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We report on a facile capsule-based platform for efficient encapsulation of a broad spectrum of hydrophilic compounds with molecular weight less than 1000 g mol. The encapsulated compounds extend from low-molecular-weight anionic Alexa Fluor 532 dye and cationic anticancer drug doxorubicin (DOX) to fluorescein isothiocyanate-dextrans with M ranging from 4000 to 40 000 g mol. The pH-sensitive hydrogel capsules with an interpenetrated network shell are synthesized by layer-by-layer assembly of poly(methacrylic acid) (PMAA, M = 150 000 g mol) and poly( N-vinylpyrrolidone) (PVPON, M = 1 300 000 g mol) on 5 μm silica microparticles followed by chemical cross-linking of the PMAA multilayers. Following core dissolution, the result is a hollow microcapsule with PVPON interpenetrated in the PMAA network. The capsules exhibit a reversible change in the diameter with a swelling ratio of 1.5 upon pH variation from 7.5 to 5.5. Capsules cross-linked for 4 h display high permeability toward molecules with molecular weight under 1000 g mol at pH = 7.5 but exclude dextran molecules with M ≥ 40 000 g mol. Encapsulation of small molecules was achieved at pH = 7.5 followed by sealing the capsule wall with 40 000 g mol dextran at pH = 5.5. This approach results in negatively charged molecules such as Alexa Fluor being entrapped within the capsule cavity, whereas positively charged molecules such as DOX are encapsulated within the negatively charged capsule shell. Considering the simple postloading approach, the ability to entrap both anionic and cationic small molecules, and the pH-responsiveness of the interpenetrated network in the physiologically relevant range, these capsules offer a versatile method for controlled delivery of multiple hydrophilic compounds.

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Background Obstetric brachial plexus palsy is caused by traction during birth. Most patients regain useful function with spontaneous recovery. In some cases, cross reinnervation occurs between the biceps and triceps muscles. In these cases, smooth active motion of the elbow joint is impaired by simultaneous biceps and triceps muscle contraction. The biceps and triceps muscle cocontraction could be treated by botulinum toxin type A injection, tendon transfer of the triceps to biceps, and intercostal nerves transfer to the musculocutaneous nerve (MCN) or to the motor branch of the radial nerve to the triceps muscle. Patients and Methods We present 16 cases (10 males and 6 females) with biceps and triceps cocontraction in spontaneously recovered obstetric brachial plexus palsy patients. They were treated by 3 intercostal nerves transfer to MCN without exploration of the remaining plexus. The mean age at surgery was 40.6 months (range, 24–65 months). Preoperative electromyography was done in all cases to confirm biceps and triceps cocontraction and to assess the contractile status of both muscles. Results The mean postoperative follow-up period was 51.7 months (range, 27–64 months). At the final follow-up, elbow flexion was graded 3 in 1 patient, grade 4 in 3 patients, grade 6 in 9 patients, and grade 7 in 3 patients using the 7-point Toronto scale. The mean active range of motion of the elbow (against gravity) increased from 38 degrees preoperatively (range, 0–75 degrees) to 96.8 °̊ at the final follow-up (range, 60–140 degrees). Conclusions Intercostal nerves transfer to MCN for management of biceps, and triceps cocontraction in spontaneously recovered obstetric brachial plexus injury is a good option with minimal morbidity and high success rate.