Recreating composition, structure, functionalities of tissues at nanoscale for regenerative medicine

Innovative Nanotechnological Approaches in Trauma and Orthopaedic Surgery: A Comprehensive Review

The application of nanotechnology to health has been one of the revolutionizing factors in the field of trauma and orthopaedic surgery over the last decade. Advances in nanomedicine, in comparison to conventional modes of treatment, have influenced immensely the approach towards trauma and orthopaedic surgery and provided some unique answers to some very complex problems like bone reconstruction, soft tissue repair, and prevention of infection. The current narrative review intends to underpin an extensive analysis of modern applications and recent advances in nanotechnology-driven therapies in orthopaedics. Having leveraged unique properties inherent in nanoparticles and nanoscale materials, novel interventions, such as nanostructured scaffolds, drug delivery systems, and bioactive coatings, have flourished into a variety of promising means to enhance osseointegration, accelerate the healing process, and reduce postoperative complications. This review at once acknowledges the huge potential of these technologies and some of the problems impeding their wide-range clinical application, including long-term safety, main regulatory hurdles, and scale-up issues. The following review aims to give orthopaedic surgeons, researchers, and biomedical engineers an overview of the present status and perspectives for the future regarding nanomedicine in trauma and orthopaedic surgery, pointing out the expectations of a much-improved outcome in patients and overall quality of life.

Ca2+-supplying black phosphorus-based scaffolds fabricated with microfluidic technology for osteogenesis

Effective osteogenesis remains a challenge in the treatment of bone defects. The emergence of artificial bone scaffolds provides an attractive solution. In this work, a new biomineralization strategy is proposed to facilitate osteogenesis through sustaining supply of nutrients including phosphorus (P), calcium (Ca), and silicon (Si). We developed black phosphorus (BP)-based, three-dimensional nanocomposite fibrous scaffolds via microfluidic technology to provide a wealth of essential ions for bone defect treatment. The fibrous scaffolds were fabricated from 3D poly (l-lactic acid) (PLLA) nanofibers (3D NFs), BP nanosheets, and hydroxyapatite (HA)-porous SiO2 nanoparticles. The 3D BP@HA NFs possess three advantages: i) stably connected pores allow the easy entrance of bone marrow-derived mesenchymal stem cells (BMSCs) into the interior of the 3D fibrous scaffolds for bone repair and osteogenesis; ii) plentiful nutrients in the NFs strongly improve osteogenic differentiation in the bone repair area; iii) the photothermal effect of fibrous scaffolds promotes the release of elements necessary for bone formation, thus achieving accelerated osteogenesis. Both in vitro and in vivo results demonstrated that the 3D BP@HA NFs, with the assistance of NIR laser, exhibited good performance in promoting bone regeneration. Furthermore, microfluidic technology makes it possible to obtain high-quality 3D BP@HA NFs with low costs, rapid processing, high throughput and mass production, greatly improving the prospects for clinical application. This is also the first BP-based bone scaffold platform that can self-supply Ca2+, which may be the blessedness for older patients with bone defects or patients with damaged bones as a result of calcium loss.

Engineering (Bio)Materials through Shrinkage and Expansion

Although various (bio)fabrication technologies have achieved revolutionary progress in the past decades, engineered constructs still fall short of expectations owing to their inability to attain precisely designable functions. Shrinkable and expandable (bio)materials feature unique characteristics leading to size-/shape-shifting and thus have exhibited a strong potential to equip current engineering technologies with promoted capacities toward applications in biomedicine. In this progress report, the advances of size-/shape-shifting (bio)materials enabled by various stimuli, are evaluated; furthermore, representative biomedical applications associated with size-/shape-shifting (bio)materials are also exemplified. Toward the future, the combination of size-/shape-shifting (bio)materials and 3D/4D fabrication technologies presents a wide range of possibilities for further development of intricate functional architectures.

Natural-Based Hydrogels for Tissue Engineering Applications

In the field of tissue engineering and regenerative medicine, hydrogels are used as biomaterials to support cell attachment and promote tissue regeneration due to their unique biomimetic characteristics. The use of natural-origin materials significantly influenced the origin and progress of the field due to their ability to mimic the native tissues' extracellular matrix and biocompatibility. However, the majority of these natural materials failed to provide satisfactory cues to guide cell differentiation toward the formation of new tissues. In addition, the integration of technological advances, such as 3D printing, microfluidics and nanotechnology, in tissue engineering has obsoleted the first generation of natural-origin hydrogels. During the last decade, a new generation of hydrogels has emerged to meet the specific tissue necessities, to be used with state-of-the-art techniques and to capitalize the intrinsic characteristics of natural-based materials. In this review, we briefly examine important hydrogel crosslinking mechanisms. Then, the latest developments in engineering natural-based hydrogels are investigated and major applications in the field of tissue engineering and regenerative medicine are highlighted. Finally, the current limitations, future challenges and opportunities in this field are discussed to encourage realistic developments for the clinical translation of tissue engineering strategies.

Biomimetic Nanosilica-Collagen Scaffolds for In Situ Bone Regeneration: Toward a Cell-Free, One-Step Surgery

Current approaches to fabrication of nSC composites for bone tissue engineering (BTE) have limited capacity to achieve uniform surface functionalization while replicating the complex architecture and bioactivity of native bone, compromising application of these nanocomposites for in situ bone regeneration. A robust biosilicification strategy is reported to impart a uniform and stable osteoinductive surface to porous collagen scaffolds. The resultant nSC composites possess a native-bone-like porous structure and a nanosilica coating. The osteoinductivity of the nSC scaffolds is strongly dependent on the surface roughness and silicon content in the silica coating. Notably, without the use of exogenous cells and growth factors (GFs), the nSC scaffolds induce successful repair of a critical-sized calvarium defect in a rabbit model. It is revealed that topographic and chemical cues presented by nSC scaffolds could synergistically activate multiple signaling pathways related to mesenchymal stem cell recruitment and bone regeneration. Thus, this facile surface biosilicification approach could be valuable by enabling production of BTE scaffolds with large sizes, complex porous structures, and varied osteoinductivity. The nanosilica-functionalized scaffolds can be implanted via a cell/GF-free, one-step surgery for in situ bone regeneration, thus demonstrating high potential for clinical translation in treatment of massive bone defects.

Review of clinical experience on biomaterials and tissue engineering of urinary bladder

PURPOSE

In recent pre-clinical studies, biomaterials and bladder tissue engineering have shown promising outcomes when addressing the need for bladder tissue replacement. To date, multiple clinical experiences have been reported. Herein, we aim to review and summarize the reported clinical experience of biomaterial usage and tissue engineering of the urinary bladder.

METHODS

A systematic literature search was performed on Feb 2019 to identify clinical reports on biomaterials for urinary bladder replacement or augmentation and clinical experiences with bladder tissue engineering. We identified and reviewed human studies using biomaterials and tissue-engineered bladder as bladder substitutes or augmentation implants. The studies were then summarized for each respective procedure indication, technique, follow-up period, outcome, and important findings of the studies.

RESULTS

An extensive literature search identified 25 studies of case reports and case series with a cumulative clinical experience of 222 patients. Various biomaterials and tissue-engineered bladder were used, including plastic/polyethylene mold, preserved dog bladder, gelatine sponge, Japanese paper with Nobecutane, lypholized human dura, bovine pericardium, amniotic membrane, small intestinal mucosa, and bladder tissue engineering with autologous cell-seeded biodegradable scaffolds. However, overall clinical experiences including the outcomes and safety reports were not satisfactory enough to replace enterocystoplasty.

CONCLUSION

To date, several clinical experiences of biomaterials and tissue-engineered bladder have been reported; however, various studies have reported non-satisfactory outcomes. Further technological advancements and a better understanding is needed to advance bladder tissue engineering as a future promising management option for patients requiring bladder drainage.

Careers in nanomedicine and drug delivery

Nanomedicine continues to be a rapidly growing and increasingly interdisciplinary field. The career opportunities available in nanomedicine are also numerous, yet not always obvious to the early-career scientist determining their individual track for maximal impact. This perspective provides a brief overview of the field of nanomedicine, then delves into the many career trajectories one could take in this field. The article concludes with thoughts on how to provide diverse training to increase supply for the variety of career paths, and the role that mentors can play in young scientists' development and exploration of these career paths.

Mapping of the available standards against the regulatory needs for nanomedicines

Appropriate documentary standards and reference materials are crucial building blocks for the development of innovative products. In order to support the emerging sector of nanomedicine, relevant standards must be identified and/or developed before the products will enter into the regulatory approval process. The anticipation of standardization needs requires a good understanding on the regulatory information requirements that can be triggered by the particularities of nanomedicines. However, robust datasets allowing firm conclusions on regulatory demands are not yet available due to a lack of regulatory experience with innovative products. Such a catch-22 situation can only be advanced in an iterative process by monitoring continuously the scientific evidence and by promoting intensive knowledge exchange between all involved stakeholders. In this study, we have compiled information requirements released by regulatory scientists so far and mapped it against available standards that could be of relevance for nanomedicines. Our gap analysis clearly demonstrated that for some endpoints such as drug release/loading and the interaction of nanomedicines with the immune system no standards are available so far. The emerging nanomedicine sector could benefit from cross-sector collaboration and review the suitability of standards that have been developed for nanomaterials used for other industrial applications. Only a concerted action of all parties can lead to a smooth translation of nanomedicines to clinical application and to the market. This is in particular important because nanotechnology-based drug delivery systems are key for the development and implementation of personalized medicine. This article is characterized under: Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine.

Engineering vascularized and innervated bone biomaterials for improved skeletal tissue regeneration

Blood vessels and nerve fibers are distributed throughout the entirety of skeletal tissue, and play important roles during bone development and fracture healing by supplying oxygen, nutrients, and cells. However, despite the successful development of bone mimetic materials that can replace damaged bone from a structural point of view, most of the available bone biomaterials often do not induce sufficient formation of blood vessels and nerves. In part, this is due to the difficulty of integrating and regulating multiple tissue types within artificial materials, which causes a gap between native skeletal tissue. Therefore, understanding the anatomy and underlying interaction mechanisms of blood vessels and nerve fibers in skeletal tissue is important to develop biomaterials that can recapitulate its complex microenvironment. In this perspective, we highlight the structure and osteogenic functions of the vascular and nervous system in bone, in a coupled manner. In addition, we discuss important design criteria for engineering vascularized, innervated, and neurovascularized bone implant materials, as well as recent advances in the development of such biomaterials. We expect that bone implant materials with neurovascularized networks can more accurately mimic native skeletal tissue and improve the regeneration of bone tissue.