Near-infrared imaging of diseases: A nanocarrier approach

Review of Chemical Sensors for Hydrogen Sulfide Detection in Organisms and Living Cells

As the third gasotransmitter, hydrogen sulfide (H₂S) is involved in a variety of physiological and pathological processes wherein abnormal levels of H₂S indicate various diseases. Therefore, an efficient and reliable monitoring of H₂S concentration in organisms and living cells is of great significance. Of diverse detection technologies, electrochemical sensors possess the unique advantages of miniaturization, fast detection, and high sensitivity, while the fluorescent and colorimetric ones exhibit exclusive visualization. All these chemical sensors are expected to be leveraged for H₂S detection in organisms and living cells, thus offering promising options for wearable devices. In this paper, the chemical sensors used to detect H₂S in the last 10 years are reviewed based on the different properties (metal affinity, reducibility, and nucleophilicity) of H₂S, simultaneously summarizing the detection materials, methods, linear range, detection limits, selectivity, etc. Meanwhile, the existing problems of such sensors and possible solutions are put forward. This review indicates that these types of chemical sensors competently serve as specific, accurate, highly selective, and sensitive sensor platforms for H₂S detection in organisms and living cells.

Near-infrared triggered ropivacaine liposomal gel for adjustable and prolonged local anaesthesia

Local analgesics effectively allow patients to relieve postoperative pain and reduce the need for inhaled general anesthetics or opioids. Compared with other similar long-acting local anesthetics, ropivacaine (Rop) is widely used due to its potential to minimize cardiotoxicity. However, the relatively short duration of Rop efficacy, which lasts for several hours after injection, is considered insufficient for long-term acute and chronic pain treatment. At present, repeated injections or indwelling catheters are used to achieve long-term drug delivery, which can easily cause infection and inflammation. To achieve externally controllable analgesia for a prolonged time, we prepared near-infrared (NIR)-responsive Rop liposomes (Rop@Lip) containing photosensitizers PdPC(OBu)₈ and unsaturated phospholipid DLPC. The particle size of the Rop@Lip was 234.73 ± 5.21 nm, the PDI was 0.42 ± 0.02, and the drug encapsulation rate was 94.62 ± 1.1%. The release of Rop was highly NIR-dependent in vitro and in vivo. To ensure that the liposomes reside around the nerve for an extended period, we next designed an in situ gel with chitosan (CS) and β-sodium glycerophosphate (β-GP) to form a liposomal gel (Lip/Gel). This Lip/Gel composite drug delivery system could be retained in vivo for 10 d, reduce the side effects caused by drug overdose, and prolong the duration of efficacy. In summary, the NIR-responsive Rop composite drug delivery system generated in this paper can effectively solve the shortcomings of traditional local injections, reduce the toxicity and side effects of free Rop, and provide a basis for a light-responsive delivery system of analgesic drugs.

Insights on functionalized carbon nanotubes for cancer theranostics

Despite the exciting breakthroughs in medical technology, cancer still accounts for one of the principle triggers of death and conventional therapeutic modalities often fail to attain an effective cure. Recently, nanobiotechnology has made huge advancement in cancer therapy with gigantic application potential because of their ability in achieving precise and controlled drug release, elevating drug solubility and reducing adverse effects. Carbon nanotubes (CNTs), one of the most promising carbon-related nanomaterials, have already achieved much success in biomedical field. Due to their excellent optical property, thermal and electronic conductivity, easy functionalization ability and high drug loading capacity, CNTs can be applied in a multifunctional way for cancer treatment and diagnosis. In this review, we will give an overview of the recent progress of CNT-based drug delivery systems in cancer theranostics, which emphasizes their targetability to intracellular components of tumor cells and extracellular elements in tumor microenvironment. Moreover, a detailed introduction on how CNTs penetrate inside the tumor cells to reach their sites of action and achieve the therapeutic effects, as well as their diagnostic applications will be highlighted.

Supramolecular ensembles modified by near-infrared dyes and their biological applications

Near-infrared dyes possess the qualities of lower interference with biological autofluorescence, low photon scattering, and deep tissue penetration, and are being increasingly involved in the development of biomaterials for sensing and precision medicine. However, dyes usually suffer from the disadvantages of poor water solubility and photobleaching, factors that limit their application in vivo. The introduction of supramolecular ensembles can provide an ideal solution. This review presents recently developed supramolecular ensembles modified by near-infrared dyes. Compared with small-molecule fluorophores, the specific size of a supramolecular-based fluorophore endows it with longer circulation time in the bloodstream, increasing its chances of reaching a specific target. In addition, the construction of supramolecule-based fluorophores with versatile functions can be achieved by simple encapsulation or doping, instead of by complicated chemical synthesis. Thus, supramolecular-complex-based fluorophores offer high potential in diagnosis and therapy. This review outlines four different species of near-infrared dye based ensembles in terms of their method of formation, including simple encapsulation or doping and copolymerisation. Recently, a new technology has employed modified fluorophores for in situ self-assembly that form supramolecular ensembles at a specific position, thus solving the problem of poor uptake of nanoparticles by cells, and is included in this review. Finally, the future of this field is considered.

The Formulation of Methylene Blue Encapsulated, Tc-99m Labeled Multifunctional Liposomes for Sentinel Lymph Node Imaging and Therapy

OBJECTIVES

Methylene blue (MB) is a commonly used dye that can be used for near-infrared (NIR) imaging and photodynamic therapy (PDT) by producing reactive oxygen species after light exposure, inducing apoptosis. The limiting factor of MB is its poor penetration through cell membranes. Its decreased cellular uptake can be prevented by encapsulation in drug delivery systems such as liposomes. Additionally, the enhanced permeability and retention effect of tumors enables enhanced accumulation of nanocarriers at the target site.

MATERIALS AND METHODS

Nanosized, MB encapsulated, Tc-99m radiolabeled Lipoid S PC:PEG2000-PE:Chol: DTPA-PE and DPPC:PEG2000-PE:Chol:DTPA-PE liposomes were formulated to design multifunctional theranostic nanocarriers for: 1) NIR imaging, 2) gamma probe detection of sentinel lymph nodes (SLNs), and 3) PDT, which can provide accurate imaging and therapy helping surgery with a single liposomal system. The characterization of liposomes was performed by measuring particle size, zeta potential, phospholipid content, and encapsulation efficiency. Additionally, the in vitro release profile of MB and physical stability were also evaluated over 6 months at determined time intervals by measuring the mean particle size, zeta potential, encapsulation efficiency, and phospholipid content of liposomes kept at room temperature (25°C) and 4°C.

RESULTS

Tc-99m radiolabeled, nanosized Lipoid S PC:PEG2000-PE:Chol:DTPA-PE and DPPC:PEG2000-PE:Chol:DTPA-PE liposomes showed suitable particle size (around 100 nm), zeta potential (-9 to -13 mV), encapsulation efficiency (around 10%), phospholipid efficiency (around 85-90%), and release profiles. Additionally, the liposomes found stable for 3 months especially when kept at 4°C.

CONCLUSION

MB encapsulated, Tc-99m radiolabeled, nanosized Lipoid S PC:PEG2000-PE:Chol:DTPA-PE and DPPC:PEG2000-PE:Chol:DTPA-PE liposomes were found to have potential for SLN imaging by gamma probe detection, NIR imaging, and PDT. In vitro and in vivo imaging and therapeutic efficiency should be definitely evaluated to enable a final decision and our studies on this research topic are continuing.