The combination of micro- or nanofluidics and strong light–matter coupling has gained much interest in the past decade, which has led to the development of advanced systems and devices with numerous potential applications in different fields, such as chemistry, biosensing, and material science. Strong light–matter coupling is achieved by placing a dipole (e.g., an atom or a molecule) into a confined electromagnetic field, with molecular transitions being in resonance with the field and the coupling strength exceeding the average dissipation rate. Despite intense research and encouraging results in this field, some challenges still need to be overcome, related to the fabrication of nano- and microscale optical cavities, stability, scaling up and production, sensitivity, signal-to-noise ratio, and real-time control and monitoring. The goal of this paper is to summarize recent developments in micro- and nanofluidic systems employing strong light–matter coupling. An overview of various methods and techniques used to achieve strong light–matter coupling in micro- or nanofluidic systems is presented, preceded by a brief outline of the fundamentals of strong light–matter coupling and optofluidics operating in the strong coupling regime. The potential applications of these integrated systems in sensing, optofluidics, and quantum technologies are explored. The challenges and prospects in this rapidly developing field are discussed.

Nanomaterials are increasingly used in the development of detection systems for various disease biomarkers as tools for reliable early diagnosis, which is a key factor in reducing mortality and increasing treatment effectiveness. The use of quantum dot–antibody conjugates allows for optical detection of various disease markers in biological fluids, tissues, and individual cells with high sensitivity and specificity. The sensitivity and specificity of detection are determined not only by the outstanding optical properties of fluorescent quantum dots but also by the type of antibodies used for binding target analytes and the methods of their conjugation with quantum dots. This review deals with methods of site-specific and site-nonspecific conjugation of quantum dots with antibodies, including full-length and single-domain antibodies, as well as antibody fragments, with a special focus on their structural features and active moieties used for binding to their targets. The review includes examples of successful applications of quantum dot–conjugated antibodies in diagnosis, environment monitoring, and food safety assessment. We also discuss the prospects of further research in this field, including new conjugation methods and issues related to the stability and specificity of probes. The review provides a comprehensive analysis of the current methods and achievements in antibody conjugation from the viewpoint of subsequent analyte detection, highlighting the importance of further research for improving the existing technologies.

Photoluminescence (PL)-based sensing techniques have been significantly developed in practice due to their key advantages in terms of sensitivity and versatility of the approach. Recently, various nanostructured and hybrid materials have been used to improve the PL quantum yield and the spectral resolution. The near-infrared (NIR) fluorescence excitation has attracted much attention because it offers deep tissue penetration and it avoids the autofluorescence of the biological samples. In our study, we have shown both spectral and temporal PL modifications under two-photon excitation of quantum dots (QDs) placed in one-dimensional porous silicon photonic crystal (PhC) microcavities. We have demonstrated an up-to-4.3-fold Purcell enhancement of the radiative relaxation rate under two-photon excitation. The data show that the use of porous silicon PhC microcavities operating in the weak coupling regime permits the enhancement of the PL quantum yield of QDs under two-photon excitation, thus extending the limits of their biosensing applications in the NIR region of the optical spectrum.

The combination of micro- or nanofluidics and strong light–matter coupling has gained much interest in the past decade, which has led to the development of advanced systems and devices with numerous potential applications in different fields, such as chemistry, biosensing, and material science. Strong light–matter coupling is achieved by placing a dipole (e.g. an atom or a molecule) into a confined electromagnetic field, with molecular transitions being in resonance with the field and the coupling strength exceeding the average dissipation rate. Despite intense research and encouraging results in this field, some challenges still need to be overcome, related to the fabrication of nano- and microscale optical cavities, stability, scaling up and production, sensitivity, signal-to-noise ratio, and real-time control and monitoring. The goal of this paper is to summarize recent developments of micro- and nanofluidic systems employing strong light–matter coupling. An overview of various methods and techniques used to achieve strong light–matter coupling in micro- or nanofluidic systems is presented, preceded by a brief outline of the fundamentals of strong light–matter coupling and optofluidics operating in the strong coupling regime. The potential applications of these integrated systems in sensing, optofluidics, and quantum technologies are explored. The challenges and prospects in this rapidly developing field are discussed.

Microparticles are versatile carriers for controlled drug delivery in personalized, targeted therapy of various diseases, including cancer. The tumor microenvironment contains different infiltrating cells, including immune cells, which can affect the efficacy of antitumor drugs. Here, prototype microparticle-based systems for the delivery of the antitumor drug doxorubicin (DOX) were developed, and their cytotoxic effects on human epidermoid carcinoma cells and macrophages derived from human leukemia monocytic cells were compared in vitro. DOX-containing calcium carbonate microparticles with or without a protective polyelectrolyte shell and polyelectrolyte microcapsules of about 2.4–2.5 μm in size were obtained through coprecipitation and spontaneous loading. All the microstructures exhibited a prolonged release of DOX. An estimation of the cytotoxicity of the DOX-containing microstructures showed that the encapsulation of DOX decreased its toxicity to macrophages and delayed the cytotoxic effect against tumor cells. The DOX-containing calcium carbonate microparticles with a protective polyelectrolyte shell were more toxic to the cancer cells than DOX-containing polyelectrolyte microcapsules, whereas, for the macrophages, the microcapsules were most toxic. It is concluded that DOX-containing core/shell microparticles with an eight-layer polyelectrolyte shell are optimal drug microcarriers due to their low toxicity to immune cells, even upon prolonged incubation, and strong delayed cytotoxicity against tumor cells.

Light–matter interactions in optical microcavities attract much attention due to their potential for controlling properties of materials. Among the various types of optical microcavities, porous silicon microcavities (pSiMCs) are of special interest because of their relatively simple fabrication procedure, tunable porosity, and large specific surface area, which make them highly suitable for a wide range of optoelectronic and sensing applications. However, the fabrication of pSiMCs with precisely controlled parameters, which is crucial for effective light–matter coupling, remains challenging due to the multiple variables involved in the process. In addition, the parameter characterizing the capacity of pSiMCs for confining light inside the cavity (the quality factor, QF) rarely exceeds 100. Here, we present advanced methods and protocols for controlled fabrication of pSiMCs at room temperature, combining theoretical and numerical simulations and experimental validation of microcavity structural parameters for enhancing light–matter interactions. This systemic approach has been used to design and fabricate pSiMCs with an about twofold increased QF and correspondingly improved optical performance; the theoretical modeling shows that its further development is expected to increase the QF even more. In addition, we fabricated hybrid fluorescencent structures with the R6G dye embedded into the optimized pSiMCs. This provided a 5.8-fold narrowing of the R6G fluorescence spectrum caused by light–matter coupling, which indicated enhancement of the fluorescence signal at the eigenmode wavelength due to an increased rate of spontaneous emission in the cavity. The proposed methodology offers precise theoretical simulation of microcavities with the parameters required for specific practical applications, which facilitates optimization of microcavity design. The controllable optical properties of pSiMCs make them promising candidates for a wide range of applications where improved spectral resolution, and increased luminescence efficiency are required. This paves the way for further innovations in photonic systems and optoelectronic devices.