Smart Biological Scaffolds Designed and Fabricated at the University of Tehran

According to the Public Relations Office of the University of Tehran, the study, supervised by Dr. Mehdi Rahaei Jahromi, a faculty member at the College of Interdisciplinary Sciences and Technologies, presents an integrated framework for developing next-generation smart scaffolds. In this framework, the concentration of carbon dots serves as a key parameter, enabling the customization of cellular responses from bone repair to soft tissue engineering.

Dr. Rahaei Jahromi, commenting on the significance of the research, said: “Given the growing elderly population and the increasing prevalence of musculoskeletal injuries, the need for novel and efficient methods to repair bone defects is felt more than ever. Traditional methods such as bone grafting face limitations, including donor tissue shortage and surgical complications, which have made bone tissue engineering a vital strategy. In this regard, the present project, by designing and fabricating biological scaffolds based on polycaprolactone (PCL) and carbon dots (CDs) through 3D printing, has taken an effective step toward addressing one of the fundamental challenges in this field.”

He added: “Despite its suitable processability in 3D printing and the U.S. Food and Drug Administration’s approval for medical applications, polycaprolactone limits favorable interaction with cells due to its hydrophobic and bioinert nature. In this research, inspired by sustainable and environmentally friendly approaches, the researchers synthesized carbon dots from black seed (Nigella sativa) using a one-step hydrothermal method. These nanoparticles possess nanoscale dimensions, oxygen-containing functional groups, stable fluorescence, and excellent water dispersion, making them suitable for combination with a polymer matrix. The resulting carbon dots were added to the polycaprolactone matrix at various concentrations through melt mixing, and composite scaffolds were then fabricated using a melt-extrusion 3D printer. This additive manufacturing method allows the design of complex geometries and controlled porosity, which are essential for cell infiltration, nutrient transfer, and angiogenesis.”

The faculty member of the Faculty of Life Sciences Engineering, College of Interdisciplinary Sciences and Technologies, University of Tehran, further explained the results: “The results showed that the addition of carbon dots creates concentration-dependent, significant changes in the morphology and surface properties of the scaffold. With increasing concentration, the filament diameter increased, the macropore size decreased, and surface micropores clearly formed on the scaffold surface. Surface roughness also increased significantly, and the water contact angle decreased, indicating a marked improvement in surface hydrophilicity due to the presence of polar functional groups of the carbon dots. These surface changes provide conditions for effective adsorption of extracellular matrix proteins and, consequently, cell adhesion and spreading.”

He added: “Mechanical evaluation of the scaffolds also showed that although increasing the concentration of carbon dots leads to a decrease in compressive strength, at low concentrations the compressive strength remains within an acceptable range for partial load-bearing applications such as repair of cranial, maxillofacial, and vertebral defects. In other words, by changing the concentration of carbon dots, a tunable trade-off is created between mechanical properties and bioactivity, allowing the design of a scaffold tailored to the intended clinical application.”

Biological evaluations on human adipose-derived mesenchymal stem cells showed that increasing the concentration of carbon dots linearly improved cell adhesion, proliferation, and density. Fluorescence microscopy images confirmed uniform cell distribution deep within the scaffold, indicating excellent permeability and suitable biocompatibility of the composite scaffolds. These findings indicate that green-synthesized carbon dots do not act merely as inert fillers but function as bioactive agents that create a favorable microenvironment for cellular activity.

In conclusion, he said: “The important achievement of this research is the presentation of a novel framework based on tuning the concentration of carbon dots as a key design parameter, which enables the customization of scaffolds for a wide range of clinical applications, from bone defect repair to soft tissue engineering, from a single material platform. This integrated approach paves the way for the development of next-generation smart scaffolds that induce different cellular responses tailored to patient needs simply by changing the concentration of a nanofiller.”

It is worth noting that these findings are derived from the doctoral dissertation of Fatemeh Massah, a graduate of Nanobiotechnology at the University of Tehran, conducted under the supervision of Dr. Mehdi Rahaei Jahromi, a faculty member of the University of Tehran, and Dr. Elaheh Esmaili from the Stem Cell Technology Research Center, with the advisory of Dr. Ali Hossein Rezayan. The results of this research have been published in the Journal of Polymers and the Environment and are available through the following link:

https://link.springer.com/article/10.1007/s10924-026-03870-y