Multifunctional inverse opal particles for drug delivery and monitoring

Hepatocellular carcinoma biomarkers screening based on hydrogel photonic barcodes with tyramine deposition amplified ELISA

Hepatocellular carcinoma (HCC), as one of the most lethal cancers, significantly impacts human health. Attempts in this area tends to develop novel technologies with sensitive and multiplexed detection properties for early diagnosis. Here, we present novel hydrogel photonic crystal (PhC) barcodes with tyramine deposition amplified enzyme-linked immunosorbent assay (ELISA) for highly sensitive and multiplexed HCC biomarker screening. Because of the abundant amino groups of acrylic acid (AA) component, the constructed hydrogel PhC barcodes with inverse opal structure could facilitate the loading of antibody probes for subsequent detection of tumor markers. By integrating tyramine deposition amplified ELISA on the barcode, the detection signal of tumor markers has been enhanced. Based on these features, it is demonstrated that the hydrogel PhC barcodes with tyramine deposition amplified ELISA could realize highly sensitive and multiplexed detection of HCC-related biomarkers. It was found that this method is flexible, sensitive and accurate, suitable for multivariate analysis of low abundance tumor markers and future cancer diagnosis. These features make the newly developed PhC barcodes an innovation platform, which possesses tremendous potential for practical application of low abundance targets.

Preparation and Application of Hemostatic Hydrogels

Hemorrhage remains a critical challenge in various medical settings, necessitating the development of advanced hemostatic materials. Hemostatic hydrogels have emerged as promising solutions to address uncontrolled bleeding due to their unique properties, including biocompatibility, tunable physical characteristics, and exceptional hemostatic capabilities. In this review, a comprehensive overview of the preparation and biomedical applications of hemostatic hydrogels is provided. Particularly, hemostatic hydrogels with various materials and forms are introduced. Additionally, the applications of hemostatic hydrogels in trauma management, surgical procedures, wound care, etc. are summarized. Finally, the limitations and future prospects of hemostatic hydrogels are discussed and evaluated. This review aims to highlight the biomedical applications of hydrogels in hemorrhage management and offer insights into the development of clinically relevant hemostatic materials.

Preparation and Characterization of a Hypoglycemic Complex of Gallic Acid-Antarctic Krill Polypeptide Based on Polylactic Acid-Hydroxyacetic Acid (PLGA) and High-Pressure Microjet Microencapsulation

Gallic acid-Antarctic krill peptides (GA-AKP) nanocapsules (GA-AKP-Ns) were prepared using a dual delivery system with complex emulsion as the technical method, a high-pressure microjet as the technical means, polylactic acid-hydroxyacetic acid (PLGA) as the drug delivery vehicle, and GA-AKP as the raw material for delivery. This study aimed to investigate the effects of microjet treatment and the concentration of PLGA on the physicochemical properties and stability of the emulsion. Under optimal conditions, the physicochemical properties and hypoglycemic function of nano-microcapsules prepared after lyophilization by the solvent evaporation method were analyzed. Through the microjet treatment, the particle size of the emulsion was reduced, the stability of the emulsion was improved, and the encapsulation rate of GA-AKP was increased. The PLGA at low concentrations decreased the particle size of the emulsion, while PLGA at high concentrations enhanced the encapsulation efficiency of the emulsion. Additionally, favorable results were obtained for emulsion preparation through high-pressure microjet treatment. After three treatment cycles with a PLGA concentration of 20 mg/mL and a microjet pressure of 150 MPa (manometric pressure), the emulsion displayed the smallest particle size (285.1 ± 3.0 nm), the highest encapsulation rates of GA (71.5%) and AKP (85.2%), and optimal physical stability. GA-AKP was uniformly embedded in capsules, which can be slowly released in in vitro environments, and effectively inhibited α-amylase, α-glucosidase, and DPP-IV at different storage temperatures. This study demonstrated that PLGA as a carrier combined with microjet technology can produce excellent microcapsules, especially nano-microcapsules, and these microcapsules effectively improve the bioavailability and effectiveness of bioactive ingredients.

Multicargo-loaded inverse opal gelatin hydrogel microparticles for promoting bacteria-infected wound healing

Nowadays, many strategies have been developed to design biomaterials to accelerate bacteria-infected wound healing. Here, we presented a new type of multicargo-loaded inverse opal hydrogel microparticle (IOHM) for regulating oxidative stress, antibiosis, and angiogenesis of the bacteria-infected wound. The methacrylate acylated gelatin (GelMA)-based inverse opal hydrogel microparticles (IOHMs) were obtained by using the colloidal crystal microparticles as templates, and fullerol, silver nanoparticles (Ag NPs), and vascular endothelial growth factor (VEGF) were loaded in IOHMs. The developed multicargo-loaded IOHMs displayed good size distribution and biocompatibility, and when they were applied in cell culture, bacteria culture, and animal experiments, they exhibited excellent anti-oxidative stress properties, antibacterial properties, and angiogenesis. These characteristics of the developed multicargo-loaded IOHMs make them ideal for bacteria-infected wound healing.

Application of colloidal photonic crystals in study of organoids

As alternative disease models, other than 2D cell lines and patient-derived xenografts, organoids have preferable in vivo physiological relevance. However, both endogenous and exogenous limitations impede the development and clinical translation of these organoids. Fortunately, colloidal photonic crystals (PCs), which benefit from favorable biocompatibility, brilliant optical manipulation, and facile chemical decoration, have been applied to the engineering of organoids and have achieved the desirable recapitulation of the ECM niche, well-defined geometrical onsets for initial culture, in situ multiphysiological parameter monitoring, single-cell biomechanical sensing, and high-throughput drug screening with versatile functional readouts. Herein, we review the latest progress in engineering organoids fabricated from colloidal PCs and provide inputs for future research.

Structural Color Mixing in Microcapsules through Exclusive Crystallization of Binary and Ternary Colloids

Colloidal crystals are designed as photonic microparticles for various applications. However, conventional microparticles generally have only one stopband from a single lattice constant, which restricts the range of colors and optical codes available. Here, photonic microcapsules are created that contain two or three distinct crystalline grains, resulting in dual or triple stopbands that offer a wider range of colors through structural color mixing. To produce distinct colloidal crystallites from binary or ternary colloidal mixtures, the interparticle interaction is manipulated using depletion forces in double-emulsion droplets. Aqueous dispersions of binary or ternary colloidal mixtures in the innermost droplet are gently concentrated in the presence of a depletant and salt by imposing hypertonic conditions. Different-sized particles crystallize into their own crystals rather than forming random glassy alloys to minimize free energy. The average size of the crystalline grains can be adjusted with osmotic pressure, and the relative ratio of distinct grains can be controlled with the mixing ratio of particles. The resulting microcapsules with small grains and high surface coverage are almost optically isotropic and exhibit highly-saturated mixed structural colors and multiple reflectance peaks. The mixed color and reflectance spectrum are controllable with the selection of particle sizes and mixing ratios.

Structural Design of Intelligent Reversible Two-Way Structural Color Films

Structural color always shows a reversible switch between reflection and transmission states when viewed from different angles, attracting increasing attention in display applications. However, this switching between reflection and transmission states of structural color suffers from the inherent lack of autonomous regulation, which is unmanageable in the case of different application scenarios. Here, we design an intelligent two-way structural color film which can reversibly change its color when applied with an extra stimulation such as voltage, heat signal, or light. A special structural feature contains a traditional photonic crystal film of polystyrene (PS) microspheres assembled by smart windows. Remarkably, our structural color film shows a prominent polarization sensitivity, and the angle dependence of the structural color broadens the gamut of display color demonstrated by both finite element theoretical analysis and experimental observation. Prospectively, this hierarchically designed film provides a promising pathway toward next-generation multicolor displays and smart windows.

Microfluidic preparation of optical sensors for biomedical applications

Optical biosensors are platforms that translate biological information into detectable optical signals, and have extensive applications in various fields due to their characteristics of high sensitivity, high specificity, dynamic sensing, etc. The development of optical sensing materials is an important part of optical sensors. In this review, we emphasize the role of microfluidic technology in the preparation of optical sensing materials and the application of the derived optical sensors in the biomedical field. We first present some common optical sensing mechanisms and the functional responsive materials involved. Then, we describe the preparation of these sensing materials by microfluidics. Afterward, we enumerate the biomedical applications of these optical materials as biosensors in disease diagnosis, drug evaluation, and organ-on-a-chip. Finally, we discuss the challenges and prospects in this field.

Encoding microcarriers for biomedicine

High throughput biological analysis has become an important topic in modern biomedical research and clinical diagnosis. The flow encoding scheme based on the encoding microcarriers provides a feasible strategy for the multiplexed biological analysis. Different encoding characteristics invest the microcarriers with different encoding mechanisms. Biosensor analysis, drug screening, cell culture, and the construction and evaluation of bionic organ chips can be realized by decoding the microcarriers and quantifying the detection signal intensity. In this review, the encoding strategy of microcarriers was divided into the optical and non-optical encoding approaches according to their encoding elements, and the research progress of the microcarrier encoding strategy was elaborated. Finally, we summarized the biomedical applications and predicted their future prospects.

Designing photonic microparticles with droplet microfluidics

Photonic materials with a periodic change of refractive index show unique optical properties through wavelength-selective diffraction and modulation of the optical density of state, which is promising for various optical applications. In particular, photonic structures have been produced in the format of microparticles using emulsion templates to achieve advanced properties and applications beyond those of a conventional film format. Photonic microparticles can be used as a building block to construct macroscopic photonic materials, and the individual microparticles can serve as miniaturized photonic devices. Droplet microfluidics enables the production of emulsion drops with a controlled size, composition, and configuration that serve as the optimal confining geometry for designing photonic microparticles. This feature article reviews the recent progress and current state of the art in the field of photonic microparticles, covering all aspects of microfluidic production methods, microparticle geometries, optical properties, and applications. Two distinct bottom-up approaches based on colloidal assembly and liquid crystals are, respectively, discussed and compared.

Multifunctional Inverse Opal Microneedle Arrays for Drug Delivery and Monitoring

Microneedle arrays (MNs) have a demonstrated value in transdermal drug delivery systems. Attempts to this technology focus on the generation of functional MNs to achieve intelligent drug delivery. Here, multifunctional inverse opal microneedle (IOMN) arrays with the abilities are reported to load various drugs and monitor drug release. The IOMNs are generated by using poly(ethylene glycol) diacrylate (PEGDA) to replicate hierarchical structure templates that are composed of self-assembled silica colloidal nanoparticles in the inverted cone structure wells. Because of their interconnected porous structures, different actives, or drugs can be loaded into the IOMNs without organic solvents and chemical polymerization. It is demonstrated that when these drugs loaded IOMNs pierce the skin at position of interest and for slow release, the average refractive index of the IOMNs decreases with the release process, resulting in a corresponding blueshift of their characteristic spectrum. Thus, by measuring the wavelength shift value of the IOMNs, the amount of released drugs can be monitored, providing essential guidance for efficient clinical treatment. These features indicate that the IOMNs are valuable smart drug delivery systems in personalized therapy.

Materials with Tunable Optical Properties for Wearable Epidermal Sensing in Health Monitoring

Advances in wearable epidermal sensors have revolutionized the way that physiological signals are captured and measured for health monitoring. One major challenge is to convert physiological signals to easily readable signals in a convenient way. One possibility for wearable epidermal sensors is based on visible readouts. There are a range of materials whose optical properties can be tuned by parameters such as temperature, pH, light, and electric fields. Herein, this review covers and highlights a set of materials with tunable optical properties and their integration into wearable epidermal sensors for health monitoring. Specifically, the recent progress, fabrication, and applications of these materials for wearable epidermal sensors are summarized and discussed. Finally, the challenges and perspectives for the next generation wearable devices are proposed.

Heterogeneous Thermochromic Hydrogel Film Based on Photonic Nanochains

The rapid and robust response to external stimulus with a large volume deformation is of huge importance for the practical application of thermo-responsive photonic crystal film (TRPCF) in actuators, colorimetric sensors, and other color-related fields. Generally, decreasing the size of thermo-responsive photonic crystals and introducing micropores are considered to be two effective approaches to improve their responsiveness. However, they usually result in a poor mechanical property, which leads to optical instability. To solve these problems, a heterogeneous thermo-responsive photonic crystal film was developed here by integrating a thermosensitive hydrogel matrix poly(N-isopropylacrylamide-co-N-methylolacrylamide) (P(NIPAM-co-NHMA)) with high-modulus, but non-thermosensitive poly(acrylic acid -co-2-hydroxyethyl methacrylate (P(AA-co-HEMA)) hydrogel-based photonic nanochains (PNCs). The as-obtained TRPCF based on PNCs (TRPCF-PNC) well combined the rapid response and improved the mechanical property. Typically, it can complete a response within 12 s from 26 to 44 °C, which was accompanied by a larger deformation of the matrix than that of the PNCs. The unique rapid thermochromic mechanism of the TRPCF-PNC is revealed here. Furthermore, it exhibits a high tensible property along the PNC-orientation direction and excellent optical stability. The response time of the TRPCF-PNC can conveniently modulate by changing the cross-linking degree of the PNCs or the content of the thermosensitive component in the matrix. The heterogeneous TRPCF-PNC is believed to have potential applications in artificial muscle and quick-response actuation devices.

Current Understanding of the Applications of Photocrosslinked Hydrogels in Biomedical Engineering

Hydrogel materials have great application value in biomedical engineering. Among them, photocrosslinked hydrogels have attracted much attention due to their variety and simple convenient preparation methods. Here, we provide a systematic review of the biomedical-engineering applications of photocrosslinked hydrogels. First, we introduce the types of photocrosslinked hydrogel monomers, and the methods for preparation of photocrosslinked hydrogels with different morphologies are summarized. Subsequently, various biomedical applications of photocrosslinked hydrogels are reviewed. Finally, some shortcomings and development directions for photocrosslinked hydrogels are considered and proposed. This paper is designed to give researchers in related fields a systematic understanding of photocrosslinked hydrogels and provide inspiration to seek new development directions for studies of photocrosslinked hydrogels or related materials.

Fabrication of Temperature- and Alcohol-Responsive Photonic Crystal Hydrogel and Its Application for Sustained Drug Release

Herein, crack-free photonic crystal templates with enhanced color contrast were first demonstrated by the coassembly of polystyrene (PS) microspheres and graphene oxide (GO). Then, photonic crystal hydrogels (PCHs) with quick responses to temperature and alcohol solution concentration changes were fabricated by photopolymerization of monomers in the gaps of the self-assembled colloidal crystal templates. The structural color of the PCHs changed from yellow to blue within 120 s as the temperature rose from 25 to 40 °C, whereas upon a decrease in temperature from 40 to 25 °C, the structural color changed from blue to yellow. The structural color of the PCHs also shows an obvious response with the concentration of alcohol solution ranging from 40 to 100 wt %. The quick responses of the PCHs' structural color to changes in temperature and alcohol solution concentration are attributed to the temperature sensitivity of poly(N-isopropylacrylamide) and preferential adsorption and swelling of the alcohol solution for the polymer chains. Furthermore, moxifloxacin (Mox) was loaded into PCHs by hydrogel swelling and exhibited sustained released by increasing the temperature. The sustained release process was facilely monitored by observing the corresponding color changes in real time. The rapid and visible response offers the fabricated PCHs great potential application prospects in the semiquantitative analysis of alcohol concentration and intelligent drug delivery.

Thermally Tunable Structural Coloration of Water/Surfactant/Oil Emulsions

Stimuli-responsive structural color in nature has fascinated scientists, directing them to develop artificial coloration materials that adjust colors in response to external stimuli. Many stimuli-responsive structural color materials have been realized. However, only a few have reported on all-liquid-type materials, which have a particularly desirable feature because they impart their function to the device of any shape. We have previously reported the development of a consistent structural color within a narrow temperature range for all-liquid-type emulsions comprising a long-chain amidoamine derivative (C18AA) and tetraoctylammonium bromide (TOAB). In the present study, we demonstrate that introducing NaCl as an electrolyte affords a highly thermo-sensitive color-changing ability to the emulsions. The structural color of the emulsions can be controlled from red to blue by tuning the temperature. Furthermore, the C18AA and TOAB concentrations can independently regulate the color and coloring-temperature, respectively, realizing that the desired color can develop at a given temperature.

Prevent or Cure-The Unprecedented Need for Self-Reporting Materials

Self-reporting smart materials are highly relevant in modern soft matter materials science, as they allow for the autonomous detection of changes in synthetic polymers, materials, and composites. Despite critical advantages of such materials, for example, prolonged lifetime or prevention of disastrous material failures, they have gained much less attention than self-healing materials. However, as diagnosis is critical for any therapy, it is of the utmost importance to report the existence of system changes and their exact location to prevent them from spreading. Thus, we herein critically review the chemistry of self-reporting soft matter materials systems and highlight how current challenges and limitations may be overcome by successfully transferring self-reporting research concepts from the laboratory to the real world. Especially in the space of diagnostic self-reporting systems, the recent SARS-CoV-2 (COVID-19) pandemic indicates an urgent need for such concepts that may be able to detect the presence of viruses or bacteria on and within materials in a self-reporting fashion.

Microfluidics for Drug Development: From Synthesis to Evaluation

Drug development is a long process whose main content includes drug synthesis, drug delivery, and drug evaluation. Compared with conventional drug development procedures, microfluidics has emerged as a revolutionary technology in that it offers a miniaturized and highly controllable environment for bio(chemical) reactions to take place. It is also compatible with analytical strategies to implement integrated and high-throughput screening and evaluations. In this review, we provide a comprehensive summary of the entire microfluidics-based drug development system, from drug synthesis to drug evaluation. The challenges in the current status and the prospects for future development are also discussed. We believe that this review will promote communications throughout diversified scientific and engineering communities that will continue contributing to this burgeoning field.

Metformin loaded porous particles with bio-microenvironment responsiveness for promoting tumor immunotherapy

PD1/PD-L1 antibody blockade-based immunotherapy has been widely recognized in the field of cancer treatment; however, only a small number of cancer patients have been shown to respond well due to the PD1/PD-L1 antibody hydrolysis induced substandard immunotherapeutic efficacy and the low immunogenicity and immunosuppressive tumor microenvironment of the patients. Here, we present a novel tumor microenvironment (TME) responsive particle delivery system with a metformin-loaded chitosan (CS) inverse opal core and a manganese dioxide (MnO₂) shell (denoted as CS-metformin@MnO₂ particles) for inhibiting the PD-1/PD-L1 signaling pathway and promoting tumor immunotherapy. Benefiting from the interconnected porous structure of the inverse opal, metformin can be easily extensively loaded into the CS particles. With the coating of the TME responsive MnO₂ shells, the particle delivery system was imparted with an intelligent "trigger" to prevent premature leaking of the drug until it reaches the tumor tissue. We have demonstrated that CS-metformin@MnO₂ particles were able to promote the apoptosis of tumor cells through immunotherapeutic means both in vivo and in vitro. Specifically, the viability of tumor cells in the drug carrier-treated group was nearly 20% less than in the untreated group. In addition, the CS particles could serve as scaffolds for the regeneration of normal tissues and promote post-surgical wound healing due to their biocompatibility and antibacterial ability. These results make CS-metformin@MnO₂ particles an excellent delivery system in tumor immunotherapy and post-surgical wound healing applications.

Biomimetic design of photonic materials for biomedical applications

Photonic crystal (PC) materials with bio-inspired structure colors have drawn increasing attention as their potentials have been rapidly progressed in the field of biomedicine. After elaborate integration with smart materials or preparations through advanced techniques, PC materials have shown significant advantages in biosensing, bio-probing, bio-screening, tissue engineering, and so forth. In this review, we first introduced the fundamentals of PC materials as well as their fabrication strategies with different dimensional outputs. Based on these diversified PC materials, their biomedical potentials as biosensing elements, cell carriers, drug delivery systems, screening methods, cell scaffolds for tissue engineering, cell imaging probes, as well as the monitoring means for biological processes were then highlighted. In addition to these, we finally listed and discussed some emerging applications of PCs integrated with functional materials and newly developed material engineering technologies. In short, this review will provide a panoramic view of PCs-based biomedicines, and moreover, the progressive discussions from fundamentals to advanced applications in this review may also encourage researchers to innovate PC materials or devices for broader biomedical applications.

Multifunctional Composite Inverse Opal Film with Multiactives for Wound Healing

A film with an elaborate microstructure and multifunctions is urgently needed in wound healing. Here, we present a multiactive encapsulated inverse opal film with a monitorable delivery system for chronic wound healing. The inverse opal film is prepared by using poly(lactic-co-glycolic acid) to negatively replicate a colloidal crystal template, which presents a high specific surface area and interconnected nanopores. It could be imparted with a potent antibacterial effect and promote angiogenesis by loading the vascular endothelial growth factor into the nanopores and encapsulating by chitosan. In addition, it is demonstrated that the structure color change of the film could intuitively reflect the drug release progress from the nanopores, which made the film a real-time drug monitoring system. In the affected wound model, the properties of the multifunctional film in promoting wound healing are certified by the faster healing speed, more granulation tissue, less inflammation, and even a distribution of new blood vessels and collagen. These results indicate that the resultant multifunctional film has a practical application value in clinical wound care.

Fabrication of SiO2/PEGDA Inverse Opal Photonic Crystal with Fluorescence Enhancement Effects

The present paper reports the fabrication of inverse opal photonic crystals (IOPCs) by using SiO₂ spherical particles with a diameter of 300 nm as an opal photonic crystal template and poly(ethylene glycol) diacrylate (PEGDA) as an inverse opal material. Characteristics and fluorescence properties of the fabricated IOPCs were investigated by using the Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), reflection spectroscopy, and fluorescence microscopy. The results clearly showed that the IOPCs were formed comprising of air spheres with a diameter of ∼270 nm. The decrease in size led to a decrease in the average refractive indexes from 1.40 to 1.12, and a remarkable stopband blue shift for the IOPCs was thus achieved. In addition, the obtained results also showed a fluorescence enhancement over 7.7-fold for the Fluor® 488 dye infiltrated onto the IOPCs sample in comparison with onto the control sample.

Photonics in nature and bioinspired designs: sustainable approaches for a colourful world

Biological systems possess nanoarchitectures that have evolved for specific purposes and whose ability to modulate the flow of light creates an extraordinary diversity of natural photonic structures. In particular, the striking beauty of the structural colouration observed in nature has inspired technological innovation in many fields. Intense research has been devoted to mimicking the unique vivid colours with newly designed photonic structures presenting stimuli-responsive properties, with remarkable applications in health care, safety and security. This review highlights bioinspired photonic approaches in this context, starting by presenting many appealing examples of structural colours in nature, followed by describing the versatility of fabrication methods and designed coloured structures. A particular focus is given to optical sensing for medical diagnosis, food control and environmental monitoring, which has experienced a significant growth, especially considering the advances in obtaining inexpensive miniaturized systems, more reliability, fast responses, and the use of label-free layouts. Additionally, naturally derived biomaterials and synthetic polymers are versatile and fit many different structural designs that are underlined. Progress in bioinspired photonic polymers and their integration in novel devices is discussed since recent developments have emerged to lift the expectations of smart, flexible, wearable and portable sensors. The discussion is expanded to give emphasis on additional functionalities offered to related biomedical applications and the use of structural colours in new sustainable strategies that could meet the needs of technological development.

Colloidal assembly in droplets: structures and optical properties

Colloidal assembly in emulsion drops provides fundamental tools for studying optimum particle arrangement under spherical confinement and practical means for producing photonic microparticles. Recent progress has revealed that energetically favored cluster configurations are different from conventional supraballs, which could enhance optical performance. This paper reviews state-of-the-art emulsion-templated colloidal clusters, and particularly focuses on recently reported novel structures such as icosahedral, decahedral, and single-crystalline face-centered cubic (fcc) clusters. We classify the clusters according to the number of component particles as small (N < O(10²)), medium (O(10²) ≤N≤O(10⁴)), and large (N≥O(10⁵)). For each size of clusters, we discuss the detailed structures, mechanisms of cluster formation, and optical properties and potential applications. Finally, we outline current challenges and questions that require further investigation.

Intelligent Drug Delivery Microparticles with Visual Stimuli-Responsive Structural Color Changes

BACKGROUND

Particle-based drug delivery systems (DDSs) have a demonstrated value for drug discovery and development. However, some problems remain to be solved, such as limited stimuli, visual-monitoring.

AIM

To develop an intelligent multicolor DDSs with both near-infrared (NIR) controlled release and macroscopic color changes.

MATERIALS AND METHODS

Microparticles comprising GO/pNIPAM/PEGDA composite hydrogel inverse opal scaffolds, with dextran and calcium alginate hydrogel were synthesized using SCCBs as the template. The morphology of microparticle was observed under scanning electron microscopy, and FITC-dextran-derived green fluorescence images were determined using a confocal laser scanning microscope. During the drug release, FITC-dextran-derived green fluorescence images were captured using fluorescent inverted microscope. The relationship between the power of NIR and the drug release rate was obtained using the change in optical density (OD) values. Finally, the amount of drug released could be estimated quantitatively used the structural color or the reflection peak position.

RESULTS

A fixed concentration 8% (v/v) of PEGDA and 4mg/mL of GO was chosen as the optimal concentration based on the balance between appropriate volume shrinkage and structure color. The FITC-dextran was uniformly encapsulated in the particles by using 0.2 wt% sodium alginate. The microcarriers shrank because of the photothermal response and the intrinsic fluorescence intensity of FITC-dextran in the microparticles gradually decreased at the same time, indicating drug release. With an increasing duration of NIR irradiation, the microparticles gradually shrank, the reflection peak shifted toward blue and the structural color changed from red to orange, yellow, green, cyan, and blue successively. The drug release quantity can be predicted by the structural color of microparticles.

CONCLUSION

The multicolor microparticles have great potential in drug delivery systems because of its vivid reporting color, excellent photothermal effect, and the good stimuli responsivity.

Immunotherapeutic silk inverse opal particles for post-surgical tumor treatment

Recurrence of malignant tumor after surgical resection is the main reason of cancer treatment failure. Here, a novel kind of silk inverse opal particles (SIOPs) for post-surgical tumor treatment is presented, and it is derived from colloid crystal bead templates by negatively replicating. Because of their abundant uniform nanopores, interconnected nanochannels and excellent biocompatibility, SIOPs could not only carry great amount of anti-tumor drugs for tumor therapy, but also could provide support for cell adhesion, proliferation and differentiation as the 3D spherical scaffolds which is beneficial to the tissue repair at resection sites. It is demonstrated that the antibody drugs could maintain their high biological activity without any influences during the preparation of SIOPs and these particles were able to enhance the therapeutic efficacy and promote tissue regeneration after surgical resection with their multifunctional features. These prominent properties indicate the great potentials of SIOPs as a promising strategy for efficient postoperative cancer therapy.

Photonic Crystal Stimuli-Responsive Chromatic Sensors: A Short Review

Photonic crystals (PhC) are spatially ordered structures with lattice parameters comparable to the wavelength of propagating light. Their geometrical and refractive index features lead to an energy band structure for photons, which may allow or forbid the propagation of electromagnetic waves in a limited frequency range. These unique properties have attracted much attention for both theoretical and applied research. Devices such as high-reflection omnidirectional mirrors, low-loss waveguides, and high- and low-reflection coatings have been demonstrated, and several application areas have been explored, from optical communications and color displays to energy harvest and sensors. In this latter area, photonic crystal fibers (PCF) have proven to be very suitable for the development of highly performing sensors, but one-dimensional (1D), two-dimensional (2D) and three-dimensional (3D) PhCs have been successfully employed, too. The working principle of most PhC sensors is based on the fact that any physical phenomenon which affects the periodicity and the refractive index of the PhC structure induces changes in the intensity and spectral characteristics of the reflected, transmitted or diffracted light; thus, optical measurements allow one to sense, for instance, temperature, pressure, strain, chemical parameters, like pH and ionic strength, and the presence of chemical or biological elements. In the present article, after a brief general introduction, we present a review of the state of the art of PhC sensors, with particular reference to our own results in the field of mechanochromic sensors. We believe that PhC sensors based on changes of structural color and mechanochromic effect are able to provide a promising, technologically simple, low-cost platform for further developing devices and functionalities.

Structural Dynamics of Neighboring Water Molecules of N-Isopropylacrylamide Pentamer

Poly(N-isopropylacrylamide) (PNIPAM) is a popular polymer widely used in smart hydrogel synthesis due to its thermo-responsive behavior in aqueous medium. Aqueous PNIPAM hydrogels can reversibly swell and collapse below and above their lower critical solution temperature (LCST), respectively. The present work used molecular dynamics simulations to explore the behavior of water molecules surrounding the side chains of a NIPAM pentamer in response to temperature changes (273-353 K range) near its experimental LCST (305 K). Results suggest a strong inverse correlation of temperature with water density and hydrophobic hydration character of the first coordination shell around the isopropyl groups. Integrity of the first and second coordination shells is further characterized by polygon ring analysis. Predominant occurrence of pentagons suggests clathrate-like behavior of both shells at lower temperatures. This predominance is eventually overtaken by 4-membered rings as temperature is increased beyond 303 and 293 K for the first and second coordination shells, respectively, losing their clathrate-like property. It is surmised that this temperature-dependent stability of the coordination shells is one of the important factors that controls the reversible swell-collapse mechanism of PNIPAM hydrogels.

Fluorescence Self-Reporting Precipitation Polymerization Based on Aggregation-Induced Emission for Constructing Optical Nanoagents

Precipitation polymerization is becoming increasingly popular in energy, environment and biomedicine. However, its proficient utilization highly relies on the mechanistic understanding of polymerization process. Now, a fluorescence self-reporting method based on aggregation-induced emission (AIE) is used to shed light on the mechanism of precipitation polymerization. The nucleation and growth processes during the copolymerization of a vinyl-modified AIEgen, styrene, and maleic anhydride can be sensitively monitored in real time. The phase-separation and dynamic hardening processes can be clearly discerned by tracking fluorescence changes. Moreover, polymeric fluorescent particles (PFPs) with uniform and tunable sizes can be obtained in a self-stabilized manner. These PFPs exhibit biolabeling and photosensitizing abilities and are used as superior optical nanoagents for photo-controllable immunotherapy, indicative of their great potential in biomedical applications.

Photoresponsive Delivery Microcarriers for Tissue Defects Repair

Intelligent responsive microcarriers have emerged as a promising class of biomaterials for therapeutic delivery and tissue regeneration, since they can respond to external stimuli and release the loaded drugs in an active manner. Among various available stimuli, near-infrared (NIR) light is particularly attractive because it can penetrate biotic tissues with sufficient intensity and minimal damage. In this work, a kind of photoresponsive delivery microcarriers (PDMs) is developed using microfluidics. The microcarriers consist of NIR-absorbing graphene oxide, thermosensitive poly(N-isopropylacrylamide), and biocompatible gelatin methacrylate. Under NIR light, the PDMs exhibit an evident volume shrinkage and effectively trigger the drug release. After the NIR light is switched off, the shrunken microcarriers return to their original size. This reversible process can be stably repeated for many cycles. An in vitro experiment demonstrates that the NIR-radiated PDMs can actively release vascular endothelial growth factors and improve the tube formation of human umbilical vein endothelial cells. The results from the in vivo experiment also show an obvious photothermal effect and superior therapeutic efficacy of these PDMs in a rat model of tissue defects. These features make the PDMs an excellent drug delivery system and represent a great potential for clinical applications in tissue repair.

Responsive Porous Microcarriers With Controllable Oxygen Delivery for Wound Healing

Microcarriers with oxygen-delivering capacity have attracted increasing interest in the field of tissue regeneration. Here, a kind of molybdenum disulfide quantum dots (MoS₂ QDs) integrated responsive porous microcarriers with controllable oxygen-delivering ability for wound healing is presented. The specific gelatin methacryloyl (GelMa) porous microcarriers are derived from inverse opal microparticles which can be decorated with the oxygen-carrying protein hemoglobin. Because of their characteristic porous structure, interconnected nanochannels, and excellent biocompatibility, the resultant microcarriers could carry oxygen extensively and provide support for tissue repair physically and biologically. Besides, since the typical photothermal effect of 2D materials and their derived 2D QDs, the inverse opal particles integrated with MoS₂ QDs are imparted with photo-responsive capacity, which makes them able to release oxygen photo-controllably. It is demonstrated that the designed microcarriers can promote the repair of abdominal wall defects effectively with their multifunctional features. These remarkable properties point to the potential value of the microcarriers in wound healing and tissue engineering.

Hierarchical Photonic Pigments via the Confined Self-Assembly of Bottlebrush Block Copolymers

Hierarchical, structurally colored materials offer a wide variety of visual effects that cannot be achieved with standard pigments or dyes. However, their fabrication requires simultaneous control over multiple length-scales. Here we introduce a robust strategy for the fabrication of hierarchical photonic pigments via the confined self-assembly of bottlebrush block copolymers within emulsified microdroplets. The bottlebrush block copolymer self-assembles into highly ordered concentric lamellae, giving rise to a near perfect photonic multilayer in the solid state, with reflectivity up to 100%. The reflected color can be readily tuned across the whole visible spectrum by either altering the molecular weight or by blending the bottlebrush block copolymers. Furthermore, the developed photonic pigments are responsive, with a selective and reversible color change observed upon swelling in different solvents. Our system is particularly suited for the scalable production of photonic pigments, arising from their rapid self-assembly mechanism and size-independent color.

A responsive porous hydrogel particle-based delivery system for oncotherapy

Liver cancer is one of the malignant cancers that seriously threatens human health. Although some common treatments including chemotherapy have been applied in oncotherapy, there are often serious shortcomings such as frequent and uncontrollable drug infusion. To overcome these limitations, here, we introduced responsive porous hydrogel microparticles loaded with 5-fluorouracil and metformin for oncotherapy. Because of the interconnected porous structures, various forms of active molecules could be loaded into the particles. In addition, the relatively higher temperature of the tumor site and the temperature-responsive shape transition of pNIPAM hydrogel enabled controllable drug release. The porous pNIPAM particles not only exhibited large loading efficiency and sustained release for the 5-fluorouracil and metformin co-delivery, but also protected drugs from being resolved. Thus, it can be anticipated that the porous microparticles will have great potential in oncotherapy.

Dynamic Optics with Transparency and Color Changes under Ambient Conditions

Mechanochromic materials have recently received tremendous attention because of their potential applications in humanoid robots, smart windows, strain sensors, anti-counterfeit tags, etc. However, improvements in device design are highly desired for practical implementation in a broader working environment with a high stability. In this article, a novel and robust mechanochromism was designed and fabricated via a facile method. Silica nanoparticles (NPs) that serve as a trigger of color switch were embedded in elastomer to form a bi-layer hybrid film. Upon stretching under ambient conditions, the hybrid film can change color as well as transparency. Furthermore, it demonstrates excellent reversibility and reproducibility and is promising for widespread application.

In vitro and ex vivo systems at the forefront of infection modeling and drug discovery

Bacterial infections and antibiotic resistant bacteria have become a growing problem over the past decade. As a result, the Centers for Disease Control predict more deaths resulting from microorganisms than all cancers combined by 2050. Currently, many traditional models used to study bacterial infections fail to precisely replicate the in vivo bacterial environment. These models often fail to incorporate fluid flow, bio-mechanical cues, intercellular interactions, host-bacteria interactions, and even the simple inclusion of relevant physiological proteins in culture media. As a result of these inadequate models, there is often a poor correlation between in vitro and in vivo assays, limiting therapeutic potential. Thus, the urgency to establish in vitro and ex vivo systems to investigate the mechanisms underlying bacterial infections and to discover new-age therapeutics against bacterial infections is dire. In this review, we present an update of current in vitro and ex vivo models that are comprehensively changing the landscape of traditional microbiology assays. Further, we provide a comparative analysis of previous research on various established organ-disease models. Lastly, we provide insight on future techniques that may more accurately test new formulations to meet the growing demand of antibiotic resistant bacterial infections.

Multifunctional Chitosan Inverse Opal Particles for Wound Healing

Wound healing is one of the most important and basic issues faced by the medical community. In this paper, we present biomass-composited inverse opal particles with a series of advanced features for drug delivery and wound healing. The particles were derived by using chitosan biomass to negatively replicate spherical colloid crystal templates. Because of the interconnected porous structures, various forms of active drugs, including fibroblast growth factor could be loaded into the void spaces of the inverse opal particles and encapsulated by temperature-responsive hydrogel. This endowed the composited particles with the capability of intelligent drug release through the relatively high temperature caused by the inflammation reaction at wound sites. Because the structural colors and characteristic reflection peaks of the composited inverse opal particles are blue-shifted during the release process, the drug delivery can be monitored in real time. It was demonstrated that the biomass-composited microcarriers were able to promote angiogenesis, collagen deposition, and granulation-tissue formation as well as reduce inflammation and thus significantly contributed to wound healing. These features point to the potential value of multifunctional biomass inverse opal particles in biomedicine.

Mesoporous Colloidal Photonic Crystal Particles for Intelligent Drug Delivery

Particle-based delivery systems demonstrate a pregnant value in the fields of drug research and development. Efforts to advance this technology focus on the fabrication of functional particles with enhanced efficiency and performance for drug delivery. Here, we present a new type of mesoporous colloidal photonic crystal particle (MCPCP)-based drug-delivery system with distinct features. As the MCPCPs were constructed by self-assembling monodisperse mesoporous nanoparticles in microfluidic droplet templates, they were composed of hierarchical macro- and mesoporous structures and could provide plenty of nanopores and interconnected nanochannels for synergistic loading of both micro- and macromolecule drugs with large quantity and sustained release. In addition, by integrating the stimuli-responsive poly( N-isopropylacrylamide) hydrogel into the MCPCPs and employing it as a "gating" to control the opening of the macro- and mesopores, the MCPCP delivery systems were imparted with the function of controllable release. More attractively, as the average refractive index of the MCPCPs was decreased during the release of the loaded actives, the photonic band gaps of the MCPCPs blue-shifted correspondingly; this provided a novel stratagem for real-time self-reporting of the therapeutic agent release process of the MCPCPs. Hence, the MCPCPs are ideal for intelligent drug delivery because of these dramatical features.