Current Developments in 3D Bioprinting for Tissue and Organ Regeneration–A Review

Thefield of Tissue engineering and regenerative medicine that work toward creatingfunctional tissue-constructs mimicking native tissue for repair and/or replacement ofdamaged tissues or whole organs have evolved rapidly over the past few decades.However, traditional tissue engineering approaches comprising of scaffolds, growthfactors and cells showed limited success in fabrication of complex 3D shapes andinvivoorgan regeneration leading to their non-feasibility for clinical applications from alogistical and economical viewpoint. In this regard, 3D bioprinting, which is an extendedapplication of additive manufacturing is now being explored for tissue engineering andregenerative medicine as it involves the top-down approach of building the complex tissuein a layer by layer fashion, thereby producing precise geometries due to controlled nature ofmatter deposition with the help of anatomically accurate 3D models of the tissue generatedby computer graphics. Here, we aim to provide a comprehensive review of the 3Dbioprinting technology along with associated 3D bioprinting strategies including ink-jetprinting, extrusion printing, stereolithography and laser assisted bioprinting techniques.We then focus on the applications of 3D bioprinting technology on construction of variousrepresentative tissue and organs, including skin, cardiac, bone and cartilage etc. Wefurther attempt to highlight the steps involved in each of those tissues/organs printing anddiscuss on the associated technological requirements based on the available reports fromrecent literature. Wefinally conclude with current challenges with 3D bioprintingtechnology along with potential solution for future technological advancement ofefficient and cost-effective 3D bioprinting methods

Immunohistochemical Evaluation of p63, E-Cadherin, Collagen I and III Expression in Lower Limb Wound Healing under Honey

Honey is recognized traditionally for its medicinal properties and also appreciated as a topical healing agent for infected and noninfected wounds. This study evaluates impact of honey-based occlusive dressing on nonhealing (nonresponding to conventional antibiotics) traumatic lower limb wounds (n = 34) through clinicopathological and immunohistochemical (e.g., expression of p63, E-cadherin, and Collagen I and III) evaluations to enrich the scientific validation. Clinical findings noted the nonadherence of honey dressing with remarkable chemical debridement and healing progression within 11–15 days of postintervention. Histopathologically, in comparison to preintervention biopsies, the postintervention tissues of wound peripheries demonstrated gradual normalization of epithelial and connective tissue features with significant changes in p63+ epithelial cell population, reappearance of membranous E-cadherin (P < .0001), and optimum deposition of collagen I and III (P < .0001). Thus, the present study for the first time reports the impact of honey on vital protein expressions in epithelial and connective tissues during repair of nonhealing lower limb wounds

Epithelial cell functionality on electroconductive Fe/Sr co-doped biphasic calcium phosphate

In the perspective of dental restorative applications, co-doped bioceramics have not been explored much. From the clinical perspective, a successful dental implant is expected to interact with peri-prosthetic bones, gingival tissue, and surrounding connective tissues. The interaction of implant and implant coating materials with bone tissue is well studied. However, their interaction with surrounding epithelial components needs scientific validation. In this context, the present study aims at quantitative evaluation of the electrical properties of Fe/Sr co-doped biphasic calcium phosphate (BCP) samples and assessment of their cytocompatibility with epithelial (vero) cells. Sr/Fe co-doped BCPs were prepared by sol-gel synthesis technique, with different dopant concentration. Impact of co-doping on conductivity was assessed and interestingly an increase in conductivity with dopant amount was recorded in different co-doped BCPs. Cellular study showed the significant (p = 0.01) increase in both cellular viability and functionality with increasing conductivity of samples. Higher epithelial cell adhesion indicates that (Sr/Fe) co-doped BCP would be favorable for faster epithelial sealing and also would reduce the chances of infection. Real-time PCR and immunofluorescence studies indicated that the expression of the epithelial marker (E-cadherin) significantly (p = 0.01) increased in 10, 30 and 40 mol% co-doped samples in comparison to undoped BCP. In contrast to E-cadherin, fold change of beta-catenin remains unchanged amongst the co-doped ceramics, implying the absence of tumorigenic potential of (Sr/Fe) co-doped BCP. In addition, immune-fluorescence signatures for cellular polarity are established from enhanced expression PARD3 protein, which has major relevance for cellular morphogenesis and cell division. Summarizing, the present study establishes the efficacy of Sr/Fe co-doped BCPs as a dental implant coating material and its ability to modulate vero cell functionality

(Fe/Sr) Codoped Biphasic Calcium Phosphate with Tailored Osteoblast Cell Functionality

Although doped bioceramics have been widely investigated for biomedical applications, the codoped bioceramics remain mostly unexplored for bone regeneration applications. For example, the impact of codoping of Sr2+ and Fe3+ ions on the phase stability and cytocompatibility is not explored so far. In this perspective, the objective of the present study is to quantitatively understand this aspect in case of Fe/Sr codoped biphasic calcium phosphate (BCP). Following sol gel synthesis, codoped BCP samples with Sr/Fe dopant concentrations of 2, 10, 20, 30, and 40 mol % as well as doped BCPs with single dopant (Sr or Fe) with similar compositions were calcined at 800 degrees C in air. Using extensive Rietveld analysis, the dopant content dependent crystallographic properties (e.g lattice parameters) and phase stability of HA/TCP are quantitatively assessed. In vitro cytocompatibility of codoped samples has been assessed using mouse osteoblast cells. An important observation is that, while singular dopant of Sr/Fe at 20 mol % or higher amount reduces cell viability significantly, osteoblast viability is not compromised to any significant extent on Sr/Fe codoped BCP, compared to undoped BCP. Our results indicate that one can tailor osteoblast functionality by controlling the codopant content. More importantly, all the codoped BCPs support cell proliferation, when single doped BCP exhibits significant reductionin cell viability, at dopant content of 10 mol % or higher. Cell morphological analysis supports extensive cell spreading on codoped BCPs. An attempt has been made to correlate the variation in cellular response with HA/TCP ratio and ion dissolution behavior. Taken together, the present work establishes unique advantage of Sr/Fe codoping approach toward realizing their bone replacement application

(Fe/Sr) Codoped Biphasic Calcium Phosphate with Tailored Osteoblast Cell Functionality

Although doped bioceramics have been widely investigated for biomedical applications, the codoped bioceramics remain mostly unexplored for bone regeneration applications. For example, the impact of codoping of Sr²⁺ and Fe³⁺ ions on the phase stability and cytocompatibility is not explored so far. In this perspective, the objective of the present study is to quantitatively understand this aspect in case of Fe/Sr codoped biphasic calcium phosphate (BCP). Following sol–gel synthesis, codoped BCP samples with Sr/Fe dopant concentrations of 2, 10, 20, 30, and 40 mol % as well as doped BCPs with single dopant (Sr or Fe) with similar compositions were calcined at 800 °C in air. Using extensive Rietveld analysis, the dopant content dependent crystallographic properties (e.g lattice parameters) and phase stability of HA/TCP are quantitatively assessed. In vitro cytocompatibility of codoped samples has been assessed using mouse osteoblast cells. An important observation is that, while singular dopant of Sr/Fe at 20 mol % or higher amount reduces cell viability significantly, osteoblast viability is not compromised to any significant extent on Sr/Fe codoped BCP, compared to undoped BCP. Our results indicate that one can tailor osteoblast functionality by controlling the codopant content. More importantly, all the codoped BCPs support cell proliferation, when single doped BCP exhibits significant reductionin cell viability, at dopant content of 10 mol % or higher. Cell morphological analysis supports extensive cell spreading on codoped BCPs. An attempt has been made to correlate the variation in cellular response with HA/TCP ratio and ion dissolution behavior. Taken together, the present work establishes unique advantage of Sr/Fe codoping approach toward realizing their bone replacement application

Bioactive Nano-Hydroxyapatite Doped Electrospun PVA-Chitosan Composite Nanofibers for Bone Tissue Engineering Applications

Combination of bioceramics with polymers to fabricate nanofibrous scaffolds holds enormous potential for bone tissue regeneration. In this study, we aim to incorporate HAp nanoparticles in trace doping amount in PVA-chitosan nanofiber matrix to fabricate PVA-chitosan composite nanofibers with improved performance for application as a bone tissue regeneration material. The diameter of the fabricated composite nanofibrous mat is estimated as 300 ± 121 nm. Beads free nanofibers mat with uniform morphology was ascertained for all sample groups by scanning electron microscopy (SEM) and the overall composition was assessed using Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray spectroscopy (EDX). SEM images showed a homogeneous distribution of HAp nanoparticles in the composite nanofibers matrix. Further, X-ray diffraction (XRD) was performed to determine the crystallinity of the fabricated scaffolds. Swelling behavior and hydrolytic degradation of nanofibrous mats were subsequently evaluated by immersing in PBS buffer at pH 7.4 at physiological temperature (37 °C). The biocompatibility study of nanofiber scaffolds was performed with MC3T3 cells. Significantly higher cellular viability was observed on HAp nanoparticles incorporated composite nanofibrous scaffold surface after 7 days of culture in comparison to scaffolds without HAp