Nanotechnology in the regulation of stem cell behavior

Development and application of nanomaterials, nanotechnology and nanomedicine for treating hematological malignancies

Hematologic malignancies (HMs) pose a serious threat to patients' health and life, and the five-year overall survival of HMs remains low. The lack of understanding of the pathogenesis and the complex clinical symptoms brings immense challenges to the diagnosis and treatment of HMs. Traditional therapeutic strategies for HMs include radiotherapy, chemotherapy, targeted therapy and hematopoietic stem cell transplantation. Although immunotherapy and cell therapy have made considerable progress in the last decade, nearly half of patients still relapse or suffer from drug resistance. Recently, studies have emerged that nanomaterials, nanotechnology and nanomedicine show great promise in cancer therapy by enhancing drug targeting, reducing toxicity and side effects and boosting the immune response to promote durable immunological memory. In this review, we summarized the strategies of recently developed nanomaterials, nanotechnology and nanomedicines against HMs and then proposed emerging strategies for the future designment of nanomedicines to treat HMs based on urgent clinical needs and technological progress.

Binary Colloidal Crystals (BCCs) Modulate the Retina-related Gene Expression of hBMSCs – A Preliminary Study

Surface topography-induced lineage commitment of human bone marrow stem cells (hBMSCs) has been reported. However, this effect on hBMSC differentiation toward retinal pigment epithelium (RPE)-like cells has not been explored. Herein, a family of cell culture substrates called binary colloidal crystals (BCCs) was used to stimulate hBMSCs into RPE-like cells without induction factors. Two BCCs, named SiPS (silica (Si)/polystyrene (PS)) and SiPSC (Si/carboxylated PS), having similar surface topographies but different surface chemistry was used for cell culture. The result showed that cell proliferation was no difference between the two BCCs and tissue culture polystyrene (TCPS) control. However, the cell attachment, spreading area, and aspect ratio between surfaces were significantly changed. For example, cells displayed more elongated on SiPS (aspect ratio ~7.0) than those on SiPSC and TCPS (~2.0). The size of focal adhesions on SiPSC (~1.6 µm²) was smaller than that on the TCPS (~2.5 µm²). qPCR results showed that hBMSCs expressed higher RPE progenitor genes (i.e., MITF and PAX6) on day 15, and mature RPE genes (i.e., CRALBP and RPE65) on day 30 on SiPS than TCPS. On the other hand, the expression of optical vesicle or neuroretina genes (i.e., MITF and VSX2) was upregulated on day 15 on SiPSC compared to the TCPS. This study reveals that hBMSCs could be modulated into different cell subtypes depending on the BCC combinations. This study shows the potential of BCCs in controlling stem cell differentiation.

Nanomaterials and their composite scaffolds for photothermal therapy and tissue engineering applications

Photothermal therapy (PTT) has attracted broad attention as a promising method for cancer therapy with less severe side effects than conventional radiation therapy, chemotherapy and surgical resection. PTT relies on the photoconversion capacity of photothermal agents (PTAs), and a wide variety of nanomaterials have been employed as PTAs for cancer therapy due to their excellent photothermal properties. The PTAs are systematically or locally administered and become enriched in cancer cells to increase ablation efficiency. In recent years, PTAs and three-dimensional scaffolds have been hybridized to realize the local delivery of PTAs for the repeated ablation of cancer cells. Meanwhile, the composite scaffolds can stimulate the reconstruction and regeneration of the functional tissues and organs after ablation of cancer cells. A variety of composite scaffolds of photothermal nanomaterials have been prepared to combine the advantages of different modalities to maximize their therapeutic efficacy with minimal side effects. The synergistic effects make the composite scaffolds attractive for biomedical applications. This review summarizes these latest advances and discusses the future prospects.

Effects of surface nanopatterning on internalization and amyloid aggregation of the fragment 264-277 of Nucleophosmin 1

The mechanical interpretation of the plethora of factors that governs cellular localization of amyloid aggregates is crucial for planning novel therapeutical interventions in neurodegenerative diseases since these aggregates exert a primary role in the proteostasis machinery. The uptake of Cell Penetrating Peptides (CPPs) conjugated with different amyloid polypeptides occurs via different endocytic processes regulated by cytoskeleton organization and cell morphology. Herein, we deepened the internalization of an amyloid system in cells cultured on nanopatterned surfaces that represent a powerful tool to shape cell and regulate its contractility. We analyzed the behavior of an amyloid model system, employing NPM1_264-277 sequence, covalently conjugated to Tat fragment 48-60 as CPP. To investigate its internalization mechanism, we followed the formation of aggregates on two kinds of substrates: a flat and a nanopatterned surface. Herein, investigations during time were carried out by employing both confocal and second harmonic generation (SHG) microscopies. We showed that modifications of cellular environment affect peptide localization, its cytoplasmic translocation and the size of amyloid aggregates.

Glial restricted precursor delivery of dendrimer N-acetylcysteine promotes migration and differentiation following transplant in mouse white matter injury model

Oligodendrocyte replacement using glial restricted precursors (GRPs) is a promising avenue for the treatment of acquired or genetic white matter disorders; however, limited long-term survival of these cells post-transplant may impede maximal recovery. Nanotherapeutic approaches can facilitate stem cell delivery while simultaneously delivering factors aimed at enhancing and nourishing stem cells en route to, and at, the target site. Hydroxyl polyamidoamine (PAMAM) dendrimer nanoparticles have been used in a variety of models to deliver therapeutics in a targeted manner to injury sites at low doses. Here, survival and migration of GRPs was assessed in a mouse model of neonatal white matter injury with different methods of dendrimer nanoparticle support. Our findings demonstrate the ability of GRPs to take up nanoparticle-drug conjugates and for these conjugates to act beyond the injury site in vivo. Compared to GRPs alone, mice receiving dendrimer-drug in parallel to GRPs, or via GRPs as the delivery vector, showed improved migration and differentiation of cells 8 weeks post-transplant. These studies demonstrate that drug-conjugated nanoparticles can enhance transplanted progenitor cell survival and migration, and suggest that combination therapies may allow engraftment without overt immunosuppression.

Translational challenges in advancing regenerative therapy for treating neurological disorders using nanotechnology

The focus of regenerative therapies is to replace or enrich diseased or injured cells and tissue in an attempt to replenish the local environment and function, while slowing or halting further degeneration. Targeting neurological diseases specifically is difficult, due to the complex nature of the central nervous system, including the difficulty of bypassing the brain's natural defense systems. While cell-based regenerative therapies show promise in select tissues, preclinical and clinical studies have been largely unable to transfer these successes to the brain. Advancements in nanotechnologies have provided new methods of central nervous system access, drug and cell delivery, as well as new systems of cell maintenance and support that may bridge the gap between regenerative therapies and the brain. In this review, we discuss current regenerative therapies for neurological diseases, nanotechnology as nanocarriers, and the technical, manufacturing, and regulatory challenges that arise from inception to formulation of nanoparticle-regenerative therapies.

Preparation of well-distributed titania nanopillar arrays on Ti6Al4V surface by induction heating for enhancing osteogenic differentiation of stem cells

Great effort has recently been devoted to the preparation of nanoscale surfaces on titanium-based implants to achieve clinically fast osteoinduction and osseointegration, which relies on the unique characteristics of the nanostructure. In this work, we used induction heating treatment (IHT) as a rapid oxidation method to fabricate a porous nanoscale oxide layer on the Ti6Al4V surface for better medical application. Well-distributed vertical nanopillars were yielded by IHT for 20-35 s on the alloy surface. The composition of the oxides contained rutile/anatase TiO₂ and a small amount of Al₂O₃ between the TiO₂ grain boundaries (GBs). This technology resulted in a reduction and subsequent increase of surface roughness of 26-32 nm when upregulating the heating time, followed by the successive enhancement of the thickness, wettability and adhesion strength of the oxidation layer to the matrix. The surface hardness also distinctly rose to 554 HV in the IHT-35 s group compared with the 350 HV of bare Ti6Al4V. The massive small-angle GBs in the bare alloy promoted the formation of nanosized oxide crystallites. The grain refinement and deformation texture reduction further improved the mechanical properties of the matrix after IHT. Moreover, in vitro experiments on a mesenchymal stem cell (BMSC) culture derived from human bone marrow for 1-7 days indicated that the nanoscale layers did not cause cytotoxicity, and facilitated cell differentiation in osteoblasts by enhancing the gene and osteogenesis-related protein expressions after 1-3 weeks of culturing. The increase of the IHT time slightly advanced the BMSC proliferation and differentiation, especially during long-term culture. Our findings provide strong evidence that IHT oxidation technology is a novel nanosurface modification technology, which is potentially promising for further clinical development.

Diverse Applications of Nanotechnology in Biomedicine, Chemistry, and Engineering

This chapter introduces the basic concepts of nano science to readers. Some novel methodologies for synthesizing nano particles are discussed briefly. Since the book title suggests diverse applications of nano materials, this chapter also summarizes the applications of nano technology in medicine (nano medicine), where tissue engineering and regenerative medicine are discussed. Other applications DNA nanotechnology in living organisms are discussed briefly. Overall, this chapter introduces the readers to broad sections of nano science and its applications in chemistry, engineering, and medicine.

Engineering a multi-biofunctional composite using poly(ethylenimine) decorated graphene oxide for bone tissue regeneration

Toward preparing strong multi-biofunctional materials, poly(ethylenimine) (PEI) conjugated graphene oxide (GO_PEI) was synthesized using poly(acrylic acid) (PAA) as a spacer and incorporated in poly(ε-caprolactone) (PCL) at different fractions. GO_PEI significantly promoted the proliferation and formation of focal adhesions in human mesenchymal stem cells (hMSCs) on PCL. GO_PEI was highly potent in inducing stem cell osteogenesis leading to near doubling of alkaline phosphatase expression and mineralization over neat PCL with 5% filler content and was ≈50% better than GO. Remarkably, 5% GO_PEI was as potent as soluble osteoinductive factors. Increased adsorption of osteogenic factors due to the amine and oxygen containing functional groups on GO_PEI augment stem cell differentiation. GO_PEI was also highly efficient in imparting bactericidal activity with 85% reduction in counts of E. coli colonies compared to neat PCL at 5% filler content and was more than twice as efficient as GO. This may be attributed to the synergistic effect of the sharp edges of the particles along with the presence of the different chemical moieties. Thus, GO_PEI based polymer composites can be utilized to prepare bioactive resorbable biomaterials as an alternative to using labile biomolecules for fabricating orthopedic devices for fracture fixation and tissue engineering.

Modulation of cellular responses: The two-photon polymerization approach in the control of the physical micro/nanoenvironment

Cells and tissues are extremely sensitive to their physico-chemical surroundings: in regenerative medicine, as an example, the maintenance of culture conditions resembling the in vivo environment is essential for a correct tissue development. In this review, we summarize our results concerning the preparation and testing of micro/nanostructures for fostering peculiar cellular behavior, prepared by exploiting an innovative technique of high resolution 3D photolithography, the two-photon polymerization (2pp).

Probing stem cell behavior using nanoparticle-based approaches

Stem cells hold significant clinical potential to treat numerous debilitating diseases and injures that currently have no treatment plan. While several advances have been made in developing stem cell platforms and methods to induce their differentiation, there are two critical aspects need to be addressed: (1) efficient delivery of nucleic acids and small molecules for stem cell differentiation, and (2) effective, noninvasive, and real-time tracking of transplanted stem cells. To address this, there has been a trend of utilizing various types of nanoparticles to not only deliver biomolecules to targeted site but also track the location of transplanted stem cells in real time. Over the past decade, various types of nanoparticles, including magnetic nanoparticles, silica nanoparticles, quantum dots, and gold nanoparticles, have been developed to serve as vehicles for targeted biomolecule delivery. In addition of being biocompatible without causing adverse side effect to stem cells, these nanoparticles have unique chemical and physical properties that allow tracking and imaging in real time using different imaging instruments that are commonly found in hospitals. A summary of the landmark and progressive demonstrations that utilize nanoparticles for stem cell application is described.

Nanotopographical Surfaces for Stem Cell Fate Control: Engineering Mechanobiology from the Bottom

During embryogenesis and tissue maintenance and repair in an adult organism, a myriad of stem cells are regulated by their surrounding extracellular matrix (ECM) enriched with tissue/organ-specific nanoscale topographical cues to adopt different fates and functions. Attributed to their capability of self-renewal and differentiation into most types of somatic cells, stem cells also hold tremendous promise for regenerative medicine and drug screening. However, a major challenge remains as to achieve fate control of stem cells in vitro with high specificity and yield. Recent exciting advances in nanotechnology and materials science have enabled versatile, robust, and large-scale stem cell engineering in vitro through developments of synthetic nanotopographical surfaces mimicking topological features of stem cell niches. In addition to generating new insights for stem cell biology and embryonic development, this effort opens up unlimited opportunities for innovations in stem cell-based applications. This review is therefore to provide a summary of recent progress along this research direction, with perspectives focusing on emerging methods for generating nanotopographical surfaces and their applications in stem cell research. Furthermore, we provide a review of classical as well as emerging cellular mechano-sensing and -transduction mechanisms underlying stem cell nanotopography sensitivity and also give some hypotheses in regard to how a multitude of signaling events in cellular mechanotransduction may converge and be integrated into core pathways controlling stem cell fate in response to extracellular nanotopography.

Nanostructured Brownian surfaces prepared through two-photon polymerization: investigation of stem cell response

Nondeterministic phenomena are at the base of plenty of biological processes that comprise physiological signaling, cellular communications, and biological architectures. Among them, natural surface topographies are often characterized by "chaotic" features that are not trivial to be recreated in vitro. Recently, some methods have been proposed to resemble the hierarchical organization of the extracellular microenvironment, through the chemical preparation of randomly rough and self-affine fractal surfaces. Notwithstanding, this approach does not allow the fractal dimension to be modulated at a desired value, being moreover the self-affinity maintained just for one decade of spatial frequencies. Here, we propose the replication of in silico generated Brownian surfaces through a two-photon polymerization technique. As a result of the direct laser writing of the desired patterns, we were able to obtain highly reproducible self-affine (in a range of two spatial frequency decades) structures characterized by the desired predetermined Hurst exponents. Rat mesenchymal stem cells were moreover cultured on the obtained substrates, highlighting interesting phenomena concerning cell adhesion, cytoskeleton conformation, and actin polymerization, strictly depending on the fractal dimension of the surfaces.

Proliferation and stemness preservation of human adipose-derived stem cells by surface-modified in situ TiO₂ nanofibrous surfaces

Two important criteria of an ideal biomaterial in the field of stem cells research are to regulate the cell proliferation without the loss of its pluripotency and to direct the differentiation into a specific cell lineage when desired. The present study describes the influence of TiO2 nanofibrous surface structures on the regulation of proliferation and stemness preservation of adipose-derived stem cells (ADSCs). TiO2 nanofiber arrays were produced in situ onto Ti-6Al-4V substrate via a thermal oxidation process and the successful fabrication of these nanostructures was confirmed by field emission scanning electron microscopy (FESEM), energy dispersive spectrometer (EDS), X-ray diffractometer (XRD), and contact angle measurement. ADSCs were seeded on two types of Ti-6Al-4V surfaces (TiO2 nanofibers and flat control), and their morphology, proliferation, and stemness expression were analyzed using FESEM, AlamarBlue assay, flow cytometry, and quantitative real-time polymerase chain reaction (qRT-PCR) after 2 weeks of incubation, respectively. The results show that ADSCs exhibit better adhesion and significantly enhanced proliferation on the TiO2 nanofibrous surfaces compared to the flat control surfaces. The greater proliferation ability of TiO2 nanofibrous surfaces was further confirmed by the results of cell cycle assay. More importantly, TiO2 nanofibrous surfaces significantly upregulate the expressions of stemness markers Sox-2, Nanog3, Rex-1, and Nestin. These results demonstrate that TiO2 nanofibrous surfaces can be used to enhance cell adhesion and proliferation while simultaneously maintaining the stemness of ADSCs, thereby representing a promising approach for their potential application in the field of bone tissue engineering as well as regenerative therapies.

Nanoengineered Platforms to Guide Pluripotent Stem Cell Fate

Tissue engineering utilizes cells, signaling molecules, and scaffolds towards creating functional tissue to repair damaged organs. Pluripotent stem cells (PSCs) are a promising cell source due to their ability to self-renewal indefinitely and their potential to differentiate into almost any cell type. Great strides have been taken to parse the physiological mechanisms by which PSCs respond to their microenvironment and commit to a specific lineage. The combination of physical cues and chemical factors is thought to have the most profound influence on stem cell behavior, therefore a major focus of tissue engineering strategies is scaffold design to incorporate these signals. One overlooked component of the in vivo microenvironment researchers attempt to recapitulate with three dimensional (3D) substrates is the nanoarchitecture formed by the fibrillar network of extracellular matrix (ECM) proteins. These nanoscale features have the ability to impact cell adhesion, migration, proliferation, and lineage commitment. Significant advances have been made in deciphering how these nanoscale cues interact with stem cells to determine phenotype, but much is still unknown as to how the interplay between physical and chemical signals regulate in vitro and in vivo cellular fate. This review dives deeper to investigate nanoscale platforms for engineering tissue, as well use the use of these nanotechnologies to drive pluripotent stem cell lineage determination.

Stem cell delivery systems inspired by tissue-specific niches

Since stem cells have the capacity to differentiate into a variety of cell types, stem cell delivery systems (SCDSs) can be effective therapeutic strategies for a multitude of diseases and disorders. For stem cell-based therapy, stem cells are introduced directly (or peripherally) into a target tissue via different delivery systems. Despite initial promising results obtained from preclinical studies, a number of technical hurdles must be overcome for ultimate clinical utility of stem cells. A key aspect of SCDSs is how to create local environments, called stem cell niches, for improvement of survival and engraftment as well as the fate of transplanted stem cells. The stem cell niches encompassing a wide range of biochemical, biophysical, and biomechanical cues play a guidance role to modulate stem cell behaviors such as adhesion, proliferation, and differentiation. Recent studies have tried to decipher the complex interplay between stem cells and niches, and thereafter to engineer SCDS, mimicking dynamic stem cell niches encompassing a wide range of biochemical, biophysical, and biomechanical cues. Here, we discuss the biological role of stem cell niches and highlight recent progress in SCDS to mimic stem cell niches, particularly focusing on important biomaterial properties for modulating stem cell fate.