Tissue Equivalents Research Articles

Rapid biofabrication of cell-free, anisotropic collagen tissues using a novel horizontal shear flow technique

Ultrastructure and organisation of collagen fibres is essential to tissue function, due to the loadbearing properties of collagen. Current techniques used to create aligned collagen tissue equivalents use the contractile ability of cells to remodel and align collagen fibres or utilise highly specialised pieces of equipment. The aim of this study is to develop a novel and rapid method to produce acellular aligned collagen sheets by combining horizontal shear flow (HSFlow) and the established RAFT method to remove excess fluid from a hydrogel.Force applied to the gel during the HSFlow process was measured to allow replication of the method. Quantification of fibres and cellular alignment revealed a significant difference between HSFlow and control samples, where both cells and collagen fibres showed alignment in the direction of shear flow, compared to the randomly aligned RAFT controls. Mechanical properties were also measured and revealed that HSFlow does not appear to improve the strength of the constructs despite the improved alignment, therefore further optimisation is needed to strengthen the constructs.In conclusion, we developed a novel and rapid technique to generate flat sheets of aligned collagen without relying on the contractile ability of cells to rearrange collagen fibres. This rapid method has potential to be used in the fabrication of a scaffold to mimic anisotropic tissues for regenerative medicine.

A Tissue‐Equivalent, Reusable Dosimeter for 3D Verification of Radiotherapy

AbstractA new tissue‐equivalent, reusable material for dosimetric verification of radiotherapy is developed and characterized. The material comprises a hydrogel matrix containing copper‐doped lithium fluoride nanoparticles that exhibit optically stimulated luminescence (OSL). Using a laser light sheet and a sensitive camera equipped with appropriate filters, the OSL signal is read out layer by layer thus constructing the 3D dose distribution. The good tissue equivalence allows the new material to register the dose from a prescribed treatment plan as if delivered to a patient. Cubic dosimeters measuring 50 × 50 × 50 mm3 are developed and used to measure 3D dose distributions (from voxels measuring 0.8 × 0.8 × 1.0 mm3) with a statistical dose precision of 5% at 100 Gy dose levels. The spatial precision of offsets in dose gradients between planned and measured dose distributions is below the voxel size. A 3% / 3 mm gamma analysis between a prescribed treatment plan and the retrieved and corrected readout yields a pass rate of 89.5%. Light scattering within the dosimetric volume affects the dosimeter performance, indicating the potential for future improvements of spatial and dose precision. In conclusion, the dosimeter system shows high promise for future clinical validation of radiotherapy.

Immune-reactive tumor organoids system to determine the effects of microbial metabolites on cancer immunity and immunotherapies

Immunotherapies are a revolutionary approach to treating cancer by utilizing the body’s immune system to target and combat cancer cells. This approach offers promising alternatives to traditional chemotherapies. Its potential to induce long-lasting remissions and specificity for cancer cells, which minimizes side effects, makes it a cutting-edge treatment with tremendous potential. With the increase of the clinical usage of immunotherapy, evidence emerges of the microbiome’s impact on both tumor growth and response to immunotherapy. The proposed involvement of the microbiome can change treatment efficacy by altering drug metabolism and reshaping the immune system response. Understanding the specific interactions between tumor cells, immune cells, and the microbiome is a critical step in the advancement of immunotherapy. To study the complex interaction between cancer immunity and the microbiome, various preclinical in vivo and in vitro models have been developed. We have recently described the use of an ex vivo preclinical model for anti-cancer treatment outcome prediction –tumor tissue equivalents (organoids). Specifically, immune-reactive tumor organoids are proposed as a novel tool for understanding how the microbiome influences cancer immunity and immunotherapy. More importantly, this platform can utilize patient samples to dissect patient-specific elements regulating cancer immune response and microbiome influence. This review presents the rationale for using the immune-reactive tumor organoids model to study the interactions between the microbiome and cancer immunotherapy. It will discuss available components of the model and analyze their interplay, summarize relevant experimental data, and assess their validity. Additionally, it explores the potential of immune-reactive organoids for personalized treatment approaches. Understanding the microbiome’s role in immunotherapy outcomes will lead to transformative cancer treatment via a simple change of diet or other microbiome manipulations. Ongoing research on microbiome-cancer interactions utilizing the described model systems will lead to innovative treatment strategies and improved patient outcomes.

Monte Carlo study of microdosimetric spectra conversion from diamond to tissue in proton therapy

Diamond is regarded as a promising material in microdosimetry. However, since the stopping power of the diamond is different from tissue, the energy deposition distribution in the diamond is not identical to that in tissue. Therefore, a conversion of the spectra in the diamond microdosimeter to the tissue site is needed. In this work, we introduced a method for the tissue equivalence conversion of diamond microdosimeters, which is developed to perform the energy deposition spectra conversion from the diamond to an equivalent size of tissue in radiotherapy. It was derived from the scaled Fourier transformation and the scaling factor. The method was tested by comparing the spectra converted from the diamond to tissue with those obtained in tissue along the Bragg curve at different locations. The results show that: i) the conversion method can overcome the defect of poor coincidence of the spectra between converted and actual results in low deposition energy zones, which is introduced by the method derived based on the distribution characteristics; ii) The equivalence between detector material and target tissue can affect the conversion results at the plateau of the Bragg curve; iii) The inconsistency between the converted and actual spectra due to the spectra shapes was also found, which occurs in the range of η from 0.117 to 1.248 for diamonds in this work; iv) the conversion at the distal part of the Bragg peak should pay attention to the range of the incident particles and the diamond microdosimeter size. To sum up, the method introduced in this work shows relatively good results in microdosimetric spectra conversion from diamond to tissue, especially in low-energy deposition regions. Nonetheless, further study is necessary to improve the practicability of this method so that it can be competent for spectral conversion on the whole Bragg curve.

In vitro vascularization of 3D cell aggregates in microwells with integrated vascular beds

Most human tissues possess vascular networks supplying oxygen and nutrients. Engineering of functional tissue and organ models or equivalents often require the integration of artificial vascular networks. Several approaches, such as organs on chips and three-dimensional (3D) bioprinting, have been pursued to obtain vasculature and vascularized tissues in vitro. This technical feasibility study proposes a new approach for the in vitro vascularization of 3D microtissues. For this, we thermoform arrays of round-bottom microwells into thin non-porous and porous polymer films/membranes and culture vascular beds on them from which endothelial sprouting occurs in a Matrigel-based 3D extra cellular matrix. We present two possible culture configurations for the microwell-integrated vascular beds. In the first configuration, human umbilical vein endothelial cells (HUVECs) grow on and sprout from the inner wall of the non-porous microwells. In the second one, HUVECs grow on the outer surface of the porous microwells and sprout through the pores toward the inside. These approaches are extended to lymphatic endothelial cells. As a proof of concept, we demonstrate the in vitro vascularization of spheroids from human mesenchymal stem cells and MG-63 human osteosarcoma cells. Our results show the potential of this approach to provide the spheroids with an abundant outer vascular network and the indication of an inner vasculature.

Study on the effects of preparation processes on OSL and TL properties of NaMgF3:Dy,Eu

OSL fading with storage time after irradiation remains a major obstacle in the development of ideal OSL materials. Dy and Eu co-doped NaMgF3 are attractive candidates for various rare earth doped matrix materials. In this study, NaMgF3:Dy,Eu was synthesized by a solid-state reaction, and the effects of heating temperature, duration, atmosphere, and cooling rate on XRD, TL and OSL properties were studied. A simple, safe, efficient, and time-saving solid-state reaction was identified as a potential method for the preparation of NaMgF3:Dy,Eu, which could be optimally prepared by heating at 750 °C for 2 h under nitrogen atmosphere (2 l/min) followed by rapid cooling. The results show that NaMgF3:Dy,Eu has a more stable OSL response and an excellent TL glow curve, with only a 0.4% decrease in the OSL signal read after 1 d of dose irradiation compared to that immediately after irradiation, and a high main TL peak at ∼320 °C. It has been indicated the OSL signal in this material seems to be strongly related to the main TL peak. The material has a considerable OSL sensitivity and decay rate than the Luxel Detector. NaMgF3:Dy,Eu will have a promising future in the field of OSL dosimetry due to its near tissue equivalence, low OSL fading without preheating, fast OSL decay rate, and predictable and easily reusable dose elimination.

Pediatric Fibromatosis Lacks the Internal Tandem Duplication of EGFR Seen in Congenital Mesoblastic Nephroma.

Classical and mixed congenital mesoblastic nephroma (CMN) are characterized by an internal tandem duplication (ITD) of the EGFR gene, in contrast to cellular CMN that usually harbors an ETV6::NTRK3 gene fusion. This same fusion occurs in infantile fibrosarcoma, and this tumor can be considered as the soft tissue equivalent of cellular CMN. A soft tissue equivalent of classic/mixed CMN remains undefined at the genetic level. Since classical CMN resembles fibromatosis of soft tissue histologically, we asked whether fibromatosis in children might show EGFR ITD. ITD was investigated using the polymerase chain reaction and primers for exons 18 and 25 of the EGFR gene. Seven of the eight cases of classical or mixed CMN were positive by this approach, but none of the five cellular CMNs. Of 11 cases of fibromatosis (six plantar, two digital, and three desmoid), none were positive for EGFR ITD. Within the limits of this small study, we conclude that pediatric fibromatosis is likely not characterized by EGFR ITD. There are isolated reports of pediatric soft tissue tumors that harbor EGFR ITD, but these have the appearance of infantile fibrosarcoma or mixed CMN rather than fibromatosis. We did not find any such cases, since all 14 cases of infantile fibrosarcoma in our study had an ETV6::NTRK3 fusion. The soft tissue tumors with EGFR ITD are not a morphologic match for the low-grade histology of classical CMN. Whether they have a similar favorable biology or behave more like fibrosarcoma with an ETV6::NTRK3 fusion or an alternative fusion involving other kinases remains to be determined.

3D printed heterogeneous paediatric head and adult thorax phantoms for linear accelerator radiotherapy quality assurance: from fabrication to treatment delivery.

This study aims to design and fabricate a 3D printed heterogeneous paediatric head phantom and to customize a thorax phantom for radiotherapy dosimetry. 
Approach: This study designed, fabricated, and tested 3D printed radiotherapy phantoms that can simulate soft tissue, lung, brain, and bone. Various polymers were considered in designing the phantoms. Polylactic acid+, nylon, and plaster were used in simulating different tissue equivalence. Dimensional accuracy, and CT number were investigated. The phantoms were subjected to a complete radiotherapy clinical workflow. Several treatment plans were delivered in both the head and the thorax phantom from a simple single 6 MV beam, parallel opposed beams, and five-field intensity modulated radiotherapy (IMRT) beams. Dose measurements using an ionization chamber and radiochromic films were compared with the calculated doses of the Varian Eclipse treatment planning system (TPS). 
Main results: The fabricated heterogeneous phantoms represent paediatric human head and adult thorax based on its radiation attenuation and anatomy. The measured CT number ranges are within -786.23 ± 10.55, 0.98 ± 3.86, 129.51 ± 12.83, and 651.14 ± 47.76 HU for lung, water/brain, soft tissue, and bone, respectively. It has a good radiological imaging visual similarity relative to a real human head and thorax depicting soft tissue, lung, bone, and brain. The accumulated dose readings for both conformal radiotherapy and IMRT match with the TPS calculated dose within ±2% and ±4% for head and thorax phantom, respectively. The mean pass rate for all the plans delivered are above 90% for gamma analysis criterion of 3% / 3 mm.
Significance and conclusion: The fabricated heterogeneous paediatric head and thorax phantoms are useful in Linac end-to-end radiotherapy quality assurance based on its CT image and measured radiation dose. The manufacturing and dosimetry workflow of this study can be utilized by other institutions for dosimetry and trainings. &#xD.

Measurement of ionising radiation dose absorbed by bones by using a bone-imitating polymer gel dosimeter

Three-dimensional radiotherapy dosimetry allows for high-resolution dose distribution measurements using dosimeters imitating various tissues. This work concerns bone-imitating dosimeters. The following are investigated: (i) manufacturing of bone-imitating dosimeters with two types of calcium hydroxyapatite, (ii) dose response characteristics after irradiation with a 6 MV photon beam, and (iii) tissue equivalence. The main findings include the dosimetric compositions with two types of calcium hydroxyapatite. For 18 % of one type of hydroxyapatite, the dosimeter imitates trabecular bone. For much higher concentrations (>40 %, another hydroxyapatite), the dosimeter approaches the properties of dense bone. The dynamic dose response is not greater than 30 Gy, the linear dose range is <20 Gy (computed tomography and nuclear magnetic resonance measurements), and the dose sensitivity is 0.11–0.18 Gy−1 s −1 (nuclear magnetic resonance measurements) for different weight fractions of hydroxyapatites. In summary, a bone-imitating polymer gel dosimeter can be used to measure the radiation dose in radiotherapy.

Nanostructured Implant-Tissue Interface Assessment Using a Three-Dimensional Gingival Tissue Equivalent.

Improved soft tissue integration (STI) around dental implants is key for implant success. The formation of an early and long-lasting transmucosal seal around the implant abutment might help to prevent peri-implantitis, one of the major causes of late implant failure. In natural teeth, collagen fibers are firmly inserted and fixed in the cementum of the tooth and emerge perpendicular to the gingival tissue. In contrast, around dental implants, collagen fibers run predominantly parallel to the implant surface, allowing bacterial migration into the peri-implant interface that might lead to peri-implantitis. Previous studies have shown that nanostructured Ti surfaces improve gingival cell response in monolayer cell cultures. Here, we aimed at evaluating the implant-tissue interface using a 3D gingival tissue equivalent (GTE). First, we evaluated the GTE response to a nanostructured (NN) and machined Ti surface after the stimulation with Porphyromonas gingivalis lipopolysaccharide (LPS), to simulate peri-implantitis conditions. Thus, GTE viability, through MTT assay, the release of metalloproteinase-1 (MMP1) and its inhibitor (TIMP1) through ELISA, and the gene expression of extracellular matrix turnover genes by real-time RT-PCR were analyzed. Second, GTE-implant interaction was characterized by serial block face scanning electron microscopy, and collagen-1 orientation at the tissue-implant interface was analyzed by immunofluorescence. While a similar GTE response to LPS stimulation was found for both implant surfaces, a higher proportion of collagen oriented perpendicular to the implant was observed on the NN implant surface. Thus, our results indicate that the nanostructuration of titanium dental implant abutments could allow the correct orientation of collagen fibers and greater soft tissue sealing, while keeping biocompatibility levels and LPS response comparable.

A comparative evaluation of polymeric materials as tissue equivalent phantoms in diagnostic radiology

In this study tissue equivalency of the polymeric materials was investigated by comparing with ICRP 110 Male Adult Computational Phantom tissues. For this purpose, radiological properties of polyamide (PA), high density polyethylene (HDPE), ultra-high molecular weight polyethylene (UHMWPE), polypropylene (PP), polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET), polyoxymethylene (POM) and polyurethane foam (PU FOAM) were evaluated in the diagnostic energy range (15–150 keV). The radiological properties of the materials and ICRP 110 Male and Female Adult Computational Phantom tissues were calculated with Phy-X/PSD software. No major differences were seen except for sex-specific organs, and comparisons were made using an adult male phantom. To confirm the results experimentally, a chest phantom was designed with the polymeric materials. The phantom was scanned by Siemens SOMATOM Edge CT device with tube voltage of 120 kVp and Hounsfield Unit (HU) values were measured. In addition, HU values were calculated using theoretical relationships and significant agreement was obtained between measured and calculated HUs. It was determined that PA, PP, UHMWPE and HDPE were equivalent to muscle and adipose tissue, PVC and PTFE were equivalent to mineral bone, PET and POM were equivalent to spongiosa bone and PU FOAM was equivalent to lung tissue.

Tissue-equivalent radiophotoluminescence dosimetry materials based on production of luminescent molecules via radiation chemical reactions

Radiophotoluminescence (RPL) has been a key phenomenon in dosimetry. Most materials exhibiting RPL are inorganic single crystals, glasses, and ceramics. Recently, similar phenomena (i.e., fluorescence after irradiation) have been realized in soft matters, such as liquids, gels, and organic solids, on the basis of the radiation-induced production of fluorescent molecules. Dosimeters showing such phenomena are attractive from the viewpoints of their tissue equivalence, flexibility, scalability, and workability. The objective of this paper is to present an overview of such dosimeters with emphasis on the radiation chemical reactions used in the materials. Moreover, the sensitivity and the measurable range is introduced.

A Comparison Study of the Solid Phantom and Water Phantom Using 6 MV and 15 MV Photon Energies, Depending on the Depth

Water is such an environmental element that is considered the best human body tissue equivalent. In the field of dosimetry studies, water is frequently used. This comparison study is conducted by a solid phantom and a water phantom with 6 MV and 15 MV photon energies, respectively. A cylindrical-type ionization chamber is used to collect charge when beams are on. The distance between the ray source and the surface of the phantom was fixed at 100 cm i.e. to SSD (Source to Surface Distance) of during the experiment. Chamber travels 1 cm to 20 cm in both phantoms and an electrometer is attached in the experimental set-up to measure the charge. The field size was 10x10 cm2. The relative deviation ratio of the solid phantom to the water phantom was calculated. In the result, the maximum deviation was 0.64%, while the minimum deviation was 0%, corresponding to the depths of 1 cm and 2.5 cm, respectively, for 6 MV and at 15 MV, maximum deviation and minimum deviation were 1.90% and 0.167% respectively, corresponding to the depths of 1.5 cm and 13 cm. Therefore, it can be said that the solid phantom can overcome the disadvantages of installation time required for the water phantom and problems while water level changing for depth measurement, simultaneously can used to measure the radiological dose precisely. Bangladesh J. Nuclear Med. 27(1): 34-38, 2024

Dynamic biaxial loading of vascular smooth muscle cell seeded tissue equivalents

An intricate reciprocal relationship exists between adherent synthetic cells and their extracellular matrix (ECM). These cells deposit, organize, and degrade the ECM, which in turn influences cell phenotype via responses that include sensitivity to changes in the mechanical state that arises from changes in external loading. Collagen-based tissue equivalents are commonly used as simple but revealing model systems to study cell–matrix interactions. Nevertheless, few quantitative studies report changes in the forces that the cells establish and maintain in such gels under dynamic loading. Moreover, most prior studies have been limited to uniaxial experiments despite many soft tissues, including arteries, experiencing multiaxial loading in vivo. To begin to close this gap, we use a custom biaxial bioreactor to subject collagen gels seeded with primary aortic smooth muscle cells to different biaxial loading conditions. These conditions include cyclic loading with different amplitudes as well as different mechanical constraints at the boundaries of a cruciform sample. Irrespective of loading amplitude and boundary condition, similar mean steady-state biaxial forces emerged across all tests. Additionally, stiffness-force relationships assessed via intermittent equibiaxial force–extension tests showed remarkable similarity for ranges of forces to which the cells adapted during periods of cyclic loading. Taken together, these findings are consistent with a load-mediated homeostatic response by vascular smooth muscle cells.

Thermal, dosimetric and thermo-mechanical characterization of ABS and PLA polymer materials via plastic injection molding for innovative bolus materials in radiotherapy applications

The impact of radiation on polymer materials, and consequently on their mechanical and physical properties, is a burgeoning field of research. This research assesses the dosimetric, mechanical, and thermal characteristics of Acrylonitrile Butadiene Styrene (ABS) and Polylactic Acid (PLA) materials developed through plastic injection molding as possible alternatives to commercial bolus used in radiotherapy. The materials were thoroughly compared with the commercial bolus material, EXAFLEX, by various tests such as Hounsfield Unit (HU) Analysis, Radiation Transmittance, Thermogravimetric Analysis (TGA), Thermomechanical Analysis (TMA), and Fourier Transform Infrared Spectroscopy (FTIR). The research indicates that ABS and PLA materials have similar radiological qualities to EXAFLEX, showing constant surface and accumulation area doses. Minor differences are seen deeper inside the phantom, indicating a stable tissue equivalency. ABS demonstrated strong resistance to radiation-induced chemical modifications, but PLA exhibited susceptibility to molecular changes. The TMA findings showed that radiation caused a decrease in softening temperatures and an increase in the coefficient of thermal expansion for both ABS and PLA, indicating changes in their thermal stability and mechanical characteristics after irradiation. The study highlights the potential of ABS and PLA materials made through plastic injection molding as efficient and safety substitutes for commercial bolus materials, particularly for large area irradiation. This requires more research into their clinical uses and consequences.

Protein‐Engineered Elastin Fibers as Building Blocks for The Textile‐Based Assembly of Tissue Equivalents (Adv. Funct. Mater. 24/2024)

Protein‐Engineered Elastin Fibers as Building Blocks for The Textile‐Based Assembly of Tissue Equivalents (Adv. Funct. Mater. 24/2024)

Characterization of pure organic NTI crystals for direct x-ray detection

Accurate detection of x-ray radiation is essential for tissue equivalence detection and safety control during medical radiotherapy. Here, a promising radiation detector based on organic 1,8-naphthalimide (C12H7NO2, NTI) single crystals is proposed. NTI single crystals with dimensions of 8 × 2 × 1 mm3 were synthesized by an optimized solvent-cooling method, and the crystal structure was characterized to elucidate the anisotropy mechanism. The coplanar detector made by NTI has a leakage current of less than 0.1 pA at an electric field strength of 1 kV cm−1 and provides excellent detection of 5.49 MeV α-particles (241Am) with a full-energy peak resolution of up to 32.3%. The calculated electron mobility (μe) and electron mobility-lifetime product (μτ)e were 7.9 cm2 V−1s−1 and 1.56 × 10−6 cm2 V−1, respectively. Additionally, the detection limit of the NTI detector was 0.35 µGy s−1 in the electric field strength range of 0.2–1.0 kV cm−1 under a 20 kV x-ray beam with a high sensitivity of 56.2 μC Gy−1cm−2. Consequently, the NTI detector achieves an excellent spatial resolution of 0.8–0.9 lp mm−1 in terms of x-ray imaging capability.

Combined use of hydrogen-rich water and enzyme-digested edible bird's nest improves PMA/LPS-impaired wound healing in human inflammatory gingival tissue equivalents.

Gingival wound healing plays a critical role in maintaining oral health. However, this process can be delayed by oxidative stress and excessive inflammatory responses. In this study, we established a human inflammatory gingival tissue equivalent (iGTE) to investigate the inhibitory effects of hydrogen-rich water (HW), enzyme-digested edible bird's nest (EBND) and sialic acid (SA) on PMA (an inducer of oxidative free radicals)- and LPS (an inflammatory stimulus)-impaired wound healing. The iGTE was constructed by human gingival fibroblasts (hGFs), keratinocytes and macrophages under three-dimensional conditions. Wounds in the iGTE and hGF/keratinocyte monolayers were created by mechanical injury. Tissues and cells were pretreated with HW, EBND, and SA, and then exposed to the inflammatory and oxidative environment induced by PMA (10ng/mL) and LPS (250ng/mL). The inflammatory cytokines IL-6 and IL-8 were quantitatively analyzed by ELISA. Histopathological image analysis was performed by HE and immunofluorescence staining. In the iGTE, PMA/LPS significantly reduced the epithelial thickness while causing a decrease in K8/18, E-cadherin, laminin and elastin expression and an increase in COX-2 expression along with ulcer-like lesions. In mechanically scratched hGFs and keratinocyte monolayers, PMA/LPS significantly impaired wound healing, and promoted the secretion of IL-6 and IL-8. Pretreatment of HW, EBND, and SA significantly suppressed PMA/LPS-induced wound healing delay and inflammatory responses in cell monolayers, as well as in the iGTE. Remarkably, the combined use of HW and EBND exhibited particularly robust results. Combined use of HW and EBND may be applied for the prevention and treatment of wound healing delay.

Tissue equivalent conversion of silicon-based microdosemeters in hadron therapy.

Silicon has been developed as a microdosemeter, as it can provide sensitive volumes at submicrometric levels, does not need a gas supply, has a fast response, and has low power consumption. However, since the energy response in silicon is not the same as that in tissue, a spectral conversion from silicon to tissue is necessary to obtain the probability distribution of energy deposition in tissue. In this work, we present a method for microdosimetric spectra conversion from silicon to tissue based on the scaled Fourier transformation and the geometric scaling factor, which shows relatively good results in the spectral conversion from diamond to tissue. The results illustrate that the method can convert the energy deposition spectra from silicon to tissue with proper accuracy. Meanwhile, the inconsistency between the converted and actual spectra due to the inherent difference was also observed. Whereas, the reasons for the disagreement are different. For the plateau part of the Bragg curve, the discrepancy between the converted and actual spectra is due to the poor tissue equivalent of silicon. For the proximal part of the Bragg curve, the spectral difference is attributed to the different shapes of the energy deposition spectra obtained in silicon and water, which is the same as that in the diamond. In summary, this method can be employed in the tissue equivalent conversion of silicon microdosemeter, but the poor tissue equivalent of silicon limited the accuracy of this method. In addition, the correction for the deviation between the converted and calculated spectra due to the difference in spectral shapes is required to improve the practicality of this mod.

Bioprinting of human dermal microtissues precursors as building blocks for endogenous in vitro connective tissue manufacturing

The advent of 3D bioprinting technologies in tissue engineering has unlocked the potential to fabricate in vitro tissue models, overcoming the constraints associated with the shape limitations of preformed scaffolds. However, achieving an accurate mimicry of complex tissue microenvironments, encompassing cellular and biochemical components, and orchestrating their supramolecular assembly to form hierarchical structures while maintaining control over tissue formation, is crucial for gaining deeper insights into tissue repair and regeneration. Building upon our expertise in developing competent three-dimensional tissue equivalents (e.g. skin, gut, cervix), we established a two-step bottom-up approach involving the dynamic assembly of microtissue precursors (μTPs) to generate macroscopic functional tissue composed of cell-secreted extracellular matrix (ECM). To enhance precision and scalability, we integrated extrusion-based bioprinting technology into our established paradigm to automate, control and guide the coherent assembly of μTPs into predefined shapes. Compared to cell-aggregated bioink, our μTPs represent a functional unit where cells are embedded in their specific ECM. μTPs were derived from human dermal fibroblasts dynamically seeded onto gelatin-based microbeads. After 9 days, μTPs were suspended (50% v/v) in Pluronic-F127 (30% w/v) (µTP:P30), and the obtained formulation was loaded as bioink into the syringe of the Dr.INVIVO-4D6 extrusion based bioprinter. µTP:P30 bioink showed shear-thinning behavior and temperature-dependent viscosity (gel at T > 30 °C), ensuring µTPs homogenous dispersion within the gel and optimal printability. The bioprinting involved extruding several geometries (line, circle, and square) into Pluronic-F127 (40% w/v) (P40) support bath, leveraging its shear-recovery property. P40 effectively held the bioink throughout and after the bioprinting procedure, until µTPs fused into a continuous connective tissue. µTPs fusion dynamics was studied over 8 days of culture, while the resulting endogenous construct underwent 28 days culture. Histological, immunofluorescence analysis, and second harmonic generation reconstruction revealed an increase in endogenous collagen and fibronectin production within the bioprinted construct, closely resembling the composition of the native connective tissues.