Smart pH-responsive nanomedicines for disease therapy.

Background: Currently nanomedicines are the focus of attention from researchers and clinicians because of the successes of lipid-nanoparticles-based COVID-19 vaccines. Nanoparticles improve existing treatments by providing a number of advantages including protection of cargo molecules from external stresses, delivery of drugs to target tissues, and sustained drug release. To prevent premature release-related side effects, stable drug loading in nanoformulations is required, but the increased stability of the formulation could also lead to a poor drug-release profile at the target sites. Thus, researchers have exploited differences in a range of properties (e.g., enzyme levels, pH, levels of reduced glutathione, and reactive oxygen species) between non-target and target sites for site-specific release of drugs. Among these environmental stimuli, pH gradients have been widely used to design novel, responsive nanoparticles. Area covered: In this review, we assess drug delivery based on pH-responsive nanoparticles at the levels of tissues (tumor microenvironment, pH ~ 6.5) and of intracellular compartments (endosome and lysosome, pH 4.5-6.5). Upon exposure to these pH stimuli, pH-responsive nanoparticles respond with physicochemical changes to their material structure and surface characteristics. These changes include swelling, dissociation, or surface charge switching, in a manner that favors drug release at the target site (the tumor microenvironment region and the cytosol followed by endosomal escape) rather than the surrounding tissues. Expert opinion: Lastly, we consider the challenges involved in the development of pH-responsive nanomedicines.

Smart pH-responsive nanomedicines for disease therapy

Background Currently nanomedicines are the focus of attention from researchers and clinicians because of the successes of lipid-nanoparticles-based COVID-19 vaccines. Nanoparticles improve existing treatments by providing a number of advantages including protection of cargo molecules from external stresses, delivery of drugs to target tissues, and sustained drug release. To prevent premature release-related side effects, stable drug loading in nanoformulations is required, but the increased stability of the formulation could also lead to a poor drug-release profile at the target sites. Thus, researchers have exploited differences in a range of properties (e.g., enzyme levels, pH, levels of reduced glutathione, and reactive oxygen species) between non-target and target sites for site-specific release of drugs. Among these environmental stimuli, pH gradients have been widely used to design novel, responsive nanoparticles. Area covered In this review, we assess drug delivery based on pH-responsive nanoparticles at the levels of tissues (tumor microenvironment, pH ~ 6.5) and of intracellular compartments (endosome and lysosome, pH 4.5–6.5). Upon exposure to these pH stimuli, pH-responsive nanoparticles respond with physicochemical changes to their material structure and surface characteristics. These changes include swelling, dissociation, or surface charge switching, in a manner that favors drug release at the target site (the tumor microenvironment region and the cytosol followed by endosomal escape) rather than the surrounding tissues. Expert opinion Lastly, we consider the challenges involved in the development of pH-responsive nanomedicines.

Prevalence and Duration of Acute Loss of Smell or Taste in COVID-19 Patients.

Initially, acute loss of smell (anosmia) and taste (ageusia) was not considered important symptoms for coronavirus disease 2019 (COVID-19). To determine the prevalence of these symptoms and to evaluate their diagnostic significance, we (approximately 150 physicians of the Daegu Medical Association) prospectively collected data of cases of anosmia and ageusia from March 8, 2020, via telephone interview among 3,191 patients in Daegu, Korea. Acute anosmia or ageusia was observed in 15.3% (488/3,191) patients in the early stage of COVID-19 and in 15.7% (367/2,342) patients with asymptomatic-to-mild disease severity. Their prevalence was significantly more common among females and younger individuals (P = 0.01 and P < 0.001, respectively). Most patients with anosmia or ageusia recovered within 3 weeks. The median time to recovery was 7 days for both symptoms. Anosmia and ageusia seem to be part of important symptoms and clues for the diagnosis of COVID-19, particularly in the early stage of the disease.