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Due to their wide application, responsive hydrogel bilayers have recently persuaded researchers to develop efficient tools to design these attractive structures. In this work, the deformation of a bilayer comprising a neutral elastomeric layer and a functionally graded (FG) pH-responsive one is investigated. The material properties of the FG hydrogel layer vary in the thickness direction. An analytical technique is developed to predict the behavior of the bilayer. To predict the pH-responsive layer behavior, a second-order ordinary differential equation (ODE) is formulated and solved such that the relevant boundary conditions are satisfied, resulting in solving the governing equations related to this layer. Also, for the under-study bilayer, numerical simulation of the considered problem is performed using the finite element method (FEM) — implementing a user-defined subroutine of UHYPER — through ABAQUS. The bending semi-angle, radial, and tangential stresses of the bilayer are studied in some cases via the proposed analytical technique and FEM. The results of both methods indicated excellent conformity. Furthermore, the effect of changes in thickness ratios of the layers was examined. Lastly, the cross-linking density of the hydrogel layer and some other parameters were studied to investigate their influence on the bilayer deformation and specify the optimal values of some of those parameters for the considered bilayers.

Amphiphilic polymer carriers (PEG–St–$R$) were prepared from cassava starch and their pH response was investigated. First, hydrophobic tapioca starch polymer (St–$R$) was prepared with octyl acyl as the hydrophobic group. The hydrophilic group polyethylene glycol (mPEG) was then introduced into the polymer by esterification to produce amphiphilic tapioca starch polymer (PEG–St–$R$). Its self-assembly behavior was characterized using fluorescent probes. The morphology of PEG–St–$R$ was investigated by transmission electron microscopy (TEM). Loading of the anti-cancer drug curcumin was used to assess the delivery and slow-release performance of the amphiphilic tapioca starch polymer. Cumulative drug release was explored at various pH conditions, with the greatest release from drug-loaded micelles being observed under acidic conditions and stable in a neutral environment. These results provide a theoretical basis for the preparation of pH-responsive nanomicelle carriers, and a platform for the preparation of novel amphiphilic starch-based polymers.

Design of high-performance drug delivery system is necessary to improve the anticancer ability of 5-fluorouracil (5-FU). In this work, we developed a pH-responsive 5-FU loaded and sodium alginate (SA) modified mesoporous silica nanoparticles (MSNs) drug delivery system (5-FU@MSN-SA). After 5-FU was loaded into the pores, MSNs were successfully functionalized with amino groups and then capped by sodium alginate. Compared to acidic conditions, the drug release rate in the neutral environment was quite low. Moreover, detailed investigations confirmed that 5-FU@MSN-SA can easily be up-taken by cancer cells and proved the high cytotoxicity to 4T1 cells. The calculated IC${}_{50}$ values for 5-FU and 5-FU@MSN-SA were 34.67$\mu$g/mL and 54.95$\mu$g/mL, respectively. These results indicated that 5-FU@MSNs-SA can be a promising nanoplatform in cancer therapy.

Graphite carbon nitride (g-C₃N${}_4)$ polymer with two-dimensional planar structure is a new star in nanodrug delivery systems in recent years because it shows characteristics of low cost, nontoxicity, biocompatibility and easy functionalization. However, conventional g-C₃N₄ shows bulk, macro size, small specific surface area and poor water solubility. To improve this, most works are always confined to physical ultrasound, oxidative peeling or template-strategy, which have the disadvantages of redundant steps, environment-unfriendliness and high cost. In this paper, a modified supramolecular self-assembled strategy was carried out to construct a novel graphitic carbon nitride nanoplatform (named by CA-MA${}_X)$ using melamine and cyanuric as precursors. The chemical structure characterization, drug loading experiment and cell tests in vitro of the CA-MA${}_X$ nanoplatform were carried out and discussed in detail. Results indicated that the obtained samples show enhanced specific surface area, more exposed groups and good biocompatibility. Compared to the traditional carbon nitride (named by MA-CN), the newly prepared CA-MA${}_X$ carrier shows improved drug loading efficiency and good pH-responsive loading, as well as releasing. Cell uptake experiment demonstrates that CA-MA₂-DOX can be swallowed by cancer cells and during treatment of the cancer cell process, the CA-MA₂-DOX complex experiences phagocytizing by the cancer cell, controlled-release DOX and kills the cancer cell after DOX was passively diffused into the nucleus. CA-MA₂-DOX exhibited significant in vitro antitumor activity. To our knowledge, this is the first time the supramolecular self-assembled method was used in carbon nitride nanocarrier construction for cancer treatment.

Targeted photodynamic therapy (TPDT) based on the photosensitizers responsive for tumor microenvironment is promising because of the better anti-tumor effect and less phototoxicity against normal tissue than the traditional PDT. Nanoparticle-based stimuli-responsive photosensitizers have been widely explored for TPDT. Based on the acidic microenvironments in solid tumors, an ultrasmall pH-responsive silicon phthalocyanine nanomicelle (PSN) (smaller than 10nm) was designed for selective PDT of tumor. PSN had high drug loading efficacy (more than 28%) and exhibited morphological transitions, enhanced fluorescence and improved singlet oxygen yield under acidic environments. PSN was renal clearable and could rapidly accumulate and be retained at tumor sites, achieving a tumor-inhibiting effect better than phthalocyanine micelle without pH response. Tumors of mice treated with PSN for PDT were completely ablated without recurrence. Thus, we have developed a phthalocyanine-based pH-responsive micelle with excellent tumor targeting ability, which is expected to realize the selective PDT of tumor.

Targeted photodynamic therapy (TPDT) based on the photosensitizers responsive for tumor microenvironment is promising because of the better anti-tumor effect and less phototoxicity against normal tissue than the traditional PDT. Nanoparticle-based stimuli-responsive photosensitizers have been widely explored for TPDT. Based on the acidic microenvironments in solid tumors, an ultrasmall pH-responsive silicon phthalocyanine nanomicelle (PSN) (smaller than 10 nm) was designed for selective PDT of tumor. PSN had high drug loading efficacy (more than 28%) and exhibited morphological transitions, enhanced fluorescence and improved singlet oxygen yield under acidic environments. PSN was renal clearable and could rapidly accumulate and be retained at tumor sites, achieving a tumor-inhibiting effect better than phthalocyanine micelle without pH response. Tumors of mice treated with PSN for PDT were completely ablated without recurrence. Thus, we have developed a phthalocyanine-based pH-responsive micelle with excellent tumor targeting ability, which is expected to realize the selective PDT of tumor.