This paper presents a systematic review of a key sector of the much promising and rapidly evolving field of biomedical engineering, specifically on the fabrication of three-dimensional open, porous collagen-based medical devices, using the prominent freeze-drying process. Collagen and its derivatives are the most popular biopolymers in this field, as they constitute the main components of the extracellular matrix, and therefore exhibit desirable properties, such as biocompatibility and biodegradability, for in vivo applications. For this reason, freeze-dried collagen-based sponges with a wide variety of attributes can be produced and have already led to a wide range of successful commercial medical devices, chiefly for dental, orthopedic, hemostatic, and neuronal applications. However, collagen sponges display some vulnerabilities in other key properties, such as low mechanical strength and poor control of their internal architecture, and therefore many studies focus on the settlement of these defects, either by tampering with the steps of the freeze-drying process or by combining collagen with other additives. Furthermore, freeze drying is still considered a high-cost and time-consuming process that is often used in a non-optimized manner. By applying an interdisciplinary approach and combining advances in other technological fields, such as in statistical analysis, implementing the Design of Experiments, and Artificial Intelligence, the opportunity arises to further evolve this process in a sustainable and strategic manner, and optimize the resulting products as well as create new opportunities in this field.

Helicobacter pylori neutrophil‐activating protein (HP‐NAP) protects DNA from free radicals as a dodecamer through its ferroxidase activity without, however, directly binding to it. The retardation that was observed at pH 7.5 could be easily attributed to an iron effect, as it was revealed by experiments in the absence of HP‐NAP. A total loss of ferroxidase activity, dodecamer formation and DNA protection in environments rich in free radicals was observed after replacement of His25, His37, Asp52 and Lys134, which are located within the ferroxidase site, with Ala. Molecular dynamics simulations revealed that dimer formation is highly unlikely following mutation of the above amino acids, as the Fe²⁺ is no longer attracted with equal strength by both subunits. These findings probably indicate that iron plays an important role in the conformation of HP‐NAP by initiating the formation of stable dimers that are indispensable for the ensuing dodecamer structure. Very surprisingly, neutrophil activation appeared to be stimulated by structural elements that are localized within the C‐terminal region of both mutant HP‐NAP and wild‐type dodecamer HP‐NAP. In particular, the dodecamer conformation does not seem to be necessary for activation, and helices H3 (Leu69–Leu75) and H4 (Lys89–Leu114) or the linking coils (His63–Thr68 and Thr76–Ser88) are probably critical in stimulating neutrophil activation.

Elastin-like polypeptides (ELPs) are protein-based biopolymers genetically produced from polypeptides composed of a repeating pentapeptide sequence V–P–G–X–G. The inherent properties of recombinant ELPs, such as smart nature, controlled sequence complexity, physicochemical properties, and biocompatibility, make these polymers suitable for use in nanobiotechnological applications, as biofunctionalized scaffolds for tissue-engineering purposes and drug delivery. In this work, we report the design and synthesis of two elastomeric self-assembling polypeptides (ELPs) that mimic the endogenous human tropoelastin. Using molecular biology techniques, two artificial genes that encode two ELP concatemers of approximate molecular mass 60 kDa, one of them carrying biotin-binding peptide motifs, were constructed. These motifs could facilitate biofunctionalization of the ELPs through tethering biotinylated factors, such as growth factors. The ELPs were heterologously overexpressed in E. coli and subsequently purified in two steps: a nonchromatographic technique by organic solvent extraction, followed by nickel−nitrilotriacetic acid (Ni-NTA) affinity chromatography. The characterization of the biochemical properties and biocompatibility of ELPs was also performed in this study. The ELP carrying the biotin-binding motifs was tested for its capability to bind biotin, and indeed, it was observed that it can bind biotinylated proteins specifically. Additionally, results concerning the cytotoxicity of the ELPs exhibited excellent compatibility of the ELPs with mammalian cells in vitro. We anticipate that these ELPs can be used as components of a scaffold that mimics the extracellular matrix (ECM) for the regeneration of endogenously highly elastic tissues.

Bone regeneration using Bone Morphogenetic Proteins (BMPs) alongside various engineered scaffolds has attracted considerable attention over the years. The field has seen extensive research in preclinical animal models, leading to the approval of two products and guiding the quest for new materials. Natural and synthetic polymers, ceramics, and composites have been used to fabricate the necessary porous 3D scaffolds and delivery systems for BMPs. Interestingly, all reported applications in the literature are triumphant. Evaluation of the results is typically based on histologic assessment after appropriate staining and radiological modalities, providing morphological identification of the newly formed bone and describing cells and the organic compound. Remarkably, while these evaluation methods illustrate mineralization, they are not capable of identifying hydroxyapatite crystals, the mineral component of the bone, which are crucial for its mechanical properties, structure, integrity, and long-term stability of regenerated bone tissue. This review aims to focus on the different scaffolds used in bone tissue engineering applications and underline the pressing need for techniques that could recognize the presence of hydroxyapatite crystals as well as their characteristics in bone tissue engineering, which will provide a more complete and comprehensive assessment of the successful results.