Hierarchical double-layer microneedles accomplish multicenter skin regeneration in diabetic full-thickness wounds

INTRODUCTION

Managing large chronic wounds presents significant challenges because of inadequate donor sites, infection, and lack of structural support from dermal substitutes. Hydrogels are extensively used in various forms to promote chronic wound healing and provide a three-dimensional spatial structure, through growth factors or cell transport.

OBJECTIVES

We present a novel multicenter regenerative model that is capable of regenerating and merging simultaneously to form a complete layer of skin. This method significantly reduces wound healing time compared to the traditional centripetal healing model. We believe that our model can improve clinical outcomes and pave the way for further research into regenerative medicine.

METHODS

We prepared a novel multi-island double-layer microneedle (MDMN) using gelatin-methacryloylchitosan (GelMA-CS). The MDMN was loaded with keratinocytes (KCs) and dermal fibroblasts (FBs). Our aim in this study was to explore the therapeutic potential of MDMN in a total skin excision model.

RESULTS

The MDMN model replicated the layered structure of full-thickness skin and facilitated tissue regeneration and healing via dual omni-bearing. Multi-island regeneration centres accomplished horizontal multicentric regeneration, while epidermal and dermal cells migrated synchronously from each location. This produced a healing area approximately 4.7 times greater than that of the conventional scratch tests. The MDMN model exhibited excellent antibacterial properties, attributed to the chitosan layer. During wound healing in diabetic mice, the MDMN achieved earlier epidermal coverage and faster wound healing through multi-island regeneration centres and the omnidirectional regeneration mode. The MDMN group displayed an accelerated wound healing rate upon arrival at the destination (0.96 % ± 0.58 % vs. 4.61 % ± 0.32 %). Additionally, the MDMN group exhibited superior vascularization and orderly collagen deposition.

CONCLUSION

The present study presents a novel skin regeneration model using microneedles as carriers of autologous keratinocytes and dermal fibroblasts, which allows for omni-directional, multi-center, and full-thickness skin regeneration.

An omnidirectional piezoelectric transducer for selective excitation and reception of high-order shear horizontal waves

Guided wave tomography, as an advanced structural health monitoring (SHM) method, has offered a feasible solution to wall thickness quantification which is essential in petrochemical industries. However, previously used low-frequency Lamb waves (A₀ and S₀) limit the resolution of tomography. Recently, the first-order shear horizontal guided wave (SH₁) was found very promising in tomography for its capability in resolution improvement. However, the SHM-required omnidirectional piezoelectric transducers for selectively generating and receiving the SH₁ wave, namely OSH₁-PT, are not available yet. In this work, a general method was developed to design an OSH₁-PT based on the thickness-poled PZT half-ring configuration. Firstly, the excitation function of the OSH₁-PT was explicitly derived and validated through finite element simulations. Secondly, a design formula was obtained and used to determine the size of the OSH₁-PT. Then, the designed OSH₁-PT was fabricated and tested by using a 2D laser Doppler vibrometer. Significant mode selectivity was observed in all directions (0 ∼ 90°) with the excited SH₁ to SH₀ ratio higher than 15 dB. Pitch-catch tests were conducted from 400 ∼ 520 kHz and the received SH₁ to SH₀ ratio was found higher than 19 dB at all frequencies and reached its maxima of 30.7 dB at 490 kHz, which is very close to the designed working frequency of 500 kHz. Finally, an OSH₂-PT was theoretically designed and validated by FE simulations. Due to its simplicity and effectiveness in designing the OSH_n-PT, the proposed method is expected to pave the road to wide applications of high-order SH wave tomography.

Carotid Endarterectomy Using Lone Star Retractor System

Cervical carotid disease is typical atherosclerosis, which is responsible for ischemic stroke. The effectiveness of carotid endarterectomy (CEA) for advanced carotid stenosis has been established in many large studies, and CEA is the gold standard in surgical treatment. On the other hand, endovascular carotid artery stenting (CAS) has become increasingly popular recently. It is very important to avoid any complications to maintain the effectiveness of CEA. The retractor device is important for the exposure of carotid arteries and for the safe surgical manipulation. We have started to use lone star retractor system (LSRS) to deploy the surgical field. LSRS provides the usability to handle and a shallower surgical field without the disturbance of surgical manipulation. And it can facilitate exposure of the distal internal carotid artery because surgeon can retract freely in whole circumference by towing with moderate strength. LSRS may bring the smoother and easier surgical manipulations in CEA.

A novel omnidirectional tin-alloyed ring retractor for craniotomy in neurosurgery: technical note

In neurosurgical operations, proper craniotomy using retractors is necessary. Various surgical instruments are used for this purpose, including standard retractors and multipurpose head frame retractor systems. However, the conventional multipurpose head frame system is often not optimal for use in some craniotomies and postures because of its size and complexity of setting. We have invented a new omnidirectional tin-alloyed (ODT) ring retractor for craniotomy with malleability and shape memory characteristics to resolve these issues. It is principally elliptical in shape, approximately 30 × 20 cm in diameter, and sufficiently firm. Accordingly, this ODT ring can retract the surgical field in all directions. Here, we report our experiences of 281 neurosurgical craniotomies using this ODT ring retractor system in various craniotomy sites and postures. Our novel ODT ring retractor is useful because of its low profile, multidirectional retractability, and less obstructiveness with its malleability. It could be used with pediatric patients where strong traction is not desirable.

Sound radiation pattern of the advertisement call of the highly territorial poison frog Allobates femoralis

Sound radiation patterns have ecological implications in the effective communication between conspecifics, like optimization of the sound propagation, increase the likelihood to reach mates and to mitigate effects of sound scattering by environmental factors like vegetation. The territorial frog Allobates femoralis advertises its territory against conspecific males and attract females with advertisement calls. Here we report the nearly omnidirectional sound-radiation pattern of the advertisement call of A. femoralis. This sound spreading pattern allows the males to attract mates and repel rivals in all directions. Furthermore, A. femoralis males direct the advertisement call to conspecific neighbours after phonotactic orientation.

A practical omni-directional SH wave transducer for structural health monitoring based on two thickness-poled piezoelectric half-rings

Structural health monitoring (SHM) has become more and more important in modern industries as it can monitor the safety of structures during the full service life and prevent possible losses of life and economics. Shear horizontal wave in plate-like structures is very useful for long distance inspection since its fundamental mode (SH₀) is totally non-dispersive. However, all the currently available SH wave transducers are not suitable for practical SHM because of their complicated structures. In this work, we firstly investigated via finite element (FEM) simulations the performances of thickness-poled d₁₅ PZT ring based omni-directional SH wave piezoelectric transducers (OSH-PT) consisting of different number of elements. Results show that the two-half-ring based OSH-PT can have perfect omni-directivity and acceptable performances in excitation/reception of SH₀ waves. Then, experimental testing on a 21 mm outer-diameter (OD), 9 mm inner-diameter (ID) two-half-ring OSH-PT shows that it exhibits acceptable but not desirable performances in both excitation and reception of SH₀ wave. Finally, size optimization was conducted on the two-half-ring based OSH-PT using FEM simulations and results showed that its performances can be fairly enhanced by reducing the outer diameter of the half-ring. Testing results on a 12 mm-OD, 6 mm-ID OSH-PT show that the SH₀-to-Lamb waves ratio in the case of self-excitation and self-reception can be over 20 dB from 115 kHz to 250 kHz, which is good enough for practical applications. The proposed two-half-ring OSH-PT is expected to be widely used in SH₀ wave based SHM due to its simple structure, easy fabrication/assembling, low cost and good performances.