Four-Dimensional (Bio-)printing: A Review on Stimuli-Responsive Mechanisms and Their Biomedical Suitability

The applications of tissue engineered constructs have witnessed great advances in the last few years, as advanced fabrication techniques have enabled promising approaches to develop structures and devices for biomedical uses. (Bio-)printing, including both plain material and cell/material printing, offers remarkable advantages and versatility to produce multilateral and cell-laden tissue constructs; however, it has often revealed to be insufficient to fulfill clinical needs. Indeed, three-dimensional (3D) (bio-)printing does not provide one critical element, fundamental to mimic native live tissues, i.e., the ability to change shape/properties with time to respond to microenvironmental stimuli in a personalized manner. This capability is in charge of the so-called “smart materials”; thus, 3D (bio-)printing these biomaterials is a possible way to reach four-dimensional (4D) (bio-)printing. We present a comprehensive review on stimuli-responsive materials to produce scaffolds and constructs via additive manufacturing techniques, aiming to obtain constructs that closely mimic the dynamics of native tissues. Our work deploys the advantages and drawbacks of the mechanisms used to produce stimuli-responsive constructs, using a classification based on the target stimulus: humidity, temperature, electricity, magnetism, light, pH, among others. A deep understanding of biomaterial properties, the scaffolding technologies, and the implant site microenvironment would help the design of innovative devices suitable and valuable for many biomedical applications.

Download Full-text

Bioresorbable Polymers: Advanced Materials and 4D Printing for Tissue Engineering

Polymers ◽

10.3390/polym13040563 ◽

2021 ◽

Vol 13 (4) ◽

pp. 563

Author(s):

Sybele Saska ◽

Livia Pilatti ◽

Alberto Blay ◽

Jamil Awad Shibli

Keyword(s):

Tissue Engineering ◽

Smart Materials ◽

Morphological Changes ◽

New Technology ◽

Three Dimensional ◽

Advanced Materials ◽

Stimuli Responsive ◽

4D Printing ◽

Responsive Materials ◽

Bioresorbable Polymers

Three-dimensional (3D) printing is a valuable tool in the production of complexes structures with specific shapes for tissue engineering. Differently from native tissues, the printed structures are static and do not transform their shape in response to different environment changes. Stimuli-responsive biocompatible materials have emerged in the biomedical field due to the ability of responding to other stimuli (physical, chemical, and/or biological), resulting in microstructures modifications. Four-dimensional (4D) printing arises as a new technology that implements dynamic improvements in printed structures using smart materials (stimuli-responsive materials) and/or cells. These dynamic scaffolds enable engineered tissues to undergo morphological changes in a pre-planned way. Stimuli-responsive polymeric hydrogels are the most promising material for 4D bio-fabrication because they produce a biocompatible and bioresorbable 3D shape environment similar to the extracellular matrix and allow deposition of cells on the scaffold surface as well as in the inside. Subsequently, this review presents different bioresorbable advanced polymers and discusses its use in 4D printing for tissue engineering applications.

Download Full-text

Redox-triggered switching in three-dimensional covalent organic frameworks

Nature Communications ◽

10.1038/s41467-020-18588-1 ◽

2020 ◽

Vol 11 (1) ◽

Cited By ~ 1

Author(s):

Chao Gao ◽

Jian Li ◽

Sheng Yin ◽

Junliang Sun ◽

Cheng Wang

Keyword(s):

Solid State ◽

Three Dimensional ◽

Molecular Switches ◽

Pore Channel ◽

Pore Surface ◽

Stimuli Responsive ◽

Conversion Yield ◽

Responsive Materials ◽

Reversible Transformation ◽

Internal Pore

Abstract The tuning of molecular switches in solid state toward stimuli-responsive materials has attracted more and more attention in recent years. Herein, we report a switchable three-dimensional covalent organic framework (3D COF), which can undergo a reversible transformation through a hydroquinone/quinone redox reaction while retaining the crystallinity and porosity. Our results clearly show that the switching process gradually happened through the COF framework, with an almost quantitative conversion yield. In addition, the redox-triggered transformation will form different functional groups on the pore surface and modify the shape of pore channel, which can result in tunable gas separation property. This study strongly demonstrates 3D COFs can provide robust platforms for efficient tuning of molecular switches in solid state. More importantly, switching of these moieties in 3D COFs can remarkably modify the internal pore environment, which will thus enable the resulting materials with interesting stimuli-responsive properties.

Download Full-text

Stimuli-Responsive Graphene Nanohybrids for Biomedical Applications

Stem Cells International ◽

10.1155/2019/9831853 ◽

2019 ◽

Vol 2019 ◽

pp. 1-18 ◽

Cited By ~ 2

Author(s):

Dinesh K. Patel ◽

Yu-Ri Seo ◽

Ki-Taek Lim

Keyword(s):

Drug Delivery ◽

Functional Groups ◽

Hybrid Materials ◽

Smart Materials ◽

Biomedical Applications ◽

Materials Science ◽

High Surface ◽

Single Layer ◽

Stimuli Responsive ◽

Physiochemical Properties

Stimuli-responsive materials, also known as smart materials, can change their structure and, consequently, original behavior in response to external or internal stimuli. This is due to the change in the interactions between the various functional groups. Graphene, which is a single layer of carbon atoms with a hexagonal morphology and has excellent physiochemical properties with a high surface area, is frequently used in materials science for various applications. Numerous surface functionalizations are possible for the graphene structure with different functional groups, which can be used to alter the properties of native materials. Graphene-based hybrids exhibit significant improvements in their native properties. Since functionalized graphene contains several reactive groups, the behavior of such hybrid materials can be easily tuned by changing the external conditions, which is very useful in biomedical applications. Enhanced cell proliferation and differentiation of stem cells was reported on the surfaces of graphene-based hybrids with negligible cytotoxicity. In addition, pH or light-induced drug delivery with a controlled release rate was observed for such nanohybrids. Besides, notable improvements in antimicrobial activity were observed for nanohybrids, which demonstrated their potential for biomedical applications. This review describes the physiochemical properties of graphene and graphene-based hybrid materials for stimuli-responsive drug delivery, tissue engineering, and antimicrobial applications.

Download Full-text

Stimuli-Responsive Materials for Tissue Engineering and Drug Delivery

International Journal of Molecular Sciences ◽

10.3390/ijms21134724 ◽

2020 ◽

Vol 21 (13) ◽

pp. 4724 ◽

Cited By ~ 1

Author(s):

Sofia Municoy ◽

María I. Álvarez Echazú ◽

Pablo E. Antezana ◽

Juan M. Galdopórpora ◽

Christian Olivetti ◽

...

Keyword(s):

Drug Delivery ◽

Tissue Engineering ◽

Smart Materials ◽

Controlled Drug Release ◽

Stimuli Responsive ◽

Responsive Materials ◽

Stimuli Responsive Polymers ◽

Responsive Polymers ◽

Stimuli Response ◽

Materials Used

Smart or stimuli-responsive materials are an emerging class of materials used for tissue engineering and drug delivery. A variety of stimuli (including temperature, pH, redox-state, light, and magnet fields) are being investigated for their potential to change a material’s properties, interactions, structure, and/or dimensions. The specificity of stimuli response, and ability to respond to endogenous cues inherently present in living systems provide possibilities to develop novel tissue engineering and drug delivery strategies (for example materials composed of stimuli responsive polymers that self-assemble or undergo phase transitions or morphology transformations). Herein, smart materials as controlled drug release vehicles for tissue engineering are described, highlighting their potential for the delivery of precise quantities of drugs at specific locations and times promoting the controlled repair or remodeling of tissues.

Download Full-text

Phenylboronic Acid-polymers for Biomedical Applications

Current Medicinal Chemistry ◽

10.2174/0929867325666181008144436 ◽

2019 ◽

Vol 26 (37) ◽

pp. 6797-6816 ◽

Cited By ~ 6

Author(s):

Ji Hyun Ryu ◽

Gyeong Jin Lee ◽

Yu-Ru V. Shih ◽

Tae-il Kim ◽

Shyni Varghese

Keyword(s):

Biomedical Applications ◽

Phenylboronic Acid ◽

Covalent Bond ◽

Self Healing ◽

Stimuli Responsive ◽

Dynamic Nature ◽

Responsive Materials ◽

Boronate Ester ◽

Reversible Bonding ◽

Reversible Covalent

Background: Phenylboronic acid-polymers (PBA-polymers) have attracted tremendous attention as potential stimuli-responsive materials with applications in drug-delivery depots, scaffolds for tissue engineering, HIV barriers, and biomolecule-detecting/sensing platforms. The unique aspect of PBA-polymers is their interactions with diols, which result in reversible, covalent bond formation. This very nature of reversible bonding between boronic acids and diols has been fundamental to their applications in the biomedical area. Methods: We have searched peer-reviewed articles including reviews from Scopus, PubMed, and Google Scholar with a focus on the 1) chemistry of PBA, 2) synthesis of PBA-polymers, and 3) their biomedical applications. Results: We have summarized approximately 179 papers in this review. Most of the applications described in this review are focused on the unique ability of PBA molecules to interact with diol molecules and the dynamic nature of the resulting boronate esters. The strong sensitivity of boronate ester groups towards the surrounding pH also makes these molecules stimuli-responsive. In addition, we also discuss how the re-arrangement of the dynamic boronate ester bonds renders PBA-based materials with other unique features such as self-healing and shear thinning. Conclusion: The presence of PBA in the polymer chain can render it with diverse functions/ relativities without changing their intrinsic properties. In this review, we discuss the development of PBA polymers with diverse functions and their biomedical applications with a specific focus on the dynamic nature of boronate ester groups.

Download Full-text

Performing calculus: Asymmetric adaptive stimuli-responsive material for derivative control

Science Advances ◽

10.1126/sciadv.abe5698 ◽

2021 ◽

Vol 7 (14) ◽

pp. eabe5698

Author(s):

Spandhana Gonuguntla ◽

Wei Chun Lim ◽

Fong Yew Leong ◽

Chi Kit Ao ◽

Changhui Liu ◽

...

Keyword(s):

Smart Materials ◽

Self Regulation ◽

Fast Response ◽

Stimuli Responsive ◽

Mathematical Operation ◽

Responsive Materials ◽

Analytical Functions ◽

Temporal Derivative ◽

Impermeable Layer ◽

Designed Materials

Materials (e.g., brick or wood) are generally perceived as unintelligent. Even the highly researched “smart” materials are only capable of extremely primitive analytical functions (e.g., simple logical operations). Here, a material is shown to have the ability to perform (i.e., without a computer), an advanced mathematical operation in calculus: the temporal derivative. It consists of a stimuli-responsive material coated asymmetrically with an adaptive impermeable layer. Its ability to analyze the derivative is shown by experiments, numerical modeling, and theory (i.e., scaling between derivative and response). This class of freestanding stimuli-responsive materials is demonstrated to serve effectively as a derivative controller for controlled delivery and self-regulation. Its fast response realizes the same designed functionality and efficiency as complex industrial derivative controllers widely used in manufacturing. These results illustrate the possibility to associate specifically designed materials directly with higher concepts of mathematics for the development of “intelligent” material-based systems.

Download Full-text

Carbocycle-Based Organogelators: Influence of Chirality and Structural Features on Their Supramolecular Arrangements and Properties

Gels ◽

10.3390/gels7020054 ◽

2021 ◽

Vol 7 (2) ◽

pp. 54

Author(s):

Rosa M. Ortuño

Keyword(s):

Smart Materials ◽

Self Assembly ◽

Rational Design ◽

Structural Features ◽

Stimuli Responsive ◽

Polycyclic Compounds ◽

Relative Configuration ◽

Responsive Materials ◽

Self Assembling ◽

Donor Acceptor

The rational design and engineer of organogel-based smart materials and stimuli-responsive materials with tuned properties requires the control of the non-covalent forces driving the hierarchical self-assembly. Chirality, as well as cis/trans relative configuration, also plays a crucial role promoting the morphology and characteristics of the aggregates. Cycloalkane derivatives can provide chiral chemical platforms allowing the incorporation of functional groups and hydrophobic structural units able for a convenient molecular stacking leading to gels. Restriction of the conformational freedom imposed by the ring strain is also a contributing issue that can be modulated by the inclusion of flexible segments. In addition, donor/acceptor moieties can also be incorporated favoring the interactions with light or with charged species. This review offers a perspective on the abilities and properties of carbocycle-based organogelators starting from simple cycloalkane derivatives, which were the key to establish the basis for an effective self-assembling, to sophisticated polycyclic compounds with manifold properties and applications.

Download Full-text

Stimuli Responsive Materials Supported by Orthogonal Hydrogen and Halogen Bonding or I···Alkene Interaction

Molecules ◽

10.3390/molecules26247586 ◽

2021 ◽

Vol 26 (24) ◽

pp. 7586

Author(s):

Pierre Frangville ◽

Shiv Kumar ◽

Michel Gelbcke ◽

Kristof Van Van Hecke ◽

Franck Meyer

Keyword(s):

Smart Materials ◽

Color Change ◽

Uv Light ◽

Halogen Bond ◽

Halogen Bonding ◽

Building Blocks ◽

Stimuli Responsive ◽

Compound I ◽

Ph Variation ◽

Responsive Materials

Smart materials represent an elegant class of (macro)-molecules endowed with the ability to react to chemical/physical changes in the environment. Herein, we prepared new photo responsive azobenzenes possessing halogen bond donor groups. The X-ray structures of two molecules highlight supramolecular organizations governed by unusual noncovalent bonds. In azo dye I-azo-NO2, the nitro group is engaged in orthogonal H···O···I halogen and hydrogen bonding, linking the units in parallel undulating chains. As far as compound I-azo-NH-MMA is concerned, a non-centrosymmetric pattern is formed due to a very rare I···π interaction involving the alkene group supplemented by hydrogen bonds. The Cambridge Structural Database contains only four structures showing the same I···CH2=C contact. For all compounds, an 19F-NMR spectroscopic analysis confirms the formation of halogen bonds in solution through a recognition process with chloride anion, and the reversible photo-responsiveness is demonstrated upon exposing a solution to UV light irradiation. Finally, the intermediate I–azo–NH2 also shows a pronounced color change due to pH variation. These azobenzenes are thereby attractive building blocks to design future multi-stimuli responsive materials for highly functional devices.

Download Full-text

Concomitant Photoresponsive Chiroptics and Magnetism in Metal-Organic Frameworks at Room Temperature

Research ◽

10.34133/2021/5490482 ◽

2021 ◽

Vol 2021 ◽

pp. 1-12

Author(s):

Bin Xia ◽

Qian Gao ◽

Zhen-Peng Hu ◽

Qing-Lun Wang ◽

Xue-Wei Cao ◽

...

Keyword(s):

Electron Transfer ◽

Smart Materials ◽

Room Temperature ◽

Color Change ◽

Metal Organic Frameworks ◽

Stimuli Responsive ◽

Responsive Materials ◽

Chiral Carbon ◽

Cotton Effects ◽

Metal Organic

Stimulus-responsive metal-organic frameworks (MOFs) can be used for designing smart materials. Herein, we report a family of rationally designed MOFs which exhibit photoresponsive chiroptical and magnetic properties at room temperature. In this design, two specific nonphotochromic ligands are selected to construct enantiomeric MOFs, {Cu2(L-mal)2(bpy)2(H2O)·3H2O}n (1) and {Cu2(D-mal)2(bpy)2(H2O)·3H2O}n (2) (mal=malate, bpy=4,4’−bipyridine), which can alter their color, magnetism, and chiroptics concurrently in response to light. Upon UV or visible light irradiation, long-lived bpy− radicals are generated via photoinduced electron transfer (PET) from oxygen atoms of carboxylates and hydroxyl of malates to bpy ligands, giving rise to a 23.7% increase of magnetic susceptibility at room temperature. The participation of the chromophores (-OH and -COO−) bound with the chiral carbon during the electron transfer process results in a small dipolar transition; thus, the Cotton effects of the enantiomers are weakened along with a photoinduced color change. This work demonstrates that the simultaneous responses of chirality, optics, and magnetism can be achieved in a single compound at room temperature and may open up a new pathway for designing chiral stimuli-responsive materials.

Download Full-text

Programmable CRISPR-responsive smart materials

Science ◽

10.1126/science.aaw5122 ◽

2019 ◽

Vol 365 (6455) ◽

pp. 780-785 ◽

Cited By ~ 54

Author(s):

Max A. English ◽

Luis R. Soenksen ◽

Raphael V. Gayet ◽

Helena de Puig ◽

Nicolaas M. Angenent-Mari ◽

...

Keyword(s):

Smart Materials ◽

Biological Information ◽

Live Cells ◽

Stimuli Responsive ◽

Structural Element ◽

Responsive Materials ◽

Guide Rna ◽

Poly Ethylene ◽

Dna Hydrogels

Stimuli-responsive materials activated by biological signals play an increasingly important role in biotechnology applications. We exploit the programmability of CRISPR-associated nucleases to actuate hydrogels containing DNA as a structural element or as an anchor for pendant groups. After activation by guide RNA–defined inputs, Cas12a cleaves DNA in the gels, thereby converting biological information into changes in material properties. We report four applications: (i) branched poly(ethylene glycol) hydrogels releasing DNA-anchored compounds, (ii) degradable polyacrylamide-DNA hydrogels encapsulating nanoparticles and live cells, (iii) conductive carbon-black–DNA hydrogels acting as degradable electrical fuses, and (iv) a polyacrylamide-DNA hydrogel operating as a fluidic valve with an electrical readout for remote signaling. These materials allow for a range of in vitro applications in tissue engineering, bioelectronics, and diagnostics.

Download Full-text