Electrochemical detection and delivery of DOX using multifunctional nanoplatform: Inhibitory effects on breast cancer cell proliferation and migration

2.1. Chemicals and measurements

All reagents were analytical grade and didn’t require further purification. On a D8 Advance diffractometer (Bruker, Germany) with Cu Kα radiation (λ = 1.5406 Å), XRD patterns were obtained. Through a Nicolet iS50 Fourier-transform infrared (FTIR) spectrometer (Thermo Fisher Scientific, USA), FTIR spectra were acquired from 400 to 4000 cm⁻¹. For identifying the molecular structure of the target compound, single-crystal X-ray diffraction (SCXRD) analysis was implemented on a Bruker D8 Venture diffractometer with a Photon II detector and Mo Kα radiation (λ = 0.71073 Å). Electrochemical measurements were implemented on a CHI760E electrochemical workstation (CH Instruments, China), encompassing differential pulse voltammetry (DPV) together with cyclic voltammetry (CV). A standard three-electrode system was employed: a modified glassy carbon electrode (GCE), a platinum wire, and an Ag/AgCl electrode were utilized as the working electrode, the counter electrode, as well as the reference electrode, separately. All crystallographic data were processed using standard Bruker APEX software packages.

2.2. Synthesis of CMCS-1-TESBA@CP1@DOX

CMCS-1-TESBA@CP1@DOX was synthesized through a multi-step procedure, with yields and purities determined at each stage. Briefly, compound 1 (1.00 mmol) was activated by treatment with HCl (2.00 mmol) in THF/H₂O (4:1, v/v) at room temperature for 1 h, affording the activated intermediate in 91% yield (HPLC purity >95%). This intermediate was subsequently reacted with CMCS (1.00 mmol) in CH₃CN using DCC (0.45 mmol) and DMAP (0.03 mmol) as catalysts, yielding CMCS-1 after 12 h of stirring at 25-30°C, with an isolated yield of 82% and confirmed purity by elemental analysis. CMCS-1 (0.50 mmol) was then treated with TESBA (0.60 mmol) in methanol for 8 h, affording CMCS-1-TESBA with pendant –Si(OEt)₃ functionalities (yield 78%, FT-IR) (Scheme S1). Hydrolysis of CMCS-1-TESBA (0.50 mmol) in water/ethanol (1:1, v/v) was conducted for 30 min, followed by incorporation of CP1 nanoparticles (0.50 mmol) at pH 5.5-6.0 under stirring for 8 h, generating CMCS-1-TESBA@CP1 in 85% yield. Finally, DOX (0.20 mmol) was loaded into CMCS-1-TESBA@CP1 (1.00 mmol) by incubation in PBS (pH 7.4) for 6-12 h. After removal of unbound DOX by centrifugation and dialysis, the final product CMCS-1-TESBA@CP1@DOX was obtained with a drug-loading yield of 75% (UV-vis quantification) and purity confirmed by high-performance liquid chromatography (HPLC) (Scheme 1).

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Scheme 1.

Schematic diagram of CMCS-1-TESBA@CP1@DOX.

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2.3. Cell culture and grouping

MDA-MB-231, the human BC cell line, was provided by the American Type Culture Collection (ATCC). High-glucose Dulbecco’s modified Eagle’s medium (DMEM) with 100 μg/mL streptomycin, 100 U/mL penicillin, and 10% fetal bovine serum (FBS) was applied to cultivate the cells. The cultures were kept at 37°C with 5% CO₂ in a humidified incubator. The cells were passaged with 0.25% trypsin-EDTA when they achieved 80–90% confluence. All tests were conducted on logarithmic phase cells. There were four groupings of cells. The control group received just serum-free DMEM treatment. Free DOX group (F-DOX): Treated with 1 μM free DOX. Blank nanoparticles group (BNP): Treated with blank nanoparticles (1 mg/mL, equivalent to the carrier concentration in drug-loaded nanoparticles). CMCS-1-TESBA@CP1@DOX group (D-NP): Treated with CMCS-1-TESBA@CP1@DOX (equivalent to 1 μM DOX).

2.4. Cell viability assay

After seeding cells at a density of 5 × 10³ cells/well in 96-well plates, they were inoculated for 24 h to allow for adhesion. Following that, 100 μL of the appropriate treatment solutions was added to the medium. After 48 h of incubation, each well received 20 μL of MTT solution (5 mg/mL in PBS), and the cells were incubated for an additional 4 h. For dissolving the formazan crystals, 150 μL of DMSO was added to the aspirated supernatant. Measurement of absorbance at 490 nm was done with a microplate reader.

2.5. Transwell migration assay

Cell migration was evaluated using transwell chambers with pores that were 8 μm in size. Trypsinization, resuspension in serum-free DMEM, and density adjustment to 3 × 10⁴ cells/mL were performed on the cells. The lower compartment received 600 μL of DMEM with 10% FBS, whereas the upper chamber received 200 μL of cell suspension (6 × 10³ cells). A cotton swab was applied to remove any non-migrated cells from the membrane’s upper surface following a 24 h incubation period. The lower surface of the migrated cells was fixed for 20 min with 4% paraformaldehyde, stained for 15 min with 0.1% crystal violet, and then washed with distilled water. An inverted microscope was employed to count the migrated cells.

2.6. Statistical analysis

All experiments were performed at least in triplicate, and the data were presented as mean ± standard deviation (SD). Statistical analyses were carried out using the GraphPad Prism 9.0 software. Comparisons between two groups were evaluated by Student’s t-test, while multiple group comparisons were analyzed using one-way analysis of variance (ANOVA) followed by Tukey’s post hoc test. A value of p < 0.05 was considered statistically significant. Significance levels were denoted as p < 0.05 (*), p < 0.01 (**), and p < 0.001 (***).

3.1. Structure description of compound 1

The SCXRD of compound 1 showed that it belongs to the tetragonal crystal system with the space group of P-42c (Table S1). As shown in Figure 1(a), the molecule structure consists of two six-membered rings (ring A: C3, C4, C6-C8 and N1; ring B: C6, C7, C9-C12) and one benzene ring C: C15-C20. The C3 atom of the ring A connects one methyl formate group (C1H₃C2O₂-_-) via the C2 atom, the C4 atom of the ring A connects a methyl group -C5H₃, the C8 atom of the ring A connects the ring C via the C15 atom, the C9 atom of the ring B connects one O3 atom via the C=O bond, the C11 atom of the ring B connects two methyl groups (-C13H₃ and -C14H₃). The ring A and ring B connect each other via the bond of C6-C7. The C18 atom of the ring C connects the S atom, and the S atom connects a methyl group (-C21H₃). And further, the neighbor molecules of compound 1 were further connected by the intermolecular H-bonds (O3-H1D…N1: 2.044Å) (Figure 1b) and van der Waals forces to produce a 3D dense packing structure (Figure 1c).

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Figure 1.

(a) The moleculer structure for compound 1; (b) H-bonds between the adjacent molecules; (c) The dense packing molecule structure of compound 1.

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3.2. Structure description of CP1

Single-crystal X-ray analysis shows that CP1 crystallizes in the monoclinic crystal system with the P21/c space group, revealing a 3D dense packing structure. The asymmetric unit consists of CP1 one organic ligands L^3-, two Y(III) ions, two coordinated N, N-dimethylformamide (DMF) molecules, one uncoordinated DMF molecule, two NO₃^- ions, one HCOO^- ions and one coordinated aqueous molecule. As shown in Figure 2(a), the Y(III) ions in CP1 adopt two coordinated model: eight-connect for Y1(III) and seven-connect for Y2(III). The eight-connect Y1(III) ions were connected by eight oxygen atoms (Three oxygen atoms are from three different carboxylic groups of three different independent L^3- ions; Two oxygen atoms are from two DMF molecules; One O atom is from one HCOO^-, and two oxygen atoms are from one NO^3- ion). The seven-connected Y2(III) ions were connected by seven oxygen atoms (Three oxygen atoms are from three different carboxylic groups of three different independent L^3- ions; two oxygen atoms are from one NO^3- ion; one O atom is from the HCOO^-, and one oxygen atom is from the coordinated aqueous molecule).

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Figure 2.

(a) The coordination environment of the Y(III) ion in CP1. The symmetry codes: #1: 1+x, 1/2-y, 1/2+z; #2: x, -1+y, z; #3: x, -1+y, z; #3: -1+x, 3/2-y, -1/2+z; #4: -1+x, 1/2-y, -1/2+z. (b) The coordination model of L^3- in CP1. (c) The 1D chain structure. (d) The 3D dense packing structure of CP1.

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In CP1, the carboxylic groups of L^3- ligands adopt one bridging coordinated model (η²μ₂χ²) with the center Y(III) ions (Figure 2b). The Y1(III) ion and Y2(III) ion were connected by the carboxylic groups to produce a dinuclear unit, and the dinuclear units are further extended by HCOO^- to give a 1D chain structure (Figure 2c). In addition, the adjacent 1D chains were further connected and extended by the L^3- to produce a 3D dense packing structure (Figure 2d).

3.3. Structural characterization of composite materials

To further validate the structural features of the constructed composite material and its stability during the drug-loading process, CMCS-1-TESBA and its composite systems were systematically characterized. In the FT-IR spectra (Figure 3a), CMCS-1-TESBA exhibited typical Si–O–Si bending and stretching vibration peaks at 793 and 1085 cm⁻¹, separately, confirming the successful silanization modification; the stretching vibration peak of C=O at 1725 cm⁻¹ was ascribed to the aldehyde group of TESBA [29]. Furthermore, CMCS-1-TESBA@CP1 displayed a characteristic C=N coordination peak at 1622 cm⁻¹, together with signals in the 1150–1000 cm⁻¹ region, collectively confirming the incorporation of coordination polymer CP1 into the composite [30,31]. After DOX loading (CMCS-1-TESBA@CP1@DOX), characteristic absorption bands of the aromatic rings of DOX molecules appeared at 1610 cm⁻¹ and 1450 cm⁻¹, indicating the successful encapsulation of the drug within the composite framework [32]. The powder-XRD (PXRD) patterns (Figure 3b) further substantiated these findings, where CMCS-1-TESBA@CP1 exhibited distinct diffraction peaks at 2θ = 8.7°, 14.6°, and 22.3°, confirming the preservation of crystallinity; upon DOX loading, these diffraction peaks became significantly weakened, suggesting partial reduction in crystallinity due to drug infiltration into the pores, while the overall framework remained stable. Moreover, the Brunauer-Emmett-Teller (BET) surface area and pore structure analysis (Figures 3c-e) revealed that CMCS-1-TESBA exhibited a typical type IV adsorption-desorption isotherm with a mean pore diameter around 3.8 nm and a specific surface area of 315 m²/g. After CP1 incorporation, the surface area markedly declined to 256 m²/g, indicating that the porous framework was partially occupied. After DOX loading, the specific surface area further decreased to 182 m²/g, and the pore volume was reduced, confirming that drug molecules had penetrated the pores and were effectively encapsulated. Moreover, scanning electron microscopy (SEM) (Figure S1) revealed a stratified structure characterized by layered stacking and abundant porosity. This rough, layered morphology provides numerous binding sites, facilitating efficient drug loading. Dynamic light scattering measurements (Figure S2) further demonstrated that the average particle size increased from 282 nm before drug loading to 358 nm after successful encapsulation, supporting the effective incorporation of DOX. Taken together, analyses of structure, porosity, and surface characteristics confirm that the CMCS-1-TESBA@CP1 system offers a stable and tunable platform for drug loading and controlled release.

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Figure 3.

(a) FT-IR spectra; (b) PXRD patterns; (c–e) N₂ adsorption-desorption isotherms of (c) CMCS-1-TESBA, (d) CMCS-1-TESBA@CP1, (e) CMCS-1-TESBA@CP1@DOX.

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3.4. Electrochemical characterization

CV measurements were implemented utilizing a standard three-electrode system in order to assess the electrochemical sensing capabilities of the material toward DOX in more detail, in which the CMCS-1-TESBA@CP1-modified glassy carbon electrode (GCE), a platinum wire, and Ag/AgCl served as the working electrode, the counter electrode, as well as the reference electrode, separately. The electrolyte was a 0.1 M PBS (pH = 7.0). Before measurements, the CMCS-1-TESBA@CP1 suspension was drop-cast onto the polished GCE surface and given time to dry. The CV tests were carried out at 100 mV/s within a potential window of 0.4–1.4 V. As exhibited in Figure 4(a), the bare GCE exhibited negligible redox activity within the selected potential range, whereas the CMCS-1-TESBA@CP1-modified electrode displayed enhanced current responses. Upon the addition of 1 mM DOX into the electrolyte, the electrochemical signals increased significantly, with the CMCS-1-TESBA@CP1+DOX system showing a much higher oxidation peak current compared with the GCE+DOX system. This result clearly demonstrates the role of CMCS-1-TESBA@CP1 in facilitating the electrocatalytic oxidation of DOX. To further investigate the electrochemical behavior of DOX, CVs were recorded at scan rates of 20-200 mV/s, as displayed in Figure 4(b). Along with a minor change in the peak potential, the anodic peak current rose proportionately with the scan rate. The linear relationship between scan rate and anodic peak current (Figure 4c, y = 0.2583x + 0.3762, R² = 0.9985) indicates that the oxidation process of DOX is primarily adsorption-controlled, suggesting efficient electron transfer at the CMCS-1-TESBA@CP1-modified electrode surface. To further evaluate the electrochemical stability of CMCS-1-TESBA@CP1@DOX under complex physiological conditions, CV measurements were performed at different pH values (7.4, 6.5, and 5.0) and temperatures (25°C, 36°C, and 42°C) (Figures 4d and e). As shown in Figure 4(d), the redox peak shapes remained consistent across all three pH environments, with no significant changes in peak current intensity or peak potential, indicating stable electrochemical responses under conditions ranging from normal physiology (pH 7.4) to the tumor microenvironment (pH 6.5) and acidic intracellular compartments (pH 5.0). Similarly, as presented in Figure 4(e), the electrochemical behavior was maintained across different temperatures, including room temperature (25°C), normal body temperature (36°C), and elevated temperature relevant to local hyperthermia (42°C). These results collectively confirm that the nanoplatform retains robust electrochemical stability and reliability under various physiological and pathological conditions, further supporting its feasibility for in vivo applications in BC therapy. Overall, these results confirm that the CMCS-1-TESBA@CP1-modified electrode significantly amplifies the electrochemical response of DOX and operates through a surface adsorption-controlled mechanism, thus highlighting its great potential for sensitive and reliable DOX detection.

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Figure 4.

CV responses for Dox detection: (a) CV curves of bare GCE, GCE+1 mM DOX, CMCS-1-TESBA@CP1, and CMCS-1-TESBA@CP1+1 mM DOX in 0.1 M PBS (pH 7.0) at 100 mV/s; (b) CV curves of CMCS-1-TESBA@CP1+1 mM DOX at 20-200 mV/s; (c) linear relationship between scan rate and anodic peak current; (d, e) CV responses of CMCS-1-TESBA@CP1@DOX at different ((d) pH values 7.4, 6.5, 5.0 and (e) temperatures 25°C, 36°C, 42°C).

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The electrochemical sensing performance of the CMCS-1-TESBA@CP1-modified electrode toward DOX was systematically investigated by DPV in 0.1 M PBS buffer solution (pH = 7.0) within the potential window of 0.5-1.0 V. As shown in Figure 5(a), the anodic peak current increased progressively with DOX concentration from 0 to 2.25 μM, demonstrating the electrode’s high sensitivity toward trace levels of DOX. To further evaluate its applicability in practical detection scenarios, a broader concentration range (0-40 μM) was examined (Figure 5b), which confirmed the electrode’s capability to maintain a reliable response across a wide dynamic range.

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Figure 5.

DPV responses of CMCS-1-TESBA@CP1 toward DOX under different conditions: (a) DPV curves at concentrations ranging from 0 to 2.25 μM; (b) DPV curves at concentrations ranging from 0 to 40 μM; (c) corresponding calibration plot with a linear relationship (R² = 0.9871); (d) scan rate-dependent analysis demonstrating excellent linearity (R² = 0.9985).

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Quantitative analysis was performed by constructing calibration curves of peak current versus DOX concentration. In the low concentration range (0-2.25 μM), a strong linear correlation was observed (slope = 4.6193 μA/μM, R² = 0.9871, Figure 5c), highlighting the excellent sensitivity of the electrode for trace DOX detection. In addition, scan rate studies (20-200 mV/s) showed a robust linear relationship between peak current and scan rate (R² = 0.9985, Figure 5d), indicating that DOX oxidation at the CMCS-1-TESBA@CP1 interface follows an adsorption-controlled mechanism. Together, these results demonstrate that the designed electrode combines high sensitivity for low-concentration DOX detection with a broad linear detection range, underscoring its potential as a robust electrochemical platform for both trace-level monitoring and wide-range quantitative analysis of anticancer drugs.

The selective sensing ability of the CMCS-1-TESBA@CP1-modified electrode toward DOX was further evaluated in the presence of common potential interferents in biological systems. As shown in Figure 6(a), interferents including NaCl, NH₄Cl, uric acid (UA), dopamine (DOP), and glucose (Glu) exhibited negligible responses under the applied potential, while the successive addition of DOX produced distinct current signals with significant intensity changes. This result highlights the excellent selectivity of the sensor toward DOX, even in the coexistence of high concentrations of common interferents. Furthermore, the electrochemical stability of the modified electrode was examined through CV measurements (Figure 6b). The nearly overlapping CV curves confirmed the structural robustness and reproducibility of the CMCS-1-TESBA@CP1-modified electrode during repeated electrochemical cycling. These findings demonstrate that the CMCS-1-TESBA@CP1-based sensor possesses both high selectivity and good electrochemical stability, ensuring reliable application in DOX detection under physiologically relevant conditions. To better highlight the superiority of the designed hybrid nanosystem, we compared the performance of CMCS-1-TESBA@CP1@DOX with several reported DOX-loaded nanocarrier systems. As shown in Table S2, compared with carbon dots, magnetic nanoparticles, lipid nanocarriers, ferritin-based carriers, and co-loaded niosomes, our system not only maintains a competitive drug loading efficiency (75%) and controlled pH-responsive release, but also integrates intrinsic electrochemical activity for real-time DOX monitoring, which has rarely been reported in previous works. These unique advantages underscore the multifunctional and theranostic potential of CMCS-1-TESBA@CP1@DOX.

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Figure 6.

(a) Amperometric responses of CMCS-1-TESBA@CP1-modified electrode toward DOX in the presence of common interferents (NaCl, NH₄Cl, Glu, DOP, UA), showing excellent selectivity; (b) CV curves demonstrating the electrochemical stability of the modified electrode.

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3.5. In vitro drug-release study

In BC therapy, the stability and targeting ability of drug delivery systems are of paramount importance. The pH of normal tissues and blood is close to 7.4, whereas the tumor microenvironment is typically weakly acidic (pH=6.5), and the intracellular lysosomes and endosomes are even more acidic (pH=5.0). Based on this, we systematically investigated the in vitro release behavior of CMCS-1-TESBA@CP1@DOX under different pH conditions (Figure 7). The results demonstrated a pronounced pH-responsive behavior: at pH 5.0, mimicking the intracellular tumor environment, the cumulative release of DOX reached approximately 74.7% within 80 h, which was significantly higher than that observed at pH=6.5 (42.6%) and pH=7.4 (29.5%). This indicates that the nanosystem can achieve efficient drug release in the acidic tumor microenvironment while maintaining stability under normal physiological conditions, thereby markedly enhancing its potential for targeted BC therapy. To further elucidate the release mechanism, the release data at pH 5.0 were fitted to different kinetic models (Figures 8a-d). As shown, the zero-order kinetic model exhibited a poor fit (R² = 0.7881), suggesting that the release process was not solely time-dependent. Similarly, the first-order kinetic model (R² = 0.6125) failed to adequately describe the release behavior. In contrast, the Higuchi model provided an improved fit (R² = 0.9274), indicating that diffusion played an important role in the release process. Notably, the Ritger–Peppas model showed the best fit (R² = 0.9923), and the release exponent n was less than 0.45, confirming that the DOX release was predominantly governed by a Fickian diffusion mechanism. Taken together, the DOX release from CMCS-1-TESBA@CP1@DOX not only exhibited distinct pH-responsive behavior but also followed a Fickian diffusion–controlled sustained release mechanism, further supporting its potential application in targeted BC chemotherapy.

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Figure 7.

In vitro cumulative release profiles of CMCS-1-TESBA@CP1@DOX at different pH values (pH = 5.0, 6.5, and 7.4) over 80 h.

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Figure 8.

Kinetic modeling of DOX release from CMCS-1-TESBA@CP1@DOX at pH 5.0: (a) zero-order, (b) first-order, (c) Higuchi, and (d) Ritger-Peppas models. The best fit was obtained with the Ritger–Peppas model (R² = 0.9923).

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3.6. Cell viability assay

Following 48 h of treatment with various groups on MDA-MB-231 cells, there was no discernible change in the cell viability of the blank nanoparticle group (BNP) in contrast to the control group, suggesting that blank nanoparticles had no influence on cell viability. In contrast to the blank nanoparticle group and control group, the cell vitality of the CMCS-1-TESBA@CP1@DOX and free DOX groups was considerably lower, and the cell viability of the CMCS-1-TESBA@CP1@DOX group was much lower than that of the free DOX group (Figure 9a), suggesting that CMCS-1-TESBA@CP1@DOX had a stronger inhibitory effect on cell viability. The number of cells that moved between the blank nanoparticle group and the control group did not differ statistically, suggesting that blank nanoparticles had no effect on cell migration. Both the CMCS-1-TESBA@CP1@DOX and the free DOX groups had considerably fewer migrated cells than the control and blank nanoparticle groups, and the CMCS-1-TESBA@CP1@DOX group had remarkably fewer migrated cells than the free DOX group (Figure 9b), suggesting that it had a superior inhibitory effect on cell migration.

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Figure 9.

(a) Cell viability and (b) migration ability of MDA-MB-231 cells after treating with various groups. Significance levels were denoted as p < 0.05 (*), p < 0.01 (**), and p < 0.001 (***).

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3.7. Discussion

The multifunctional hybrid nanosystem CMCS-1-TESBA@CP1@DOX designed in this study is not a simple combination of components, but rather a synergistic integration of functional units to specifically address the key bottlenecks of free DOX in BC therapy, systemic toxicity caused by non-specific drug distribution, low drug concentration at tumor sites due to insufficient targeting, and the lack of real-time monitoring for dynamic therapeutic regulation.

From a component-function synergy perspective, CMCS, a natural polysaccharide, provides excellent biocompatibility through its abundant carboxyl and hydroxyl groups, thereby reducing irritation to normal tissues. In addition, steric hindrance enhances nanoparticle dispersibility in physiological media, preventing aggregation and rapid clearance in vivo. 3-(Triethoxysilyl)benzylamine (TESBA), as a silane coupling agent, contributes to structural stability by forming Si–O–Si bonds with CMCS and CP1, preventing premature drug leakage. Moreover, its benzyl and amino groups serve as potential anchoring sites for further functionalization, such as targeted ligand conjugation. The copper-based coordination polymer CP1, with its large surface area and porous structure, ensures high DOX loading capacity while the intrinsic redox activity of copper ions provides a reliable electrochemical signal foundation. Together, these components form a synergistic framework of “biocompatibility–structural stability–functional loading,” laying the foundation for the system’s multifunctionality.

Importantly, the introduction of electrochemical functionality breaks the limitation of traditional drug carriers as “delivery-only” systems, establishing a closed-loop therapeutic feedback mechanism for precision BC therapy. The CMCS-1-TESBA@CP1-modified electrode exhibited stable oxidation responses to DOX, attributed to the synergistic electron transfer between copper ions in CP1 and the quinone moiety of DOX. In the low concentration range (0-2.25 μM), the system displayed high-sensitivity linear detection suitable for monitoring trace DOX levels in tumor cells to evaluate effective therapeutic concentrations. Furthermore, the wide linear detection range up to 40 μM enables dynamic monitoring throughout cellular uptake and release processes, avoiding detection interruptions due to concentration fluctuations. Scan-rate studies confirmed an adsorption-controlled oxidation mechanism, suggesting that DOX molecules are stably adsorbed on the electrode surface, thereby minimizing nonspecific adsorption interference. This integrated “delivery-monitoring” capability not only allows real-time tracking of DOX concentration dynamics in tumor cells but also provides a foundation for clinical personalized dosing.

In terms of drug release performance, the pH-responsive behavior of the nanosystem precisely matches the pathological features of the BC microenvironment, acidic intracellular compartments such as endosomes (pH 5.0-5.5) and lysosomes (pH 4.5-5.0) contrast with the neutral pH (7.2-7.4) of blood and normal tissues. Experimental results demonstrated a cumulative DOX release of ∼74.7% at pH 5.0 after 80 h, which was significantly higher than that at pH 6.5 (42.6%) and pH 7.4 (29.5%). Such selective release minimizes premature leakage during circulation, thereby reducing systemic toxicity, particularly cardiotoxicity, the major side effect of free DOX, while ensuring sufficient drug release in tumor sites to achieve effective therapeutic concentrations. Further kinetic analysis revealed that the release profile followed the Ritger-Peppas model (n < 0.45), indicating a Fickian diffusion-controlled mechanism. This sustained and controlled release avoids burst effects that could cause local toxicity and prolongs intracellular drug exposure, aligning with the proliferative cycle of tumor cells to improve therapeutic efficacy.

From a biological performance perspective, CMCS-1-TESBA@CP1@DOX exhibited stronger inhibitory effects on BC cell proliferation and migration compared to free DOX, while blank carriers displayed negligible cytotoxicity. These findings highlight the clinical potential of this nanosystem from two aspects: (i) synergistic therapeutic enhancement, where CP1 ensures high drug-loading efficiency and pH-responsive release enables site-specific accumulation, thereby elevating intracellular DOX concentrations and enhancing antitumor effects under the same dosage; and (ii) biosafety assurance, as the low toxicity of the blank carrier confirms that CMCS, TESBA, and CP1 meet biomedical material standards, minimizing the risk of immune rejection or tissue damage, and lowering safety barriers for in vivo and clinical translation.

Compared with reported BC nanocarriers such as conventional liposomes or unmodified MOF carriers, the superiority of this system lies in its multifunctional integration and synergism: high drug-loading addresses the “dosage challenge,” pH-responsive sustained release resolves the “spatiotemporal distribution challenge,” and electrochemical monitoring overcomes the “therapeutic feedback challenge.” Collectively, these features fulfill the clinical demand for precision chemotherapy and personalized medicine. In the era of molecular subtyping and individualized treatment of BC, CMCS-1-TESBA@CP1@DOX not only provides a novel nanoplatform but also offers a generalizable design strategy, “therapeutics + monitoring” integration, for next-generation smart drug delivery systems in oncology.