Photonic crystal materials and their application in biomedicine

Nanochemistry of gold: from surface engineering to dental healthcare applications

Advancements in nanochemistry have led to the development of engineered gold nanostructures (GNSs) with remarkable potential for a variety of dental healthcare applications. These innovative nanomaterials offer unique properties and functionalities that can significantly improve dental diagnostics, treatment, and overall oral healthcare applications. This review provides an overview of the latest advancements in the design, synthesis, and application of GNSs for dental healthcare applications. Engineered GNSs have emerged as versatile tools, demonstrating immense potential across different aspects of dentistry, including enhanced imaging and diagnosis, prevention, bioactive coatings, and targeted treatment of oral diseases. Key highlights encompass the precise control over GNSs' size, crystal structure, shape, and surface functionalization, enabling their integration into sensing, imaging diagnostics, drug delivery systems, and regenerative therapies. GNSs, with their exceptional biocompatibility and antimicrobial properties, have demonstrated efficacy in combating dental caries, periodontitis, peri-implantitis, and oral mucosal diseases. Additionally, they show great promise in the development of advanced sensing techniques for early diagnosis, such as nanobiosensor technology, while their role in targeted drug delivery, photothermal therapy, and immunomodulatory approaches has opened new avenues for oral cancer therapy. Challenges including long-term toxicity, biosafety, immune recognition, and personalized treatment are under rigorous investigation. As research at the intersection of nanotechnology and dentistry continues to thrive, this review highlights the transformative potential of engineered GNSs in revolutionizing dental healthcare, offering accurate, personalized, and minimally invasive solutions to address the oral health challenges of the modern era.

Molecular Imprinted Polymers Coupled to Photonic Structures in Biosensors: The State of Art

Optical sensing, taking advantage of the variety of available optical structures, is a rapidly expanding area. Over recent years, whispering gallery mode resonators, photonic crystals, optical waveguides, optical fibers and surface plasmon resonance have been exploited to devise different optical sensing configurations. In the present review, we report on the state of the art of optical sensing devices based on the aforementioned optical structures and on synthetic receptors prepared by means of the molecular imprinting technology. Molecularly imprinted polymers (MIPs) are polymeric receptors, cheap and robust, with high affinity and selectivity, prepared by a template assisted synthesis. The state of the art of the MIP functionalized optical structures is critically discussed, highlighting the key progresses that enabled the achievement of improved sensing performances, the merits and the limits both in MIP synthetic strategies and in MIP coupling.

Synthesis of High-Performance Photonic Crystal Film for SERS Applications via Drop-Coating Method

Silica nanospheres with a well-controlled particle size were prepared via a nucleation-to-growth synthesis process. A facile method is proposed for improving the self-assembly behavior of silica colloidal particles in droplet coatings by the simple controlling of the drying temperature. It is shown that a periodically arranged, opal-structured, photonic crystal film with a large area of approximately 4.0 cm2 can be prepared, even when the particle size is up to 840 nm. When the band gap of the silica photonic crystals falls in the visible-light region, the crystals exhibit distinct structural colors. Moreover, the wavelength of the reflected light increases with an increasing particle size of silica. When the photonic band gap overlaps the wavelength of the laser source, the overall Raman spectrum intensity is significantly enhanced. Accordingly, the proposed nucleation-to-growth process and drop-coating method provides a cheap and simple approach for the manufacture of uniform sized silica and surface-enhanced Raman scattering substrates, respectively.

Detection and sensing of hemoglobin using one-dimensional binary photonic crystals comprising a defect layer

Believing that the detection of hemoglobin possesses a vital role in the discovery of many diseases, we present in this work a simple method for sensing and detecting hemoglobin based on one-dimensional photonic crystals. Implementing hemoglobin as a defect layer inside the proposed photonic crystal results in a resonant peak evolving within the bandgaps. The strong dependence of these resonant peaks on concentration and the consequent refractive index are the essential bases of the detection process. The role played by these parameters together with the angle of incidence on performance and efficiency of our sensor is demonstrated. In the vicinity of the investigated results, we demonstrate the values of sensitivity, figure of merit (FOM), signal-to-noise ratio (SNR), and resolution to optimize the performance of our sensor. The numerical results show a significant effect of polarization mode on performance of this sensor. For TE polarization with an angle of incidence equal to 45°, we investigated sensitivity of 167nmRIU^-1, SNR of 0.23, FOM of 0.63RIU^-1, and resolution of 257 nm.

One-dimensional defective photonic crystals for the sensing and detection of protein

The sensing of protein is of great importance because of its prominent role in building and repairing tissues. In this work, we present a simple design for the detection and sensing of protein using one-dimensional defective photonic crystals. The main idea of our work is included in the theoretical investigation of the transmittance properties of the resonant mode produced inside the photonic band gap. Our study uses the characteristic matrix method and curve fitting. The main reason for our study is to detect the concentration of a protein solution using an efficient, accurate, and simple method. Here, the defect layer is filled with a protein solution. Our idea depends on two hypotheses, and the first one is based on the appearance of a resonant peak on the photonic band gap. The second one depends on a change in the position of this resonant peak with the concentration of the protein solution. The effect of many parameters on the performance of our sensor, such as the thickness of the defect layer and the sensitivity, is demonstrated. The numerical results could present a simple way to design an accurate, stable, efficient, and low-cost protein sensor compared to other current methods and techniques.

Recent advances in merging photonic crystals and plasmonics for bioanalytical applications

Photonic crystals (PhCs) and plasmonic nanostructures offer the unprecedented capability to control the interaction of light and biomolecules at the nanoscale. Based on PhC and plasmonic phenomena, a variety of analytical techniques have been demonstrated and successfully implemented in many fields, such as biological sciences, clinical diagnosis, drug discovery, and environmental monitoring. During the past decades, PhC and plasmonic technologies have progressed in parallel with their pros and cons. The merging of photonic crystals with plasmonics will significantly improve biosensor performances and enlarge the linear detection range of analytical targets. Here, we review the state-of-the-art biosensors that combine PhC and plasmonic nanomaterials for quantitative analysis. The optical mechanisms of PhCs, plasmonic crystals, and metal nanoparticles (NPs) are presented, along with their integration and potential applications. By explaining the optical coupling of photonic crystals and plasmonics, the review manifests how PhC-plasmonic hybrid biosensors can achieve the advantages, including high sensitivity, low cost, and short assay time as well. The review also discusses the challenges and future opportunities in this fascinating field.

Non-dye cell viability monitoring by using pH-responsive inverse opal hydrogels

Recent advances in the field of drug screening focus on accurate, rapid and high-throughput screening methods. In our work, hydrogel inverse opal photonic crystal microspheres (HPCMs) were fabricated through a templating method and exhibited a robust and reversible response to temperature and pH. The response performance was tested under various temperature (25-55 °C) and pH (1.5-7.5) conditions and the reflective peak shifted noticeably within the visible wavelength range. Furthermore, HPCMs were used as drug delivery carriers and not only displayed high doxorubicin (DOX) drug loading but also presented thermo/pH-induced drug release properties. More importantly, these carriers were shown to be good reporters for monitoring cell viability due to their tunable colour variation. This capability was applied to H460 cell cultures with or without DOX. The structure colour of HPCMs varied in different cell culture microenvironments, and cell apoptosis was able to be distinguished. In this way, this fast, non-dyeing method for reporting cell viability in tumour cytotoxicity assays has potential in the field of drug screening and may give new insights into the use of structural colour to report results in drug screening systems.