting the desired functional property to the design, it also introduces porosity. To show the efficacy of the technique, four different large craniofacial defects due to maxillectomy are considered, and their respective implant designs with multi-materials are shown. These designs show good potential in developing patient-specific optimized designs suitable for additive manufacturing.

Advanced Therapies for Severe Tracheobronchomalacia: A Review of the Use of 3D-Printed, Patient-Specific, Externally Implanted, Bioresorbable Airway Splints

Tracheobronchomalacia is a condition of dynamic collapse of the trachea and mainstem bronchi. The clinical significance of tracheobronchomalacia depends on its severity. Mild cases may be medically managed with limited symptomology, while severe cases require advanced therapies, lengthy hospital stays, and carry significant morbidity and mortality. Current therapies for severe tracheobronchomalacia include tracheostomy with prolonged mechanical ventilation, aortopexy, tracheobronchopexy, and intraluminal metallic, silicone, or bioresorbable stents. Three-dimensional (3D)-printed, patient-specific, bioresorbable airway splinting is a novel treatment option that is undergoing investigation in a cohort of critically ill children with severe tracheobronchomalacia. At the time of our last review of our data, 29 splints had been implanted in 15 children with intrathoracic tracheobronchomalacia. The median follow-up was 8.5 months. There were 12 long-term survivors, and all but one lived at home. This article discusses the details of our institution's development and use of 3D-printed, patient-specific, bioresorbable splints for treatment of severe tracheobronchomalacia in the pediatric population.

The role of bioresorbable intraluminal airway stents in pediatric tracheobronchial obstruction: A systematic review

INTRODUCTION

Tracheal stenosis and tracheobronchomalacia are complicated, patient-specific diseases that can be treated with intraluminal stenting. Most commonly, silicone and metal stents are utilized, however, they pose significant early and late morbidity and are further complicated by growth of the airway in the pediatric population. Given recent improvements in materials science, there is a growing body of evidence suggesting a strong role for bioresorbable intraluminal stents in treating pediatric tracheobronchial obstruction.

METHODS

A PubMed.gov literature search was performed on December 3, 2019 and May 15, 2020, and a 2-researcher systematic review was performed following the PRISMA criteria. The following search query was utilized: (((((((bioresorbable) OR bioabsorbable) OR resorbable) OR absorbable) OR biodegradable AND airway) OR trachea) AND stent. A pooled statistical analysis was performed on all reported pediatric patients using SPSS software.

RESULTS

1369 publications were screened and 26 articles with original data were identified. Materials used included polydioxanone (PDO), poly-l-lactic acid (PLLA), polyglycolic acid/poly-l-lactide co-polymer with Proglactin 910 (Vicryl®-PDS®), polycaprolactone (PCL), magnesium alloys, and co-polymers in varying proportions. Twelve articles presented data on human subjects, 8 of which were case series and case reports on pediatric populations using polydioxanone (PDO) stents. Pooled statistical analysis demonstrated an average age of 19 months (range 0.25-144), 56.5% associated with a cardiovascular anomaly, and overall complication rate of 21.7%, with a stent fragment foreign body being the most common (8.7%), followed by significant granulation tissue (4.3%), stent migration (4.3%), and local stenosis (4.3%). Comparative analysis demonstrated short-term improvement (up to 1 month) has a statistically significant association with tracheobronchomalacia versus tracheal stenosis on chi-squared test (p = 0.001). The remaining analyses did not yield statistical significance.

CONCLUSION

The reported application of bioresorbable materials as intraluminal airway stents is positive. All comparative animal studies report biocompatibility and fewer morbidities compared to metal and silicone stents, however, in human studies there are concerns over the short interval of degradation and the potential for obstructive foreign bodies in poorly seated stents. Overall, there are clear, reproducible advantages to bioresorbable intraluminal stents in pediatric airway obstruction, as well as common pitfalls, that warrant further research.

The role of 3D printing in pediatric airway obstruction: A systematic review

BACKGROUND

Tracheomalacia and tracheal stenosis are complicated, patient-specific diseases that require a multidisciplinary approach to diagnose and treat. Surgical interventions such as aortopexy, slide tracheoplasty, and stents potentially have high rates of morbidity. Given the emergence of three-dimensional (3D) printing as a versatile adjunct in managing complex pathology, there is a growing body of evidence that there is a strong role for 3D printing in both surgical planning and implant creation for pediatric airway obstruction.

METHODS

A structured PubMed.gov literature search was utilized, and a two-researcher systematic review was performed following the PRISMA criteria. The following search query was utilized: (((((3D printing) OR three-dimensional printing) OR 3D printed) OR three-dimensional printed) AND trachea) OR airway.

RESULTS

Over 23,000 publications were screened. Eight literature reviews and thirty-seven original papers met inclusion criteria. Of the thirty-seven original papers, eleven discussed 3D printing for surgical planning and twenty-six discussed 3D printing implants for interventions.

CONCLUSION

The reported application of 3D printing for management of pediatric airway obstruction is emerging with positive and broad applications. 3D printing for surgical planning not only improves pre-operative assessment of surgical approach and stent customization, but also helps facilitate patient/family education. 3D printing for custom implantable interventions is focused on bioresorbable external airway splints and biological grafts, with both animal studies and human case reports showing good results in improving symptoms.

Progressive 3D Printing Technology and Its Application in Medical Materials

Three-dimensional (3D) printing enables patient-specific anatomical level productions with high adjustability and resolution in microstructures. With cost-effective manufacturing for high productivity, 3D printing has become a leading healthcare and pharmaceutical manufacturing technology, which is suitable for variety of applications including tissue engineering models, anatomical models, pharmacological design and validation model, medical apparatus and instruments. Today, 3D printing is offering clinical available medical products and platforms suitable for emerging research fields, including tissue and organ printing. In this review, our goal is to discuss progressive 3D printing technology and its application in medical materials. The additive overview also provides manufacturing techniques and printable materials.

The Fabrication and in vitro Evaluation of Retinoic Acid-Loaded Electrospun Composite Biomaterials for Tracheal Tissue Regeneration

Although relatively rare, major trauma to the tracheal region of the airways poses a significant clinical challenge with few effective treatments. Bioengineering and regenerative medicine strategies have the potential to create biocompatible, implantable biomaterial scaffolds, with the capacity to restore lost tissue with functional neo-trachea. The main goal of this study was to develop a nanofibrous polycaprolactone-chitosan (PCL-Chitosan) scaffold loaded with a signaling molecule, all-trans retinoic acid (atRA), as a novel biomaterial approach for tracheal tissue engineering. Using the Spraybase® electrospinning platform, polymer concentration, solvent selection, and instrument parameters were optimized to yield a co-polymer with nanofibers of 181-197 nm in diameter that mimicked tracheobronchial tissue architecture. Thereafter, scaffolds were assessed for their biocompatibility and capacity to induce mucociliary functionalization using the Calu-3 cell line. PCL-Chitosan scaffolds were found to be biocompatible in nature and support Calu-3 cell viability over a 14 day time period. Additionally, the inclusion of atRA did not compromise Calu-3 cell viability, while still achieving an efficient encapsulation of the signaling molecule over a range of atRA concentrations. atRA release from scaffolds led to an increase in mucociliary gene expression at high scaffold loading doses, with augmented MUC5AC and FOXJ1 detected by RT-PCR. Overall, this scaffold integrates a synthetic polymer that has been used in human tracheal stents, a natural polymer generally regarded as safe (GRAS), and a drug with decades of use in patients. Coupled with the scalable nature of electrospinning as a fabrication method, all of these characteristics make the biomaterial outlined in this study amenable as an implantable device for an unmet clinical need in tracheal replacement.

3D printing for tissue engineering in otolaryngology

Airway and other head and neck disorders affect hundreds of thousands of patients each year and most require surgical intervention. Among these, congenital deformity that affects newborns is particularly serious and can be life-threatening. In these cases, reconstructive surgery is resolutive but bears significant limitations, including the donor site morbidity and limited available tissue. In this context, tissue engineering represents a promising alternative approach for the surgical treatment of otolaryngologic disorders. In particular, 3D printing coupled with advanced imaging technologies offers the unique opportunity to reproduce the complex anatomy of native ear, nose, and throat, with its import in terms of functionality as well as aesthetics and the associated patient well-being. In this review, we provide a general overview of the main ear, nose and throat disorders and focus on the most recent scientific literature on 3D printing and bioprinting for their treatment.

Polycaprolactone: How a Well-Known and Futuristic Polymer Has Become an Innovative Collagen-Stimulator in Esthetics

Compared to other domains, tissue engineering and esthetics have dramatically expanded in recent years, leading to both major biomedical advances and futuristic perspectives. The two share a common approach based on biomaterials, especially polymers. This paper illustrates this with the example of polycaprolactone (PCL), a polymer synthesized in the early 1930s, and one of its most recent applications, a PCL-based collagen stimulator, a filler used in esthetics. PCL is biocompatible and biodegradable. Its specific physicochemical and mechanical properties, viscoelasticity and ease of shaping led to the production of PCL-based products with various shapes and durations dependent on its biodegradation kinetics. PCL has been safely used in the biomedical field for more than 70 years, from sutures to tissue and organ replacement by 3D printing. The PCL-based collagen stimulator is composed of PCL microspheres suspended in a carboxymethyl-cellulose gel carrier providing immediate and sustained volumizing effects when injected; the morphology, the biocompatibility of the PCL microspheres embedded with the collagen fibers produced all contribute to the creation of a unique 3D scaffold for a sustained effect. Its safety has been investigated in clinical studies and vigilance surveys. Recently published experts' recommendations on injection modalities and techniques should help further optimize treatment outcome and safety. This paper also integrates reviews and recommendations on the prevention and management of adverse events related to dermal and subdermal fillers including the PCL-based collagen stimulator. In addition, in terms of efficacy and safety, this product benefits from its daily clinical use in esthetics worldwide and continuous extensive fundamental and clinical research, both on it and the PCL polymer. Forthcoming data from further investigations will reinforce knowledge of the product and procedures in the field.

Long-segmental tracheal reconstruction in rabbits with pedicled Tissue-engineered trachea based on a 3D-printed scaffold

Long-segmental tracheal defects constitute an intractable clinical problem, due to the lack of satisfactory tracheal substitutes for surgical reconstruction. Tissue engineered artificial substitutes could represent a promising approach to tackle this challenge. In our current study, tissue-engineered trachea, based on a 3D-printed poly (l-lactic acid) (PLLA) scaffold with similar morphology to the native trachea of rabbits, was used for segmental tracheal reconstruction. The 3D-printed scaffolds were seeded with chondrocytes obtained from autologous auricula, dynamically pre-cultured in vitro for 2 weeks, and pre-vascularized in vivo for another 2 weeks to generate an integrated segmental trachea organoid unit. Then, segmental tracheal defects in rabbits were restored by transplanting the engineered tracheal substitute with pedicled muscular flaps. We found that the combination of in vitro pre-culture and in vivo pre-vascularization successfully generated a segmental tracheal substitute with bionic structure and mechanical properties similar to the native trachea of rabbits. Moreover, the stable blood supply provided by the pedicled muscular flaps facilitated the survival of chondrocytes and accelerated epithelialization, thereby improving the survival rate. The segmental trachea substitute engineered by a 3D-printed scaffold, in vitro pre-culture, and in vivo pre-vascularization enhanced survival in an early stage post-operation, presenting a promising approach for surgical reconstruction of long segmental tracheal defects. STATEMENT OF SIGNIFICANCE: We found that the combination of in vitro pre-culture and in vivo pre-vascularization successfully generated a segmental tracheal substitute with bionic structure and mechanical properties similar to the native trachea of rabbits. Moreover, the stable blood supply provided by the pedicled muscular flaps facilitated the survival of chondrocytes and accelerated epithelialization, thereby improving the survival rate of the rabbits. The segmental trachea substitute engineered by a 3D-printed scaffold, in vitro pre-culture, and in vivo pre-vascularization enhanced survival in an early stage post-operation, presenting a promising approach for surgical reconstruction of long segmental tracheal defects.

3D-bioprinted tracheal reconstruction: an overview

Congenital tracheomalacia and tracheal stenosis are commonly seen in premature infants. In adulthood, are typically related with chronic obstructive pulmonary disease, and can occur secondarily from tracheostomy, prolong intubation, trauma, infection and tumors. Both conditions are life-threatening when not managed properly. There are still some surgical limitations for certain pathologies, however tissue engineering is a promising approach to treat massive airway dysfunctions. 3D-bioprinting have contributed to current preclinical and clinical efforts in airway reconstruction. Several strategies have been used to overcome the difficulty of airway reconstruction such as scaffold materials, construct designs, cellular types, biologic components, hydrogels and animal models used in tracheal reconstruction. Nevertheless, additional long-term in vivo studies need to be performed to assess the efficacy and safety of tissue-engineered tracheal grafts in terms of mechanical properties, behavior and, the possibility of further stenosis development.

Preclinical assessment of resorbable silk splints for the treatment of pediatric tracheomalacia

OBJECTIVE

Tracheomalacia is characterized by weakness of the tracheal wall resulting in dynamic airway collapse during respiration; severe cases often require surgical intervention. Off-label external splinting with degradable implants has been reported in humans; however, there remains a need to develop splints with tunable mechanical properties and degradation profiles for the pediatric population. The objective of this pilot study is to assess the safety and efficacy of silk fibroin-based splints in a clinically relevant preclinical model of tracheomalacia.

METHODS

Silk splints were evaluated in a surgically induced model of severe tracheomalacia in N = 3 New Zealand white rabbits for 17, 24, and 31 days. An image-based assay was developed to quantify the dynamic change in airway area during spontaneous respiration, and histopathology was used to study the surrounding tissue response.

RESULTS

The average change in area in the native trachea was 23% during spontaneous respiration; surgically induced tracheomalacia resulted in a significant increase to 86% (P < 0.001). The average change in airway area after splint placement was reduced at all terminal time points (17, 24, and 31 days postimplantation), indicating a clinical improvement, and was not statistically different than the native trachea. Histopathology showed a localized inflammatory reaction characterized by neutrophils, eosinophils, and mononuclear cells, with early signs suggestive of fibrosis at the splint and tissue interface.

CONCLUSION

This pilot study indicates that silk fibroin splints are well tolerated and efficacious in a rabbit model of severe tracheomalacia, with marked reduction in airway collapse following implantation and good tolerability over the studied time course.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:2189-2194, 2019.

Exploring polycaprolactone in tracheal surgery: A scoping review of in-vivo studies

INTRODUCTION

Tracheal pathology can be life-threatening if not managed appropriately. There are still some surgical limitations today for certain pathologies, such as in severe tracheomalacia, or when long segments of trachea need to be resected. Poly(ε-caprolactone) (PCL) is a polymer that has recently gained popularity for its use in tracheal surgeries in animal models and in certain human pediatric cases in hopes of addressing these difficult situations. PCL can be 3D printed or manufactured through molds to create tracheal stents, splints, patches and even to reconstruct full circumferential tracheal defects.

OBJECTIVE

To perform a scoping review, and explore insights into the applications of PCL for tracheal surgeries in-vivo.

METHODS

A literature search in Embase, MEDLINE, and BIOSIS was performed to include all articles available prior to December 21, 2018 without any language restrictions. We included all original research that investigated the use of a PCL implant, stent, splint, scaffold, or graft in tracheal surgeries in-vivo. Assessment of all articles were performed by two independent authors prior to inclusion for analysis.

RESULTS

A total of 27 articles were included in the study. All articles were original research studies, primarily consisting of interventional studies (92.4%), there was also 2 case reports (7.4%). Articles were published in the last decade, publications range from 2009 to 2019. The most common animal model used for the tracheal surgeries were the New Zealand rabbits (n = 19, 70%). Two studies (7%) also described the use PCL in a total of 4 human cases. To investigate the PCL reconstructed airways, histology and bronchoscopy were the most commonly implemented methods of analysis in 88.9% and 70.4% respectively. Airway analysis was also done using imaging modalities including CT scan (n = 9, 33.3%), MRI (n = 2, 7.4%), X-ray (n = 1, 3.7%). 17 (62.9%) of the studies used 3D printing processes to create their PCL implants.

CONCLUSIONS

Overall, this review demonstrates the feasibility of PCL in tracheal reconstruction and tracheal stenting/splinting. It highlights common trends and the limitations of the literature thus far on this topic.

Feasibility and potential of three-dimensional printing in laryngotracheal stenosis

Background

The use of three-dimensional printing has been rapidly expanding over the last several decades. Virtual surgical three-dimensional simulation and planning has been shown to increase efficiency and accuracy in various clinical scenarios.

Objectives

To report the feasibility of three-dimensional printing in paediatric laryngotracheal stenosis and discuss potential applications of three-dimensional printed models in airway surgery.

Method

Retrospective case series in a tertiary care aerodigestive centre.

Results

Three-dimensional printing was undertaken in two cases of paediatric laryngotracheal stenosis. One patient with grade 4 subglottic stenosis with posterior glottic involvement underwent an extended partial cricotracheal reconstruction. Another patient with grade 4 tracheal stenosis underwent tracheal resection and end-to-end anastomosis. Models of both tracheas were printed using PolyJet technology from a Stratasys Connex2 printer.

Conclusion

It is feasible to demonstrate stenosis in three-dimensional printed models, allowing for patient-specific pre-operative surgical simulation. The models serve as an educational tool for patients’ understanding of the surgery, and for teaching residents and fellows.

Challenges With the Development of Biomaterials for Sustainable Tissue Engineering

The field of tissue engineering has tantalizingly offered the possibility of regenerating new tissue in order to treat a multitude of diseases and conditions within the human body. Nevertheless, in spite of significant progress with in vitro and small animal studies, progress toward realizing the clinical and commercial endpoints has been slow and many would argue that ultimate goals, especially in treating those conditions which, as yet, do not have acceptable conventional therapies, may never be reached because of flawed scientific rationale. In other words, sustainable tissue engineering may not be achievable with current approaches. One of the major factors here is the choice of biomaterial that is intended, through its use as a "scaffold," to guide the regeneration process. For many years, effective specifications for these biomaterials have not been well-articulated, and the requirements for biodegradability and prior FDA approval for use in medical devices, have dominated material selection processes. This essay argues that these considerations are not only wrong in principle but counter-productive in practice. Materials, such as many synthetic bioabsorbable polymers, which are designed to have no biological activity that could stimulate target cells to express new and appropriate tissue, will not be effective. It is argued here that a traditional 'scaffold' represents the wrong approach, and that tissue-engineering templates that are designed to replicate the niche, or microenvironment, of these target cells are much more likely to succeed.

Tracheomalacia and Tracheobronchomalacia in Pediatrics: An Overview of Evaluation, Medical Management, and Surgical Treatment

Tracheobronchomalacia (TBM) refers to airway collapse due to typically excessive posterior membrane intrusion and often associated with anterior cartilage compression. TBM occurs either in isolation or in association with other congenital or acquired conditions. Patients with TM typically present non-specific respiratory symptoms, ranging from noisy breathing with a typical barking cough to respiratory distress episodes to acute life-threatening events and recurrent and/or prolonged respiratory infections. There are no definitive standardized guidelines for the evaluation, diagnosis, and treatment of TBM; therefore, patients may be initially misdiagnosed and incorrectly treated. Although milder cases of TBM may become asymptomatic as the diameter of the airway enlarges with the child, in cases of severe TBM, more aggressive management is warranted. This article is an overview of the clinical presentation, evaluation, diagnosis, medical management, and surgical treatment options in pediatric tracheomalacia.

The Applications of 3D Printing in Pulmonary Drug Delivery and Treatment of Respiratory Disorders

BACKGROUND

Pulmonary diseases are the third leading cause of morbidity worldwide, however treatment and diagnosis of these diseases continue to be challenging due to the complex anatomical structure as well as physiological processes in the lungs.

METHODS

3D printing is progressively finding new avenues in the medical field and this technology is constantly being used for diseases where diagnosis and treatment heavily rely on the thorough understanding of complex structural-physiology relationships. The structural and functional complexity of the pulmonary system makes it well suited to 3D printing technology.

RESULTS

3D printing can be used to deconstruct the complex anatomy of the lungs and improve our understanding of its physiological mechanisms, cell interactions and pathophysiology of pulmonary diseases. Thus, this technology can be quite helpful in the discovery of novel therapeutic targets, new drugs and devices for the treatment of lung diseases.

CONCLUSION

The intention of this review is to detail our current understanding of the applications of 3D printing in the design and evaluation of inhalable medicines and to provide an overview on its application in the diagnosis and treatment of pulmonary diseases. This review also discusses other technical and regulatory challenges associated with the progression of 3D printing into clinical practice.

High-throughput scaffold-free microtissues through 3D printing

BACKGROUND

Three-dimensional (3D) cell cultures and 3D bioprinting have recently gained attention based on their multiple advantages over two-dimensional (2D) cell cultures, which have less translational potential to recapitulate human physiology. 3D scaffold supports, cell aggregate systems and hydrogels have been shown to accurately mimic native tissues and support more relevant cell-cell interactions for studying effects of drugs and bioactive agents on cells in 3D. The development of cost-effective, high-throughput and scaffold-free microtissue assays remains challenging. In the present study, consumer grade 3D printing was examined as a fabrication method for creation of high-throughput scaffold-free 3D spheroidal microtissues.

RESULTS

Consumer grade 3D printing was capable of forming 96-well cell culture inserts to create scaffold-free microtissues in liquid suspensions. The inserts were seeded with human glioblastoma, placental-derived mesenchymal stem cells, and intestinal smooth muscle cells. These inserts allowed for consistent formation of cell density-controllable microtissues that permit screening of bioactive agents.

CONCLUSION

A variety of different cell types, co-cultures, and drugs may be evaluated with this 3D printed microtissue insert. It is suggested that the microtissue inserts may benefit 3D cell culture researchers as an economical assay solution with applications in pharmaceuticals, disease modeling, and tissue-engineering.

Pore architecture effects on chondrogenic potential of patient-specific 3-dimensionally printed porous tissue bioscaffolds for auricular tissue engineering

OBJECTIVE

This study aims to determine the effect of auricular scaffold microarchitecture on chondrogenic potential in an in vivo animal model.

METHODS

DICOM computed tomography (CT) images of a human auricle were segmented to create an external anatomic envelope. Image-based design was used to generate 1) orthogonally interconnected spherical pores and 2) randomly interspersed pores, and each were repeated in three dimensions to fill the external auricular envelope. These auricular scaffolds were then 3D printed by laser sintering poly-l-caprolactone, seeded with primary porcine auricular chondrocytes in a hyaluronic acid/collagen hydrogel and cultured in a pro-chondrogenic medium. The auricular scaffolds were then implanted subcutaneously in rats and explanted after 4 weeks for analysis with Safranin O and Hematoxylin and Eosin staining.

RESULTS

Auricular constructs with two micropore architectures were rapidly manufactured with high fidelity anatomic appearance. Subcutaneous implantation of the scaffolds resulted in excellent external appearance of both anterior and posterior auricular surfaces. Analysis on explantation showed that the defined, spherical micropore architecture yielded histologic evidence of more robust chondrogenic tissue formation as demonstrated by Safranin O and Hematoxylin and Eosin staining.

CONCLUSIONS

Image-based computer-aided design and 3D printing offers an exciting new avenue for the tissue-engineered auricle. In early pilot work, creation of spherical micropores within the scaffold architecture appears to impart greater chondrogenicity of the bioscaffold. This advantage could be related to differences in permeability allowing greater cell migration and nutrient flow, differences in surface area allowing different cell aggregation, or a combination of both factors. The ability to design an anatomically correct scaffold that maintains its structural integrity while also promoting auricular cartilage growth represents an important step towards clinical applicability of this new technology.

Controlled degradability of PCL-ZnO nanofibrous scaffolds for bone tissue engineering and their antibacterial activity

Up to date, tissue regeneration of large bone defects is a clinical challenge under exhaustive study. Nowadays, the most common clinical solutions concerning bone regeneration involve systems based on human or bovine tissues, which suffer from drawbacks like antigenicity, complex processing, low osteoinductivity, rapid resorption and minimal acceleration of tissue regeneration. This work thus addresses the development of nanofibrous synthetic scaffolds of polycaprolactone (PCL) - a long-term degradation polyester - compounded with hydroxyapatite (HA) and variable concentrations of ZnO as alternative solutions for accelerated bone tissue regeneration in applications requiring mid- and long-term resorption. In vitro cell response of human fetal osteoblasts as well as antibacterial activity against Staphylococcus aureus of PCL:HA:ZnO and PCL:ZnO scaffolds were here evaluated. Furthermore, the effect of ZnO nanostructures at different concentrations on in vitro degradation of PCL electrospun scaffolds was analyzed. The results proved that higher concentrations ZnO may induce early mineralization, as indicated by high alkaline phosphatase activity levels, cell proliferation assays and positive Alizarin-Red-S-stained calcium deposits. Moreover, all PCL:ZnO scaffolds particularly showed antibacterial activity against S. aureus which may be attributed to release of Zn²⁺ ions. Additionally, results here obtained showed a variable PCL degradation rate as a function of ZnO concentration. Therefore, this work suggests that our PCL:ZnO scaffolds may be promising and competitive short-, mid- and long-term resorption systems against current clinical solutions for bone tissue regeneration.

New frontiers and emerging applications of 3D printing in ENT surgery: a systematic review of the literature

3D printing systems have revolutionised prototyping in the industrial field by lowering production time from days to hours and costs from thousands to just a few dollars. Today, 3D printers are no more confined to prototyping, but are increasingly employed in medical disciplines with fascinating results, even in many aspects of otorhinolaryngology. All publications on ENT surgery, sourced through updated electronic databases (PubMed, MEDLINE, EMBASE) and published up to March 2017, were examined according to PRISMA guidelines. Overall, 121 studies fulfilled specific inclusion criteria and were included in our systematic review. Studies were classified according to the specific field of application (otologic, rhinologic, head and neck) and area of interest (surgical and preclinical education, customised surgical planning, tissue engineering and implantable prosthesis). Technological aspects, clinical implications and limits of 3D printing processes are discussed focusing on current benefits and future perspectives.

3D bio-printing technology for body tissues and organs regeneration

In the last decade, the use of new technologies in the reconstruction of body tissues has greatly developed. Utilising stem cell technology, nanotechnology and scaffolding design has created new opportunities in tissue regeneration. The use of accurate engineering design in the creation of scaffolds, including 3D printers, has been widely considered. Three-dimensional printers, especially high precision bio-printers, have opened up a new way in the design of 3D tissue engineering scaffolds. In this article, a review of the latest applications of this technology in this promising area has been addressed.

Multi-dimensional printing in thoracic surgery: current and future applications

Three-dimensional (3D) printing has been gaining much attention in the medical field in recent years. At present, 3D printing most commonly contributes in pre-operative surgical planning of complicated surgery. It is also utilized for producing personalized prosthesis, well demonstrated by the customized rib cage, vertebral body models and customized airway splints. With on-going research and development, it will likely play an increasingly important role across the surgical fields. This article reviews current application of 3D printing in thoracic surgery and also provides a brief overview on the extended and updated use of 3D printing in bioprinting and 4D printing.

An Official American Thoracic Society Workshop Report 2015. Stem Cells and Cell Therapies in Lung Biology and Diseases

The University of Vermont College of Medicine, in collaboration with the NHLBI, Alpha-1 Foundation, American Thoracic Society, Cystic Fibrosis Foundation, European Respiratory Society, International Society for Cellular Therapy, and the Pulmonary Fibrosis Foundation, convened a workshop, "Stem Cells and Cell Therapies in Lung Biology and Lung Diseases," held July 27 to 30, 2015, at the University of Vermont. The conference objectives were to review the current understanding of the role of stem and progenitor cells in lung repair after injury and to review the current status of cell therapy and ex vivo bioengineering approaches for lung diseases. These are all rapidly expanding areas of study that both provide further insight into and challenge traditional views of mechanisms of lung repair after injury and pathogenesis of several lung diseases. The goals of the conference were to summarize the current state of the field, discuss and debate current controversies, and identify future research directions and opportunities for both basic and translational research in cell-based therapies for lung diseases. This 10th anniversary conference was a follow up to five previous biennial conferences held at the University of Vermont in 2005, 2007, 2009, 2011, and 2013. Each of those conferences, also sponsored by the National Institutes of Health, American Thoracic Society, and respiratory disease foundations, has been important in helping guide research and funding priorities. The major conference recommendations are summarized at the end of the report and highlight both the significant progress and major challenges in these rapidly progressing fields.