Biomaterials
stability is required. Stimuli-responsive systems equipped with gripping tools may also be able to take biopsies. “You can extract a little bit of tissue and then guide it out of the body,” says Majidi. Researchers are also designing adhesive patches to respond to stimuli. Wound dressings incorporating liquid crystal elastomers can be designed to contract in response to heat, applying mechanical force that draws wound edges together. Animal studies have reported faster wound closure or skin regeneration than comparison dressings, but clinical efficacy in humans has yet to be established.
Ongoing research is also investigating stimuli- responsive materials in regenerative medicine. While conventional scaffolds provide cells with a microenvironment in which they can grow, they may not reproduce all the biochemical or mechanical signals involved in tissue regeneration. Responsive scaffolds offer a way to introduce some of those dynamic properties. Hydrogel-based scaffolds can be designed to mimic aspects of tissue environments and are being investigated for cardiovascular, musculoskeletal and other applications. There is also growing interest in wearables that go beyond sensing stimuli to responding to them in real time. Many use haptic feedback, which can be cutaneous or kinaesthetic. Cutaneous systems provide tactile cues through the skin and are being investigated for sensory substitution, rehabilitation and surgical teleoperation. Gloves, skin-like interfaces and other wearable systems can provide substitute or augmented tactile information, while haptic interfaces may give surgeons additional information during robot-assisted procedures. Kinaesthetic feedback can also feature in wearables designed for neuromuscular rehabilitation and physical assistance.
“Think about these as wearable robotic systems that augment sensory or motor capabilities,” says Majidi. Wearables with soft actuators can assist movement and adapt their output to an individual user’s movement or force patterns. Clinical evidence varies by device and indication.
Challenges in integrating responsive biomaterials
Responsive functional materials are used in industries including consumer electronics, automotive and sports. Although some are already manufactured at industrial scale for other sectors, scaling them for medical devices can present additional challenges, including material consistency, reproducibility, sterilisation, traceability and regulatory compliance. Hybrid and volumetric additive manufacturing can improve fabrication efficiency and enable complex geometries. Their suitability, however, depends on factors including material compatibility, resolution, process control and the validation requirements of the finished device.
www.medicaldevice-developments.com
But, says Majidi, “medical device companies need to take these materials and find what those use cases are where you can’t provide the therapy or medical intervention required without them.” Integrating responsive biomaterials into medical devices presents other challenges. First, handling and logistics may be more complicated than for conventional devices. “Manufacturers need to make sure that the device does not experience the stimulus during long-term storage or transport,” says Messersmith.
It also remains to be seen how many of the new devices will perform over the long term. Materials can degrade and lose their sensitivity to stimuli. Manufacturers will need to assess how physiological conditions affect device performance and safety and, where applicable, use long-term studies and post-market surveillance to evaluate durability. Regulation can present another complication. Classification depends on factors including a product’s intended use, composition, principal mode of action and claims, particularly when a product combines device, drug or biological components. Messersmith points to the potential for manufacturers and regulators to view a product differently. “There have been in the past surgical adhesives that the manufacturer thinks of as a device, and then the FDA regulates it as a drug,” he adds. Under the FDA’s current framework, topical tissue adhesives and some internal tissue adhesives are regulated as devices, while products incorporating drug or biological components may be regulated as combination products. Lastly, as some medical devices become smaller or incorporate multiple sensing and actuation functions, conventional rigid circuit boards may be unsuitable for particular designs. “There’s a need for new types of soft materials that can be miniaturised, combine sensing and actuator capabilities, and mimic muscle, nervous, or skin tissue,” says Majidi. “I think that will be a big materials science challenge.” ●
77
Hydrogels can be designed with enzyme- sensitive components.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102
