Foreign body response to implanted hydrogels and consequently fibrotic overgrowth on implanted spheres will decrease in vivo performance of these biomaterials.Considering the previous reports related to the immune-privileged properties of mesenchymal stem cells (MSCs), we hypothesized that encapsulated human placentaderived MSCs (HP-MSCs) will mitigate the foreign body response against alginate hydrogels. The HP-MSC-laden alginate hydrogel was cross-linked with a CaCl 2 solution. Morphological and mechanical properties of alginate spheres were determined by scanning electron microscopy imaging, degradation, and swelling tests. The HP-MSC-laden alginate spheres or cell-free spheres were implanted into the peritoneal cavity of BALB/c mice. After intraperitoneal implantation of spheres into BALB/c mice over a period of 14 days, capsules were recovered and precapsular fibrotic tissue on their surfaces was investigated. Assessment of encapsulated HP-MSC viability using acridine orange/propidium iodide staining revealed that foreign body response against cell-laden hydrogel results in fibrous overgrowth on spheres and consequently leads to the HP-MSC necrosis. In spite of immunomodulatory effects of MSCs, the introduction of spheres into the body induces foreign body response that affects the viability of immuno-isolated HP-MSCs during 14-day posttransplant period. The presence of HP-MSCs within alginate hydrogel could not reduce the fibrotic overgrowth on spheres compared with cell-free spheres. Therefore, there is an essential need for hydrogels that mitigate the foreign body response as a key challenge in the development of tissue engineering and drug delivery technologies. K E Y W O R D S alginate, encapsulation, foreign body response, hydrogel, mesenchymal stem cell

In vivo tracking and monitoring of adoptive cell transfer has a distinct importance in cell‐based therapy. There are many imaging modalities for in vivo monitoring of biodistribution, viability and effectiveness of transferred cells. Some of these procedures are not applicable in the human body because of low sensitivity and high possibility of tissue damages. Shortwave infrared region (SWIR) imaging is a relatively new technique by which deep biological tissues can be potentially visualized with high resolution at cellular level. Indeed, scanning of the electromagnetic spectrum (beyond 1000 nm) of SWIR has a great potential to increase sensitivity and resolution of in vivo imaging for various human tissues. In this review, molecular imaging modalities used for monitoring of biodistribution and fate of administered cells with focusing on the application of non‐invasive optical imaging at shortwave infrared region are discussed in detail.

Graphene‐based nanocomposites have recently attracted increasing attention in tissue engineering because of their extraordinary features. These biocompatible substances, in the presence of an apt microenvironment, can stimulate and sustain the growth and differentiation of stem cells into different lineages. This review discusses the characteristics of graphene and its derivatives, such as their excellent electrical signal transduction, carrier mobility, outstanding mechanical strength with improving surface characteristics, self‐lubrication, antiwear properties, enormous specific surface area, and ease of functional group modification. Moreover, safety issues in the application of graphene and its derivatives in terms of biocompatibility, toxicity, and interaction with immune cells are discussed. We also describe the applicability of graphene‐based nanocomposites in tissue healing and organ regeneration, particularly in the bone, cartilage, teeth, neurons, heart, skeletal muscle, and skin. The impacts of special textural and structural characteristics of graphene‐based nanomaterials on the regeneration of various tissues are highlighted. Finally, the present review gives some hints on future research for the transformation of these exciting materials in clinical studies.