Biomimetic Bilayered Scaffolds for Tissue Engineering: From Current Design Strategies to Medical Applications

Tissue damage due to cancer, congenital anomalies, and injuries needs new efficient treatments that allow tissue regeneration. In this context, tissue engineering shows a great potential to restore the native architecture and function of damaged tissues, by combining cells with specific scaffolds. Scaffolds made of natural and/or synthetic polymers and sometimes ceramics play a key role in guiding cell growth and formation of the new tissues. Monolayered scaffolds, which consist of uniform material structure, are reported as not being sufficient to mimic complex biological environment of the tissues. Osteochondral, cutaneous, vascular, and many other tissues all have multilayered structures, therefore multilayered scaffolds seem more advantageous to regenerate these tissues. In this review, recent advances in bilayered scaffolds design applied to regeneration of vascular, bone, cartilage, skin, periodontal, urinary bladder, and tracheal tissues are focused on. After a short introduction on tissue anatomy, composition and fabrication techniques of bilayered scaffolds are explained. Then, experimental results obtained in vitro and in vivo are described, and their limitations are given. Finally, difficulties in scaling up production of bilayer scaffolds and reaching the stage of clinical studies are discussed when multiple scaffold components are used.

In Vivo Evaluation of Permeable and Impermeable Membranes for Guided Bone Regeneration

Background: The degree of biodegradation and the inflammatory response of membranes employed for guided bone regeneration directly impact the outcome of this technique. This study aimed to evaluate four different experimental versions of Poly (L-lactate-co-Trimethylene Carbonate) (PTMC) + Poly (L-lactate-co-glycolate) (PLGA) membranes, implanted in mouse subcutaneous tissue, compared to a commercially available membrane and a Sham group. Methods: Sixty Balb-C mice were randomly divided into six experimental groups and subdivided into 1, 3, 6 and 12 weeks (n = 5 groups/period). The membranes (1 cm²) were implanted in the subcutaneous back tissue of the animals. The samples were obtained for descriptive and semiquantitative histological evaluation (ISO 10993-6). Results: G1 and G4 allowed tissue adhesion and the permeation of inflammatory cells over time and showed greater phagocytic activity and permeability. G2 and G3 detached from the tissue in one and three weeks; however, in the more extended periods, they presented a rectilinear and homogeneous aspect and were not absorbed. G2 had a major inflammatory reaction. G5 was almost completely absorbed after 12 weeks. Conclusions: The membranes are considered biocompatible. G5 showed a higher degree of biosorption, followed by G1 and G4. G2 and G3 are considered non-absorbable in the studied periods.

Biocompatible Materials in Otorhinolaryngology and Their Antibacterial Properties

For decades, biomaterials have been commonly used in medicine for the replacement of human body tissue, precise drug-delivery systems, or as parts of medical devices that are essential for some treatment methods. Due to rapid progress in the field of new materials, updates on the state of knowledge about biomaterials are frequently needed. This article describes the clinical application of different types of biomaterials in the field of otorhinolaryngology, i.e., head and neck surgery, focusing on their antimicrobial properties. The variety of their applications includes cochlear implants, middle ear prostheses, voice prostheses, materials for osteosynthesis, and nasal packing after nasal/paranasal sinuses surgery. Ceramics, such as as hydroxyapatite, zirconia, or metals and metal alloys, still have applications in the head and neck region. Tissue engineering scaffolds and drug-eluting materials, such as polymers and polymer-based composites, are becoming more common. The restoration of life tissue and the ability to prevent microbial colonization should be taken into consideration when designing the materials to be used for implant production. The authors of this paper have reviewed publications available in PubMed from the last five years about the recent progress in this topic but also establish the state of knowledge of the most common application of biomaterials over the last few decades.

Healing Process with the use of a New Resorbable Synthetic Membrane

Background:

Currently, absorbable membranes tend to be used most frequently for guided bone regeneration. They have many advantages and the most commonly reported complication is early exposure.

Objective:

This retrospective study reports the healing process of soft tissues over a four-week period using synthetic absorbable membranes.

Study Design:

One-hundred and ten cases were included. Soft tissue healing was assessed from anonymized photographs, in accordance with the criteria of the Early Healing Index (EHI) (Watchel et al., 2003). Cohen's Kappa (K) test was used to estimate the reliability of the measures and the variability between the examiners. Chi-squared test and Fisher’s exact test were used to assess the combination of healing outcomes with respect to the type of surgical intervention.

Results:

At 1-week, 81% of the cases showed a Primary Closure (PC) when the membrane was not initially exposed. The score increased to 98% at 4-weeks. Healing at 1-week varied significantly according to the type of intervention, with 73% of primary closure for bone augmentation during implantation, versus 60% for bone augmentation before implantation and 46% for alveolar preservation (Chi-square test, p = 0.049). No statistically significant differences in the healing process were observed between the smoking and non-smoking groups.

Conclusion:

This clinical study shows that the safety and exposure rates of this new synthetic membrane are comparable to the data gathered in the literature concerning non-cross-linked collagenous membranes.

Prospective randomized controlled clinical trial to compare hard tissue changes following socket preservation using alloplasts, xenografts vs no grafting: Clinical and histological findings

PURPOSE

To compare dimensional changes and bone quality of two different grafting materials used for socket preservation.

MATERIALS AND METHODS

Thirty-three patients requiring extraction were recruited and randomly assigned to receive: biphasic calcium sulfate/ hydroxyapatite (BCS/HA); bovine derived xenograft (BDX) or no grafting (Control). Ridge width (at -3 and -6 mm) and vertical distance from a stent were measured at the time of extraction/grafting. Measurements were repeated at reentry and core biopsies were harvested.

RESULTS

Baseline vertical distance for the BDX, C and BCS/HA groups were 7.45 ± 3.1, 7.69 ± 4.2, and 6.75 ± 3.5 mm, respectively (P = .830). Post-op, C group had greater vertical loss (1.71 ± 0.4 mm) compared to BCS/HA (0.65 ± 0.5) and BDX (0.25 ± 0.2 mm), P = .059. Mean baseline width at -3 mm was 8.69 ± 1.1 mm, 8.31 ± 1.4 mm, and 9.0 ± 1.1 mm, respectively (P = .509). Post-op, this width was reduced by 2.96 ± 0.3 mm (C), 1.56 ± 0.4 mm (BDX), and 0.5 ± 0.4 mm (BCS/HA), P = .001. Mean ridge width at -6 mm for the C (6.5 ± 1.7 mm) was significantly smaller than BCS/HA (7.95 ± 2.8 mm) and BDX (8.85 ± 1.9 mm), P = .043. Histologically, the BDX group had greater residual scaffold material and less vital bone compared to the BCS/HA group. Pain scores were relatively low for all groups.

CONCLUSIONS

BCS/HA may be used for socket preservation with similar or better results compared to BDX. The significance of greater residual scaffold found in the BDX group is yet to be determined.