Multimaterial Shape Memory Polymer Fibers for Advanced Drug Release Applications

Abstract

Stimuli-responsive polymers offer unprecedented control over drug release in implantable delivery systems. Shape memory polymer fibers (SMPFs), with their large specific surface area and programmable properties, present promising alternatives for triggerable drug delivery. However, the existing SMPFs face limitations in resolution, architecture, scalability, and functionality. We introduce thermal drawing as a materials and processing platform to fabricate microstructured, multimaterial SMPFs that are tens of meters long, with high resolution (10 μm) and extreme aspect ratios (> 10⁵). These novel fibers achieve highly controlled, sequential drug release over tailored time periods of 6 months. Post thermal drawing photothermal coatings enable accelerated, spatially precise drug release within 4 months and facilitate light-triggered, untethered shape recovery. The fibers' fast self-tightening capability within 40 s shows their potential as smart sutures for minimally invasive procedures that deliver drugs simultaneously. In addition, the advanced multimaterial platform facilitates the integration of optical and metallic elements within SMP systems, allowing highly integrated fibers with shape memory attributes and unprecedented functionalities. This versatile technology opens new avenues for diverse biomedical applications, including implantable drug delivery systems, smart sutures, wound dressings, stents, and functional textiles. It represents a significant advancement in precise spatio-temporal control of drug delivery and adaptive medical devices.

Supplementary information: The online version contains supplementary material available at 10.1007/s42765-025-00571-4.

Keywords: Drug delivery; Multifunctionality; Multimaterial fibers; Sequential drug release; Shape memory polymers.

Fig. 1

Microstructured, multimaterial SMPF manufacturing. a Schematic thermal drawing fabrication. The inset depicts optical cross-sectional images of the thermally drawn SMPF at different ddr conditions (i) and a 50-m-long continuous fiber (ii). Scale bar in (ii), 1 cm. b Post-fabrication of photothermal PDA coatings and infusion of various drugs. c Schematic multifunctionality of the SMPF. d Oscillatory shear rheological properties of PDLLA as a function of temperature. e Complex viscosity comparison between PDLLA and PLGA variants. f Static tensile curves of the SMPF at room temperature. The curves correspond to multiple fiber samples. g Images of a knot, a woven 2D scaffold, and a 3D stent. Scale bars, 5 mm

Fig. 2

Sustained multiple drug release and morphological evolution of the SMPFs. a Release profiles from the SMPF with PLGA1 encapsulating Dox and PLGA2 encapsulating Cur. b Release profiles from the SMPF with both PLGA variants encapsulating Dox. c Release profiles from the SMPF with both PLGA variants encapsulating Cur. Inset pictures in a–c show the respective SMPFs loaded with different drugs (Scale bars, 1 mm). Morphological changes of d PLGA1 and e PLGA2 during the degradation periods at 1, 2, and 3 months. Scale bars, 100 μm (Inset: 2 μm)

Fig. 3

Photothermal conversion and stability of the PDA@SMPFs. a Schematic of PDA nanoparticle synthesis. b Morphology of the PDA nanoparticles. Scale bar, 1 μm. c NIR light-triggered photothermal curves of the PDA@SMPFs with varying PDA concentrations in PBS buffer (light intensity: 1 W cm⁻²). d Photothermal response of the PDA@SMPF with a PDA concentration of 6 mg mL⁻¹ over five cycles of laser on (blue background) and off. e Real-time thermal images of the PDA@SMPF at a PDA concentration of 6 mg mL⁻¹ in air. f Cell viability of HDF cells cultured for 1, 2, and 5 days on the SMPF and PDA@SMPF. g Fluorescence image of HDF cells with the SMPF and PDA@SMPF in 5 days. Green and red colors correspond to live and dead cells, respectively. Scale bars, 250 µm

Fig. 4

Light-triggered spatio-temporal control of multiple drug release from the PDA@SMPFs with PLGA1 and PLGA2 encapsulating Dox and Cur, respectively. a Release ratio of Dox. b Enlarged view of Dox release. c Release ratio of Cur. d Enlarged view of Cur release. e Schematic and experimental setup for spatially resolved drug release. f–g Local Dox release when NIR light irradiates the channel sealed by the PLGA1 film. h–i Local Cur release when NIR light irradiates the channel sealed by the PLGA2 film. Scale bars, 1 mm

Fig. 5

Shape memory properties of the multimaterial SMPF and PDA@SMPF. a Comparison of G′ and tan δ between the SMPF and compression-molded SMP film. b Shape memory cycles at a recovery temperature of 80 °C. c Quantitative shape memory properties. d Shape programming and recovery of a spiral fiber at 80 °C. Scale bar, 5 mm. e Shape programming of the PDA@SMPF into an elongated temporary shape. Scale bars, 1 cm for (i)–(iii), 200 μm for (iv). f Self-tightening behavior of the PDA@SMPF closing a gap between two films under NIR light (light intensity: 1 W cm⁻²). Scale bar, 1 cm

Fig. 6

Integration of functional elements within SMPFs. a Schematic convergence drawing process of a fiber wire-integrated SMPF. b Cross-sectional and side-view images of a metallic wire-integrated SMPF. Scale bars: left, 100 μm; right, 200 μm. c Application of a metallic wire-integrated SMPF as an electrical component to trigger an LED light using a 3 V power source. Scale bars, 5 mm. d Relative resistance change of the metallic wire-integrated SMPF during five shape memory cycles. Inset images show the SMPF in the temporary bent and recovered straight states. Scale bars, 5 mm. e Schematic cross-section of an optical fiber-integrated SMPF and the merged shape recovery process at 80 ℃ while guiding green light. Scale bar, 2 mm. f Light transmission performance of the optical fiber-integrated SMPF during fifteen shape memory cycles. Inset image illustrates the detection of output light power. Scale bar, 5 mm

Fig. 7

Rader plot of three actuation parameters and three processing parameters compared to reported SMP fibers