Biomimetic self-assembly of calcium phosphate templated by PNIPAAm nanogels for sustained smart drug delivery

Tissue Regeneration on Rise: Dental Hard Tissue Regeneration and Challenges-A Narrative Review

Background

As people live longer, there is an increasing need for hard tissue regeneration and whole-tooth regeneration. Despite the advancements in the field of medicine, the field of regenerative dentistry is still challenging due to the complexity of dental hard tissues. Cross-disciplinary collaboration among material scientists, cellular biologists, and odontologists aimed at developing strategies and uncovering solutions related to dental tissue regeneration. Methodology. A search of the literature was done for pertinent research. Consistent with the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) 2020 Statement, the electronic databases looked at were PubMed, Science Direct, Scopus, and Google Scholar, with the keyword search "hard dental tissue regeneration."

Results

Database analysis yielded a total of 476 articles. 222 duplicate articles have been removed in total. Articles that have no connection to the directed regeneration of hard dental tissue were disregarded. The review concluded with the inclusion of four studies that were relevant to our research objective.

Conclusion

Current molecular signaling network investigations and novel viewpoints on cellular heterogeneity have made advancements in understanding of the kinetics of dental hard tissue regeneration possible. Here, we outline the fundamentals of stem hard dental tissue maintenance, regeneration, and repair, as well as recent advancements in the field of hard tissue regeneration. These intriguing findings help establish a framework that will eventually enable basic research findings to be utilized towards oral health-improving medicines.

Recent advances in GTR scaffolds

Periodontitis is a serious chronic inflammatory condition that can cause periodontal tissue deterioration and, eventually, tooth loss. Periodontal regenerative therapy using membranes and bone grafting materials, as well as flap debridement and/or flap curettage, have all been used with varying degrees of clinical effectiveness. Current resorbable and non-resorbable membranes serve as a physical barrier, preventing connective and epithelial tissue down growth into the defect and promoting periodontal tissue regeneration. The "perfect" membrane for use in periodontal regenerative therapy has yet to be created, as these conventional membranes have several structural, mechanical, and bio-functional constraints. We hypothesised in this narrative review that the next-generation of guided tissue and guided bone regeneration (GTR/GBR) membranes for periodontal tissue engineering will be a graded-biomaterials that closely mimics the extracellular matrix.

Graphene oxide-hydroxyapatite nanocomposites effectively deliver HSV-TK suicide gene to inhibit human breast cancer growth

Gene therapy with herpes simplex virus thymidine kinase gene (HSV-TK), which is also known as "suicide" gene therapy, is effective in various tumor models. The lack of a safe and efficient gene delivery system has become a major obstacle to "suicide" gene therapy. In this study, the cytotoxicity and transfection efficiency of graphene oxide-hydroxyapatite (GO-Hap) were analyzed by MTS and flow cytometry, respectively. A series of assays were performed to evaluate the effects of GO-HAp/p-HRE/ERE-Sur-TK combined with ganciclovir treatment on growth of human breast normal and cancer cells. The results showed that GO-HAp nanocomposites effectively transfected cells with minimum toxicity. GO-HAp/p-HRE/ERE-Sur-TK combined with ganciclovir treatment inhibited the proliferation and induced cell apoptosis in cancer cells, while the cytotoxic effects are tolerable in normal breast cells. We conclude that the GO-HAp nanocomposites have significant potential as a gene delivery vector for cancer therapy.

Advanced smart biomaterials and constructs for hard tissue engineering and regeneration

Hard tissue repair and regeneration cost hundreds of billions of dollars annually worldwide, and the need has substantially increased as the population has aged. Hard tissues include bone and tooth structures that contain calcium phosphate minerals. Smart biomaterial-based tissue engineering and regenerative medicine methods have the exciting potential to meet this urgent need. Smart biomaterials and constructs refer to biomaterials and constructs that possess instructive/inductive or triggering/stimulating effects on cells and tissues by engineering the material's responsiveness to internal or external stimuli or have intelligently tailored properties and functions that can promote tissue repair and regeneration. The smart material-based approaches include smart scaffolds and stem cell constructs for bone tissue engineering; smart drug delivery systems to enhance bone regeneration; smart dental resins that respond to pH to protect tooth structures; smart pH-sensitive dental materials to selectively inhibit acid-producing bacteria; smart polymers to modulate biofilm species away from a pathogenic composition and shift towards a healthy composition; and smart materials to suppress biofilms and avoid drug resistance. These smart biomaterials can not only deliver and guide stem cells to improve tissue regeneration and deliver drugs and bioactive agents with spatially and temporarily controlled releases but can also modulate/suppress biofilms and combat infections in wound sites. The new generation of smart biomaterials provides exciting potential and is a promising opportunity to substantially enhance hard tissue engineering and regenerative medicine efficacy.

Influence of Ethylene Glycol Methacrylate to the Hydration and Transition Behaviors of Thermo-Responsive Interpenetrating Polymeric Network Hydrogels

The influence of ethylene glycol methacrylate (EGMA) to the hydration and transition behaviors of thermo-responsive interpenetrating polymeric network (IPN) hydrogels containing sodium alginate, N-isopropylacrylamide (NIPAAm), and EGMA were investigated. The molar ratios of NIPAAm and EGMA were varied from 20:0 to 19.5:0.5 and 18.5:1.5 in the thermo-responsive alginate-Ca2+/P(NIPAAm-co-EGMA) IPN hydrogels. Due to the more hydrophilicity and high flexibility of EGMA, the IPN hydrogels exhibited higher lower critical solution temperature (LCST) and lower glass transition temperature (Tg) when the ratio of EGMA increases. The swelling/deswelling kinetics of the IPN hydrogels could be controlled by adjusting the NIPAAm/EGMA molar ratio. A faster water uptake rate and a slower water loss rate could be realized by increase the amount of EGMA in the IPN hydrogel (the shrinking rate constant was decreased from 0.01207 to 0.01195 and 0.01055 with the changing of NIPAAm/EGMA ratio from 20:0, 19.5:0.5 to 18.5:1.5). By using 2-Isopropylthioxanthone (ITX) as a photo initiator, the obtained alginate-Ca2+/P(NIPAAm-co-EGMA360) IPN hydrogels were successfully immobilized on cotton fabrics. The surface and cross section of the hydrogel were probed by scanning electron microscopy (SEM). They all exhibited a porous structure, and the pore size was increased with the amount of EGMA. Moreover, the LCST values of the fabric-grafted hydrogels were close to those of the pure IPN hydrogels. Their thermal sensitivity remained unchanged. The cotton fabrics grafted with hydrogel turned out to be much softer with the continuous increase of EGMA amount. Therefore, compared with alginate-Ca2+/PNIPAAm hydrogel, alginate-Ca2+/P(NIPAAm-co-EGMA360) hydrogel is a more promising candidate for wound dressing in the field of biomedical textile.

Synthesis and evaluation of temperature- and glucose-sensitive nanoparticles based on phenylboronic acid and N-vinylcaprolactam for insulin delivery

Poly N-vinylcaprolactam-co-acrylamidophenylboronic acid p(NVCL-co-AAPBA) was prepared from N-vinylcaprolactam (NVCL) and 3-acrylamidophenylboronic acid (AAPBA), using 2,2-azobisisobutyronitrile (AIBN) as initiator. The synthesis and structure of the polymer were examined by Fourier Transform infrared spectroscopy (FT-IR) and (1)H-NMR. Dynamic light scattering (DLS), lower critical solution temperature (LCST) and transmission electron microscopy (TEM) were utilized to characterize the nanoparticles, CD spectroscopy was used to determine if there were any changes to the conformation of the insulin, and cell and animal toxicity were also investigated. The prepared nanoparticles were found to be monodisperse submicron particles and were glucose- and temperature-sensitive. In addition, the nanoparticles have good insulin-loading characteristics, do not affect the conformation of the insulin and show low-toxicity to cells and animals. These p(NVCL-co-AAPBA) nanoparticles may have some value for insulin or other hypoglycemic protein delivery.

Hollow hydroxyapatite/polyelectrolyte hybrid microparticles with controllable size, wall thickness and drug delivery properties

Hollow hydroxyapatite/polyelectrolyte microparticles with controllable size, wall thickness and drug delivery properties have been fabricated via the green hydrothermal method and the LbL self-assembly technique.

Advances in synthesis of calcium phosphate crystals with controlled size and shape

Calcium phosphate (CaP) materials have a wide range of applications, including biomaterials, adsorbents, chemical engineering materials, catalysts and catalyst supports and mechanical reinforcements. The size and shape of CaP crystals and aggregates play critical roles in their applications. The main inorganic building blocks of human bones and teeth are nanocrystalline CaPs; recently, much progress has been made in the application of CaP nanocrystals and their composites for clinical repair of damaged bone and tooth. For example, CaPs with special micro- and nanostructures can better imitate the biomimetic features of human bone and tooth, and this offers significantly enhanced biological performances. Therefore, the design of CaP nano-/microcrystals, and the shape and hierarchical structures of CaPs, have great potential to revolutionize the field of hard tissue engineering, starting from bone/tooth repair and augmentation to controlled drug delivery devices. Previously, a number of reviews have reported the synthesis and properties of CaP materials, especially for hydroxyapatite (HAp). However, most of them mainly focused on the characterizations and physicochemical and biological properties of HAp particles. There are few reviews about the control of particle size and size distribution of CaPs, and in particular the control of nano-/microstructures on bulk CaP ceramic surfaces, which is a big challenge technically and may have great potential in tissue engineering applications. This review summarizes the current state of the art for the synthesis of CaP crystals with controlled sizes from the nano- to the macroscale, and the diverse shapes including the zero-dimensional shapes of particles and spheres, the one-dimensional shapes of rods, fibers, wires and whiskers, the two-dimensional shapes of sheets, disks, plates, belts, ribbons and flakes and the three-dimensional (3-D) shapes of porous, hollow, and biomimetic structures similar to biological bone and tooth. In addition, this review will also summarize studies on the controlled formation of nano-/microstructures on the surface of bulk ceramics, and the preparation of macroscopical bone grafts with 3-D architecture nano-/microstructured surfaces. Moreover, the possible directions of future research and development in this field, such as the detailed mechanisms behind the size and shape control in various strategies, the importance of theoretical simulation, self-assembly, biomineralization and sacrificial precursor strategies in the fabrication of biomimetic bone-like and enamel-like CaP materials are proposed.

Hollow hierarchical hydroxyapatite/Au/polyelectrolyte hybrid microparticles for multi-responsive drug delivery

Hollow hierarchical hydroxyapatite/Au/polyelectrolyte hybrid microparticles with a hollow HAP core and polymer multilayer/Au nanoparticle shell for multi-responsive drug delivery have been prepared via an LbL technique.